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Re: Re[2]: Throw-out bearing (theory/operation)

To: triumphs@Autox.Team.Net
Subject: Re: Re[2]: Throw-out bearing (theory/operation)
From: Barry Schwartz <bschwart@pacbell.net>
Date: Tue, 24 Mar 1998 06:47:27 -0800
               < snip >
>Lemme back up a bit here and try to sort this...in the case of a
>Spitfire anyway.  
>The slave cylinder has an internal spring that acts on the piston,
>always trying to extend it.  The purpose of the spring to remove any
>lost motion between the piston, clutch release lever, pivot pins,
>throwout bearing and pressure plate spring
                < snip >
>Practically then, it appears to be specifically designed to allow *no*
>clearance between the TO bearing and the pressure plate springs.
>The TO bearing is always lightly touching the pressure plate with the
>force of the internal slave spring.
*******************************
Tom,
No you don't have it mixed up.  Actually most slave cylinders have a return
spring inside, but most clutch systems (the ones that have adjustments)
have a spring on the actuating lever or rod to counter this.  This
(Spitfire and GT6, which also has no adjustment) appear to be one of the
few systems where they were designed with little or no free play in the
system (provably the reason that the release bearing is fairly beefy and
for the GT6 is different than the TR6 )  Chances are they figured on a MTBF
life of around 50000 miles for these cars and you would be replacing
something anyway (just kidding guys/gals)  They may have also been designed
with the idea that the normal release operation of the clutch would provide
just a tad of clearance by "bouncing" the throw-out bearing and assy back a
slight amount, and it would stay there because of the weight and friction
of the system countering the return of the slave spring (which is fairly
weak and really only designed to return the piston and not the entire throw
out bearing assy)  I noticed that even on the GT6, when I release the
clutch normally, that there is still a slight amount free play before
actually contacting the pressure plate - Not having access to the design
specs/records of these cars I can only speculate being a mechanical
designer myself as to the actual design intent.  At any rate they work, and
it's rather nice not to have to adjust them isn't it!

Barry Schwartz (San Diego) bschwart@pacbell.net

72 V6 Spitfire (daily driver)
70 GT6+ (when I don't drive the Spit)
70 Spitfire (project)
73 Ford Courier (parts hauler, rain vehicle, getting a V6 soon!)

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