Triumph Spitfire 1500 Spigot Brush

[Black Cat]

I'm about to fit a reconditioned  gearbox to the engine, have a new clutch plate and clutch cover, had the flywheel skimmed and ordered a new spigot bush from Moss Brother’s, The part number for the spigot bush on a 1500 is 105143. The spigot bush duly arrived and fitted it onto the main shaft and there is a little play in the fit, I through it should be a relative tight fit.

1.      Am I correct in thinking it should be tight?

2.      I assume as the gearbox is reconditioned that the main shaft would be the correct size or am I wrong is this thinking?

3.      Could the part from Moss Brothers have been incorrectly manufactured?

Any thoughts on what could be wrong?

 

[johny]

I know theyre not a tight fit as the bush is only a support because the gearbox shaft already runs in two bearings inside and also it has no type of external lubrication. However my Vitesse workshop manual (very similar gearbox but not sure if identical) shows a max clearance of 0.316mm between tip and bush with the latter designed to have an ID between 12.795 and 12.813mm.... 

[Pete Lewis]

I would expect a very light clearance   no  rattling good fit its supports the input shaft , any play will invoke clutch judder

The input only has one support bearing ,    give it a  wiggle it will move around within  the single row bearing the main shaft tip bearing only supports the mainshaft  the same as the flywheel  spigot must  support  the   Input shaft 

Pete

 

[johny]

I would argue that the mainshaft, as it runs in two ball race bearings, uses its tip bearing to support the input shaft but either way the bush ordered is used in all gearboxes, 3 and single rail. I suppose part number 150763 (spigot bush for Stag, Sprint and Tr7) could have been supplied incorrectly and is a different size..... 

[Pete Lewis]

Not really the tip isnfar too closentomthe stemwheel bearing to offer much support the spigot takes the support  being more distant and 

Central to the clutch disc trying to  escape when taking up drive 

A modern box has a very short  shaft and often no spigot and probably a double row casette bearing which

   is self supporting compared to our  single row wobbly setup 

Pete

[johny]

I think the next step has to be accurate measurement of the tip (you can usually visually confirm if this is worn) and bush to see if they are within the WSM spec....

[Clive]

As the bearing is fitted into the crank, that is usually a snug, but not tight, fit. It can't be a tight fit on the gearbox input shaft as you would never get the gearbox bolted to thege engine. But not loose. Difficult to describe, but I would not expect to be able to wobble the bush on the shaft if it is sound all the way on.

 

Yes to no3. Entirely possible that a bush is out of tolerance. But before you go down that route you need to check that it is wrong. A digital Vernier caliper is a Very useful addition to a garage, all plastic ones about £4.50 off fleabay, stainless ones about £8. Both accurate but I prefer the stainless one as tougher, and I use it to scribe lines on steel...

[Black Cat]

I need to get a digital caliper, which I will get today and check the outside diameter of the bush. Anybody know what the outside dimension should be for the bush?

[Pete Lewis]

sorry I cant see any clues about the bush other than one wsm just says fit it  !!

pete

 

[johny]

I would guess the crank bore is 3/4" so the bush should be a few thou smaller but no exact figures....