Brian Schlorff wrote:
>I always insist on installing a heavier pin to prevent sleeve rotation.
>Pete's theory
>certainly makes sense, but let me present another THEORETICAL viewpoint.
>
>When engaged (foot off the pedal), the throwout bearing is just riding
>against the
>face of the fingers of a diaphram clutch. Witness this by the fact that
>if you try to
>push the lever back by hand, it does not move - therefore there is no
>clearance. If
>you push forward, and then back, you will hear the "clink" of the throwout
>contacting
>the fingers. This riding pressure occurs due to force applied by a spring
>that is
>located behind the piston in the slave cylinder. The throwout bearing spins
>constantly due to this light contact. Since there is only an
>insignificant load on
>the bearing, wear in the bearing as a result is not a factor. However,
>friction is
>present in the bearing, and drag also occurs due to the heavy grease
>inside the
>bearing. This drag has the effect of wanting to spin the sleeve. Going
>down the
>highway, inertia will bring the speed of the throwout close to the speed
>of the
>engine. If the resultant drag is greater than the friction between the
>sleeve and the
>pilot on the trans, the sleeve will also spin constantly. Again, under
>light loading,
>this may or may not be a problem.
I always understood that there was supposed to a certain amount of
"freeplay" between the pressure plate and the TO bearing when the clutch
was engaged. I guess we're talking about Triumphs, though, huh!?? I'll
have to concede defeat on this one!
>Without side-by-side testing, I can't really say one way or the other
>which would show
>the least wear. The engineers at Triumph certainly thought this important
>enough to
>specify an extra machining step to drill that hole for the pin, and we all
>know how
>cheap they were! I suspect the reason that the hole is omitted on the new
>sleeves is
>that the extra drilling operation added too much to the cost of a low volume
>production run.
A slight and interesting correction, Brian: The new sleeve that I ordered
from Moss Motors AND the new "custom" sleeve supplied with the Toyota TO
bearing both had the hold drilled where this pin would go. But, neither
had the pin.
Thank you for your input!
Pete Chadwell
1973 TR6
|