nasty knock for the ABC at Brooklands

My colleague and I recently took on the responsibility of getting the ABC in the Brooklands Museum into running condition. Unfortunately the engine has a nasty knock under load. Inspection with the barrels off found what we felt was acceptable levels of wear. Following advice from an ABC expert we removed the crown wheel and found significant cross plane movement in the main shaft, which have also cause damage to the crown wheel. Not sure if this is the cause of the knock, however it needs to be fixed. So the engine needs to come out and the gearbox stripped. Will keep the forum informed of progress on getting another ABC back on the road and track.

Sounds like you will be quite busy but let us know if you need any parts, I'm sure the members (who will register at some point) will be able to help
You might also want to post an advert as "wanted" if you end up looking for something specific

Good luck and keep us posted
Gio

Interested in the outcome?
Best of luck with it.

This week we got the engine out, on the bench and the bevel gearbox apart (picture attached). The crown wheel is badly worn through one quarter, this is at least partly attributable to a heavily worn roller on the drive side.

The self aligning roller is a SKF RL7A and whilst it has a standard OD of 2 inchs, its ID is a strange .93inch (as best I can measure on the shaft - I loathed to press it off and destroy the roller completely, before I am sure I can find a suitable replacement). Also the ID looks to be on a steel sleeve which itself is push fitted onto a .75inch OD on the crown wheel shaft. As catalogued the standard RL7 is 2 inch OD / .875 inch ID.

Can you provide any advice what rollers you have on your machine and whether this sleeve is standard?
many thanks Ian

This week we got the gearbox apart. 2nd gears have certainly had a hard life.

There is a lot of play on the clutch end 'rollers within rollers' arrangement, which is allowing the clutch end of the gearbox main shaft to move.

This is certainly contributing to the relative movement between main shaft bevel gear and crown wheel. No sure what we can do about reducing this play? The only option seems to be oversized rollers - appreciate the experience of the forum.

We also found significant rocking and fore-aft movement on the clutch! Has the clutch come loose on the crank. Is this the primary source of our problems. Hopefully we will find out next week.

Aha! Doctor Button's Dispensary for Sick Sopwiths is now open.
(1) The knock you report is almost certainly down to a loose flywheel. I hope the crankshaft keyway isn't badly chewed, or that's another problem. Normally a sort of protruding grub screw, embedded in the flywheel itself, prevents the flywheeel nut from coming undone.
(2) Loose bevel gears don't knock, they only whine! Evidently, the plumbers have had a go at your cross-driveshaft, which should be dia. 0.875" where it fits the self-aligning driveside ballrace (no rollers here). (The ballrace on the other end of this driveshaft is also self-aligning, though smaller. Self-aligners were in vogue in the early 'twenties: typically, their use was unnecessary, and their life and load-capacities were somewhat limited. There is usually sufficient angular compliance on modern deep-groove bearings to accomodate the slight misalignments due to vintage machining tolerances. These Imperial sizes are still available).
You say that your gears are in poor shape: they look as good as new to me, after some of the gears I've seen in recent times! "Don't worry".
A bit of play in the gearbox' front bearing shouldn't bother anyone, certainly not if the rear bearing is good: a few thou more or less engagement of the gear-teeth won't upset them.
(3) Recommended treatment: Renew as many bearings as you can, of course, and perhaps remake the sleeve you mentioned, if it's not a good fit. I'm reserving comment on the flywheel until you've looked at it.
Good luck! Paul.