wheelies

[Jesse Wens]

I have a theory also.
This picture shows a neutral suspension.
the forces are on the springplate. The wheel finds traction and pushes the springplate. The springplate in turn pushes the car, which also pushes back with the same force on the springplate.
In this case the spring plate is balanced out
 
In the picture below the car is in a raised position which means the springplate is inclined.
Again the tire pushes the springplate en because the springplate pushes the car the car pushes back.
The difference is this time the forces are spaced by a distance over there line of work.
This distance creates a turning force of X Newton Meters on the springplate.
It wants to turn around. The tire can compress a bit and the rest of the turning force goes into lifting up the rear of the car. Because the car has inertia it will give more force on the tire aswell and give more traction

If you set up you're car the other way around, lower it untill the suspension in the other way around the car will want to squat even harder than it always wants to do because of the diff like stated above by spanners.

If you think what happens to the forces when you actualy engage in a wheelie it will increase the traction even more by turning the springplates even more oposed toi the direction of force.

That is the main reason you dont want to squat to much, you need to keep above the neutral point

[Typ3racing]

Thats cool!

Physics of Wheeliying:  

At first you need the torque to lift the front:

As common a beetle got 2400mm Wheelbase.

Maybe for example 300kg in the front. (approx. 3000N)

So you need 7200Nm to lift it. Lots of torque  

If you calculate with a very common trans ratio of 3,78 first and 3,875 final drive the trans ratio will be 14,65.

so divide 7200Nm by 14,65.

That means you need 491Nm at the clutch to lift this . Without slipping tires or clutch.

Static.

In real life dynamics are different, e.g. weight transfer, as ratios and weights are.

But this is a good example, that its not that easy.

[richie]

Thats cool!

Physics of Wheeliying:  

At first you need the torque to lift the front:

As common  ab beetle got 2400mm Wheelbase.

Maybe for example 300kg in the front. (approx. 3000N)

So you need 7200Nm to lift it. Lots of torque  

If you calculate with a very common trans ratio of 3,78 first and 3,875 final drive the trans ratio will be 14,65.

so divide 7200Nm by 14,65.

Thar means you need 491Nm at the clutch to lift this . Without slipping tires or clutch.

Static.

In real life dynamics are different, e.g. weight transfer, as ratios and weights are.

But this is a good example, that its not that easy.

Don't you need to factor in tyre diameter as well?


cheers Richie

[richie]

I have a theory also.
This picture shows a neutral suspension.
the forces are on the springplate. The wheel finds traction and pushes the springplate. The springplate in turn pushes the car, which also pushes back with the same force on the springplate.
In this case the spring plate is balanced out
 
In the picture below the car is in a raised position which means the springplate is inclined.
Again the tire pushes the springplate en because the springplate pushes the car the car pushes back.
The difference is this time the forces are spaced by a distance over there line of work.
This distance creates a turning force of X Newton Meters on the springplate.
It wants to turn around. The tire can compress a bit and the rest of the turning force goes into lifting up the rear of the car. Because the car has inertia it will give more force on the tire aswell and give more traction

If you set up you're car the other way around, lower it untill the suspension in the other way around the car will want to squat even harder than it always wants to do because of the diff like stated above by spanners.

If you think what happens to the forces when you actualy engage in a wheelie it will increase the traction even more by turning the springplates even more oposed toi the direction of force.

That is the main reason you dont want to squat to much, you need to keep above the neutral point

Jesse, that's a good diagram to show the basis of what happens, the other variable is the clutch and how hard it hits

cheers Richie

[Andy Sykes]

There also another part the length of the control arm and the height it is positioned this has a massive difference on traction/wheelie and getting it right off the line ( pls note I'm not talking from experience just what I've learnt from others lol) I find this subject very intersting as it's what will make a car work off the line.

 There are some very interesting on line calculators that model 4 link on a live axle it's interesting how the centre of the car changes just from changing the height of the control arms.  It's. A shame our cars don't work the same but it's interesting non the less.

http://www.motorsportsvillage.com/suspension1.html

Cheers Andy.

[Typ3racing]

Don't you need to factor in tyre diameter as well?

I dont think so.

The lever (Wheelbase) remains the same. Simple Maths

[spanners]

the mechanics of the geometry shown above are sound, and a good case for me to raise the torsion housing lol, exactly as Porsche had to do with the 911, their trailing arms always angle down even on very low race cars, the technique of the launch on a race track , tho much different to a prepared drag strip, is the most important aspect, i line up against cars that should be crap off the lights and invariably get a shock as to how well they launch, any layout has a 'sweet spot' look at front wheel drive now days,  F1 cars with all their trickery can still make a balls of it,  but mine has reached the point power wise, where it needs electronics, , if i get it 500 rpm wrong it smokes the tyres, the same with the shift too second, i cant be clumsy with it. on the other hand, the very best swing axle drivers in the BBT cup cars use rear end squat to advantage, keeping the throttle nailed and there fore hunkered down at the back and into negative camber is the way to go quick round a circuit, true also with IRS cars but thats a lot 'tamer' in 'lift off' situations.

[modnrod]

It's all about squat and anti-squat.
I've had full size sedan leaf-spring cars that only run flat 13s, but 60ft in the mid 1.5s.
The Ramchargers had it sussed really well in the early 60's. A Google on old-school slapper bar tech stuff will tell you more if you're interested.

And yes, following that old-school tech and experience, RAISING the rear of a Beetle (or at least the torsion assembly), using softer bars, and "drooping" the axle plates more in the set-up will probably be a bit quicker, definitely using limited traction tyres, you're using the weight of the car to leverage the tyres into the track on launch. Too soft and the top end might get a bit interesting though. It's all about instant centres and CofG's that someone with better drawing skills than I can share.

Since my Beetle is only going to run 16s and that's it, I'll let you guys try it all out though! 
It's a science experiment!

[Jon]

There are some very interesting on line calculators that model 4 link on a live axle it's interesting how the centre of the car changes just from changing the height of the control arms.  It's. A shame our cars don't work the same but it's interesting non the less.

Our cars DO behave the same way as a live axle, but with a difference.
Where a live axle can convert torque in to heaps and bounds of anti-squat, an IRS will only give you 25% of that anti-squat to play with.
Regardless if it's a swing or IRS, the chassis suck up a lot of the force, producing wheelies or whatever. The remaining 25% can be dealt with along the lines of a four link car, if you wish.

The normal Doorslammer book, comes just short to explain this, but Herb Adams Chassis engineering book has a pretty good section on the IRS and its workings.
Here is a link to the specific pages, if it works:
http://books.google.no/books?id=rY2ujnNrhf0C&pg=PA73&lpg=PA73&dq=Herb+adams+corvette++IRS&source=bl&ots=HfQuj8uU4x&sig=j8OuT_RUFRSOihZ7ZoXrM-l3z4Q&hl=no&sa=X&ei=IKZKUqrCCKXe4QSljYDIBw&ved=0CC8Q6AEwAA#v=onepage&q=Herb%20adams%20corvette%20%20IRS&f=false

[spanners]

all this drag racing stuff aint wasted on me you know.... as for slapper bars, theres one near the 'shop.... love it.

[Fiatdude]

Guys -- and this is just from my experience -- There is NOT that much force transmitted to the car through the swing/control arm -- What do you hear breaking first as the power goes up --

first it is the trans mounts, got to go to solid mounts and add a mid-mount,
second it is the axles,
third, it then the Ring and pinon and gears

When the Fiat was built, angle of and placement of the trans was the number one issue, and that car really hooked, with street tires no less.  And it wasn't until I got the turbo engine really humming (200+ HP), did I bend the stock fiat 600 swing arms that were designed for 21 HP

[Andy Sykes]

Guys -- and this is just from my experience -- There is NOT that much force transmitted to the car through the swing/control arm -- What do you hear breaking first as the power goes up --

first it is the trans mounts, got to go to solid mounts and add a mid-mount,
second it is the axles,
third, it then the Ring and pinon and gears

When the Fiat was built, angle of and placement of the trans was the number one issue, and that car really hooked, with street tires no less.  And it wasn't until I got the turbo engine really humming (200+ HP), did I bend the stock fiat 600 swing arms that were designed for 21 HP

this is my understanding to of how it works not like a live axle

cheers andy

[Jon]

According to the theory you only have 25% of the forces to play with, so it's vastly more important what you do with it, as I see it personally.
The 25/75 split ties nicely inn with all the last posts... 75% is sucked up by the gearbox. No wonder it takes a beating.

[modnrod]

When the Fiat was built, angle of and placement of the trans was the number one issue, and that car really hooked, with street tires no less. 

I'm listening........intently!

How were you able to position the gearbox different to the usual Beetle setup to take advantage of the extra forces at play without breakage?
Slightly nose down? Angled so that on launch the box went parallel with the road surface? Just enough droop on the axles so that on launch they were dead-level with the road (and so CVs were also level, no angular power transmission)?

If it's a secret, I used to have a clearance. 

[Fiatdude]

Think of the installation as using long ladder bars -- we just made sure that the torque was able to be transfered to the front of the car easily and we mounted the trans 1/2" to the left to keep the front wheels lifting at the same time rather than jerking the front left up first (the CG was set up 4" left of center with my big arse in the car, remember this was in my light weight Fiat) -- the IRS suspension was setup so it was flat and centered when the car was launched

[nicolas]

because i have simply a lack of experience i can't comment much anymore. but i sure am learing some intresting things here.

[Prowagen]

Wheelies are always slow.

[FUgly]

I had the same Car/Engine combo with a "stock" 4.12 Transmission and it would not Pull a wheelie.(180-200Hp) on Street Tires.
Had Gary Berg built a transmission with a 3.88 R&P and a 4.11 1st Gear, Added 6" M&H Slicks. Now I cant keep the thing on the Ground, Even with a Friend driving and the 2 Step turned All the way down
but then I/We race for the Fans and Love Big Wheelies 

Aloha's !
EBT Racing

[dannyboy]

i wound up the coilovers from the position they have been for the last few years and got my first big arsed wheelie 
60ft was shit though 

[Neil Davies]

Is that because you broke the beams with the back tyres though Danny?

My car used to squat the back and skim the front tyres on the ground but just the once it picked them up about 18" - never did it before or afterwards.

[Bernard Newbury]

Is that because you broke the beams with the back tyres though Danny?

My car used to squat the back and skim the front tyres on the ground but just the once it picked them up about 18" - never did it before or afterwards.

I was doing this but could not work out why my 60ft were not as I wanted. It was when I watched some slo mo's that it came to light.

[NoBars]

I have a theory also.
This picture shows a neutral suspension.
the forces are on the springplate. The wheel finds traction and pushes the springplate. The springplate in turn pushes the car, which also pushes back with the same force on the springplate.
In this case the spring plate is balanced out
 
In the picture below the car is in a raised position which means the springplate is inclined.
Again the tire pushes the springplate en because the springplate pushes the car the car pushes back.
The difference is this time the forces are spaced by a distance over there line of work.
This distance creates a turning force of X Newton Meters on the springplate.
It wants to turn around. The tire can compress a bit and the rest of the turning force goes into lifting up the rear of the car. Because the car has inertia it will give more force on the tire aswell and give more traction

If you set up you're car the other way around, lower it untill the suspension in the other way around the car will want to squat even harder than it always wants to do because of the diff like stated above by spanners.

If you think what happens to the forces when you actualy engage in a wheelie it will increase the traction even more by turning the springplates even more oposed toi the direction of force.

That is the main reason you dont want to squat to much, you need to keep above the neutral point

I buy into this theory. It is the same as a swing arm on a bike.  I'm not great with calculations, but am a decent "eyeball engineer" and that seems logical to me.

I raced a GS 1100 streetbike in the late 90s/ early 00s, eventually working down into the high 7s at 180+ One of the biggest improvements I made was to raise the swing arm pivot 1", improving the swing arm angle, keeping it closer to horizontal and also putting the chain pull closer to the pivot. The suspension worked really well.

This is a similar concept minus the forces of the chain...

I have a 1" trans raise in my car. I sometimes wonder if this is counterproductive. It puts the plates in a downward slope  to the torsion housing. I have been raising the rear slowly to get the car to square the tire better at the hit. I think I am finally where I want to be. But I do not think it is optimal. I keep thinking about a torsion raise and stock height mounts. Raise up the torsion as much as I can get away with under  a stock package tray.

I'm good at creating work for myself.

[NoBars]

My hero shot.

1.48 60 on muscle. The tires look pretty square to the track surface rather than decambered which is what I kept seeing in photos. A small change in axle angle made a big difference in rear camber at the hit.

[richie]

Anthony

your ideas are pretty much correct going on what I have found in real life, the more I move the springplate upwards[ effectively lowering the car at rear] the more it squats and the worse traction their is, stock ride height seems to give really good traction
I understand why on swingaxle cars people use the 1inch trans raise but in reality I am not convinced it really helps. A 2-3 inch torsion raise would be really effective but it does take it along way from a regular street car 

cheers Richie

[modnrod]

When I played with small sedans it was always difficult to get traction off the mark AND get the car low enough to help stability at the top end, small light cars get blown around a lot more than a 360 Valiant, as I'm sure you all know well! 

I ended up changing tyre size to help. I have since always used a 23.5 x 8" or a 24.5 x 8" tyre on a 13" rim. It has the same sidewall height, and therefore "bite" as a normal 26 x 8" on a 15" rim, but lowers the back a good inch on it's own. My best 60ft using the McCreary 23.5" was 1.52, but that was with the hard compound that lasted for better than 50 passes, the medium and soft would hook harder I reckon.

One more option to consider to get the back down a bit for you guys maybe?

[spanners]

with swing axle, as the front comes up, so the rear wheel load de creases because the trailing arms are going nearer vertical, this is also allowing the rear toe to increase because the rear is increasing its positive camber which becomes toe in all on its own as the geometry rotates, all because the applied load is diminishing, irrespective of the drive shaft/engine torque applied to it, basically its becoming a Ballet dancer up on points, not good and easy to push over,,,keep 'em  down nice and low, but its another plus point for IRS with its reduced camber change.