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RE: Steering Ratio

To: "Theo Smit" <theo.smit@dynastream.com>
Subject: RE: Steering Ratio
From: Tom Hall <modtiger@comcast.net>
Date: Wed, 15 Mar 2006 18:11:51 -0800
At 08:33 AM 3/15/2006, you wrote:

>I remembered you had mentioned your quicker rack in some earlier discussion.
>Is anyone still making the parts for it, or complete assemblies?
>
>Best regards,
>Theo

Besides the pieces made in the San Diego area, Ken Mattice and Bill 
Miller manufactured some quick rack components of the same 
approximate ratio in the 70's time frame.  These were not copies of 
the rack used in the #55 car but were spur gear pieces that fit the 
OEM housing without machining.  Ken also made another production run 
during his residence in France.  These pieces featured helical cut 
gears and were made in two configurations.  One used the OEM tie rod 
ends and the other used rod ends from a TVR rack.  I don't have 
production figures for either of these runs, but I'd guess that they 
were in the range of 20 to 40 each time.  I've had a quick rack in my 
white Tiger since the 70's.  They are not common, but they are sought 
after by dedicated Tiger enthusiasts.  They are also totally stealth 
in that you can't tell by looking, you have to turn the steering 
wheel lock to lock.

A couple of years ago, I purchased the remains of Ken's inventory of 
quick rack components.  I currently have three unassembled rack and 
pinion sets in inventory, one set of which is sold and being 
assembled as I write this.  One of the interesting challenges the 
helical gear design produced, is the increase in side thrust on the 
rack gear.  This in some ways, has made this design less desirable, 
as it can cause the thrust damper to bend and cause an increase in 
steering effort.  I have designed and installed improvements to this 
helical rack system and this has substantially reduced the occurrence 
of this situation.

The MG rack system is similar in ratio to the Tiger quick rack, but 
it does limit the steering angles and increase the turning radius, 
particularly when used with the MGB steering arms.  This is one of 
the reasons that the claim is made that it reduces the Ackerman angle 
error inherent in the OEM design.

Tom Hall
ModTiger Engineering LLC
www.tigerengineering.net




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