Hi Ruairidh, Could it have any thing to do with the Spline jamming.
very interesting it is one of those problems you need to know the answer to before you fit the next one.

Good luck
Colin

Location: TINOPAI NZ

Yes but not with a seven. On a rally to the Pyrenees in 2009 a pal with a Pembleton Brooklands tore the centre out of his clutch plate and 3 years ago I did the same with mine. Cured with a new "sprung" clutch plate.
I had a job to dissuade the RAC call centre not to send an inspector to find out why I had lost motive power. Fortunately after 20 minutes of explanation they just sent a recovery truck and I only had to wait one hour...

This looks very much like a fatigue failure,caused by the plate being under stress.
The photo shows no marks on the boss, but is there a possibility that it has been in contact with the flywheel nut? I know its an unlikely long shot, but I can't think of any other reason that would cause such a failure.
J

Location: As far east in Kent as you can get

Charles - totally agree :)

Colin - spline 'very' loose in the gearbox female spline.

With bent cranks, worn and lapped tapers etc it is not surprising that flywheels run out but the chance of a random countering mate seems low In many cases careful scraping may be more beneficial than lapping. .030 run out would not be much near the centre.

Various situations can be imagined but all would lead to problems operating the clutch unless it had exceptional travel, and/or show rub marks on the flywheel. With the wrong front bearings the crank can move excessively but would take little to resist. It is unlikely the hub would be bent, but a major engine fail might have set it crooked in the plate. Considering that in their day many Sevens were run with very worn mains, it is surprising that even more loose rivets, worn splines and damged gearbox nose bearings are not encountered.

Perhaps all was soaked in rust killer acid at some stage.

If the hub is not bent and the splines good do not discard!

Location: Auckland, NZ