Kitlooney1000
|
| posted on 7/4/04 at 07:54 PM |
|
|
Front Spoiler
After driving the car to the chassis inspection last week, noticed that the front was light at speed, just wondered if anyone had any ideas for an
fter SVA spoiler that would pin the front down a bit at speed, just an idea
|
|
|
|
|
Dave Ashurst
|
| posted on 7/4/04 at 08:38 PM |
|
|
Hi Kitlooney
Depends what sort of speed you mean (!) but it's much more likely to be due to the steering geometry IMO.
Personally I'd start with a check on the tracking and bump steer and sort them out. (If not too far out the latter can be minimised a bit by
finding the optimal front ride height.)
Your car isn't that different to mine and that's what mine was like. No probs since the steering/suspension was set up - a DIY
day's work max. I'll tell you all about it offline if you want. 
regards
Dave
|
|
|
stressy
|
| posted on 8/4/04 at 07:14 AM |
|
|
I agree with Dave.
Check chassis set up and get some good testing before doing anything crazy. Try and set the front suspension so that the lower arm mounts at the
chassis end are at the same level above ground as the centres of the outer end ball joint. DONT set the lower arm parrallel to the ground. It should
effectively run downwards to the wheels. set the rear ride height so all four training arms and the panhard rod are parrallel to the ground. I found
a large increase in front end grip by adding more rake to the chassis, i.e. front ride height lower than the rear, this stops air pressure build up
under the car. Check also that you have your tyre pressures right. I ran mine hard for SVA to give good self centering then knocked them back 10 psi
for normal usage, seems ok.
On the topic of the spoiler....Caterham's Sv-R has an optional front spoiler to deal with what the measured as about 100lb of lift at the front
axle line at 100mph, however from memory i believe they ended up abondoning for the time being as it created an aerodynamic centre of pressure so far
forward that it unloaded the rear wheels and turned in to a wild oversyteering monster. Still in development i believe.......
|
|
|
locost_bryan
|
| posted on 15/4/04 at 12:27 AM |
|
|
Stressy,
If I understand you right, we should keep the front lower pivot points parallel to the ground, which means the wishbone itself slopes down to the
wheel (by the length of the balljoint pin)?
And if we set up the rear links parallel to the ground, raking the chassis forward would require lowering the front slightly (i.e. raising the inner
pivot point slightly to maintain the above geometry)?
Bryan Miller
Auckland NZ
Bruce McLaren - "Where's my F1 car?"
John Cooper - "In that rack of tubes, son"
|
|
|
stressy
|
| posted on 15/4/04 at 10:57 AM |
|
|
I agree with your comment, the best compromise is to try and keep the front lower wishbone looking like its pointing down abit to the wheel and the
upper so it pointing up to the wheel.
setting the rear arms parrallel means equal bump steer in left and right turns at the rear. As nuetral as the design will permit.
This gives fairly onsistent handling if nothing else.
|
|
|
Kitlooney1000
|
| posted on 17/4/04 at 07:29 PM |
|
|
have looked to see if the car is sloping towards the front, it isnt, there is about 5 mm difference between the front and the back, the back is lower.
will that make a difference. the wishbones look fine, bottom pointing down the tops are level.
|
|
|
stressy
|
| posted on 17/4/04 at 07:39 PM |
|
|
alright kitlooney
If as you decribed was my car i would drop the front ride height by say 10mm or a bit more if possible. Keep the lower arms sloping down or level and
the upper will start to point up a little, thats fine.
All sevens suffer from front end lift at speed but if the nose starts higher than the tail to begin with then you are effectivly using the air at
speed as a wedge to lift the front wheels off the ground, i.e. the steering gets ligher the faster you go.
Turning the wedge the other way around (i.e back higher) creates a better, reduced lift, option.
Happy testing, let me know if it improves
Cheers
|
|
|
