Hey guys (series 2), what's your wheel travel at the limited turning situation?

[lcy1989]

our car's maximun wheel travel can reach +25mm/-25mm theoretically.
here I'd like to kown,when the car is actually in the max lateral gravity,what do you recommend the wheel travel in term of the 25mm??

[lcy1989]

our car's maximun wheel travel can reach +25mm/-25mm theoretically.
here I'd like to kown,when the car is actually in the max lateral gravity,what do you recommend the wheel travel in term of the 25mm??

[oz_olly]

I think what you are getting at is the roll angle due to lateral acceleration. If you have exactly +-25mm travel with a track of 1m you would have a roll angle of about 2.8 degrees. If this was to occur at 1.5 lateral g you would havea roll rate of 1.86deg/g. Our car has beam axle suspensio so we aren't too concerned about what our roll angle is. If you have an independent suspension then my guess is you should care if you are trying to run your tyres at a specific camber angle.

So really if roll angle is what you are asking then it depends on your suspension type and camber change in roll. Do you know what camber settings do to the lateral force your tyre is capable of?

Out of curiosity, what is your first language?

Cheers

Olly

ACME Racing

[lcy1989]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by oz_olly:
I think what you are getting at is the roll angle due to lateral acceleration. If you have exactly +-25mm travel with a track of 1m you would have a roll angle of about 2.8 degrees. If this was to occur at 1.5 lateral g you would havea roll rate of 1.86deg/g. Our car has beam axle suspensio so we aren't too concerned about what our roll angle is. If you have an independent suspension then my guess is you should care if you are trying to run your tyres at a specific camber angle.

So really if roll angle is what you are asking then it depends on your suspension type and camber change in roll. Do you know what camber settings do to the lateral force your tyre is capable of?

Out of curiosity, what is your first language?

Cheers

Olly

ACME Racing </div></BLOCKQUOTE>


thanks a lot

My question might have a little problem
what I actually want to ask is when the lateral acceleration reaches 1.5G..what roll angle the car should be? the less the better or what?
Our wheel travel is+- 25mm but we don't need to reach the maximum travel when the car reaches the limit lateral acceleration,and the question is when the wheel travel reaches the maximun, what wheel load is recommanded? Equal to the Axle load and just use anti roll bar to keep the wheel load transfer at a small amount?
And if we set the wheel load very large,and assume it can sustain 1.5G later acceleration. Does that mean our car will have a very small roll angle? and does anti roll bar be necessary?

My English is so poor~~~
what a shame!! -_-##

[HoggyN]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by oz_olly:

Out of curiosity, what is your first language? </div></BLOCKQUOTE>

Curious question, but my money would be on Chinese.

[oz_olly]

You need to decide what your roll angle should be. If you make your roll stiffness such that you are using your full suspension travel at 1.5g what happens if you clip a cone or hit a bump? It will result in a violent variation in the vertical load your tyre experiences. Would this be a good thing?

My understanding for independent suspension is that your roll angle should be chosen to control wheel camber. There are other things that come into it as well like roll speed etc. I would suggest getting your hands on a copy of Race Car Vehicle Dynamics by Milliken.

Unless you have designed a car with suspension that has decoupled ride and roll motions it is highly likely that extremely high roll stiffness will mean you also have high ride stiffness which will mean your tyres will get very hot and the vertical load will be subect to higher frequency variation. The way I understand the problem is to chose a ride stiffness and then add roll stiffness with antiroll bars until you have the desired roll stiffness.

You need to answer questions such as what is my roll stiffness distribution front to rear, what is your weight distribution, what happens to the tyre lateral force as the front wheels are steered (hint: how much longitudinal force is applied to the car and how does it effect the yaw moment). I'm not sure about the answer to that question yet.

Hope this is helping. These topics have been talked about many times on this forum but there isn't too much interesting discussion going on at the moment.

Cheers

Olly