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 about15" 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 & Rita Forbes Email Address: firstname.lastname@example.org Web Pages for Engine Preservation: