Ackerman is always important--even in a kid's wagon--for some reason it's
just rarely understood. Picture the basic radio flyer negotiating a turn,
the inside wheel follows a tighter track than the outside, which means it's
should be pointed differently. The sliding of the front wheels and lousy
steering of a radio flyer is a direct effect of not having any Ackerman and
having no flex to the wheels.
One of the many reasons that Radial tires make even a relatively crappy car
handle a little better is that the sidewall flex makes up for the limited
Ackerman.
To gain Ackerman you need angled steering arms, or a complex steering
system. As the steering is increased, the inner wheel, which needs to be
pointed at a sharper angle (it's traveling around a tighter radius) is
turned more sharply if you have angled arms. That generally isn't
intuitive--you need to draw the thing out with various steering angles to
see how it works. But the angle of the arms means the lever angle between
the inner pivot point of the link and the end of the steering arm changes as
the wheel angle increases. On the outer wheel the travel is less per degree
of steering than it is when the wheel is centered, on the inner wheel it's
more.
There's nothing inherent in a rack over a worm and pin that induces
Ackerman--it's all in the steering arm angle. But if you're setting
everything else up, you can add Ackerman to the list of things you are going
to shoot for in compromising on the tunable parameters. Generally you'll be
constrained by bump steer in how much Ackerman you can add. Stock TR3
steering has very little Ackerman. Peyote has what is called "more Ackerman"
which means the inner wheel points a little more inward at the extremes of
turning than it needs to. This could induce a little oversteer (you'd think
it would understeer, but remember that the inner wheel is fairly unweighted)
but in practice, "more Ackerman" really means the right amount of Ackerman
at the beginning of steering, which helps turn in.
-----Original Message-----
From: owner-fot@autox.team.net [mailto:owner-fot@autox.team.net] On Behalf
Of N197TR4@cs.com
Sent: Saturday, July 30, 2005 7:45 AM
To: dtalbott@archrepro.com; fot@autox.team.net
Subject: Re: TR 3 Steering
This is the first time I have seen "Ackerman Effect" mentioned relative to
Racing Triumphs. Is it really important or relevant to a TR sliding through
the corners and sometimes with a locked rear?
Joe (A)
> Speaking of rack and pinion options for TR3's, does anyone have any
> experience with the Revington kit? From what I've seen and read about
> them on-line, they seem to say all the right things with respect to
> minimizing bump steer and adding some Ackerman effect, and it appears
> to be a very sturdy weld-in affair.
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