Weekend Rails

what we do for our kids

Of hot and cold

4th January 2015

2014 went out with rather more of a bang than a whimper as snow suddenly covered over everything. Just before though, I had been up to our favourite battery suppliers and acquired a couple of nice new ones for James, which had “hand-me-downs” from another loco and which frankly weren't up to the task.

Now, I do not usually mention commercial jobs on this blog because it is all about Andrew's collection, but by a simple quirk of fate it fell to one of my bits of paid work to become the first loco into the shed, and that honour should be recognised. On the 1st of January, the fuel pump having been refitted fresh back from overhaul, the loco was fired up, and proceeded to shunt the two wagons out of the way and bring the loco into the shed, so here is the sight of a loco sat inside the shed, or rather compound....

IMG 3715 blog

Just when any others join it from Rowsley remains to be seen.

In the afternoon we swapped to Rowsley, and although Peak Rail management had chosen to change the locks on the shed just before Christmas and neglected to issue fresh keys, thus denying us access to our equipment, or washing/toilet facilities, we fitted the new batteries to James, filled the cooling system with fresh anti-freeze/coolant and fired it up. Satisfied that all was well and that the coolant pump was not leaking, we went over to 14 901 and continued removing parts of the previous coolant pipework that required re-arrangement.

We had always known that the cooling system on this loco suffers from poor de-aeration and is unpressurised – it was only on that day we discovered that in part this was due to the fact that a small bore pipe connected to the filler elbow and we had assumed previously was an air bleed from lower down, was in fact a drain which effectively prevented any pressure being generated, now matter how tight the filing cap was screwed down.

Andrew started with pain and deafness in one ear, which may well be a recurrence of an infection, so although we had planned to go to Scunthorpe on Saturday, he was up late, bunged up with cold in addition and so we scrubbed the trip, spending what was left of the day back at Rowsley. Some weeks ago we cut the baseplate in half that fits over the Voith oil cooler in 14 901. Originally fitted by Barclays utilising the exhauster brackets it had probably carried a couple of compressors for train air purposes, but the single Broom&Wade on 14 901 today has proven more than adequate (after all, it kept D9525 going as well back in 2010) even if it is showing a little wear by passing oil into the air system. So the part of the plate that compressor is not sat on was cut away, and we extracted the last retaining bolts and lifted it out. We can now access the pipes and flanges around the socking great cooler that straddles the loco from one side frame to another and passes heat from the Voith to the engine coolant for dissipation.

As an aside, it always fascinates me that engineers seldom seem to consider that a heat exchanger will always pass heat from the hotter to the colder, and that in their mind's eye the unit that has the higher heat rejection at full chat will therefore always be the hotter. I was to be fair, niaive like that too, and in 1982 conducted tests on a Vanguard loco on the Andover-Ludgershall line which was operated by the MoD Army Railways. I had taken with me a set of thermocouples, which connected, via rotary switching unit, to a single device which then told me what temperature the thermocouple it was connected to was experiencing. I had neglected to clarify which pipe on the torque converter was which (hey, I was young) so as soon as I saw a differential between the theromocouple on one converter fluid pipe to another, assumed that it was the out one and the other was the returning cooled fluid. This I established while doing miscellaneous shunting in the yard, but the main show of the day was to attempt to take a couple of hundred tons down the long slope from Ludgerhall to Andover.

With the train formed and ready to roll, all went well until half a mile or so when we cleared a run-round loop which marked the summit of the line at Faberstown. The driver opened up, the speed rose to about 15-20mph, and the temperatures I was monitoring rose dramatically. The MoD Railway Officer was shouting at me, demanding to know why we couldn't travel at this speed, downhill, without everything overheating and I was somewhat stunned to see the fluid temperature in what I had thought to be the cooled, return line climb and pass the temperature in what I had thought to be the hot, output line. In my panicking mind I thought – had by some freaky circumstance the fluid started to flow the other way round?

In a short space of time the temperature hit the shutdown level, the protective switch opened, the engine shutdown (sending the temperatures even higher as the cooling system stopped), brakes applied, and we sat and talked for a few minutes until it naturally cooled off sufficiently for the switch to close and thus be able to restart the engine, which brought the temperatures down more rapidly.

We then set off and accelerated, and sure enough after a half mile or so, everything shutdown again. And we repeated this 5 or 6 times before finally making it to the level at the former Junction, into the platform at Andover, run round and set off back. The return run, though slower, was under power all the way and the temperatures stayed within limits and without shutdown.

The moral of all this? In essence there were two (apart from that I should have done my homework beforehand and known which pipe was which). Firstly, with the locomotive not doing much work, the engine was heating up to a “working temperature” (it has thermostats designed to make it do so) but as the transmission was doing next to nothing, it remained cooler than the engine so the heat exchanger proceeded to take engine heat and warm the converter up with it, which slows down the engine warm-up (bad news for fuel efficiency and general engine wear) and heats the converter for no real benefit. So what I had deduced was the converter fluid outlet pipe because it was hotter than the other (as I had been taught that the converter was cooled by the engine) was in fact the other way round. Secondly, the effect of running a converter downhill had been a known issue for years – my boss recounted riding a Portuguese Railways Sentinel on a local train (they were bought as shunters but used more extensively) and it had suffered from similar problems. I was to learn much more about this later, but at the time it was explained by our Service Department that recommended practice to put the loco brakes on and “convert a downhill into an uphill”. I kid you not, that was the official solution, without regard to the cost of fuel and brake blocks.

We were back in to Rowsley today, fitted the first of the new pipes to the cooling system and removed the last of the rubbish ones, including the discovery of a hitherto un-noticed restriction where the pipe drops to a smaller diameter for no good purpose, and I have passed Andrew for his consideration a brand new radiator pressure cap/neck for possible inclusion. As we remarked this evening, with better flow, full de-aeration and pressurisation, we may have to put the thermostats back in or it won't warm up at all!

More in this category: Of being stuck in 2nd gear »

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