Adjustable Ackermann methods?

[SeanLindsay]

I was wondering how other teams acheived their adjustable ackermann. For the 2004 race car, we're moving the steering rack forwards and back while keeping the point on the upright the same.

For 2005, shock packaging makes this way a bit difficult. Has anyone here tried adjusting the mount on the upright?

[Dipper]

We had good luck using shims to adjust ackermann. If you shim out the mount on the upright, and reduce the length of the rack (distance between its two ends) correspondingly then you adjust your ackermann without changing the length of your tie rods or moving the rack. It also means you can adjust the ackermann and drive again without adjusting the car's alignment.

Keep in mind that the rack is a critical and highly stressed component. Compliance anywhere in the steering system is bad news, so if you plan to adjust the position of the rack, make sure the adjustment system is solid. (Problem here is that this usually means the system will be heavy...)

Victory is Today!
Justin

[SeanLindsay]

Do you have any photos of the shim?

[Dipper]

Yeah, sure do. Just need to figure out how to post it. Alternately, give me your e-mail and I'll send it your way.

Justin

[SeanLindsay]

Thanks, it's slindsay@erinbooks.com. I'd like to see how the steering mount attaches to the upright.

[vinHonda]

You can have different mounting points laterally at the upright. A clevice that picks up the rod end from the tie rod with a fastner in double shear can have many various locations laterally (ie, along the width/tread of the tire) and that will give you various ackermann settings.

Simple way to do it, pre calculate how much ackermann you're gonna get, drill the holes in the clevice. Done.

Cheers

Vinh

University of Toronto Formula SAE Racing Team
www.fsae.utoronto.ca (http://www.fsae.utoronto.ca)

[Dipper]

Hopefully this works for showing the image I mentioned earlier. On the upright end of the tie rod you will see a "pinch mount." By packing shims under this mount and adjusting the length of the clevis on the end of the rack by an equal amount you change ackermann without needing to re-align your tires.

http://img.villagephotos.com/p/2003-12/545239/front_sus_assy.jpg