[TR] Triumphs Digest, Vol 16, Issue 39

[aribert neumann]

>
> Dave:   Thank you for your thoughtfull reply!   The groove in the main
> shaft that locates the split collars is not as bad as it looks - most of
> the taper turns out to be material worn off of the split collars and welded
> onto the main shaft.  I have cleaned up the groove, to the same dimesion as
> the groove on the new main shaft I bought (that has the oversize issues)
> and that took out all the taper.



> The concern I still have is *how to prevent the split collars from
> spinning in the future* to prevent this from happening again - either on
> the old shaft or on a new shaft.   The split collars are not bearings or
> bushings and if they keep spinning in the future I'll see the same problem.
>
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> From: DAVID MASSEY <dave1massey at cs.com>
> To: "aribertn at gmail.com" <aribertn at gmail.com>, "triumphs at autox.team.net" <
> triumphs at autox.team.net>
> Cc:
> Bcc:
> Date: Mon, 20 Mar 2023 12:39:48 +0000 (UTC)
> Subject: Re: [TR] Calling anyone with transmission rebuilding experience -
> second attempt, part 1
> It has been many years (< 25, I think) but I once rebuilt a TR6
> transmission with a used mainshaft that had similar wear on a shoulder like
> that.  There was a thrust washer that fitted up against shoulder.  A few
> years later I was rebuilding it again.  The thrust washer had broken into
> parts.  My solution was to buy a new mainshaft (that is a story in itself)
> along with some other parts.  25 years later that part is still soldering
> on.  (I had to rebuild again for layshaft issues but that's unrelated)
>
> I would be very reluctant to reuse that mainshaft.  The raised ridge is
> not what worries me it is the fact that the edge of the grove is not square
> and the thrust applied by the helical gears will point load the split
> collars and they will fail again.  The TR6 transmission si probably
> different but the basic design is similar and the force loading is also
> similar.  Helical gears are sued to keep tooth noise down but the fact that
> they are wound in a helical manner around the axis means the forces applied
> to the gears is at an angle to that axis.  Part of that force is used to
> rotate the shaft but the other is applied to the bearings at either end of
> the transmission meaning the split collars in your case will take up that
> force as an interface between the shaft and the bearing inner race.  I
> don't have enough experience to say whether the transmission will last a
> week, month, year or 10 years with that shaft but I would have much more
> confidence in a new, quality shaft.
>
> Dave
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> ---------- Forwarded message ----------
> From: DAVID MASSEY <dave1massey at cs.com>
> To: "aribertn at gmail.com" <aribertn at gmail.com>, "triumphs at autox.team.net" <
> triumphs at autox.team.net>
> Cc:
> Bcc:
> Date: Mon, 20 Mar 2023 13:30:54 +0000 (UTC)
> Subject: Re: [TR] Calling anyone with transmission rebuilding experience -
> 2nd attempt, part2
> That looks like the heat treated, hardened  surface is starting to break
> up.  That is what happened to my layshaft.  Another reason to abandon that
> mainshaft.  If you have an alternate bearing combination that doesn't relay
> on that surface for the bearing rollers then the hardened surface is no
> longer critical.  But this is above my pay grade.
>
> BTW, I misinterpreted one of your previous photos.  The split washers
> transfer the lateral forces from the synchro hub to the mainshaft but the
> end result is the same, with a compromised groove surface like that the
> split collars will fail prematurely.   If you open the grove to clean up
> the shoulder will the split washers stay in place?  If they fall out you
> have serious problems.  Even if they stay in place will it increase
> backlash?  Can you get oversized split collars?  Make shims?  All this is
> above my pay grade.
>
> Dave
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