Ackerman Theory (this one's a doosie)

[3spd on floor]

Ok, so i'm in charge of the steering and suspension design for my schools SAE mini baja car project for this year, and i'm starting to take a look at steering theory. Now i've read several websites and articles that describe how to achieve ackerman steering, but i'm at a loss for the proof/reason that it works. Also, i'm not 100% sure how to determine how much ackerman is in a specific design, or how much ackerman is needed for different race classes, or how it even affects handling characteristics. So basically i'm checking to see if any of you guys are familiar with this stuff and could maybe point me in a good starting direction(opentracker, gp001 looking in your direction ). I've searched over on CC.com but i'm a little scared to post about it, they're pretty brutal.

also, can you reccommend any really good higly technical books about steering/suspension design?

thanks again.

 

[1970 slantroof]

There was an article in one of the stock car rags a few months ago on Ackerman. It explained it pretty well. In a nutshell, it causes the inner wheel to turn sharper than the outer wheel when you go around a corner. Makes sense since it needs a tighter radius. I know the spindle to steering arm relationship is different on a drag link steering than on rack and pinion. That is needed to get correct ackerman. Maybe some of Steve Smith Motorsports books have coverage of the subject.
Howard

 

[reenmachine]

Here's a pretty simple explanation from the T-Bucket guys:

http://www.nationaltbucketalliance.com/tech_info/chassis/ackerman/Ackerman.asp

The key blurb:

How do we get the geometry such that this desired effect is achieved? Fortunately Mr. Ackerman came along and figured out that if he arranged the mechanical parts of the steering system so that the pivot points of the linkage (tie rod) that connected the two front wheels were closer than the pivot points for the front wheel mounting assembly (spindles with their kingpins), it would affect how the wheels reacted when turning was occurring. He apparently noticed that if he made these points such that if you drew a line from the center of the kingpin to the center of the rear axle housing and placed the tie rod ends center on that line, it would give the desired change in the angles that the two wheels turned.

This pretty much sums it all up. Good luck!

-Pete

 

[kslushy]

If its on an off-road car, I doubt you need to be thinking about ackerman. I'd probably be more interested in the anti's, as well as bump steer.

 

[67coupe351w]

Hey, MiniBaja, and your getting a good early start on it too, Im impressed.

I designed the front suspension last year for Portland State University. Perhaps youve seen pictures lol...I wouldnt be suprised. Us crazy boys with our 4 link suspension and ungodly amounts of suspension travel.

It would be cool to talk to you about Baja.

 

[302 coupe]

I worked on the mini baja while I was at Georgia Southern, lots of fun. There are a few diagrams available online, its really simple to get it figured out and set-up properly. Kudos for getting started on it already, we were always in a serious time crunch to get it done on time. And normally our performance showed a lack of testing because we would finish building the car only a few days before the race.

Is your team planning on entering the formula SAE? Big time fun, plus you'll get to meet Carroll Smith(THE suspension man).

 

[BobV]

Decent Article Here

Ackermann is every bit as important as bumpsteer. Too much or too little can basically create a condition SIMILAR to bumpsteer while turning.

You might also try a google search on it - plenty of good reading out there.

 

[3spd on floor]

Thanks for the info guys, i'm sure i'll get it all sorted out.

yeah, we're getting a really early start this year cause last years team had huge time crunch issues, and the car ended up breaking before the endurance race, so we came in like 120th or something awful like that. We've got a hell of a team this year though, shooting for top ten placing, and the professor in charge has told us that he wants the car done april 1st. I'm heading up steering, suspension and i'm also designing the frame.

67coupe351w and 302coupe - do you guys have any pics of your cars? unfortunately my school doesnt have the funding or the means to be competitive in formula SAE. i wish we did.

 

[67coupe351w]

This is Our car at the West competition here in Portland. We went with a manual transmission but had serious clutch problems in the west so it sucked. Like 302coupe said..dont get your car done the day before competition, its what killed us in the west event, had we driven our car more than ina parkinglot before the competition it would have been obvious our clutch wasnt holding on the hills and we could have fixed it BEFORE the race

We lost the "batmobile wings and all the mud flaps for the midwest competition. Mudflaps are only a good idea if they actually keep mud out of your eyes

 

[302 coupe]

I think our ASME page is down right now, but here is the link if you want to check it out.
http://studentorg.georgiasouthern.edu/asme/