Weekend Rails

what we do for our kids

Of air, locks and engines

23rd September 2012

This has been one of those weeks where it has gone way beyond the "Weekend" of the title. On Monday I went off to collect "Pluto's" fuel pump from our tame fuel pump expert. Later in the day I got a call from the shotblasters to say that "Libby's" casing parts were ready, so I hired a pick-up for Thursday. On Tuesday I popped in to the fabricators to collect the 'power bulge' that will go over the exhauster on D2128. Finally on Friday I touched base with a company who have the tackle to press the louvres in the doors for the said 03 - they don't seem to think it much of a problem and will get back to me shortly. Given that in between I have received back Steph's Micra after 8 days in the bodyshop for a job that was only supposed to take two and you may well wonder whether I have managed much (profitable) work this week and you're not the only one.

Andrew was away again on Saturday but after some essential work at and around the Briddon Country Pile I headed in to Rowsley to continue on "Tom". It was a very pleasant autumnal day, with just the air for fine smoke effects.

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First task was to give the batteries a boost - while they were on I then set about nipping up the flange at the rear of the converter cooler to stop the oil leak and ease the clutch cylinder operating arm along the splined shaft so that it lined up with the axis of the air cylinder destined to operate it. I don't think this arm is actually original to the loco, or where it has come from. We had already sawed off a lug which fouled the ballast block underneath and now I found that the thickness of the arm where the pin must pass through is actually greater than the slot in the jaw of the cylinder it is to join with. Ah well. I checked that the gearbox was free to operate and having given the batteries a reasonable boost, fired the engine up. I should have added that on an earlier late afternoon sojourn in to Rowsley Andrew had found a loose connection on the compressor delivery line that suggested a chance for the compressor after all. And sure enough, air pressure built quite rapidly, and after it had reached 75-80psi I found that, surprisingly, the gearchange pneumatics appear to function - after a fashion.

When Rolls-Royce designed the Sentinel in the late 1950s they took advice from loco operators and were assured that an essential feature for a shunting loco was the ability to select (say) reverse while going forwards, so that a change of direction was instant on coming to rest. That was possible on a steam loco, but given that large final drive gearbox that needs the selector shaft to be moved to disengage one gear and engage the other, not feasible. But Rolls' did the next best thing and came up with a "pre-selective" gearchange which meant you could play with the forward/reverse control as much as you liked as you went along, but if, as you came to rest, you had the opposite direction selected, you could merely press the throttle lever against a spring stop and the pneumatics automatically took out the clutch, moved the gears over and re-engaged the clutch in less time than it takes to type it. It was a cleverly worked out sequence, and if the so-and-sos had thought to put in a test point or some other aid, successive fitters sent out to fault-find a recalcitrant Sentinel would have thanked them for it. My old friend Albert for example, went in to rectify a loco that had baffled fitters for days, and was lucky to discover that a pipe that formed the exhaust from one valve had been accidentally flattened, and, unable to vent, had gummed up the entire system with symptoms that suggested something else entirely. When it works, it is a good system, but nowadays its components are mostly obsolete and nobody has an arrangement like it. Even Thomas Hills, as successors and latterday champions of all things Sentinel, went for simpler pneumatics.

So as I say, as I operated the throttle lever the gearbox moved to and fro and the clutch cylinder moved up and down, but with the accompaniment of various leaking noises that suggested that all is not entirely well, and sufficient that air pressure fell back noticeably, more than the operations I was carrying out should have required. The straight air brake too, was working, with a lot of noises reminiscent of dodgy plumbing, but left in lap the brake pressure needle fell steadily, though whether this was a leaky brake valve, or brake cylinder seal, I had not time to find out. Meanwhile under the casings the flange I had nipped up appeared to have done the trick, but I could still see a steady drip of oil on to the track from the ballast block under the converter. That rather depressing discovery brought my day to a close, though I did take the opportunity, as the Austerity came back to shed, to fire up the Drewry for a few minutes to warm things through and check that the batteries were OK.

Andrew re-appeared Sunday morning and after loading the van, we set off for Scunthorpe. My first task was to adjust the cover for the exhauster and then drill and tap its fixings to the casing frame of D2128. Although the exhauster is mostly within the casing line, the filter bowl at the back (and the oil filler when we have time to swap it from the inside to the out), stick outside and required a bulge to make best use of the sawn-off door reallocated there. Later on I will manufacture a suitable hinged door and vent arrangement that will enable the operator check the exhauster oil level pump grease into the nipples for the hornguides.

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Andrew meanwhile had started reassembling the injectors into Beverley's engine, followed by the rocker boxes and other lumps. He had asked me to start on the casing door locks for Bev. When we first started on these Hudswell Clarkes, the budget locks that secured the doors were obsolete and had mostly disintegrated from wear and corrosion, so I designed a replacement using a currently manufactured lock and a packer. Both the (departed) "Claire" and "Grace" have benefited, and we had a batch of parts left over for Bev, which Andrew had found while clearing the garage at Briddon Towers. So I started on a few doors, grinding off the old rivets, knocking off the locks and shims, grinding it smooth then marking out and drilling for the new parts.

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Later in the afternoon I re-measured the cover required for the compressor on D2128. I had done this a month or two ago but apart from difficulty reading my own scribbles it had been a rather ungainly arrangement intent on preserving the lower budget lock position on the remains of the casing door. The new plan cuts the door off evenly and affords a simpler, straightforward box with access door therein.

During the day and on our way back we discussed "Pluto". I had carried out investigations over the last few weeks about an alternative filter arrangement, but there does not appear to be a market for 'automotive' filters at pressures higher than automotive applications yet well below hydraulic ones. The cause of filter failure is now quite clear - the fuel pump had become so gummed up (what went through we don't know but the DVLR had let the fuel level run low so maybe next year we should flush the tank out) that the valves inside were stuck, making life hard for the governor and causing the engine to run straight up to high rpm on starting. Various arguments about alternative unloading valves and layouts were voiced, and the consensus appears to be to lower the setting of our hydraulic pressure relief valve but instead of routing the excess as a by-pass, return it to sump and so retain the Fleetguard filter (plus carry out a long-planned up-grade of the fuel filters to later standards, possibly borrowing "Libby's" for quickness).

Finally: The spambot that I found dumping rubbish comments on one entry in Weekend Rails finally gave up trying there but managed to find another way in in the last couple of days, so I have sadly closed off the Comments sections here. As so few people actually use it, this is no real loss, but I resent being forced to abandon it by the selfish, anti-social actions of those who seem to think that everybody in the world wants to buy their Viagra.

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