An entertaining experiment is to measure the distance between the strut tops, and then repeat with the front wheels free. I've seen 6mm. Mazda used to tie bits of string around the car and see which bits went slack when cornering.
Cheers
Greg Locock
New here? Try reading these, they might...
Many successful circuit cars have been designed using 3 2 1, although I think 3 2 2 (Z X Y) is probably wiser. Those are very much the lower end of what a production car is designed to, although for the last 40 years dynamic loading is used, not static equivalents. for actual component design...
It is, to say the least, surprising that we develop a car around a target tire, and then the consumer is free to fit any old cheap black round thing when the first set wear out (and I've never tracked understeer vs tire wear if it comes down to it). And then they sometimes only change tires on...
One of the more entertaining things to do with a bicycle model is to try a step steer with an understeer, oversteer and neutral setup. The results are not what armchair drivers expect.
Here's one way to approach an understeer budget https://en.wikipedia.org/wiki/Bundorf_analysis but there are...
Also Program Office. But the decision that all product must be BIC for number of cupholders or whatever is from the high muckity mucks.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376 http://eng-tips.com/market.cfm?
It's science.
The marketing team don't set ride and handling targets, we do, by looking at competitors and deciding where we want to be compared with them. For instance there may be a corporate direction that we are to be best in class for vehicle dynamics, or among the leaders, or average, or...
Kinematics is usually pretty good, if you've CMMed the hardpoints properly. This is pretty crucial, typical production tolerances on the height of theUCA and rack compared with the lower arm bushes, which controls your toe curve, is enough to mess things up.
Compliances not so good, we measure...
The disadvantages of excessive roll steer are (1) makes the car darty on rough surfaces - in Australia we expect to drive comfortably at 100 (or more) kph on gravel roads, including dropping one side off the track to allow an oncoming car through. Not all manufacturers quite managed that. (2)...
I'd have thought roll center migration in roll was of much greater magnitude.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376 http://eng-tips.com/market.cfm?
The elephant in the room is the tolerance stack in height between the inner tie rod and the lower arm bushing, snd the same for the lateral location.
In the case of MacPherson you've also got the front view installed angle of the strut, since the spring tower's relationship to the lower...
On the front wheels you just get steering wheel off centre which is primarily an aesthetic issue, although if you have your hookes joints set up to give fast or slow on centre it'll affect the symmetry of that as well, but not to any noticeable extent. If you've got it on the rear wheels you'll...
You always need both, although if pushed for rig time in phase is more important. Opposing is diagnostic for steering arm stiffness etc, but not directly as useful as parallel
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376 http://eng-tips.com/market.cfm?
1 You are basically measuring the rack/subframe contribution in the in phase test
2 beam axle? no
3 Not much, so long as the pnhard is relatively horizontal. Laterall location of the RC is something that some people think is important. Milliken, Milliken and me don't.
Cheers
Greg Locock
New...
Yes, because your suspension always give you the mechanical trail.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376 http://eng-tips.com/market.cfm?
Pneumatic trail is what you are after, from your tire model divide the self aligning torque by lateral force at the operating condition. This gives you the pneumatic trail.
The mechanical trail is fixed by your geometry and is automatically present when you do a K&C test.
In the absence of...
Front View Instantaneous Center, very closely related to roll center height.
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376 http://eng-tips.com/market.cfm?
Thinking about it the main driver for this on a production car is tire wear. I don't have a good tire wear model so I can't check that out, but it isn't entirely unreasonable to think that continually generating small slip forces as the car bounces along in a straight line is not a great idea...
Our FAQ calls it out as
2.6 Track
track gain in roll
semitrack gain, ie lateral displacement of contact patch per unit of jounce travel
Targets are a little harder to find. Obviously it is a function of the FVIC location. My gut feel is that given the relatively low wheel vertical velocities...
