multi steer axles

[Oilpatch]

Can anyone enlighten me as to how the reduced turn angles are handled in multiple steer situations. Since each subsequent steer axle has a smaller turning radius, the resulting turn angle should be less to avoid scrubbing.

I understand Ackerman and the side to side turning angle differential based upon different tie rod arm shapes.

Confusion sets in when identical axles are tied together with a tie rod on one side only.

Is this handled in the tie rod arm somehow?

 

[zeusfaber]

The ones I've seen have bellcranks on each axle, with each successive crank being a different size.

A.

 

[rmw]

I never looked closely at how they do it, but the eyeball can see on the twin steers that I have seen that the steering angles are different on each steer axle.


rmw

 

[mloew]

Oilpatch,

Please see the thread All Wheel Steer Mechanisms (thread60-54516).

Indeed all the steer angles are different to try to converge on a single turn center point. A good deal of mechanism synthesis is required to develop a mechanism with minimal scrub.

Best regards,

Matthew Ian Loew


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

 

[Oilpatch]

Thanks for the info everyone. I will look closer at the bellcranks.

I know how to calculate the turn radii for each axle based on carrier length and axle spacings. I just couldn't see how the decreased turning angles were accomplished on subsequent axles.

I've been looking at a unit in our shop that exhibits the reduced turn angle on axle 2. However, the tie-rod from axle 1 to 2 uses the exact same axle arm shape and is nearly perfectly level. Therefore, my first thought of the arm angle being altered doesn't seem to pan out. Maybe the arms are different, but just not visible by the naked eye.