12 replies to this topic

[zac510]

Last weekend I travelled to Paris to see the Andros Trophy at Stade de France.

I had spent up for a Paddock ticket but unfortunately got there late not realising the paddock pass was limited. The pits were only open for 1 hour, 2.5 hours before the start of the event I was pretty disappointed because I wanted to have a real close look at the cars. It has been very hard to find out anything technical about these cars.

It was quite easy to spot different driver styles. Some drivers flicked the car quite a lot while other drivers like Prost just turned the car in quite viciously to induce the slide.

I don't think Prost and Panis used much 4WS whereas Lagorce seemed to use quite a lot of angle - it was very visible when he was setting the car up for the corner.

This thread could be quite apt given our recent discussions of driver/car setups.

I was also wondering how the 4WS setup works and more specifically, how the driver actuates it. At one point I noticed a driver use the 4WS when spinning the car around in 1st gear to point it back in the proper direction.

Do these cars have a hydraulic system that provides control of the rear wheels?

Thanks!


PS - I shot a poor video and some fuzzy photos if you would like to see these cars in action.

[-RM-]

A few years back, it was just a steering rack with a quite large deadzone.

[RDV]

zac510- I was also wondering how the 4WS setup works and more specifically, how the driver actuates it.

Rear rack is quite simple--- rack itself hasnt got any teeth, just a pin that runs in a roughly cardioid shaped slot on a disk (this is connected to a shaft that comes from front rack). No perceptible movement for small angles of lock of ft wheels , but as front steering angle get bigger rear steers in opposite direction. At Stade de France basicaly running on an oval... other tracks have hairpins where you will see much more 4WS action.

The approved maneuver for hairpins incidentaly is using 4WS to flick car into corner in reverse... this way you are going into corner backwards, at say 60 kpk, but with wheels spinning like mad at @ 130kph, this will slow car down (using the spikes on the tyres) , and then slingshot you out of corners... also keeps engine from bogging down. Quite interesting to see the data logging traces...(easy to see wheel speed, but only way to see car speeds is by using a laser-doppler ). Other interesting item is the front wheels run at roughly 5 to 10% overspeed compared to rears to be able to have some steering control, (friction circle not an elipse as usual, but perfectly circular and between 0.2 and 0.3)

Yvan Muller started using this technique... not surprising he now has won ten Andros trophies in a row...

[zac510]

Thanks! Sounds like I was thinking of a really complicated solution when a simple one works just fine

Do you think that some drivers prefer to run with more or less rear steering angle?

It was hard to tell how much Prost used because he turned in from the outside of the straight where as some drivers like JP Dayraut turned in from the inside and stayed there.

When you referred to the overspeeding of the front wheel, do you mean that the gearing or tire diameter is configured to make the front wheel speed faster than the rear?

Also do you know what engines they run? Is it a control engine or manufacturer engine? I wish i had got to the pits on Sat

The backwards entry sure looks spectacular. I'm hooked. Gotta get to a proper event next season.

[RDV]

zac510-When you referred to the overspeeding of the front wheel, do you mean that the gearing or tire diameter is configured to make the front wheel speed faster than the rear?

Front bevel drive slightly overgeared. All diffs are locked.

As to steering angle the rear slotted disc can have different rates to suit drivers preference.

Re engines , last had a car in the Andros in 2003, presume they are still the same, heavily modified production engines, we had a 3.5 lt with @ 450bhp

[zac510]

Thanks RDV. If I read the event programme correctly, they are 6 cyl, 3 litre engines now. Does 340CV = 340hp?

Can you tell me more about the cars? You have been my best source of information so far! Even the usually reliable google turns up very little.

[hydra]

CV=PS=0.985bhp or something like that

[zac510]

ah French PS, thanks

[Breadmaster]

CheVal = PferdStarke?

[David Beard]

Originally posted by RDV


Rear rack is quite simple--- rack itself hasnt got any teeth, just a pin that runs in a roughly cardioid shaped slot on a disk (this is connected to a shaft that comes from front rack). No perceptible movement for small angles of lock of ft wheels , but as front steering angle get bigger rear steers in opposite direction.

I think I understand that....but I'm struggling to imagine what feedback the driver will get through the old fashioned seat of pants when the rear steer is reacting to lots of lock applied to correct a loose rear end?

[zac510]

Yes, I know where you are coming from. at stade de france I spent a while staring at the rear wheels and I didn't often see them turning once the car was in the slide. I think this is a function of the surface that they are running on - they don't need to make drastic corrections to the steering. It is much more slippery than a typical dirt/gravel surface. I wonder, if you can't set the car up for the corner properly you will get bitten.

How do you think Andros is good for young drivers, especially the celebrated young females like Justine Monnier?

[Greg Locock]

On bitumen 4 wheel steer is sensed as a modification to the relationship between yaw velocity and lat acc, both of which human beings seem able to sense to some extent - yaw velocity is crudely the rate at which you are spinning, lat acc is the rate at which you are going around a corner. If you are on rails there is a direct relationship, otherwise slip angles and so on come into it.

The starting point for the cars I work on is to basically make all the rear passive steer mechanisms as understeery/neutral as possible.

Production active 4ws tend to use understeer at high speed and oversteer at low speed. As you can tell, active 4ws is a fad that has come and gone, now we use the brakes to get the high speed effects.

[zac510]

I drove a Prelude 4WS once and it was quite a shock!

If you tune the rear steer towards understeer it kind of anulls the 4WS - whch must lead us to the point about production 4WS having been and gone.

Perhaps you would like to have a look at the video, but it isn't detailed enough to see the 4WS in action.

http://rapidshare.de...all.00.avi.html