Sunbeam ( Tiger ) ackerman

[Tmoose]

Over on a Studebaker group the conversation has shifted to the importance/necessity of ackerman in the steering.
My "contribution" was that Carrol Smith said it doesn't matter much.
Some Stude owners apparently are/were Tiger owners, and one said that due to Carrol Shelby's manufacturing expediencies (for the Tiger prototype Shelby gruffly told them "...to just bend the d*mn steering arms") the ackerman was real bad, and as a result Tiger owners ever since have suffered failures of the suspension's lower fulcrum pins. he provided pictures of some fancy replacement pivots he had made. Snooping around the internet some Tiger owners are fitting 245/50 tires which I expect the engineers at Roots probably never counted on.

Anyway, I'd think bad ackerman would at worst drag the tires sideways, which would be no worse than a maximum cornering effort at 0.7 gs or whatever the tire friction would allow. And, in order to accumulate thousands of cycles to provoke fatigue MULTiple steering applications or an endless succession of corners and straights would have to be navigated.

Are the forces from bad ackerman really high enough to shorten suspension life?

 

[MikeHalloran]

The one Tiger owner that I knew had problems getting the static toe right, because rocket scientist alignment techs would check their work by stretching a wire over the front and rear tires. ... which is the wrong thing to do when the front and rear track are different by a couple of inches.

I'd suspect that suspension failures now are more likely associated with old age than with nonideal geometry.





Mike Halloran
Pembroke Pines, FL, USA

 

[dynatune]

I have seen the discussion on Ackermann for about 3 decades now and I would like to suggest one simple test which can be made either in the real world or with any suspension analysis software.

Ackermann % is being calculated out of the difference angle between the inside and outside wheel angle over steering angle and basic vehicle parameters. In all of these calculations the point of departure is a static toe of 0°. Now do try to calculate Ackermann % with a static toe angle of -0,25° or 0,25° and have a look at your Ackerman %. You will be terrified to see what those little numbers do to your Ackermann curve. And that by itself concludes the argument about the importance of Ackermann. Don't get me wrong, there is some importance but unless you are looking at reducing tire squeal noise in a parking lot or trying to put artificially heat into a slick tire that is running around monte carlo there is no big gain to be made. In this particular case Mr. Caroll Smith was right.

Cheers,
dynatune,

http://www.dynatune-xl.com