Maybach - Bristol Siddeley

Funny how things pop out of the woodwork when you least expect them.

We were down at Old Oak Common rail depot yesterday (the place is crawling with rail depots, this was First Great Western) looking at a 110V/24V battery discharge tester that we supplied earlier this year. The unit was having problems, but it was battery-related, not the unit!

Anyway, in the workshop was D1015, a diesel loco built in 1963 and now in private ownership. Some huge propshafts were on a pallet, the flanges were about

15" across! and the transmission was out and over in Germany receiving some TLC from its makers, probably either Voith or ZF.

Down below the loco stood a V12 cylinder block. A box nearby had suitably large pistons with forked conrods and big ends that most cylinders would look up to. Naturally such things need to be investigated...

The engine handbook was close by, and it was headed Bristol Siddeley MD650 diesel engine. That set my thoughts running, as I knew of no British-designed diesel of this particular design.

Main bearings were huge roller bearings which gave the first clue, then I looked inside the block and it was entirely fabricated from steel castings, welded up and machined.

Maybach were users of such arrangements in WWII, and I think Mercedes may also have used big rollers on their crankshafts, certainly Heldt and another have drawings of these arrangements in their books and the MD650 confirmed that this was in fact a licence-built Maybach diesel.

We had a fascinating half-hour while waiting for the FGW staff to arrive, looking all inside the block and the pistons and bearings. I think the engine was a spare as the big ends were a little worn and the surface was crumbling away through oil erosion and hydraulic pounding, something we used to see on old truck engines that had passed their prime.

The forked con-rods were interesting, as the shells wore on both the inner surface on the crankshaft and the outer surface where the rods ran. A thin individual shell is also fitted on each of the con-rod pieces, two on the split rod and a single one on the middle rod.

Oil is fed up telescopic tubes to the underside of the pistons for cooling, an interesting arrangement and probably better than sea water which was used for some years on big marine engines.

I didn't see a turbocharger, but I believe it would have been a blown engine, Holset made the crank torsion damper and the bearings were SKF as far as I could see.

We are back down there next week again, so I'll have another look around and take the camera this time to get some pictures.

Peter

-- Peter & Rita Forbes Email Address: snipped-for-privacy@easynet.co.uk Web Pages for Engine Preservation:

formatting link

Reply to
Peter A Forbes
Loading thread data ...

Saurer were another that went in for the roller crank..

The MD series shares something with the old Bentleys, Aston Martin and the Fergie with Standard diesel, the crank is fitted through the end of the engine, the crankcase is like a tunnel, I once "played" with a 16 cylinder model. The rollers on it's crank must of really whistled as IIRC it was rated at about 1800 rpm and the mains are full discs that incorporate the throws. I think the valve gear designer was a wannabe F! designer! Twin over head cam, 4 valves with lever roller followers. Then it had unit injectors as well.

Tom

Reply to
Tom

see

formatting link
for instance.

ISTR seeing a cutaway drawing of these engines years ago, with lots of lightening holes in many of the components.

Cheers Tim

Reply to
Tim Leech

And the Lister JP

Cheers Tim

Reply to
Tim Leech

Rolls Royce Bristol recently gave us some literature including a 1960 Bristol Siddeley Maybach brochure. Some nice photographs of the disc-webbed crankshaft, fork and blade rods, tunnel crankshaft etc. Made in 4,6,8, 12 and 16 cylinders - 346 to 1728 hp.

Paul

-- ____________________________________

Internal Fire, Museum of Power, Wales

formatting link
Internal Fire Museum of Power is a Not-for-Profit company registered in the UK

Reply to
Paul Evans

I suppose the CS and other Lister diesels come in to that category where the crankshaft has to come out lengthways and cannot be dropped out?

Peter

-- Peter & Rita Forbes Email Address: snipped-for-privacy@easynet.co.uk Web Pages for Engine Preservation:

formatting link

Reply to
Peter A Forbes

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.