Wings/aerofoils Are they really needed? and if so when?

[Jyrki]

So it didn't increase from 240 -> 250, good!. But it still raised 4cm ahead of 240...

At the bottom of the screen you can see the suspension data. Rear suspension height is in blue and front suspension height is in red. Rather steady through 3rd and 4th gears:

[ Attachment: You are not allowed to view attachments ]

[Trond Dahl]

Thanks for sharing :-)
It's a bit hard to see, but how much does the blue(rear) actually go up as speed increases? I would imagine having a rear wing would/could prevent this. But maby it is so little as it doesn't matter?
Or perhaps it is actually pushed down by power and just returns to neutral?

[Neil Davies]

I'd like to see the same data for a stock style suspension cal looker - I suspect the suspension on Jyrki's car plays a part in its smoothness.

[Roman]

Jyrki: can you put a bathroom scale on your floor jack and lift your front 40 mm?
It would be interesting to see the lift force!

[spanners]

I'd like to see the same data for a stock style suspension cal looker - I suspect the suspension on Jyrki's car plays a part in its smoothness.

Indeed it does, or should do, and the old Skool cal look reference is significant,  a USA show on UK TV last night called "Jay Lennos garage" featured a "wheelie car" think it was a mustang with lots of rear Wright bias, mid mounted supercharged V8, big power, big tyres, narrow track and high CoG, just like our old Skool lookers, he was a pro driver, retired big name drag driver, he did his wheelie demo, got off the gas and bang, over it went, big time, they were lucky, very lucky having been grasping the A pillar durung the run, no window nets and arms flung about as expected, all shown by In car footage, the point was the cars high setup as mentioned above, and dropping the throttle! It snap over steered, got onto the edge of the tall drag slick and was history, by that time it looked like it was on track banking and it just kept going over, big accident, thankfully no injury to anyone. The point of no return as I saw it, was dropping the throttle, I have to say I cringe when I hear of drivers not only dropping the throttle but also going neutral and coasting after a run, I've spun in top more than once after taking the flag for doing just that, at least in the early days and with swing axle cars, and they were likely lower than a drag car of the day, tho I 'spose drag cars parachute is big savour on a proper fast bug, then, when it's REALY gone sideways, IRS COULD be got back, if you got swing axle back I guess a big dose of luck was involved, I've had swing do the oddest things in physics you could emagine, even sorted with ALL the quick tricks, sometimes they remind you who's boss, having said that, there are a couple of tracks were I would chose swing over IRS For a quick lap, I love em for grins factor, but dropping the throttle is bad if you have no room to get back on it to squat it down again.
Then we come to aero on jyrki's car, he's got down force from underfloor activity with low pressure, witness the flutter on the splitter, can't tell wether air dam or proper splitter with front Venturi from the vid, but it may be getting too low with the air then going viscous and into stall, pushing the front back up into fluid flow and back to downforce and so on, it may not react on the suspension potentiometers if it's flexing the bodywork.  Next time you see a car on the motorway with the front under tray fluttering madly you'll know what's going on lol! Harness that power and f@#k the wings.
The vid of course I refer to was mexx's.

[BeetleBug]

Indeed it does, or should do, and the old Skool cal look reference is significant,  a USA show on UK TV last night called "Jay Lennos garage" featured a "wheelie car" think it was a mustang with lots of rear Wright bias, mid mounted supercharged V8, big power, big tyres, narrow track and high CoG, just like our old Skool lookers, he was a pro driver, retired big name drag driver, he did his wheelie demo, got off the gas and bang, over it went, big time, they were lucky, very lucky having been grasping the A pillar durung the run, no window nets and arms flung about as expected, all shown by In car footage, the point was the cars high setup as mentioned above, and dropping the throttle! It snap over steered, got onto the edge of the tall drag slick and was history, by that time it looked like it was on track banking and it just kept going over, big accident, thankfully no injury to anyone. The point of no return as I saw it, was dropping the throttle.

Here you go:

https://www.youtube.com/watch?v=LabX19ocJZA

The problem here was not that he got off the throttle. It is the huge dump they hit that makes the car jump and the fact that they had to do the turn to avoid hitting the wall.

-BB-

[Jyrki]

Thanks for sharing :-)
It's a bit hard to see, but how much does the blue(rear) actually go up as speed increases? I would imagine having a rear wing would/could prevent this. But maby it is so little as it doesn't matter?
Or perhaps it is actually pushed down by power and just returns to neutral?

Exactly, it is pushed down by power and just returns to neutral. This just shows that the car is lacking power  
At the end of 3rd gear the rear suspension is -5mm from neutral, at the end of 4th gear (250km/h) it is +-1mm from neutral height, and after the pass it raises 5-10mm (which is not what I want it to do).

We will have to wait for the measurements a few months; the engine and transmission are out.

Jyrki

ps. I always pull the chute first, then push clutch and drop to neutral, let it coast a while, and then gently apply the brakes. However, without the chute the suspension data is similar (in SCC this year the chute droped under wheelie bars, speed was almost 250km/h), just need to brake a bit sooner and harder  

[neil68]

Picked up a front air dam to try on my street-strip Beetle.  It's a close reproduction of the rarely available Kamei product (that usually sells at high prices on Ebay):

http://www.thesamba.com/vw/classifieds/detail.php?id=1976266

[richie]

I did find with the Mk2 version of the front airdam/splitter I made this year for the new cabrio that the front ride height dropped downwards a lot more than needed after 1/8mile mark [135-140mph], so much so that I was able to reduce the lead ballast I have in front of car by 75lbs  , it still lowers the front ride height more than needed so I will reduce the splitter size gradually and see what difference that makes.

cheers Richie

[jim martin]

This was a great topic with lots of terrific information.
I recently build and tested a front air-dam. Easy to remove and install .
When I was staging the car I found it was tripping the staging bulbs quickly with the air-dam, so I will need to trim
A bit off the bottom.
One thing I don’t have on the air-dam on the bottom
Edge which I see many having is a fwd lip 90 deg to the air-dam that appears to be about
1” in length .
Should I add that once I trim the bottom 1/2”. I take it the idea is to not allow any air to roll under
The air dam . Any input always appreciated

[richie]

I think the lip helps in 2 ways, 1st to stop air roll under off the airdam and 2 to add some strength along edge of airdam but this is dependant on how it is attached.

The regs most of places i have raced at require 3inches ground clearance minimum on front of car, and beams are usually about 1.6-2inches off ground so something must be pretty low to flicker beams on?


cheers Richie 

[PPRMicke]

The aerodynamics thing, there are many ways to look at it
Front surface (in square meters) and what happens there is as you think it is
Many forget what happens when the air flows under the car and you create lift even behind the part, it can be tricky to get rid of lift from the air that flows under the fenders
Happened to be part of Volvo's wind tunnel with a racing car during a few weekends Then you got food for thought how the air went There were several things that you had to change your mind
Adding a simulation of how the air can go on a Vw Typ1
/// Micke
https://www.youtube.com/watch?v=LtXOUrTc_dA&ab_channel=Ramooo25

[jim martin]

Thanks for the input.
Now that I have a prototype and even better the pattern,
I will make another air-dam and add the forward lower lip,
Makes total sense for not allowing air to easily roll off and under the air-dam and add rigidity.

- I found out what’s triggering the staging lights .
After my burnout I come out fast and Finnish hard on brakes .
This ends up loading the frt suspension and causing it to drop .
Now my air-dam is lower by about 1 to 1.5 inches.
I tested The frt end and yep if i push down on the frt end it drops but does not
Spring back up , but if I lift the frt end  it comes up easily .
I’ve regreased the beam , but figured this is due to the urethane bushings .
Maybe time for a needle bearing beam
 

[PPRMicke]

If I were you, I would check how the air can get into the front fender then under the car which creates lift
It is not only in the front surface that the air enters
One thing I learned in Volvo's wind tunnel is that you have to have a small angle on the car so that the air atom cannot grow in size due to the heat created by the resistance, so it becomes an air cushion under the car, then you create lift
There is a damn good book about Aero that might be worth buying
Race Car Aerodynamics: Designing for Speed
Book
/// Micke

[jim martin]

This winter I will also add front and rear level sensors.
And Work on my frt suspension movement.

Will look up that book sounds like a great resource.

I have made some card stock mock up inner fender wells to fill
behind the frt wheels . They look like big air scoops
I think this is what you are talking about.