Quote:
Originally Posted by sjelby
tAnyone know how independant
front ends work?
I am putting together a front end with mustang 11 upper and lower control arms from Heidts.
I would think they would be parallel to each other.
The crossmember plans i have seem to be out of proportion in some aspects.
IE: top contol arm hitting the shock tower.,
arms not parallel.
photo added where the top one is going to be located.
i think i need to make it sit higher.
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Generalizing here....typically, the upper wishbones /arms are around 75% of the length of the lower arms. The arms are not parallel. The upper arm chassis mounts will be higher that the upper arm ball joint.
Basic reasoning...if your wishbones /arms were the same length and parallel, all OK when going in a straight line and hitting a bump, but when cornering and body rolling, the wheels would still move up and down parallel to the body, so you would have significant positive camber on the outside wheel (with reference to the road surface).
Steering rack length (the actual rack itself without the links) needs to match the distance between the lower wishbone inner mounts.
Height of rack needs to match the vertical position of the lower wishbone inner mounts.
Angle of the links on the ends of the rack needs to match the angle of the lower wishbones. All of this is so that if you hit a bump, the wheels don't toe-out or toe-in excessively.
To top it off, the steering knuckle (on the stub-axle) needs to be the correct length and the correct angle to achieve 'Ackermann steering'. This needs to be reasonably correct so that when you're on full lock, the inside wheel turns through a greater angle than the outside wheel. It's related to the angle of the steering knuckle being in line with the midpoint between the rear wheels.
It might sound involved, but the principles are reasonably simple. Remember that a manufacturer spends a lot of time trying to get this as good as he can, so you spending a while working out the what and the why, will pay off with better and safer handling, better braking, less scrub on the tyres, and a nicer 'feel'.
Cheers,
Glen