D2128 in action - well, sort of!

5th June 2012

We had been working towards having D2128 in operation for the AFRPS Gala weekend on the 12th May and had put a lot of time and money in to achieving it. With barely a week to go the engine was started for the first time - and was hurriedly stopped again as the oil pressure whizzed over to the top stop! There was nothing for it but to strip out the oil pump and check the regulating valve. By the following Friday this had been examined by a Cummins-agent and declared OK, but in the meantime e-mails flying between Andrew and Cummins Technical revealed that there was a second oil pressure relief valve.

Actually, cranking the engine with the relief spring removed indicated over 1 bar! This engine was built in a period where Cummins opted for higher oil pressures than they had hitherto. But using oil pressures over 150psi runs the danger of scouring white metal from mains and big ends, and we know - from past experience(!) - that spin-on filter canisters tend to dismantle themselves at pressures over 300psi. In the end, after adding a thick washer under the relief valve cap and not revving the engine, we could maintain 5-6 bar oil pressure which was bad enough, but enabled us to get on filling the transmission units through the engine-driven charge pumps. That done, and with a couple of minor electrical problems resolved, we should have been all systems go but the transmission simply failed to operate. Nothing we could do on either the Saturday or Sunday of the Gala would persuade the powershift to deliver, though the loco did "take a bow" at Frodingham station on the Saturday.

With the disappointment of the Gala behind us we opened one of the two valve blocks on the side of the powershift and found a defective Neutralling valve and a joint in the wrong way round - clearly someone had tampered with this long ago. The block was duly repaired commercially and we hoped that that would cure it, but no such luck. The Branch Line Society were visiting on June 2nd and had requested D2128, so we weren't giving up, but the complicated nature of the Twin Disc hydraulic layout - 3 external visible valves controlling internal spool valves, plus venturi and other valves hiding away in the depths - and few test points does not make it easy. In the event, on June 2nd Andrew decided to remove temporarily the return spring of the neutralling spool valve, and after some delay and without warning, D2128 suddenly moved backwards.

You might think that was it and we'd be cheering from the roof tops, but of course it wasn't. Firstly because without the return spring, the transmission seemed reluctant to disengage when the control valves were de-energised - but as we experimented further, with the spring in place or not, we found that drive would only last for between 30 and 60 seconds at which point it disappeared and would not re-engage until left for 5 minutes or so with the engine off.

So we are enlisting professional advice. One option is to swap the whole powershift with our other one (earmarked for the "Hunguard") having first had it tested, or delve further into the existing powershift - we'll have to wait and see. There will be a You-tube of D2128 moving under its own power (as proof!) shortly but the Briddon-family internet connection has been unbelievably slow the last couple of days.

**You can see it in operation on the Weekend Rails website.**

Elsewhere:

We squeezed in a day to get over to Telford and proceeded on Sentinel 0-6-0DH "Tom", replacing the fuel pump, throttle linkage, transmission cooler and sundry smaller bits. Andrew is considering moving the loco somewhere nearer home in order to speed up the work.

The transmission cooler on "Libby" has been cleaned, installed and plumbed at Rowsley. The transmission oil reservoir has been remounted on the fuel tank and the small bore converter lines will shortly be re-made to suit. With the weather improving, the remaining casing parts will shortly go for shotblast with a view to completing the paintwork and getting the loco into Peak Rail works traffic.