"Interesting point, Steve, and worth checking by someone with a good stock of track arms."

I know no-one reads my comments - possibly because I don't speak from great knowledge or experience in high speed road transport but I did point out-

"The Cross Tube Levers were BM 91 and BM 92 from 1926 to 1936 at least!"

I also quoted -

"A simple approximation to perfect Ackermann steering geometry may be generated by moving the steering pivot points inward so as to lie on a line drawn between the steering kingpins and the centre of the rear axle."

Note this states 'a simple approximation'

Experts can now attack.

Tony.

Location: Malvern, Melbourne, Victoria, Australia.

Apologies to long suffering Vince and Jon

I have long known that full Ackerman does not suit modern cars ie those made since 1900. I have not been advocating for full Ackerman, simply responding to the initial post which suggested that for full Ackerman the axis meet at the diff. (A notion I also had loosely in my head years ago. I guess it arises from confusion with the turning centres.)

I did slog through Bastow years ago. Unless higher maths is a hobby, I do not recommend. I suspect most using this Forum will get a better understanding of slip angle and the effects of from the flat tyre analogy. Books such as that by Carrol Smith are more understandable.

(Incidentally, Bastow worked for Jowetts in their dying days. Their designs were then old so I do not know what he contributed. Perhaps the very satisfying handling of the Javelin prompted him to ponder the subject of handling. Like the Seven the Javelin has an element of roll induced oversteer which gives it a very responsive and lively feel. But the steering geometry is fully adjustable and can be and normally is set up for no front bump steer and negligible free travel!)

Ackerman effect applied to typical 1960 cars gets more involved as there is often three track rods moving in small arcs and with slave levers, and often with one rod behind the pivots.

And Tony, the fact that contributions are not all acknowledged does not mean these are not appreciated. If everything was acknowledged would get very cluttered. If not quite to the point and comment is made with a reservation it may offend so many don’t, but it does not mean the contribution was not useful. All Ackerman with pivoted instead of sliding links is an approximation, except at one angle.
I suspect you reflect the thoughts of many on occasions. Without your comment this post would probably have died!! Vince and Jon clearly wish it had, but others less experienced seem to have found some interest. The Forum is not only for the old hands.

A problem is that most understandably do not always read every word of every post that has gone before, but respond to a quick general impression. Some repetition helps ideas to sink in!

Bob Culver

Location: Auckland

Bob,

I didn't need acknowledgement - just making the point that sometime ago I mentioned that the 'track arms' which were in fact called 'Cross Tube Levers' by The Austin didn't change angle from the original pieces (going by Part Numbers) even though the chassis lengthened and the Ackermann steering was an regarded as an approximation when defined by a line drawn between the steering kingpins and the centre of the rear axle anyway.

Tony.

Location: Malvern, Melbourne, Victoria, Australia.