Engines Update

Photos by Rob Bishop, Matt Wolstenholme, Emily High

Just to pick up briefly from the last report with some chassis news: ‘while your wheels are important to us, they have been placed in a queue’ - so they remain sat in the yard at Boston Lodge waiting  for a turn on the wheel lathe, behind an NNG16 Garratt (which has a lot of wheels) and a tram from Beamish.  As one chapter enters a state of hiatus, another one begins.

Engine news and a brief history lesson  

KS4415 is of course a Diesel pioneer, and when built was fitted with a 60HP 4 cylinder McLaren- Benz MDB4 engine. The reference code is an acronym; Mclaren Diesel Benz, with the 4 a reference to the number of cylinders. McLaren also produced similar MDB2 & MDB6 models. The MDB4 in KS4415 was replaced in 1945 by an 80HP McLaren MR4 (one of the differences being the use of a Ricardo whirlpool head). The MR4 looked rather derelict when the loco returned to the UK and it was clear that restoring it would take a considerable amount of effort. 

MDB4 engine

MR4 engine

In 2007 another 1945 McLaren egine was acquired, a 90hp M4 Mk2. The M4 engine (which was once part of a standby generator set) was the one which the team had running at the 2014 Superpower weekend. Although of the same vintage the M4 and the MR4 do not appear to have very much (if anything) in common and on stripping the loco it became apparent that the M4 will not fit inside the loco's frames; the sump of the M4 is massive.

M4 Mk2 engine

The narrow, automotive type sump of the MDB4 & MR4 can be appreciated in these views, in comparison with the huge square lump of the M4. Both the MDB4 and the MR4 sumps are a similar shape and the mounting bolts for both engines are in the same location. The photo of the MR4 shows the engine in situ, supported by two steel channels above the floor plate. The big issue with the M4 the amount of original material which needs to be cut away to lower the engine down so that the centre line of the engine is in line with the gearbox.  This includes frame stretchers (which pick up the sub frame) and also a bracket for the brake gear which is hung from the floor plate.

Restoration of the MR4 has been contemplated. However a rumour that Armley Mills Museum in Leeds had an MDB4 in store proved to be true. After some patient negotiation we now have agreed a loan of this engine (which is also in need of restoration). Fitting the MDB4 will allow the locomotive to be restored to its original condition. Exciting stuff!

The MDB4 has now been stripped down. This has revealed damage to both the cylinder block and the crank case that originated from a catastrophic failure of the crankshaft. So of the 3 engines we have, the one that works (M4) does not fit and the MDB4 is in far worse condition than the MR4 it arrived with. But the MDB4 is a very rare beast and the opportunity it provides to return the loco to original condition is compelling, so despite it requiring the most work this is the horse we are now backing.

The crank shaft of the MDB4. 

Drive to the gear train which powers the fuel pump and valve rockers to the RHS. 

Output to the flywheel lying forlornly in the middle  -  this should be on the LH end of the shaft. 

If you are thinking that these minutiae only appeal to blokes in dirty macs, you could well be right. 

Rob Bishop steam cleans the cylinder block while Dave High cleans the sump.

Unsurprisingly the pistons had seized in the cylinder block. 

One has a chunk missing out of it

While three of the pistons yielded readily to a bit of gentle jacking, piston four took more persuasion. 
The photo of the Wolstenholme patent piston puller doing its thing undersells the two hour application of ‘pocket rocket’, sledge hammers, gas and cursing which preceded it.

One of the MDB4's unusual features is the separate casting on the rear of the engine which carries the cam shaft. Removal of the casting from the cylinder block was relatively straightforward, removal of the cam shaft from the casting less so. 
After a good soak in Diesel and with more ‘Pocket Rocket’ to the fore,
 Matty introduces the cam shaft assembly to the Talyllyn Railway wheel press.

The camshaft, casing and followers await restoration

The sump and cylinder block palleted up and ready for dispatch to Cast Iron Welding Services for repair