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Re: How a clutch works

To: Triumphs <triumphs@autox.team.net>
Subject: Re: How a clutch works
From: "Power British Performance Parts, Inc." <britcars@powerbritish.com>
Date: Fri, 28 May 1999 18:45:37 -0400
References: <A856B51E4CB2D211954B00A0C924E48B05E312@SEWSCOMSRVNT01>
Stinocher, Bryan D. wrote:

> Listers,
>
> I am basically an ignorant cuss when it comes to cars. I can figure a lot of
> things out (hence, my attempt to restore my car), but for the life of me I
> can't figure out how the clutch works. I rebuilt everything (yes, it is in
> correctly), but how does it work?
>
> You press on the clutch pedal. It is hydraulically activated at the clutch
> master cylinder and pushes on the clutch shaft. This moves the fork, which
> pushes the TOB into the clutch housing (for lack of a better term) springs.
> What happens from there? I am assuming that somehow the clutch disc is then
> engaged/disengaged from the flywheel, and this allows you to shift. But in
> looking at the whole assy, you can have the mainshaft going in and out of
> the clutch disc (it seems that the "gearing" on both the mainshaft and the
> clutch disc would get boogered up quickly that way).
>
> Anyway, I'm not able to imagine this, and would like to. Any gurus out there
> that can explain in simple terms what happens?
>
> Thanks.
> Bryan Stinocher
> bdstinocher@sewsus.com
> 502-782-7397  xt 2284
> 1968 TR250 CD 5853 L

Bryan,

Clutch assemblies consist of the flywheel, the clutch cover plate which is 
bolted to
the flywheel, the clutch disk which sits between the flywheel and cover, and the
throwout bearing.  A clutch is basically a big vise that rotates.  When you 
press the
throwout bearing into the clutch assembly, it acts on a diaphragm spring inside 
the
clutch cover (older cars including TR-2/4 used a slightly different 
arrangement, but
the theory is similar).  The spring acts as a lever, with a fulcrum inside the 
clutch
cover.  Pushing the center of the spring in forces the outside of the spring 
out.
This pulls a large heavy ring called the pressure plate, which is inside the 
clutch
cover, away from the clutch disk facing.  The facing is a friction material 
similar to
brake lining.  Now that clearance exists between the pressure plate and the 
clutch
disk, the disk is free to rotate independently from the flywheel and cover.  
When you
release the clutch or allow the throwout to spring back, the force of the spring
acting on the pressure plate clamps the disk between the flywheel and the 
pressure
plate/cover assembly.  Friction transmits the engine's torque from the flywheel 
to the
clutch disk, which is connected to the transmission's input shaft by means of a
spline.  Just picture a vise and trying to turn something clamped inside.  Now
gradually loosen the vise and your object will begin to spin.  Loosen it all 
the way
and it will spin freely, just like your clutch does when you press on the pedal.


Cheers!



Brian Schlorff    '61 TR-4     '64 TR-4     '72 TR-6     '79 Spit
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