Weekend Rails

what we do for our kids

Of fans

2nd June 2013

Well of course last Monday was a Bank Holiday and so we went back to Rowsley, this time armed with another drum of 15w/40 for the fan system on 14 901. It only took a little more to bring the oil levels into the inspection windows on the side of the reservoir and, with some trepidation, and after Andrew had bled the pump through (the last shutdown, in April, had been by shutting the cock on the delivery pipe) we fired 14 901 up again. After a few seconds of prevarication it condescended to fire, but hunted somewhat until Andrew had a further go at bleeding the pump (which, being a hydraulically governed one, can be a swine if any air gets trapped in it).

It was apparent almost immediately that the fan was turning, but the new program waits 5 minutes after a "cold" start and when the by-pass valve closed and the oil routed entirely to the motor, it accelerated with a very audible snatch and the air flow above the fan was significant - if our memories are correct, transferring more air than it used to do. Two things stopped us going further - firstly I had forgotten to dig out the microbore test gauge, so we had no idea what pressure the system was operating at, and secondly we found a pool of oil forming underneath - we had a leak.

The delivery hose from the pump was a new one we fitted in 2008 or thereabouts, replacing a Heath-Robinson-ish combination dating back to its days in Scotland. However, Andrew remembered that he had difficulty getting it to seal then, and this time, it simply wasn't going to oblige. We shut it down and called it a day.

Not long after we were joined by Paul Martin and his father. Paul is involved with the Swindon & Cricklade and, I discovered, a regular reader of this blog, to the extent of being able to quote the odd bit. He has challenged me to use the phrase "State of the Ark" at some point - well, not this week Paul, but it has been filed in 'pending'...

Anyway, they had called to collect an exhauster and after we'd unloaded it from the VBA, we did the usual tour of the collection before passing them to the tender mercies of the HST.

Oh: as I see some people actually come to this site looking for news of Dr Ben Riley may I announce that Heanors collected his brake van from Shackerstone on Friday and it is now at Rowsley.

This weekend was always going to be a bit awkward - for Andrew had a test run to oversee on the mainline network so had to leave after lunch Saturday and arrive back in the early hours of Sunday. On Saturday morning, therefore, we popped in to Rowsley with a new hose, and did a hurried replacement of the defective one. This time I had the microbore gauge so we started the loco up with the gauge on the test point and I went forward to see what was happening. You may recall that the hoses are 2-wire, rated for upwards of 180bar (2700psi for old fogies like me). With the by-pass closed, and the fan therefore taking full pressure, I was disappointed to see it was only registering 10-15 bar, and even when accelerated it would only peak at around 60bar momentarily. Clearly the hoses are over-spec'd and a single wire would probably have done. We could not resist holding a piece of rag over the fan grille and letting go - it rose 10-15 feet in the air before drifting to one side and returning to earth. Andrew also wanted to adjust the pressure relief valve to prevent the fan over-speeding (we have been told it must not exceed 2100rpm) but as we had not brought the hand-tacho this time, this was left and we returned home.

Andrew got back as dawn broke over the Derbyshire hills and crashed out, surfacing again about noon. Just as we were about to set off we had a phone call that our next visitors, Dave Fisher and his wife, were awaiting us. Dave and Andrew have worked together professionally and he owns a Ruston 0-6-0 - we fired up 14 901 for him and showed him around some of the others.

Andrew had promised another Dave, Timperley, the owner of the former NCB/WHR tamper on the Derbyshire Dales railway, that he would assist him in replacing the wheel motor that had been seized. Today had been nominated and Andrew left me with 901 while he swung the motor and brake parts up into place. Having remembered to pick up the hand-tacho, I clambered up on 901 and stuck a reflective target on top of the fan hub for the optical sensor to see. Getting on to 901's casing tops is something Swindon never saw the need for. It is a scramble which, with my advancing years, I look forward to with less and less enthusiasm, actually the getting down being worse than up, as from that height the running plate looks unpleasantly narrow. The solution, which I had not bothered with before, was simple - I headed over to the VBA, opened up and collected one of the sets of steps. These steps - ladders really - came off a Steelman loco of 1967, scrapped during the 1990s, and gave access up the side of the fuel tank to the filler. With one lashed to the handrail I could climb up after starting and see what the fan was doing.

In the by-passed state, as I have said, some of the oil causes the fan to spin, and although Andrew thinks you could easily stop the blades rotating in this condition I am not so sure. The fan is rotating at about 280rpm. Its momentum, given it is a nice cast aluminium one (and slightly eccentric it spins true but the hole for the motor shaft is slightly off the hub centre), would I suspect chop up a stick quite effectively. Once the by-pass closed however the fan sped up to 820rpm with the engine idle showing 650. That would suggest that the fan is running at about 1.25 x engine speed, and as the pump and motor are fixed displacements, that relationship, bar losses, should remain throughout the rev range. But later, when Andrew was back, he accelerated the engine to 1400rpm and the fan speed only got up to 1200-1300. It may be that the pressure relief was opening and restricting pressure (I cannot see the pressure gauge while on top of the casings with the tacho) or it may be that something else is restricting the flow - we shall investigate more later. In fact, despite my adding a reflective spot, the tacho worked perfectly well simply by using the blades of the fan, and dividing the resultant answer by 8.

Sitting on top of the casings with the hand tacho had other unforeseen aspects - not only was I blasted with a considerable woosh of air (think wind-tunnel) but that stream was picking up bits of material - paint flakes, grit, etc and launching them upwards until I began to think my handsome, mature countenance was being shot-blasted.

Later on, once the steamer had returned to shed, we fired Tom up and headed up the access track. Andrew flicked the "deadmans (partial) isolate" switch and I towed the 14 back with Tom without the deadmans interfering. Time to ask for that test run.

Finally, I have added a link to Andy Chapman's blog on his restoration of Sentinel steamer 7109 down on the revived S&D at Midsomer Norton, and he has to Weekend Rails. Welcome to any of his readers that have found their way here, and I commend you to sample his progress reports by clicking HERE.

 
 

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