Steering Angle Effects

[Tony71502]

Hey,

From what I've been reading throughout the web, steering angle is the angle between the tie rod shaft and the tie rod itself? Is this correct? Also, I have read that this angle is a considerable factor in a car's turning ability.

When considering two different spindles for my car, the only difference is the location of end of the steering arm. The spindles have the exact same dimensions on everything except the vertical location of the end of the steering arm. The horizontal locations are the same. The steering arm on spindle A is completely horizontal, where the steering arm on spindle B makes an s shape which locates the tie rod hole about an inch above, but at the same location in the x-z plane, as that on spindle A.

What I'm wondering is should I make the effort to find a set of "spindle A's" in order to lower the steering arm/tie rod location in order to decrease the steering angle and provide a slightly increased turning radius.

Or am I completely wrong in my understanding of these concepts.

Thanks,
-Anthony

 

[evelrod]

If I am reading your inquiry correctly, raising or lowering the tierod /steering arm to effect "slightly increased turning radius" won't do it. Typically these steering arm variations are to correct clearance or bump steer issues...This is not usually a 'big' problem on street driven cars unless it gets way out of hand, not likely these days. On race cars, particularly ones that are softly sprung and utilize a lot of wheel travel, e.g., off road, bump steer problems can be dramatic. Altering the length of the steering arm and/or Pittman arm is what will alter turning radius.

I'm sure that some of the suspension design engineers here can explain it better.

Rod

 

[GregLocock]

" the x-z plane" What coordinate system are you using? guessing y is vertical?

" steering angle is the angle between the tie rod shaft and the tie rod itself? Is this correct?" I wouldn't call that the steering angle, in top view it is related to ackerman, in front view it is part of bump steer. I do plot it for plan view and there it is called the toggle angle, but is only important for full lock.

If you can sketch out what you are talking about, and attach it to your post things might get resolved more quickly.

Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[patprimmer]

I am not a suspension guy, but I always called steering angle the angle of the wheel to the centre line or axis of the chassis.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[BrianPetersen]

There are many many "angles" involved in the steering. It's better to state precisely which one is under discussion ... Caster angle, camber angle, toe angle, steering axis inclination angle, etc etc etc.

The angle of the tie-rod (steering link) relative to the rest of the suspension linkage affects bump-steer (in front view), and Ackermann effect (in top view).

Regarding the specific question in the original post, raising the outer tie-rod attachment point will affect the bump-steer effect if nothing else is changed. (But, it isn't the only factor involved.) What really needs to be done, whether by computer simulation or by physical tests, is to "map" out the path taken by the tie-rod connection point as the suspension moves through its travel, and compare that to the arc swung by the tie-rod, and thereby pick the location of the other end of the tie-rod to achieve the desired effect ... This is the only way to make the choice between the two spindles at hand.

Practical suspension designs always have some bump steer; the trick is to minimize its effect in the normal range of suspension movement.

 

[Tony71502]

Thanks for the help.