The Cal-look Lounge

Seeing a alarming high number of crashes at the top end of the drag strip over the last few years, I think it`s time to put the searchlight on and ask, what is really the problem using the beetle as a drag race car?
Knowing that involved in these crashes are all top notch cars and experienced drivers (but this thread is not about the individual race cars), I think there has to be a common factor that makes these accidents. Compared to "traditional front end engine" drag race cars, the beetle seems problematic, and accidents are more "common". So what is the problem and what can we do about it?

Is it the aerodynamic problem that causes the car to be unstable at high speed? We know the beetle has little weight at the front wheels, and tends to rise at the end like a wing at high speed, but is this really the problem or problem alone? Other drag race cars with similar aerodynamics, as hot rods and `30 - `40`s style cars does not appear to have a similar problem?
 
Is the use of a high HP/torque turbo engine contributing to the problem? Is the fact that this type of engine makes maximum effect at the end of the drag strip an issue? Compared to a blower/supercharger engine, the turbo engine has a more "champagne bottle cap behavior", and is this why so many experience unstable car or tire slip at the end of the track? Do we need a engines that delivers more stable hp/torque?

Or is it the weight distribution, the rear engine? Maybe there is a limit to how fast a car with the beetle type of weight distribution can go? Thinking of an arrow, we all know the only way to make a arrow go straight, is to have most of the weight at the tip of it. Try to add weight at the tail, and it never goes straight.

Maybe we have to face the fact that a mid 8 sec beetle is at the limit, and to go faster we have to really "think again"?

I know there are many, many experienced beetle drag race drivers here at the lounge, and I hope that we can use the experience and our minds to come up with some new ideas and maybe solve some of this challenge.

Berger   

yes that give us somthing to think about when building cars.

many of the cars crashing is tube chassis cars and many of them with struts. names like Geers, alan fore, vw paradise, tekken, and now nystrøm. all struts cars. maby it is just me or does it effect the cars in the top speed end.

hope you guys have commets to this.

I have several thoughts on this issue,some I will not post as they are far to contraversial for a public forum, Peter makes a valid pint,but there are thousands of strut cars out there that dont have any problems with the engine in the front,I dont see Stians problem caused by the struts and i know the Hater crash wasnt caused by that,or my own crash either

Of those cars you mentioned Peter,which chassis were designed and built by which builder?

And mostly the cars were already out of shape way before the top end,but we keep in it to long,learning to get out of it,slow the car down,pull the chutes whatever you need to do but not to grab anohter gear and keep on it is the most difficult thing to learn.it seems to take a bad accident to make you realise its not worth it to get a time,if you get out of it there will be another chance to run "that number"

Also I feel alot of tracks dont take VWs seriously,what some of the cars need in the way of track prep and conditions is better than a Top fuel car,and similar to a Pro mod car,at Tierp last year i had this problem,the track was good,but then someone oiled one lane,and the clean up was rushed,and after that it just wasnt good enough for a high hp car but they are only VWs right so it doesnt matter >:(

This year at santa pod they have a problem,which has been admitted by the big man who runs the show,around the 1/8 mile the track had some problems,so they leveled it and scraped it just beofre the easter thunderball,but watching yesterday it still hasnt recovered completely,cars are still wandering around at the 1/8th mile area,several cars have crashed after loosing control there  since this track improvement !!!!
Jim smiths crash was a year ago,happened at the same spot before they made the improvements!!!

The picture is from one of my passes at easter,it go so out of shape I was sure i was going to crash,but imidiately go of the power,tried to control it,breaked but couldnt get it right,then pulled the chute and managed to save it.[thanks to Julian Hunt for the photo]
Having struts made no difference to what happened,now suspension design and set up,that is a different subject altogether

I am still working on a front end aero improvement that i can fit to my car,and hopefully will be able to fit onto the front of other cars as well to help them


Berger for your stats,I think at least 5 cars and one dragster have crashed in england this year,and NO VWs ;)  We are only aware of what affects our little world to a certain extent :) 

We really need the input of all the experienced drivers to give there own feelings on what happens or happened to get a good selection of views

cheers richie

Look at a airplane wing, curved on top and flat underneath. Any similarities with the shape of a beetle? Then listen to the guys with height sensors on their cars and they will tell you that their car is higher at high speed compared to when it stands still and this goes for both the front and the rear. Then I take it for granted that you somewhere on the strip need to either let of the throttle and perhaps even touch the brakes. This will of course also effect the handling. I also find it really interesting that the serious racers have started to add weight at the right places on their cars making them more stable. Not to forget the short wheel base on our cars and the fact that driving a beetle is like trying to throw a hammer and asking it to fly with the handle first.

BB

Also add in the manual transmission which when you shift allows the car to unload,then the torque as it comes back onto boost and loads the chassis back up trys its hardest to un-settle the car,having watched the video of the 2 cars I know[new beetle from brazil and rotary engined black mamba 1303] that are using sequential or clutchless shifting go down the track so much smoother I think it is another huge step forward,when do you see a car suddenly get out of shap for no reason? if they are hard in 3rd or 4th gear it doesnt happen,but change gear and all hell can break loose :o

As kalle wrote more and more are adding weight to make the cars un VW like in weight distribution,getting nearer to 50/50 weight split which has to help keep the car stable at speed,and maybe we have to accept that the beetle shape we all love may become "ugly" to make it safer with aerodynamic additions but they sure look ugly all scratched up after its gone wrong :(

Richie

Don't know if I count as being an experienced driver any more, but I have put in my fair share of passes over the years in both tube chassis and pan cars, some good, some bad, some plain dangerous.

I know very few people will want to agree but a lot of accidents I've witnessed over the years have been ultimately down to driver error. You have to accept that a SWB car like a Beetle, with the shape it is, is not the most obvious vehicle to build an all-out race car. But as long as you accept the limitations, then fine. The important thing – as Richie demonstrated – is to read your car: don't be a hero, and don't fight it. Many accidents are caused by over-correction or simply holding onto the wheel too tight. Most cars want to move around a little – OK, let them. I usually hold the wheel fairly lightly in one hand, occasionally two, and allow the steering wheel to move as it wishes. If the alignment is correct and there's plenty of caster built in, a car will want to run straight. It's when you feel it move and try to prevent it that things get ugly.

There are situations when external forces come into play, of course: track condition, cross-winds etc, but part of being a good driver is making yourself aware of the situation before you make a pass. If you don't trust a lane, if at all possible, don't run in it. There's nothing worse than staging with the thought in mind that you might crash. Chances are you will because you won't be thinking logically (or 'safely'), and will tend to fight the car.

If the car is properly aligned, there is no binding in the suspension, the corner weights are equal side for side (how many VW racers corner-weight their cars – with a tank of fuel and a the fully-suited driver in place?), tyre pressures are equal – and the circumference of each rear tyre is the same (yes, they do vary...), then you should be OK.

Car prep and driver prep – get them right and you have a fighting chance of making it the finish line in one piece.

OK, I'll go back to the retirement home now... :)

To add to your point, look at the 6 second Latam To#¤ta Starlet as a example of a really fast, short wheel based car.

Yes another good example of it can be done :)

I think you have enough passes to qualify or out qualify most of us ;)

it takes a long time to get the mentality of "what if" out of your head after stuff goes wrong.

I bought some scales as I was so aware of what simple changes made to the corner weights,expensive but so is towing a car half way across europe to make a few sh3t passes as the set up is wrong,scaling it  with me in it,then remembering to put my race suit and crash helmet on made a worrying amount of difference.

Also you need to keep checking the corner weights,it will change even after 1 race,wth the work it does towing etc

richie

That is a very good point and one which few people think about. It's especially valid if your car is a chassis car on coils all round. When your car is on a trailer, or in a transporter, you should tie it down with blocks/struts to stop any suspension movement. Otherwise, on a long tow, your car's suspension is doing the equivalent of hundreds of passes, causing springs to soften, rates to change...

I agree – it's no good doing your chassis set-up at the beginning of the season and expecting it to last...

Richie, counting incidents it may not look to bad, but in percent of how many potential 8-sec cars there is in our vw community, it does not look good..
I think you have a very interesting point about the transmission. Keeping the torque from the engine to the wheels as equal as possible all the way, helps to keep the car stable.

why not make the scc lules so the limit is 9,00 sec in that way we can run a real final sunday and more racers have the chance to win.. and maby 10,00 for na and 11,00 for na street tyres.. that way it comes up to the driver.


just my 2..

I am not sure I understand the logic,this really doesnt have anything to do with the topic does it?confused?

And maybe I am wrong in my conclusion before,but cars dont crash in 4th gear on a perfect pass,they crash becasue of somthing that already happened,which will still happen running 9.0 with the brakes hard on at 1000ft so as not to go to fast,which is way more dangerous than running it flat out

and didnt Johan win last year running 9.0???

Your are right Richie, and what we want, really, is to make the beetle go as fast as we want, without risking the car. That is the goal with this thread (and SCC is the arena to make it happen ;) )

I had front ride height sensor in my '65 street car. The front didn't rise at top end (but it was only doing 230km/h). No aero stuff in the car, 930kg. I am also aware of one very fast Beetle with ride height sensors; no issues at very high speed. That car has a rear wing, but not any (ugly) front spoilers.

The '65 was horrible the first year with decent power due to a raised gearbox and spring plates at wrong angle. With a raised rear frame it was still unstable at speed; no sudden moves, but felt a little loose and scary all the time. It got a lot better when the bump-steer was corrected (never toe-out, but lots of toe-in in certain situations). Later with the ladder bar rear setup it was really easy to drive and felt safe, but let's put this into perspective; it only ran mid 9s at 230km/h, and running mid 8s or quicker at 250-280km/h is a different game.

For the new car I have tried to do as much as possible to make it safe; lots of weight in front,  clutchless shifting (Finnish dog-ring gears available from Jussi / Kuplapaja + ignition cut) etc, but still no aero mods...

Jyrki

One thing I can certainly vouch for from my experience was the fitting of a wing - it made a night and day difference to my car. Before the wing the Oval was so unstable at speeds above 130 mph that it made me not want to drive the car above 125 mph; it was just too dangerous - the back end became so unstable and the car started to 'steer from the rear'.

Reading past posts on this subject it appears there's almost a prejudice against running wings on a Bug, and as such people are quick to dismiss it, even though they haven't tried it for themselves. However, I can report that in my case it made all the difference as the car's top speed increased (upping the boost) to over 146 mph and I literally could drive through the top end with one hand on the wheel and not use the chute. That was without any other changes. My rule has always been to make only one change at a time and try it out. That way I always know when a particular mod works. I remember speaking to Fastbrit on this subject a few years back and he confirmed positive results from running a wing on 'No Mercy'. Defo worth a try ;)

Aerodynamics obviously play a great part on VWs, along with the arrow head weight theory etc. so don't rule out trying a wing asomen of your options. A good design such as BigWig's (I based my design on his, but added much taller spill plates into the design) should be considered as part of a 'getting it straight' programme.  Other mods I made include paneling the framehead area under the front axle. That's one huge air trap, which needs consideration and addressing. The flat panel I made runs from the front wings to beneath the axle beam and has cutouts for the front wheel arcs etc. The fake 'crotch coolers' I made for the car allow any pressurised air to escape. Slow mo video shows my car's nose fairly level at the top end, which is good.

This is interesting stuff Jyrki, no lift in the front end? But you also talk about the angle of the spring plates, you don't say exactly what was wrong with it, but I would guess your arms was pointing down to the torsion bars. What angle do you use on your ladder bars?

In general when I read about chassis design I see a lot of focus points in a normal V8 race car that you never read about in the VW world.
What I get from that is that our game is different from theirs... but topics like this makes me wonder, does anyone have our "game" figured out?

I have just read that John Troxell crashed his new out Pro/mod - Outlaw/turbo car yesterday at irwindale Drag day,I dont know anything else about what happened,he is ok,the car is not and it was only a 1/8 mile track,no big mph involved so it still happens.

I like Jyrkis idea with the clutchless shifting which should really help keep the car straight if it is already going that way and have sensors to fit to my car,I am in the process of making some major changes to the car and will include the fitting of the sensors while i am making the changes.

Matt why do you think your car was so nervous for want of a better word at only 125-130mph before? I dont doubt the wing made it feel safer but I would want to know what caused it before when so many other bugs have gone 125+mph without those problems

 I don't think the beetle is the problem , but a combination of compromises people make to go fast.  Richie has alot more experiance than I do so I hope he chimes in here . I have run 66% rear weight on my tube chassis N/A Ghia and felt pretty good on the top end at about 120 mph, but my turbo pan car at the same weight bias would drift sideways in third.   My point is this, every car is differant and requires differant combinations of shocks, limiter straps , weight bias, ect...  to handle and be safe. The type of rear suspension and the weight of the cars are two critical factors I see in top end crashes. Swing axle cars that are improperly setup roll easier than IRS, light cars are more twitchy than heavier ones especially in cross winds on top end. Richie have you ever taken the time to write an article on how to set up a chassis properly for safety and performance ?  Mike McCarthy

Good question Richie, and one which I can't further answer as the wing was the cure and therefore I no longer needed to address the issue.

I guess one possible explanation is that my car has lot of weight in the rear, so was probably more sensitive than lighter cars. The Wasserboxer is a lumpy unit!

I did wonder about the extra rear weight,do you know what the corner weights are? I still have mine here somewhere from being weighed at Shakey at its last meeting in the UK,would be interesting to compare


cheers richie

Mike I totally agree on most of this,we are stupid enough to make the huge compromise of ignoring most of the infomation available and putting the engine in the wrong end ;) and the more weight the more controlled it seemed to be,proberly right up to the limit and then it is proberly worse as that extra weight makes what happens more violent.

 
I really dont know a great deal about swingaxle set ups,a mid 11s pan car I am fine with after that I would be getting the cutter & welder out and making it IRS :)


On my own cars I found the pan car stable and predictable and the chassis car nervous and dangerous,but and this is a big but,I have well over 1000 passes in the pan car and only a few dozen in the chassis car,[for reference they are less than 10lbs difference in weight]
even though I know they are very diferent cars to me  there is something very wrong with the chassis car and I am now changing alot of the "must have" items after they seemed to not be what I was sold,only time will tell

On of the problems with the bug design is that there are no truly flat places on the side of the body -- basicially like a turtle shell on wheels -- and when it starts to get out of shape there is no flat side to 'push' it back where it belongs -- a lot of the ProMod guys are going to the notch body for this very reason -- it is also why the Box design for the rear spoiler came into being, it gave something flat for the wind to push against when things get out of hand. And I've always thought that the "rule" that the  spoiler could not be above the rear window really limited it effectiveness.

as far as weight and balance.... When I was playing with my 600, getting it up to speed (130-135 mph) and making it to handle on the road courses, the addition of 60 pounds to the front end made a HUGE difference to stability and handling.

Now, in my latest endevor of going out and playing on the salt, I've talked to everyone that will stand still for a few seconds and they all say that while a wing on the back helps the air leave the car at high speeds and gives  down force to the car at speed, it is the side panels the really gives the car stability at high speed and a lot of thought needs to be given into how they are designed and where they are placed on the car so that they can be effective.

I have never driven a bug at high speed but my notch is very stable. I have added 30 kg in the front compared to when i started out. Mostly fo better starts. From what i have read  the notch was the first car that Vw took to the windtunnel and it has a very low CW  i think it is 32, correct me if i am wrong. But this thread is not about T3s, sorry.

a lot of points have been spoken about in the "wings and aerofoils" thread started by Richie, it makes for interesting reading.

I can only speak from personal experiance, my car is a "back halfed car" and not a chassis car

I learned a lot from the chassis data logging and have had a few scary moments., and when you look into the data for the Scary moments you can see the rear shocks were extending at a greater rate than the fronts.

the single best thing i have fitted to my car is the front air dam, to stop as much air going under the car as posible. the car feels planted and also provided better steering input.

Ive got a rear Keno wing to fit to my car to guide the air over the roof, Im going to try a few runs without it first, log the chassis data then a few runs with it. to see if i can come up with a difinative results


the only proper results are going to be found in a wind tunnel, quite a few bad handeling v8 cars have made the visit to the tunnel and all have come out all better than before.



I'll share any findings with you guys.

To be fair if you take to any Chassis constructors in England they just shake there head and say were crazy for even contimplate going that fast in a beetle ! lol



Martin

This is a good and important topic,the cars are getting more and more horsepower and its becoming a problem handling it safe.

I think a huge problem is the design of the rear suspension and ladderbars/springplates IRS or swing,i do belive they are flexing to much.
This a is a huge problem for big hp (700-1000)BMWs and Supras who also run IRS suspension,they are always all over the track.
You dont see the same problem with fourlink and 9" rearend no matter what body they are using.

A clutchless gearbox would help a lot to not shock the drivetrain banging in gears,im using the Finnish gear and they are not really clutchless,
they seem to work fine in a NA application but not with the tourqe a turbomotor is producing,you just cant get it out of gear under load
 whitout using the clutch

just my 2 cents on the topic

//Patte

I have wondered about the type 3 and the ghia front shape,it is no doubt better than a beetle design,but the front curve under the bumper area must still create soem lift at speed and would be more difficult[ugly] than a beetle to shut that area off to stop the air going underneath,any thoughts?




You dont get out of it that easily :D  you still have a lawn dart the same as the rest of us ;D so your input is just as valuable as the bug owners :-* :) and its a strut car ;)

cheers richie

   I like the swingaxle setup but again I am only racing 1/8th mile and feel comfortable that the car is safe( 8.50 Cert) . Limiting rebound I think is one of the things people overlook, tires tuck in and she rolls over on decelleration, have seen it too many times.  I have limiter straps that stop the axle drop to 1/2 inch before my shocks stop traveling. I never thought about the flat surface , maybe my running boards are helping me, they are wide and high.
(http://i91.photobucket.com/albums/k300/dragvw2180/april07011.jpg)
     I have been looking at these posts, you guys have some fast cars .  Mike McCarthy
Richie, my Ghia had so much downforce that the top center of the glass tilt front end would cave in on 1/4 mile passes .

i am not an expert at all, but i do want to make a comment on the air that gets underneath the car. i think a lot of air can pass underneath and that is a problem, but not the biggest issue. i think the bigger issue is air getting trapped at the rear (in the engine compartment, or behind the valance). but is this is true this would certainly affect the type3 as it has a huge air trap at the back, but it is also very heavy compared to a type 1 body (stock). if i look at Roger Crawfords ghia it has the rear lights that act as air outlets and i think this is a good idea, the wing will help put the car down, but then you get in a situation where two forces act against each other and hopefully cancel each other out. if the  downforce fails or is not sufficient enough (when you shift, unload, accelerate, catch wind, bump,...) things get out of shape at the back.

as a sad note, there was a notch that crashed at SCC a few years back at the topend as well...

I don't have the corner weight info to hand, but the car weighs 255kg up front and 482kg at the rear. It's got a fat ass! :)

I for one believe a wing makes a big difference, but I still try to manage without one (I like my cars to have standard looks if possible).
Jyrki

Hi,
Maybe the word 'angle' was not correct. With the first setup a long time ago the transmission was raised too much and it messed the rear suspension. Later with the ladder bars (32") I started with 11" Instant Center height; it was ok, maybe a little too big wheelies. After the first test raised them one step to 12". This seemed to work with the Center of Gravity etc. of that car.
I can check my corner weights - they're in the note book in the garage.
Jyrki

Patte, that's what I have. I have zero experience as the car is still under construction. Do you use ignition cut when shifting?
Jyrki

The angle of the springplates does seem to make a huge difference to traction and hence grip all the way down the track,finding the balance between ride height and traction is quite difficult,that is the only reason I can see for doing a torsion raise,to get the center of gravity down and keep the springplate at the correct angle

cheers richie 

What would be considered the correct angle of the spring plate at ride height?

Here's a good write up on how to launch a v8 car http://www.how-to-build-hotrods.com/tuning-4-link.html (http://www.how-to-build-hotrods.com/tuning-4-link.html)

(http://www.how-to-build-hotrods.com/images/neutral.jpg)

Reading this gives the impression we are in the same boat... We have a fixed instant center lengthwise, and a fixed wheel base. But center of gravity can be adjusted slightly up and down, and can be moved forward by adding weight up front. The instant center can be moved down by raising the gearbox... A lot of work yes...but can the laws of physics actually tell if the engine is in the rear or the front if the center of gravity is in the same place?

I understand that a live axle is a different beast to the IRS since that does all sorts of movements by design. But I believe that Pattes rear suspension would behave like a live axle with ladder bars.

I think there are too much bad chassis out there . a lot of people think they can do it better or can save money. For me the only ones are the RLR , he has the most experiance . I looked around for a longer time to find a good car - i like the old mild steel chassis from ron most . And i also think the new chrom molly chassis are sometimes too light weight. V8 chassis must be different - engine in front -

Udo

Now I think we are getting somewhere!  
A lot of useful information has been provided her now, thanks, and keep it coming :)

As for the suspension I think we need someone to calculate and design a 4-link setup for the beetle that bolts into place where the torsion spring used to sit. As far as I can understand, we do not need to go for the ladder-bars if the 4-link is designed to hit the correct instant center. If the 4-link also is designed strong enough to handle enough hp, the problem with "steering rear wheels" is solved.

It also seems like removing weight from the front of the beetles body is just making things more difficult, so I guess keeping all the steel up front, and removing as much as possible in the rear is a good idea to equal the weight and make a more reasonable center of gravity.

It also seems like the traditional rear wing needs to be redesigned, because it`s main function is to add side stability, brake the wing effect of the car, and not to make downforce. I guess it needs to be moved further up on the roof, have larger side panels and a zero degree mid section with a brutal flip at the rear.
  
Also focus one making a automatic/clutch-less transmission that works would be of great benefit I think.

This is my summary, this far.. :)

The 4 link needs to be double to be able to control the IRS side on each side... or you need to connect the IRS hubs with a tube beneath the gearbox, going side to side.  Like 4x4 Voyagers have:
(http://www.kfz-tech.de/Bilder/Kfz-Technik/Radaufhaengung/DeDionAchse02.jpg)

4 links is a smart way to get the instant point where you cant practically have them, but they only sort of work(the point moves as the suspension is traveling thru the arc). Meaning they are not optimal either. But when you are building a race car, I cant see the problem of adding ladder bars...?  But also they need to need to be double.

If, and that's a big IF, you can get the same point of gravity in a bug by weighing it down... as in a V8 car... the chassis would not know where the engine was.

That is one of the points I was trying to make,get theweight bias better and it makes less difference where the engine is,as I have some down time with the car at the moment I have been trying to take weight from the back of the car by using different materials etc,but then I will add the weight back in to the front of the car where it is needed,I dont need a light car thats for sure ;)

cheers richie

What do you mean "The 4 link needs to be double to be able to control the IRS side on each side.."?

By the way, the De Dion tube design you hinted at was used on the original Frameworks-chassied Bugpack Pro-Sedan back in 1988/89. It never handled, but I don't know why. It was rebuilt as a swing-axle car and finally went on its roof in a big way...

Here (sorry for poor pics) is the rear end of No Mercy under construction – probably the most stable, consistent chassis car in its day:

(http://i163.photobucket.com/albums/t318/Photokernow/Rear2.jpg) (http://i163.photobucket.com/albums/t318/Photokernow/Rear3.jpg)

What I mean is to be able to use the collected knowledge of the V8 boys, our rear wheels needs to move in the same way as they do on a live axle.
I not believe for a minute that just changing things to work the same fixes anything, but when you are at that point you can follow the v8 boys lead...  you have people and books to guide you.


I knew of that, and there is a current bug in Sweden that use/used the same set up. I don't think he had to much luck with it( in the tens?).


Yes that's another way of getting it "linear"...  I don't think using swing with 4-link is same thing at all...

I dont see any benefit using a fourlink suspension unless you mount the whole drivetrain in a subframe and use a live axle
letting the tranny and motor work as a rearaxle on a frontmotor car with fourlink  ???

As our rearaxle(tranny) is fixed in one place, the only adjustment we can do(as i see it) is by moving the ladderbars up or down
or with a trannyraise increase the angle on the the springplates making it squat more(ladderbarsin lowest point) or less(highest point)
Its the tranny that lifts the car so making the car heavier in front is probably the right way to adress wheelie problems and lift at high speeds.

The De Dion design is probably the only way to keep the rearwheels from steering under load,but it is a heavy desing.
Pizzo bros used it with a fourlinksetup on the fastback in the 80s  :)

//Patte

bear in mind i know nothing about chassis design but formula v cars flip the diff and run the motor mid mount would this not help balance out the weight in a tube chassis car?
i think there would still be plenty of room behind the seat to fit it in?  :-\

Bingo -- There is the VW problem -- -- No matter how we mount the axles -- 98% of the torque the is transmitted to the car goes through the transmission and it's mounts -- until someone comes up with a way of tuning that we will be mired in the 50's suspension design

The biggest problem with a beetle as a drag racer (as I see it) is weight bias.

A V8 ProStock car is probably the most efficient leaving setup you can possibly get, so that's our benchmark.

Now take ~600lbs. off the nose of the car and re-attach it 2ft past the centerline of the rear tires.

Just for fun, take away half the treadwidth from the slicks

AND half the sidewall height from the slicks
AND cut the wheelbase down to about a skateboard
AND give it huge relative frontal area and a really bad shape

- Now see if it will go straight.

I am really failing to see why we can not use the 4-link with the same effect as on a front engine car? Please explain :)

Here is a example of what I have in mind

(http://www.bimmerboost.com/images/imported/2011/05/normal_photo287297E0-1.jpg)

I guess there was no point in my posting photos of the rear end of No Mercy... IRS and four-link set-up that ultimately ran 9.80s in 1994 (yes, 18 years ago...) on just 2.1-litres. Chassis was one of two VW chassis built by a V8 chassis expert - the only other VW chassis he built was Kawell's 'Blackie'. So this was the only rear-engined VW he ever built. He started with a clean sheet and applied his V8 knowledge to the VW. It worked and very well. So I have no idea at all why people keep either suggesting four-bar on a VW won't work or asking 'why can't we use four-bar on a VW?  I guess either my car never existed or there are people here who have built similar designs and proved it doesn't work. Jon Webster, who I consider (as do many others) to be the best chassis builder in the UK and certainly Europe, too, measured and drew out my chassis when I took the car to him for set-up. He concluded that it was just about perfect. We did discuss a strut front end but no point as we didnt want to lose any more weight from the nose. OK, I'll just sit back now and let the experts get on with the discussion!  ;D

red9 design in the UK make somthing like that for T2 its all bolt on ther were going to do it for T1 as well but dont know if they have done yet, heres my take on the rear suspension not sure what you make of it i have posted pictures before but comments welcome :)

(http://i71.photobucket.com/albums/i149/gluemixer/21579a4a.jpg)

cheers andy

Keith, I sympathise. You had a car that ran super straight and consistent and almost two decades ago, when most were happy running 15s. When I considered a rear wing on my car, I made an educated decision to seek advice from those with experience; like yourself. It paid off, and my car benefitted massively, though perhaps not aesthetically  :D. Yet, like your four link, the wing also seems to be cast aside and given only passing consideration. Why is it we feel the need to re-write the rules on how a Bug should or shouldn't work when there are already cars out there proving the point?

Ok,it appears the main issue is we dont actually know what we are doing :o :D  There are several different ways that work,to a certain extent,but as we dont build every car the same there is no real data to say how well it will work,and to what performance/hp level.
I think we have suspension solutions in place that will get the power to the ground ok,but what happens when you throw in some variables? track conditions changings over the 1/4,track temp,winds,both side winds and head or tail winds,oil on the track from a previous car[how many actually have a diaper on there car? WHY NOT?

Keiths old car worked well,but what happens if you add 500lbs to it in the wrong places? or 500hp more,the engines have been gaining in hp and torque the last few years,the developemnt is there along with better more efficient turbos and the Efi allows us to control it,the transmissions are stronger but really the chassis design hasnt changed at the same pace
Leif's car was a development of his old car,pressumably built better and stronger,he knows what he is doing,has lots of experience as a driver and I have no idea what happened to cause the incident that started this thread,but sh$t happens

Udo,
you wrote that you think the chromoly chassis are sometimes to lightweight?but we as the customer dont size the tubing or thickness,that is up the the chassis builder,I personally dont think they take into account what the customer is actually going to try and do with the car,they just build the same chassis regardless of what its going to be,N/A,turbo,blower,nitrous whatever.I think they need to stop thinking of keeping it as thin and light as possible,we dont have 260hp N/A engines or 400hp turbo engines anymore,things have moved on from that,we add weight to our cars anyway so why not start with thicker stronger tubing?


Rudy's new beetle has a four link rear suspension on it,with 3 lateral links from the hub to chassis rails,its similar to No mercy in the pics Keith posted,it seems to work well,but he is still at the beginning of the journey with that car,only time will tell if it is good enough when more hp and speed is applied to it.

But how many of us actually use the adjustment built into the suspension? and know what is going to happen when we make those changes,moving the arms up or down in th eholes,spreading them further apart at the front or narrowing them down? with the previosly mentioned V8 pro stock car all the data is there,they have done more passes testing this year alone than most of us have just done passes in our lives


The main reason we crash is >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>  



 BUDGET  :o


Its true if we had the budget we would have the ability to employ all the brains and tools needed[software,wind tunnels,experts,tuners etc]



cheers richie

Keith i didnt say that a fourlink dont work on a vw,my point is that we can not use it the way it was design for,setting the pinionangle etc.
In our application it will just work as a ladderbar with the possibility to move the instantcenter alot more forward than a ladderbar by setting the angle
of the upper and lower bars.

there is at least 2 VWs in Sweden that runs a Chassis shop fourlink setup and they seems to work fine but they are NA,in USA there have been a few
crashes using Chassis shop chassis with high hp turbos,so the problem seems to be there regardless of the setup we use.

I agree with Richie and i think one of the solutions would be accepting the fact that our enginens are producing more hp and tourqe now and build the rearends
strong enough to handle it and not just as light as possible.

//Patte

Keith, Bergers reply was not aimed at you, as you obviously have beliefs in the V8 way, it was aimed at the ones that do not.

Can you tell us anything more about your set up? In you pictures the 4 link seem to be parallel? Was this how you ran it? Did you and your chassis builder tune it on the track together, or did you follow something like the diagram I posted earlier?
Why do you think no one (?) have followed your lead? Are people aware of your chassis set up, I mean did you do any chassis articles on the car or something like that?

Matt, Ricihe wrote something about your car being nervous at the same speeds as other bugs without wings are still stable. If that is true, how can a lacking wing be the source of your problems? With all due respect!
If going middle eights and sevens are going to be done *safely* the setting out point must be as good as possible before fitting the wing... of course the wing is needed to do the numbers no doubt about that.

This threads starting point was Leif's accident... his car, along with several other cars that have crashed in the last year were all following the rules as you call them, built by the best out there...  So should we stop trying, ignore the losses (keep going), or have a debate about the rules?

Who says in what way a four-link should be used? Four link technology has been used on all kinds of cars for many years – look at every Grand Prix car in the 1960s and early '70s – they all ran four-link at the back. More than anything it's a simple way to offer a no-bind, yet adjustable, way to locate the rear wheels/hubs. That a V8 live-axle car can then use it to adjust pinion angle is a bonus but not necessarily the whole raison d'etre behind the four link. Just my 2c.


OK, sorry – I misread the message... The links were parallel in those photos purely by coincidence simply because that was when I first got hold of the chassis as a pile of parts – I just bolted it together like that as it was an obvious simple way to do it. I also ran the car quite often like that – it results in a very 'soft' launch (the Instant Centre is at infinity – in front or behind the car...). The one advantage of this if you are at a track with varying conditions (as is often the case in the UK, with varying track temperature, inconsistent track prep – maybe that's improved now!) then you could rely more easily on using rear shock settings, tyre pressures and changing the length of the limiting straps on the front shocks. All quick and easy changes that could be made in the staging lanes.

By running the top link horizontal, and the lower one raised at the front, the car would hit fairly hard but keep the nose planted on the ground. I didn't like the way it felt, from what i remember, and the one time I experienced tyre shake (NEVER to be forgotten!) was with it set like this. By dropping the bottom link, the car pulled the wheels more easily but would 'bog'. Now, when I set it so the instant centre was behind the car, it became a different animal altogether. Wit the top link on the upper setting, the bottom link on the lowest, the car felt more like a pan car to drive, and didn't respond well to shock adjustments.

In the end, because I was more interested in consistency (I had a championship to win/defend), I generally ran the car with the bars parallel (OK, a cop-out!) or with the IC set low.

Bear in mind, these are my memories from nearly 20 years ago – I may not be 100 per cent correct, but all I do know is it was a lovely, easy car to drive.

As for why no-one followed my lead, well, at least one other UK car was built using a 'copy-cat' rear end, but not very well executed. That was the 'Cold Sweat' channelled sedan of Murray Griffin. Since then, I have had several requests over the years for details of the rear end – there is one chassis builder in the UK right now who is building a car for a customer who has asked for details "because it worked".

Turning briefly to the matter of CDS or chrome-moly – everyone is forgetting the main advantage C/M has over CDS: it has a fantastic 'memory'. CDS chassis will gradually twist with time – do your corner weights, alignments etc after several runs, and the chances are you'll discover things have moved. A chrome-moly chassis doesn't suffer from this – that's another reason why my car was very consistent, I think. Overall, the car was no lightweight, and probably heavier than most CDS chassis cars with lightweight bodies.

Cheers all for listening to the ramblings of an old git. :D

A car being currently built in USA by a lesser known chassis build[no offence Doug ;) ] were they are not following the "monkey see,monkey do" path followed by so many,will be intersting to see how it all works,

then how to get the weight bias nearer a front engined car by the quickest and fastest vw style car around

Keith,

as I am not totally sure of what affect what changes  what affect on a 4 link car as in relation to bar angles can you tell me how you would set it up for ultimate ET with say twice the hp you had back then? oh and so as not to crash :)

i am reading "Doorslammers,The chassis book" by Dave Morgan at the moment to try and learn more but it is making my head hurt ::)  I am much better at understanding by trying things and seeing what happens than by theory :)


cheers richie

Ah, a kinaesthetic learner!  :D Richie, it is great that you are willing to try different things - I've never seen suspension like in the back of your new cab before, like I think I said to you at Shakey earlier this year. How do you think it compares to a regular IRS rear end given that you've run very similar times in both cars?

Keith, I had a quick look at the pictures on my phone but I can't see them on the big monitor here at school, but it looks like the two lower links that make up the lower wishbone were completely independent to each other, and rose jointed at each end? Would that allow the rear hub carrier to rotate as it moves up, controlled by the four-link bars? I'm trying to get my head around how it works before I can think about the why!

And you never will again on my car,its going in the bin :o >:(       

There are some things that apparently I cant say on the internet ::)


Version 2 should be ready for SCC :)

Easy - drive more slowly! Oh, and post on Internet forums a lot – that always seems to make cars go faster!  ;D ;D ;D

(PS – I'd start by running the bars parallel so you can optimise shock settings...).

I remember reading that book, too. Shares in Ibroprufen went up sharply.

Thanks for elaborating for us Keith! I think I also like the long bars your car had, do you remember if they ended in front of the center of gravity? Any thoughts on this
Just one thing, that is a swing gearbox used for mockup, right?

Good point Keith ,there are more ways to use a fourlink than just to dragrace  :o :)

But there is still the problem with the power that lifts the whole chassis when its transmitted thru the
solid mounted tranny but with a live axle it plants the tires to the track trying to lift the chassis making it a diffrent ballgame
adjusting it with shocks and springs,instant centre,bodyroll,antirollbars.
Im probably way off in my thoughts on the matter but thats the way i see it  :)

//Patte

I think that another big issue is the need for heavy springs and shocks we need to handle
the launches,making it to stiff when we go down the track and making the tires take most of
the hits when it becomes a bit bouncy.
The V8 promods uses electronic shocks to adress this problem,setting them stiff at the start
and looser down the track.Expensive? yes, but maybe worth it

//Patte

I had a chat with Chris Isaacs a couple of years ago when I first thought about building custom IRS A Arms. If we had gone down the chassis car route we would have gone 4 link IRS but we were restricted with the design being a pan car. There was an interesting thread over on UAC about rear ends which I sent Chris, I can't seem to find the other emails I had but I think this one relates most to the adjustment of the 4 link bars and what happens..

"Hi Steve, very interesting thread.  As you say, similar to what we discussed, and I like the idea of the adjustable height front mounting points.  The relevant bit on this thread is, as we were saying, that an independent suspension setup does not react engine torque through the chassis in the same way that a live axle car does.  The 'pitch rotation' which happens on a live axle car is determined by Newton's Second Law,  the 'equal and opposite reaction', whereby the drive torque rotating the ring gear 'forwards' also causes the pinion gear to 'climb up' the ring gear (due to the resistance of the vehicle mass to moving forwards in response to the ring gear rotation), thus rotating the axle housing rearwards and thus rotating the chassis through the suspension links.  (Hope you got all that!).
 
Now... with an independent suspension, the ring and pinion gear is not solidly mounted to the suspension links via a solid axle case, therefore this rearward rotation is reacted to the chassis via the transaxle case, not the suspension links (as someone correctly pointed out on the thread you sent me).  Also, with a VW which has a 'reverse' engine, ie the front of the engine faces rearwards, but which runs in the conventional direction, the pinion gear actually tries to climb DOWN the ring gear, not up (hope you got all that too!).  This will make the car squat, not lift, due to torque reaction.
 
However, as the car moves forwards (via the thrust of the rear wheels) the hub carriers and suspension links are what is pushing the mass of the vehicle forwards through the chassis mounting points, and the position of those links determines how the chassis reacts.  If those chassis mounting points are REAL high, it is easy to imagine how the rear wheels would try to 'drive underneath' the chassis, thus lifting the rear of the car, the reverse would be true with a low mounting point.  Therefore, having for example a three- or five-hole vertical adjustment for the arm chassis mounts, with the centre hole at standard height, would give the facility to tune the system for the optimum performance.
 
Interesting stuff!  I'm sure a setup like that could be done fairly easily, and give you your narrowed hub width as well.
 
Cheers, Chris"

This is a really interesting topic, for me I think the thing i'd most like to see is some wind tunnel testing or even some CAD fluid dynamics results. There are numerous chassis designs that one person will swear by and the next person will swear by another but for the most part the basic shape of the body has stayed the same. All chassis types have crashed so for me personally if I had the money I would love to stick it in a wind tunnel!

I'm pretty sure this is wrong? Our engine turns clockwise so when the ring gear stays put, the pinion climbs up!  But anyway,s a brilliant piece of information there Steve!


Found this on pinion angles:
"Pinion angle is a term I hear tossed about as some sort of magic incantation quite often. Let’s dispel the myth.

Pinion angle in and of itself does not affect the way a car launches. A change in pinion angle does change the angle of the four link or ladder bar brackets on the rear axle housing. So a change in pinion angle will change the angle of push and pull on your rear suspension components, but, and this is the important part, we do not want to use pinion angle as a rear suspension tuning aid."

http://www.jimobalek.com/pinion-angle/

Patte, that live axle subframe approach looks promising  ;D

Fair enough! At least you thought about it and tried it rather than just dismissing it out of hand. I'd like to see what you're trying next - I won't be at SCC but I'm trying to get to the rest of this season's events at Shakey - are you going to any of them?

Hope to see you at the august open nat. ?

Udo

If it works I will be racing at the open nationals in august :)   if not I maybe looking for another cabrio body :o


Neil it wasnt my design or manufacture ::)  I just tried to make it work,got to stop now before i type something I am not allo

Jhu... I think it's difficult to compare my car too closely to others because I believe the problem of stability at the rear was exaggerated on my car because of the extra weight it carries at the rear. The wasserboxer is very heavy, I have a water radiator at the rear carrying 11 L of h2o. The 915 tranny is 20kg heavier than a bug box, 930 Cvs, huge turbo, big water filled intercooler... It all adds up. Cheers, Matt

The Stance on the hater maker is fantastic. Who built that chassis?

Lee

[attachment=1]

I'm not a drag racer but this is one of the best threads I've read here in a while

Its an older chassis that crashed a while ago,Kris repaired and updated it,and added his own suspension

Turbo is over gearbox correct?intercooler tank is at the front? just trying to get it clear in my head as to the layout,I am sure we can get rid of that wing ;D



I make that 34/66 weight bias,not good but not that bad,its a shame its up for sale,would be interesting to see how it reacted to adding weight to the front

Back to the subject:

we can add weight to the front to help,but what if we can make the front create the downforce on the front end to give the same effect as adding the weight but without the negative of the weight on the startline,that was one of my main thoughts on the aero thread


cheers richie

If the car wants to go up in the start, then it want to go up down the track as well, and as speed gets higher, the wing shape helps the "want to go up" attitude. So breaking the wing shape and making the the suspension push the car forward only, not up, I think is the key elements.

My car weighed 780 kg with the old turbo setup , the new is about 11 kg lighter. I had very similar numbers as Matt with 33/67. Should be a little better now. This is with driver, forgot to write that

For reference my '65 street car WD was 61%-39% with driver. Big battery, 12l fuel cell, 10l water tank (for intercooler) and 5l oil tank in the front, turbo above transmission, exhaust behind driver's seat and intercooler behind co-driver's seat. The ladder bar setup most likely lost some weight in the rear compared to torsion bar setup? Height of CG estimated to be 500mm from ground.
Jyrki

Those are nice numbers Jyrki, did you do anything to lift the Center of gravity, or did it give itself?

About chassis construction, are tests being done on flexible chassis or is rigid the way to go? The reason I ask is the Rudi's new beetle chassis.
I would think this damper was between two fixed points, but seems to me there must be some movement to justify this damper?
(http://static.skynetblogs.be/media/119427/1041279009.JPG)

I would think with a suspended car rigid is important,so the suspension does the work,and i am pretty certain that is the ghia chassis,and that shock is for the wheelie bar,and worked on a cantilever,he tried it on the new beetle as well but went back to conventionally mounted bars

cheers richie

Richie. The weight does not include my 100kg in the middle and to the right (rhd). This must also be factored in ;)

I have never had a problem with the front end going light, even before the wing. I am pretty sure the paneling under the front end helps with this respect no end. Also, I run a homemade zero bump steer steering setup and a good amount of caster.

I personally believe cars that are setup with a heavy rake angle (nose down) are the most susceptible to dodgy handling when coming off the gas. It's all in the camber and toe change at the rear. Swing axle cars behave particularly badly with rake... Just about every Looker then!

I have done a lot of measurements of tracking and toe changes with suspension movements. With the results I vowed never to race a swing axle car with a stock steering setup. Are you guys aware that the toe change through the typical suspension movement on the track on the front (stock steering) can be close to 2 degrees? I have wheelie shots of well known cars where you can clearly see the wheels towing out massively at full suspension drop. This is why swing axle cars are prone to rolling over shortly after the wheelie. Massive toe out, wheels land, massive toe in and driver tries to correct the steering based on the momentary 'incorrect' reading from the steering wheel.

For this reason one of the single most important mods you can do to your cars is the zero bump steer steering ;). On my car, throughout the entire front suspension movement, there is no noticeable toe change. Night and day handling difference.

Omg... I have just realised I have opened a can of 'zero bump steer worms'...

The same here.

But I don t hear anybody about using a spool instead of a lsd in the box, I read somewhere on here that a spool does strange things on the end of the strip. Or is this internet rubbish?

Regards Edgar

A spool is fine on a well set up car,if it doesnt go straight a spool will most likely make it worse,also its not for badly prepped tracks,it needs to be consistent all the way down or one tyre can get more grip than the other and try to turn the direction of the car,they are much stronger and lighter than any diff

 ;D

with your weight in it then it would be even better front to rear.


I wouldnt be suprised if the tow change was more than 2degrees,it can be quite bad,I think a ball joint beam car suffers less from this than a king & link beam car,but dont have any data,just my own feelings when driving them,how many people use limit straps on the front suspension? it would help with this and control the weight transfer better as well.

On the old cab the front is pretty stock,steering is all factory,no fancy single arm steering mods :o :),and only 1 pair of thin caster shims,seems alright to me,it doesnt have lots of rake though.

I think the answer here is to keep the front wheels in the air as long as possible then the driver cant try to correct the steering and th problem you describe doesnt happen ;D


cheers richie

Something else to consider is wheels,how many cars use thin alluminium dished wheels? I wont use the common name as thats not actually who makes them.When you go to chevy pattern[the most common non vw] which is alot smaller than wide 5 the wheels have the ability to flex alot more,add 500+hp and a car that moves around,at what point does the wheel flex? then to look different you decide to get a pattern cut into the wheel[star cut etc] now it is really likely to flex.
There is a reason they make SFI certified wheels

When you start to add up all those little things[steering angle change,rear camber and tow change,wheel flex,chassis flex,weight bias wrong etc] its amazing anyone gets down the track at all :o   

I'm thinking away about the drawing from the v8 boys...  first of all, there seems to be something strange going on in that drawing, as the lengthwise placement of the CG doesn't have any influence on the line between the wheels. That seems really strange.
With the weight as far back as we have it the line should be much steeper...  and I suspect that the attack point also moves as speed goes up....    think about doing a wheelie on a dirt bike (or a bug with way to little weight on the front wheels) at slow speed you need a steep angle to do it... the faster you go the less angle you need to still maintain a wheelie...  :)

Therefor we should all be racing buses... maintain your stock spindles and you wont have any bump steer at all...    now that's just crazy talk right? ;)

Richie... The toe change becomes more acute with narrow beams. Drastically so, in fact...

I think your approach is the best solution; just wheelie your way down the track  :D

The other thing that really affects the steering is a narrowed beam. That exaggerates the arc that the steering arms pull in, so the compromise between fitting the wheels in the highest part of the front fender and the width of the beam must be factored in too.

EDIT: Balls, tree'd again! ;D

Damn Richie when you put it like that it sounds almost dangerous what we do  ;D

Nah,its just exciting,just like being at the fairground on a ride and seeing one of the main fixing bolts is loose,you know sooner or later its going to crash/fail but you cant help having another go :o ;)



For those of you that havent seen these 2 cars run,the benifits of clutchless shifting can be seen


1st the Black mamba rotary engined with mendeola trans bug testing clutchless shifting form 3rd to 4th gear,1st  - 2nd shift will be clutchless soon



http://www.youtube.com/watch?v=L-ka1OtWBU8

2nd Brazilian sequential shifted turbo new beetle

http://www.youtube.com/watch?v=qmksGJH-0Pc&feature=player_embedded

 http://youtu.be/qmksGJH-0Pc

It looks like the new Beetle is using the clutch.
Another benefit with clutchless shifting is that it usually knocks off 3 tenths in a quartermile  :)

having watched it again it does look like his clutch foot moves on some shifts,from the outside if the car video it looks very smooth as it changes though,I cant see my car hitting that bump and staying the right way up >:( :o

Have you figured out a way to allow yours to dissengauge the gears without the clutch?

cheers richie

[/quote]

having watched it again it does look like his clutch foot moves on some shifts,from the outside if the car video it looks very smooth as it changes though,I cant see my car hitting that bump and staying the right way up >:( :o

Have you figured out a way to allow yours to dissengauge the gears without the clutch?

cheers richie
[/quote]

It sure looks smooth and fast,especially on that bumpy track,they have had couple of nasty accidents with VWs there lately  :o

Fredde is looking at buying the Finnish gears without heat treatment and make some changes close to the G-force clutchless system  :)

I have given up on trying to make it work  and just flatshifting it with just touch on the clutchpedal
Without boost,driving it like an NA its noproblemo just move the shifter and there it is  8) and down shifting is also slick,but who cares  ;)

//Patte

In my opinion its all about the X-Weight and the shifting....

My gearbox is converted to full sequential....
If anyone is interested as well....let me know ;)

Cheers,
Basti

I had an idea yesterday about this, what if you ran softer shocks on the rear, and installed an air cylinder right next to it, like the dual shocks you see on Baja bugs.
This cylinder would contain some pounds of pressure and act as support shock. Its there during the start and starts to bleed out thru a electronically operated valve as you hit second or third gear... by fourth the car would be in its softest mode again...
Just throwing it out there...  :)

Yes I am interested,how does it work? have you driven it?

cheers richie

A funny thing I found on ground effects on formula 1 cars:
"There are legends of a BRM "ground-effects" car designed by Tony Rudd in 1969, which was never built, but I would regard the 1977 Lotus 78, indeed largely designed by Rudd and Peter Wright, to be the first ground-effects car.

For the first time, air was invited to the underside of the car in order to create higher air-speed and lower pressure through the "Bernoulli-principle", where higher dynamic pressure (Rho*v^2/2) leads to a lower static such.

Before the Lotus 77, racing car designers were largely pre-occupied with preventing air from getting under the car."

http://www.f1technical.net/forum/viewtopic.php?f=6&t=7880

Hi Richie,

the gears are changed to dogrings and the shifting mechanics are changed as well.
So you just pull on the leaver. Gearcut and gearposition for ECU Strategys can be added.

Yes i drove it in a hillclimb beetle with big Typ 4 and 5 gears.

My Mendy is in build now and I will test it next spring in my car...

Cheers,
Basti

I see Russ Fellows has come even closer to an '8' with his 9.18 - all this with a stock floor pan, stock VW IRS design and some playing around with aerodynamics. 155 mph and very stable. Russ's car is proof that if you pay attention to airflow you can make a stock body shape work at speed. I guess not lightening the front end probably helps in his case, too.

It would be absolutely awesome if he breaks the 8, especially as its a street driven car. :)

OK, got the new car weighted today, though it is still missing the body, wheelie bars and chute. We estimated how the weight of the body distributes between front and rear and came up with 57-43 weight distribution race-ready. There is only 43kg of ballast in the front now – I will most likely add more.

[attachment=1]

Anyway, it seems we all agree that any drag race beetle should have all the basic things done (for example complete alignment through suspension travel), and as one approaches the 9 and 8 sec zone aerodynamics and weight distribution of the beetle makes it a poor basis for drag racing. Since we can’t totally fix the root problems, we have to come up with a good design of the chassis/suspension/aero and address details that are not relevant to other makes and models running same et’s and speeds.

Jyrki

Have we got any video footage of beetles either crashing or getting out of control? It would be really interesting to see which end starts to get light. The lightweight front end makes you think that the front would lift and start to wave about, but the wing shape of the beetle body makes you think about the car generating lift and the back end lifting. Do we really know how a beetle crashes?

What about the weight transfer when drivers lift off after crossing finish line? The relationship between the relevant positions of centre of mass and aero centre of pressure are critical considerations for vehicle stability....

Not helped by nose-down stance either...

I know some racers/drivers use different techniques in relation to throttle/clutch/brake when running through the top end and lifting, but I guess we will never know what happened in actual crash circumstances...

For more info/theory concerning aerodynamics then there's lots of goodness, not to mention a bloody good read, at www.bloodhoundssc.com
(might take a while for people to find the right bits so enjoy dyor)

i have been cornerweighting my car today after several changes

I ended up with total 1956lbs with fuel tank fuel,driver with racesuit,helmet etc  and the best i have been able to get it is

37/63 front to rear weight bias with 50lbs lead right at the front of the car,more lead passenger side opposite my feet,and another block of lead passenger side behind the firewall which offsets the dry sump tank.
I have worked quite hard on placement and materials to try make it better,I need to find some more lead now to put up front to help some more

My conclusion is they would be much better if we didnt put a driver in the car ;)

cheers richie

What about in the middle?  :)

Nah... it hurts so dam much if you experience a sudden stop.

Did you find you find center of gravity at the same time Richie?

Here is a nice calculator to find it: http://www.longacreracing.com/articles/art.asp?ARTID=22 (http://www.longacreracing.com/articles/art.asp?ARTID=22)

just going back to the "aero" side of the subject.

I have downloaded all the logs from my car at bug jam.

car back ground -  back half car, swing axle koni double adjustable dampers and 800lb springs with 10 mm of preload. 2200lb with the fat driver and full tanks a spot on 60/40 split.


the DATA ive been looking at the most is the suspension..

test 1) no front air dam or rear 'Keno wing' anything past 135 -140 and the car is lifting at the front and rear, enough to not know which way the car wants to go

test 2) front air dam fitted. easy drive past 145 the car is lifting very slightly at the rear, the front is lower than without the Dam, car feels good 2 still want 2 hands on the wheel though.

test 3) Front air dam and 'keeno wing' fitted, front suspention is extending to the same amount as the previous runs, and the rear is slightly lower (2-3 mm) car feels fantasic, one hand on the wheel with no concern at all


what i can conclude from my personal findings are:


the front air dam is stopping too much air getting under the car, and the rear wing is just breaking up the air trailing from the roof, as the extra down force was minimal. but the spill plates on the sides are taller than usual 'keno wings' and i personaly feel that this is giving extra strait line stability to the car (bit like a rudder)

so the next outing we shall be turning up the power to push through the 150, and re visit the chassis data.



just as i side note Russ Fellows's car was going though the top end at 155mph running his front air dam and a small rear wing (most of its an oil cooler) and he felt it was rock solid. mind you he is complaining that its harder to make the first turning now ;)

Martin

Hi Jon,

no nothing like that,making a solid bar to replace the front strut might prove difficult for me as well :o

LOL 

And no doubt still using the same burnout braking technique... ;)  ;D

Good info Martin!
Thanks for sharing.

Yep, he is  ::)   lmao

would be interested to hear why this is a no no  :)

might as well put it in the front then as its not a VW as I know it after that :o 

Getting real data for a rear engine VW is rare enough,getting data for a mid engined version is non existent making it even harder

cheers richie

Great info Martin. It's nice to have hard evidence to back up the 'seat of the pants' theory. Hopefully people will take note of your experience and apply it to their projects if they intend going faster than 125 mph. That tends to be the 'magic' number when things get hairy on a Beetle.

Good luck...it seems all videos of VW crashes share the same hand-steadiness as recorded UFO sightings. You'd think it was an earthquake that causes the crash.


It pains me to say that it would be very informative for a car that datalogs suspension position/steering position to crash. How much of the problem is strictly aerodynamics versus inappropriate driver input or overreaction. FWIW, and just my opinion, the use of small-diameter steering wheels worries me. These are not long-wheel base cars that are slow to react to quick steering inputs; we drive short-wheel base cars that are going to quickly respond to quick steering inputs.

What do you consider inappropiate driver input or overreaction? It is not like we`re trying to do a slalom run. We`re just trying to go as straight, and fast, as possible and you do not need to turn the steering wheel before something tells you that it is about time to do so. Yes, a slick can give you "false" input meaning that it sometimes feels like the rear end is moving more than it actually do.   


I do not agree. The car "feels" more "nervous" with a bigger steering wheel and this can caouse inappropiate driver input. I think a old drag racer told us to go with the flow somewhere in this thread. There is cars with shorter wheelbase doing 6 second runs with a tops speed of 190 mph and you do not see them use a truck size steering wheel.

Mmmmm,thinking about this,my theory with the stock size steering wheel was more wha i was used to from the old cabrio,I ended up with a same size wheel and same amount of turns lock to lock so in theory I should have the same input to what I am feeling,the factthat the car behaves so diffferently to steering input kind of threw that idea out the window.
Maybe the next improvements will include a smaller wheel,[and put it on the other side ;) ]

as for the cars running 6s with less wheelbase,how many are clutch cars,one thing that I really noticed is my natural instinct to move the steering wheel slightly everytime I change gear,auto trans would take this away?


cheers richie

With regards to the steering wheel debate, I had a problem this year on the Sunday morning at Bug Jam.  The car was running fine all weekend, but, Sunday morning I went out first run & the back end of the car felt all over the place.  I got back to the pits convinced that i'd broken something.  I checked the car over, couldn't find anything wrong, went out again, same thing (although not quite as bad this time).  Weird.  Thought i'd give it one my try, it was on this run that I realised I was holding the wheel in a different position than I usually do (3 o'clock as opposed to usually around 12 o'clock) everytime I shifted gear i'd yank the wheel to the right.  This was obviously upsetting the car.  Next run I consciously held the wheel at about 12 o'clock, no more problem.

It's amazing what little things can do.  How many of us think about tyre pressures with one side of the car sitting in direct sunlight, especially if there's an oil down or some other delay on the track.

Inappropriate input would be steering input when no steering input is necessary, and overreaction would be more steering input than necessary in reaction to the situation.

The steering wheel simply takes movements of a lever-system (our limbs) and restrains it to circular motion. The total input to the steering is a function of the angular movement of the joints in our arm and the inverse of the diameter of the wheel. And, while a drag race is not a slalom, how many crashes are related to too much steering input? Do we simply say, "he got out of the groove" and we think no more? How do you get out of the groove? Why couldn't you get back into the groove as easily as you got out of it? The fact of the matter is VW drag racers often put cars into the wall at speeds slower than where aerodynamic issues would otherwise come into play; I'd argue that some of these crashes are linked to steering inputs, and that at much higher speeds where aerodynamics contribute to upsetting the stability of the car, steering inputs are even more important. All I'm pointing out with the steering wheel size is it's ability to amplify the movements of the driver and contribute to an overreaction. If there's not a happy medium then you can postulate to use the smallest steering wheel possible.

I read somewhere that if you wanted a circuit racing car to become more stable (when it comes to cornering) one could lengthen the wheelbase, as the stability is the result of the relationship between length and axle width. (as I read it)
Now we usually don't want to make our bugs longer than they are, but if you go with a narrower axle width you should gain the same...??  Think of those small Mazdas and starlets....  not long... but very narrow.
I just thought it was interesting...

The low speed crashes are more often than not directly related to the steering toe changes and steering input from the driver. As mentioned  earlier, a stock Vw steering setup experiences EXTREME toe in and toe out at launch and when shifting gears. And wheelies? Absolutely massive toe change. A driver often tries to correct steering in a split second based on an input from the steering wheel which is in a perpetual state of flux. That's why they often end up on their roof inexplicably and only just passed the sixty foot... Driver error based on incorrect feedback from the steering. A lose - lose situation that is easily remedied by the Pro-Stock type steering.

Sort out the steering on your racecars, then address the aerodynamic issue present above 125 mph on Sedans and then, as Martin experienced, you can drive thru the top end at 150 mph with one hand on the wheel.

Very good reading guys. Can't want to see what everyone comes up with. New times, new ideas = changes for the better I hope!

I think that's the Idea really, to make the VW world a lot safer place.

There are so many suspension dynamics and aero dynamics we are trying to understand and equate into a better, safer car.

I think a lot of people are not looking at the basics first, how many out there has actually made/used a bump steer gauge to measure the bump steer in the front ends over its suspension travel? and have you considered how much travel you might need down the track?

I also think there is no best rear suspension, just one set up correctly.  eg red baron - swing axle hitting 170mph+,  Hater maker - irs also hitting 170mph+ so i don't feel theres and argument for ether, just what your more comfortable with.

Personally I'm willing to put my finding out there for the benefit of the VW world that Ive grown up in. I don't get as many runs in as some, but i acquire more data in 1 run than most get in a year.

Speaking out loud, i feel that if a car has gone through all the BASIC suspension setups and there is no bump steer, and the Castor, camber and toe for all 4 wheels is correct and the car gets the power down in the 60' and is happy in the 1/8 (120mph+) then after all that its getting fucked up past that point you really need to be looking at the aero side of things. as them forces can be massive (who has stuck there head up past the windscreen on a bike at 150mph +? there will be a few of you ;))


As ever guys, we just want fast / Safe VW's out there.


Martin

This is great info for me building my car so thanks for that, what would be the good attributes of a front air dam

Cheers andy

You want to try and stop as much air from getting under the car as posible, but if your racing MSA then take a look at the rule book as there is a limit to how low you can be, i think (looking towards Jim Smith) its 3"

Martin

I think Tor Oyvinds achievements this weekend, 8,02 and 281km/h is a good reason to bring this topic up again!

The new wing seams to work well, and I am pretty sure it is because of it`s high position, actually working where the air leaves the roof breaking the wing effect.
Also worth noticing is that this car does not have a raised tranny and much closer to stock ride height that any other beetle racing in the eights.

(http://www.raceinfo.no/temp/tn_DSC01638_1.JPG)

http://www.youtube.com/watch?v=SVKvNhbfbi4&feature=player_embedded

I talked to Skinne about the new wing at Kjula and he told me that they noticed that the car started to lift the rear after mounting the front splitter. That was the reason for mounting the new wing, to increase the down force. Also worth noticing is that the driver did not pull the brake chute after crossing the finish line.

-BB-

I'm having a good time reading Herb Adams Chassis Design book in the evenings. It has a good section on IRS rear ends, and according to that, on a IRS car the laderbar/fourlink would handle only 25% of the force that an normal live axle would see.
But on a 1000hp car that is still 250hp! The book is a great read on many other topics as well, even if most of the information is about circuit racing. 
 

Which book is that again?  ;D

Kalle, the pic you took of Skinne's rear end is probably somewhat exaggerated by the wide angle lens and close-up standpoint?

Nope Walter, no such fancy thing. I´m standing 2 meters from the car with a simple Sony camera.

Here is the builder and the tuner standing next to the car in the staging lanes:

(http://www.raceinfo.no/temp/tn_DSC01672.JPG)

Behind them is the Volvo that won the 4to6 class with a 7.62 run on a 7.60 break out. Basically a HUGE Holset HX80 with a Volvo wrapped around it.

And the front splitter:

(http://www.raceinfo.no/temp/tn_DSC01675.JPG)

Best rgs
BB

Tnx mate, excellent pics and your right, that is a HUGE wing from all standpoints! :o

Looking at that picture to me it seems that the width of the wing proberly helps as much,if not more than the height as there is so much of it out in relatively clean air,particularly the spill plates being right out there.

Raised trans is only really a swingaxle thing anyway,IRS doesnt need it in the same way,when you lower the swingaxle springplates the wheels go into horrible negative camber,raising the trans helps cure this..
Now there center of gravity must be alot higher than most quick cars I agree,my old cab doesnt have a raised trans or torsion raise etc so will suffer similarly,its nearly time to drag it back out again,as someone wrote to me and told me after the success of this car this weekend


"put too much power to a factory IRS car and see what happens"   sounds like a good plan to me ;D

wow that front spliter is low.....

I think the wing and splitter on skinnes car sure helps it to "keep" it on the ground for his new record, but what amasses me is, this is a heavy almost all steel car... So is it not that this weight is helping it to keep it on the ground.....
Now days there is a lot more powerfull engines, and we keep trying to save a lot of weight, for better power to weight ratio,
maybe to much weight?

just a thought.

After a long summer of no racing i have decided to make some changes to the Fasty making it steadier at speed(i hope)  :)

This thread has brought out some really good input from experienced drivers and after  seeing what Skinne has done to
make the beetle not to be all over the track, i think i will do a little bit of everything to make it fun to drive at 150+mph again  ;D

I have increased the caster angle to 10 degrees.
Changed the steeringwheel from a 12" to a 14".
Making a frontspoiler/splitter.
Mounting an adjustable  roofwing in combination with my rearwing or a 2plane wing on the engine lid.
Make a serious attempt to make the clutchless shifting work.
Move the lever for the chute so i don't have to take my eyes off the track to  see it  ???
Take care of the small bumpsteer i have.
Move the turbo and IC forward.
Add some bars at the rear

I have probably forgotten a few things  ::)

Will be good to see you racing agian Patte!

Stian "Tekken" had some good arguments for having all the wheels (especially the rear) at zero degree to-in. If he is on this tread he might explain, I`m not so good at referring this in english. Anyway, it might be worth looking into also.

Good luck with the changes :)

I could understand the reasoning behind that. But...static alignment means 'nothing' as opposed to what happens when the car 'digs in' on the launch and on acceleration.
Seeing what happens to toe when the suspension moves up and down could be whats most interesting.
Maybe making the suspension keeping its set toe angle at the full suspension arc is what matters?

What matters as I understand is to have zero to-in at high speed. Reason for this is the high traction the slicks have, and to-in makes them sideways unstable. Hard to explain, sorry my vocabulary is to bad.....Richie, help?!? :)

You're on your own now Berger ;D Richie is all alone in bitburg right now ;D ;D ;D
Thanks for that info, really thought that toe-in was the way to go. Putting it on zero now.


Michael

I run zero at the rear and 1 degree toe in at the front.

Thanks  :)

I run zero toe-in at the rear and 1mm in the front.
With the IRS ladderbar design i use there is no changes in the toe-in when it moves up and down,but under load i have no idea what happens  ???  ::)
It probably is a lot of toe-in at takeoff

I run zero toe at front and zero rear. Car always went nice and straight.

One thing you guys really need to do stop drastic rear toe change is to tie the torsion bar housing into the roll cage in at least three axis ;)
If you ever get a chance to see a floorpan separated from a body, push the torsion housing with your foot. See how it flexes badly. Now imagine the only thing holding it is a piece of 18 guage steel where it attaches to the body them picture what 200+ horsepower is going to do in terms of flex... All that flex = toe change and a car that 'rear steers'.   :o

Sorting the front end so that it zero toe changes over full up and down movement is much more simple. Do away with the twin steering arm setup from the steering box and run a single rose jointed tube from the steering box to the farthest spindle then link the two spindles with a rose jointed tube. This is a popular mod in the US, though strangely not here in Europe. I will say it one more time then I'll shut up for good as I'm probably boring the piss out of you guys... Do this mod, you will never look back ;)

good point well made.  :)

I trust everyone that zero toe-in is good (or best).
In the '65 street car I had very little (maybe 1mm) toe-in in rear, and 2-3mm toe-in in front. Torsion bar housing was tied to roll-cage, then later moved on to ladder bars. With the ladder bars it went straight, was very easy to drive and felt safe at 230+km/h.
Jyrki

Good point Matt! I never thought about it that way.
Would running torsion bars be any different then running coil-overs with IRS in ^^ that respect?

I would think it would mark no difference weather you run run torsion bars or not the force on launch will be the same on the torsion tube
IRS may spread the load though down the tunnel
Cheers andy

Like Andy says, if you put load onto the torsion tube - whether it be thru torsion bars or IRS points - it will still flex unless supported.

I am glad that Skinne's car has awakened people's interest in aerodynamics, I was beginning to think I was flogging a dead horse on here with my own personal experience. Play it safe folks, a standard VW sedan will start to take off at speeds around and above 125 mph. this is serious stuff, not to be taken lightly. Martin Taylor's data should also be studied and accepted as hard evidence as to what happens to a Bug's rear end at speed without a wing and then with a wing. Read his post several pages back. Very
Educational.

It's a shame that Richie's cab doesn't fall into the same aerodynamic category as the rest of our cars, as data and results from aerodynamic aids on his car would be interesting juxtaposed against a Sedan's. However, the two shapes are poles apart so comparing a cabrio with a Sedan is like comparing apples and oranges. Still would be interesting to hear Richie's aerodynamic results from any mods. Rich, you have any info you can share?

Cheers, Matt

Matt, richie has a bloody big wing on his car already, he pretends its his hood ;)

Getting rid of bump steer is a matter of playing around with the placement of the inner rose joint. If you do, you get rid of it the same way for both sides.
The lengths of the steering rods does NOT affect bump steer on a trailing arm front suspension, so don't change them, and DO NOT fit a single rod from one spindle to the other!

The reason I say this because I'm seriously worried for the safety of the drivers of cars with the JCL conversion, as it WILL reproduce the bump steer (however minor) from one spindle to the other, thereby making the making the car steer.
I think all will agree that having toe in or out during suspension travel is minor problem compared with a car that actually turns the wheels the same way while you are racing. But when only one wheel is going thru a bump that's when the single bare is really going to bite you, since it then will produce the bump steer (you do not have independent suspension anymore). The reduction of bump steer you may or may not get with JCL set up comes from playing with placement of the rose joints... and NOT the length of the bars.

Stay safe.

Jhu... Do you have any experience with the steering mod or are you speculating? If it's speculation, please can you elaborate on your theory and explain why I have had amazing experience with it both on the track and on many air ride systems I have done for the street?

If you have actual experience with the steering mod, please can you give us your findings and explain how the car failed you and in what respect?

Having done thousands of street miles and 100's of track passes myself, I find it very hard to believe you dismiss this mod as dangerous. We even towed an Eriba Puck from Cornwall to European Bugin slammed on air with the steering mod. It handled perfectly the entire journey, including over cobbled streets whilst towing. I am very interested to hear your own personal experiences, as I am pretty sure you must have got something wrong on your install... Done correctly, the mod is awesome. I fail to see how you call it dangerous  ???

Yours very interested and intrigued, Matt

Jhu... I totally disagree with the above statement. The length of the steering rod totally affects bump steer and is simple physics.  The shorter the steering rod from the steering box to the spindle, the more acute the angle of steering rod. The greater the angle, the greater the multiplication of movement at the spindle when the car hits a bump. This is why cars with narrowed beams are so much more susceptible to bump steer: because the steering rods are narrowed and their respective angles become acute!  

Another point I need to clarify is your understanding of the single tube running from spindle to spindle. When working on your theory, do you take into account the movement afforded by the rose joints at either end? These allow a great deal of independent travel side for side before locking out. On my race car I can jack one spindle four inches in the air before any kind of lift at the other side, so the suspension is still independent to a massive degree.

I would never personally recommend any mod that I thought would in any way to be dangerous. Nor would I ever champion anything I haven't personally tried and tested for years myself. My background in engineering started at college aged 16 years old and I have been working in the historic race car industry for over 25 years, so I have a good deal of experience. Sure, there are plenty of ways to mess such an install up; it's all down to correct conception, design and execution. Do it right and it's an awesome mod.

The proof in the pudding is in the tasting ;)

This is how Remmelemotorsport support the torsionbars.
http://remmelemotorsport.com/bodengruppe.html

It's not speculation, what I'm saying is just facts.

Once you understand the geometry of the trailing arm front suspension you will see that there is only one given design that will cancel bump steer.
It's only really simple math's, I have showed "my" formula/method/findings to multiple engineers and they all say it would take a good engineer about 10 minutes to figure it out. Yet no one does??
The solution is just too simple I guess.

Nothing has changed in the 12 years since I figured this out, it's the same stuff I showed you on the airport. Since that time I have made a model of this and shown it to big names in our industry to get a bolt on kit into production. They all tell me, that they have newer seen it solved before, but I know that the boys in Wolfsburg knew, and some of their cars came of the line without bump steer ;). But common practice with these cars reinstate bump steer in a BIG way.
With the model in hand it's really easy to see that it works, and how fragile/exact the placement of the components must be to work. 1 mm off in either X or Y axis and you have bump steer (this is also why it's close to impossible to get it right with just testing.

I have shown this model to some of the contributors to this thread as well, and the reason I did that is that I feel that I have to show them, so they can remove one of the hidden dangers of our cars.

The trailing arm front suspension may be significantly flawed in the way it deals with corners, but its the only front suspension on the marked that will allow you to cancel any and all bump steer. That makes it IDEAL for dragracing, and with this in mind fitting STRANGE components is downgrading the bug as a dragracer.


And finally Matt, I'm not saying that your stuff isn't reducing bump steer, what I'm letting you know Is that the reason you get better results has very little to do with the lengths of the steering arms, and nothing to do with the parallel bar.

Best regards
Jon Hroar Ulstad
+4792495271

Because the gearbox and engine hang off the suspension the back of the car is a cantilever.  Any bracing will only reduce downward flex not prevent it.

The heavier the gearbox and engine the more this becomes a problem.  The only solution is to stop it been a cantilever and provide support at the very back of the car.  Ideally from underneath!

Jon I respect what you say and I recall our conversation at the airport fondly. But a fact becomes a fact only when it is proven. Until then it is speculation. If your mod is so amazing why have you not seen it through to some kind of development, even if just on your own car? 10 years plus is quite some time to have at least one modded car, surely? If you have the answer to the problem then it's a sure-fire seller as a product.

I am not trying to dismiss any mod you may have devised, in fact I actively encourage a simple solution to a well known problem. My issue is perhaps that you say the mod I have done is dangerous and you actively discourage others from doing so based on your own theory. I wish I could let you drive some of the cars I have built with this mod. Ten year's of nothing but positive feedback from proven experience, to me goes a long way to becoming fact.

The simple physics of the steering rod length can be proven by this simple test: take a 12" rule and place on a piece of paper. Draw a line beneath the rule along its entire length. Now pivot the rule from one end to raise the rule two inches at the other end.  Draw vertical line down from the raised end of the rule so that the vertical line touches the line that you drew originally beneath the rule.  Measure the distance from where the vertical line touches the horzontal line to the end of original line and note measurement.

Now do the exact same test, with a six inch rule and compare the two noted measurements! Quite a difference and still with only two inches of movement. Now this 'measurement' is the direct effect on movement of the spindle and turning of the wheel. So you can see that by narrowing the steering rod by half, you increase the turning movent of the wheel drastically for the same amount of wheel travel.

Converesly, lengthen the steering rod and the effect it has on turning the wheel during suspension movement is reduced. Hence running just one long steering rod from the steering box and doing away with the troublesome short steering arm. It really is that simple folks...simple math and physics that can be proven with a rule and paper. Try it yourself and the cause of the problem is immediately obvious and hence the solution is staring you in the face ;)

Both you and I have engineering background, so I know you will get this; when you project to build a draw bridge, are the plans speculations until the bridge is built?  Surely not?
What I did was good old fashioned engineering work.
 
Quite frankly I don't understand this question??   My personal life has nothing to do with me figuring out how to do something? I know lots of stuff that I don't go out and build. THAT being said, I fitted a Porsche rack n' pinion some months after I figured this out... But I have not driven my bus since. The years up to 2008 I spent trying to teach away my findings, I would say without ANY luck! I have discussed this in many forums and made drawings and flash animations. But the solution is TO simple, no one takes my word for it.... It kind of a leap of faith... "it must be harder" you can see it in their faces :)
 
All I have is the answer, someone else must take care of the development, because you want it bolt on, and it CAN be. Many people have signed nondisclosure contracts and seen it, but no one starts doing the work. There are many reasons for this probably, but the biggest point, I think, is that most of the Volkswagen owners don't even know what bump steer is. So will it sell?
 
 

This is something I have given a lot of thought! And I have kept my tongue many times you have mentioned the JCL solution in the past.
But I don't think I would sleep to well if one of these 9 8 or 7 second cars got built with that solution AFTER this thread, what if a car crashed? This thread is very much about keeping these guys alive. So no stone should be left unturned IMHO.
But like I say, I'm not saying your stuff is not working (except the parallel bar) , you get it better every time your adjustments makes the total geometry come closer to "my" layout. Again, I have only rediscovered what Volkswagen knew/did, but omitted from our favorite car.
 

I can see that this is seems seriously over the top, but "my" theory is along the lines of a statement that says "the center of a perfect circle is in the middle",  and you are saying that you have found a "second center in the circle". Unless your new center is on top of the old center, with incredible luck, it's just wrong.  I take no risk in saying this.
 
 

You are absolutely right, this is a great way to reduce bump steer, but it's has no part in getting rid of it... at all.  In fact this line of thought is what has concealed the right approach since the 1930's.
 
So, short getting it right, I too suggest as long steering arms as you can fit. Just don't mount the parallel bar.
 
Best regards,
Jon Hroar
004792495271

these pictures may be of some interest if you havent seen how thin a gauge the frame horns are and also the torsion tube

(http://i71.photobucket.com/albums/i149/gluemixer/3CD19C76-C30B-452C-9EB5-7A7185F2B4FF-8216-00000266980A61BC_zps1728f1e1.jpg)

(http://i71.photobucket.com/albums/i149/gluemixer/E0E97677-D078-4AA8-BCA0-5DE80FA7A717-8216-00000266A3E7176B_zpsd0192720.jpg)

cheers andy

This last page debate between JHU and All Torque caused some questions on my nervous mind if I'm doing now some hazardous set-up with this R&P steering system to my beetle... Any comments or experiences, please!

(https://lh6.googleusercontent.com/-3AxXFBRlrPY/T-nPGl2A-1I/AAAAAAAAOPI/VqDn0ymSqWM/s640/kuplan+hammastankosarja.jpg)

That looks fine to me at least.

Good to see some debate going on here without anyone throwing their rattle out of the pram!

Interesting topic and given I do have the straight rod linking the trailing arms it is one I have a particular interest in.

Like Matt I have been impressed with the way the car drives since converted relative to the way it drove before. That said I appreciate it does not resolve the bump steer in its self but as Matt has explained it certainly reduces its effect. When I first did the modification I found that as Jon suggests the tie rod location at both ends (pitman arm and trailing arm) was critical. That said I only adjusted them in the z plane (up and down). I've stuck with the standard x y locations at each end.

when I set it up I plotted the change in toe in / out with a laser mounted on the hub pointing to a wall about 1.5m away. At first it was all over the place but with some adjustment I got to a point where there was no noticed change in toe it just followed the vertical line I'd drawn on the wall. I did all this with the long arm but didn't even try the short arm as I was not planning on using it. But at this point I was thinking great no bump steer. So I just joined the two trailing arms together and off I went.

Jon are you suggesting if I had tried the short arm I could get the same result?

The planes of movement at work at the same time are quite complex in my mind but I'm no engineer.

Peter

If you look at the shape of the stock pitman (sixties linkpin) arm you see that the pivot points are not placed the same distance from the axis of the steering box. This is a problem, if you get them the same distance from the axis the rods will work more or less the same.
Why more or less?, because if you don't have it quite right you have some bump steer, a long rod will then help you (like Matt said). The short one will not help you as much. So they will not work quite the same.
But when you get the placement of all the components RIGHT, you don't have any designed bump steer, so you don't need help from the lengths, and therefor you can run them as sort as you like. Or like stock.

To me, the big gain is that the wheels operate separately, I feel that is a safety point. 

PS. I'm also no engineer, I only took the first two years, and moved on to areas where my creative brain has better use.     ;D

I am curious about this set up. It looks good!
Is it a kit, or is it someting you have put together yourself.

i feel as if i must chip in to this great thread again,

I can only comment on my own personal finding and as ive said before I'm willing to share with my fellow VW friends.

My car suffered from Bump steer a long time ago, you could 'feel' that steering was going to extremes and the short arm of the system was pulling in the wheel, effectively making the wheels toe out.

after a trip to JCL with a buddy, Jimmy showed us his way of steering. Link the two stub axles to each other to control toe through the entire movement of the suspension, then link one stub axle to the steering box (the long arm) keeping the long arm parallel to the linking arm at ride hight.

We took this information away with us and made it work on our cars, the transformation was amazing, you could twitching from the wheelie disappeared and the whole feel was so much better than before.

now i know, if one side of the suspension is fully compressed and the other is fully decompressed then the toe will alter by a small amount, but lets be honest if the front suspension is like this on a 9 second run, something else has gone very wrong and your going in the wall!

after driving the car on the road and getting a little err sideways a few times, the steering feels so natural, i have no fear of not knowing where the car is going. the feedback is on a par with my 911, may be a little better....


JHU, has shown me his idea, and yes i have signed his papers to keep it to myself, when i do finally get time to tinker i'll build it up and put it through its paces. but until then the system I'm running at the moment gives me great confidence and feel and have no reservations about taking the car past 150mph (its been to 149 already).


The creative pool we have going is working great, just look through the speculation and look at the facts.


arnt vw guys great ;)


Martin

Shure would be nice to see some pics or scetches of these ideas guys. I'm not totally following you. I am at the point on my car where I'm ready to do the steering and am very curios as to your findings.

My buddie did the single bar that JCL recommended. He didn't like it or wasn't set up right and ended up putting it back to conventional.

Thanks Jon,

Before really thinking about it I always assumed the offset of the inner tie rod points on the pitman arm was a very intentional design feature to do with steering geometry not a potential design hindrance.

I can see that it would be possible to site the pitman arm inner tie rod point at the centre of what would in effect be the base circle described by the arc of the outer tie rod point, sort of like a cone on its side, the tip of which being the pitman arm tie rod and the base being the outer tie rod as it travels through it arc. Is this is the point you are making?

Unfortunately I don’t have the car at home to just go and have a look at the moment, and I’m much better at looking at things to understand how they work than mathematics, but if you were able, would it be possible to swinging the torsion arms and stub axel and outer tie rod 360 degrees to describe a true circle or is there some kind of cam effect going on, I’m sure you can see where I’m going with this if there is.

The other potential issue is the relationship between the inner and outer tie rod as the pitman arm and outer tie rods move to turn the car. Needless to say if the tip of the cone and the base circle move at different rates this would I assume cause bump steer again (not that the straight link rod does anything to help this) as the inner point moves away from the centre of the base circle.

I understand the point of independence of each steering arm as this must be preferable, but in practice and for what ever reason like Matt and Martin have said I have not had a problem. There are some older production cars with the straight rod steering arrangement, so I’m not sure its such a fundamental problem, but I don’t suppose any of these exist on modern cars given they all use racks rather than boxes now.

Interested to know what you think, but whish I could just go and have a look at the car in the garage (with a cup of tea of course, the drink that powers the nation).

Peter

Ps  Freakpower, if what I’ve said above is correct the rack looks good in principal but be careful where you site the inner pivot points!

You are on the right track Peter, you understand it so much better when you figure it out yourself... now you see how fragile this system is, and how ingenious VW has constructed the front suspension (seen from this standpoint(and this standpoint alone)).

Regarding the pit man arm thing, the split bus doesn't have this "feature", I suspected it could have something to do with ackerman, but I have found nothing in my books supporting this theory.

When thinking about this it always helps me to remember that the tubes in the beam are parallel.

The straight rod arrangement is used exclusively (from what I have seen) on solid beam suspensions. This means the spindles keep their relationship to each other during suspension travel, and therefor will not suffer from the solid rod.

As I was away racing when the last couple of pages were posted I thought i would take some time today and have a read back through it all,somethings stuck out to me, and as I was asked/mentioned in my absense heres some thoughts I have from this year,first this still bugs me




Really? you seem to be suggesting this is an improvement,then wrote this below





Again,really?   :o

 I am not dissing the wing or any other mod i haven't tried, but from your 2 quotes it does seem like there was something else going on with your car,if it was that dangerous how could you recomend the steering mod you used,is it only safe when used in conjunction with a wing? plenty of cars without out it go straight at 130+
I am not attacking you at all Matt, but you are in a position as the technical wiz on Volksworld magazine that people will look up to you and trust 100% everything you write or say, to me this means you have to be 110% certain that something works before saying so,

and you seemed upset that people werent taking any notice of supposed data posted up by someone else that backed up your claims, anyone can post claiming something they learnt, hell i think everyone should cut the roof off there cars to make them safer ;D  but without actually seeing data why would anyone believe it? and in the real world data is taken from 100s of passes, not 2 passes in 3 years, no one cares what a 18 second car does,its not relavent to this topic

As for my own findings this year,well I didnt get enough track time to try the aero mods I have for my car,I want to get another 20-30 passes with the car as it is,assess that data, see if there are any patterns then make the changes to see what happens and go from there, I can say i finally have a decent handling car and it is still far from perfect,time and parts availability meant I had to just make do with some things this year, I will make a couple of minor changes ready for next year and go from there, I have said this before but will say it again,I am NOT trying to build an 8 second car, that has been done lots of times now, I am trying to build a quicker than that car ;) so the developement might not be as quick as some expect, it is a huge learning curve for sure and apparently I don't know anything ::) which slows it down even more.     

.

I have looked at Jons ideas,i see some positives there and if it gets to a stage that there is a "kit" available I would like to test it on my old cabrio for sure as if we can make that car go straight run after run :o,that should be enough proof for anyone ;D

I am nearly at zero tow at the rear now,and 1 degree at the front to add that to the other info posted.


Finally for now,Stretch very true, but how often do you get you tyre pressure gauge checked or calibrated?   ;)


cheers richie

Richie...

As I developed the car over the years I learnt a lot of info. The steering mod worked fantastically and cured the front end. When I started to get to speeds of 125 mph + the aerodynamics of the rear end began to take over - nothing to do with the steering - and started to make the rear end 'shimmy' as in feel really loose and wobble. The faster it went, the more prominent the problem. The wing totally cured this and made 145 mph a 'one hand on the wheel and no chute deal' as opposed to a 'grip your butt cheeks, pull the chute and hope for the best.'

I like to isolate problems and address them as separate issues, and I only ever change one thing at a time and test it. Again, as I have stated many times, all my posts are based on personal experience. Perhaps the rear end on All Torque is slightly more sensitive as it has a lot of weight there, being a WBX.

Now thats a cool thread here! (no updates?)

Ive been thinking a lot about those problems.

First thing to get the car more stable is lengthening the wheelbase for sure.
Almost unpossible with a beetle, but i will add about 50mm to notchback.

So far i never had any problems. My really heavy car always went straight like a arrow.

Even at 250km/h (not on the 1/4 mile, but on the german autobahn)

Is it the weight (1140kg incl. driver) or the better aerodynamics of a type 3 keeping a stable ride??

Next best thing, narrow the rear axle track width. Not impossible to do, and has the exact same effect.
Check this out, a narrow To#¤ta Starlet with a narrow real axle, and rims that pushes the physical center of the slick even further in.
It looks quite undramatic for a 7.621 ET and the 7.555 looks even better... remember this is a super short car.

http://www.youtube.com/watch?v=PFAQbLDoJgE

Holy mother. That last pass was more dramatic than I would've liked had I been driving! LOL

Short Wheel Base cars are FUN

(http://i586.photobucket.com/albums/ss306/Fiatdude/FiatDragDay.jpg) (http://s586.photobucket.com/user/Fiatdude/media/FiatDragDay.jpg.html)

Even with the Abarth front steering mods to the Fiat you can see the toe out has increased during this wheelie -- but I never had any issues with it when I was going around corners or down the strip -- -- but this car had the A-arm geometry vs the beam geometry that is on VW

But maybe you can see that the seat has disappeared a little -- I has the stock seats in the stock floor rails at this point and they had just ripped away from the floor pan on this launch .. took me a couple of days to get all the upholstry out from between my cheeks -- lol

I thought I would drag this back given the ET barriers that been broken this year. With the Hater maker going 7.70@186 at vegas last month with ease realistically can we now look to mid 7s being possible? and more & more cars running 8s and no crashes what has been discovered to make this possible?

cheers Richie

Out of the box thinking and making it happen

i think it was just a big tailwind  :D

This, ^^^^^ the best front end to get right, if you can't get a beam and 'box set up right, a rack and strut system will kill you,I've seen so many wrong moves from folk that should know better,  zero bump comes right out the factory door,  but understand how to set it up for zero bump, it's all down to the steering gear installed angle, it a delightful system with independent caster adjustments completely removed from geometry changes, rack and strut cars need re bump steering after castor adjustment, I regularly spank double wishbone equipped sports cars with my B/J car, they don't bother me, but I seem to worry them ;D