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## RE: Do it yourself alignment question (TR3A)

 To: RE: Do it yourself alignment question (TR3A) "Jim Muller" Tue, 25 May 2004 21:44:48 -0400 <40B252FB.17329.C86AF58@localhost>
 ```On 24 May 2004 at 21:54, Randall Young wrote: > It's called Ackerman steering, and the TR3 has it as well, so it does > make a difference. As usual, Randall is on the mark. Rudolph Ackerman developed this scheme in 1810 (well before Daimler or Ford or anyone else automotive!) to improve the steering of carriages. In its theoretically complete form, a line through the axle of each wheel passes through the center of the circle transcribed by the car as it turns. Since the rear wheels don't steer (and assuming zero toe-in at the rear), this means the car pivots around a point inline with the rear axle. In practice this isn't ideal because it assumes no slip angle for the tires. But if you assume slip angles, the rotation point is moved forward, sometimes referred to as "modified Ackerman steering". As Randall points out, in practice the slip angles are somewhat ill-constrained because so many things can make them bigger or smaller. Thus one wouldn't necessarily design for theoretically correct geometry. In any case, the designers would be expected to have chosen a geometry for slip angles expected from the contemporary tire technology. Presumably they would also have taken into account the weight transfer and camber changes expected at maximum lateral G's. Then again, maybe not! They certainly wouldn't have been as good at it as modern computer modelling allows. Even so, any asymmetry in the system would mean asymmetric behavior. And if one side gets better when it doesn't meet the original specs, the other side should get worse. All this would become worse as you cranked in more lock, but fortunately we tend to do our high G's at high speed with a large turning radius rather than at full lock at lower speeds. The only reason I mentioned it as an issue for the Spitfire/GT6 is because it allows such severe lock, but then, one doesn't usually try to pull high G's around a 24ft skidpad. :-) Unless perhaps you own a tire factory. > As I recall, Triumph Herald & derivatives implement > "anti-Ackerman" steering ... don't know about the Spit & GT6. Yow, I don't recall ever hearing the term anti-Ackerman. Would it mean that the outer wheel turns in more, that toe-in increases as your turn the steering wheel??? I've read the Spitfire/GT6 described as modified Ackerman. At full lock it might be anti-Ackerman. Now I'm curious. I'll have to go out to the garage and start measuring things. (Thanks, Randall. I really needed one more thing to do! :-) Don't anybody hold ye'r breath for me to post results though. Joe C., help me out here! I'm sure you've done it already!) -- Jim Muller jimmuller@pop.rcn.com '80 Spitfire, '70 GT6+ ```
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