BMC to Newage Coventry Coupling Plate?

I have been advised that one or two of you technical wizzes may be able to help me.

I recently had my second-hand BMC 2.52 narrowboat engine rebuilt by Peter Atkinson at Farncombe Boathouse on the River Wey. He was THE man for marine BMCs. Unfortunately he died two weeks ago. Luckily for me he had rebuilt the engine and bench tested it before that sad day, so things could have been far worse.

However, the marine gearbox, a Newage Coventry Ser No: 24-14565 is still off the engine. I can't find a type plate on the box, but it is one of the bigger ones about 25 years old [though hardly used, like the engine.]

There is a circular aluminium drive plate that bolts on to the engine flywheel. It has three shaped lugs on it facing back towards the gearbox. On the gearbox shaft is a similar circular plate made of steel, also with shaped lugs projecting forward. It appears to be held in place by a bolt tapped into the end of the splined shaft. The 'shapes' on the lugs don't match up, but the two halves face up together nicely, giving about a quarter of an inch play in rotation.

When Peter stripped the engine he told me that 'rubber biscuits' should have been fitted between the lugs, but they were never there! However, as the engine had only done about 30-40 hours running in its

25 plus years, no real wear had taken place on the lugs.

Having inspected the drive coupling myself, I don't see how loose rubber 'biscuits' could be located on assembly. After all, the coupling is inside the bellhousing, so on assembly you couldn't get at it. But also if the coupling is bolted on to the gearbox shaft, you couldn't get to the flywheel bolts either!

I am now wondering if these two plates, one on the engine, and one on the gearbox shaft are in fact two halves of a coupling assembly that broke apart when Peter took the gearbox off. The only other gearbox drive couplings I have seen were shock-absorbing assemblies that replaced a clutch.

I suspect I will have to find a new coupling from somewhere.

Can any of you stationary engine types shed any light?

Much appreciated.

Tony Haynes nb Dreamcatcher Basinsgtoke Canal Centre

I suggest you identify the gearbox model, I should think Newage/PRM could do that from the serial no. if they're interested enough, otherwise ask someone who works with these things regularly. I assume you're talking about a PRM type hydraulic box, or is it one of the older mechanical boxes? If you can identify the box, or failing that measure up the splines, then talk to R&D or their agents about a drive plate. Yours sounds a bit odd, usually they're a unit which bolts to the engine flywheel, then the gearbox splines are slid into the hub without any means of retention. You may be right that yours fell apart when the gearbox was removed. Some of the older PRM boxes have a spline configuration that's no longer used, you might struggle with them :-(

HTH

Tim

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