Weekend Rails

what we do for our kids

Of springs and things

26th August 2013

There were a couple of things I neglected to mention in last week's blog. The first is that I am now on the Minor Railways Extended Trunk Dialling system and can be reached on 056 2026 – Andrew will be on shortly, but first I must drill a hole through the wall to get a further phone wire through!

The second was that over at Scunthorpe, the AFRPS members had taken “Tom” out on a tour of the site with the sole purpose of getting the power unit heated up in a manner that we had been unable to do at Peak Rail, in order to try and get the rings freed off if that was the cause of the engine's tendency to breathe. In the latter, I gather, they think there is a significant improvement, and although the exhaust is still a little smokey, that may settle when we get time to put new injectors in.

But, and there always has to be a “but”, towards the end of the operation, Tom's front left wheel left the track again, and this time on a largely straight section of line. Obviously this was rather concerning. Although the loco never left the rails at Peak Rail, nor so far as we are aware, at any time when it was being dragged around at Telford. But it did derail just as it was leaving Rutland and has done so twice now at Scunthorpe. Andrew, who has done a de-railing study course as part of his employment with a train leasing company, decided that he would investigate the cause while I spent my time on the 03. He anticipated he was going to find a seized spring pillar pin, or maybe an axlebox stuck in the hornguides, both of which are rare in a Sentinel whose ability to tread safely over tracks that would give the average mainline p/way engineer heart failure is legendary. (Of course, this was because Sentinel were prevented from joining what was then LAMA (the Locomotive and Allied Manufacturers Association) for many years because of what LAMA members felt were ungentlemanly sales practices (demo locos). Thus Sentinel, instead of slavishly copying LAMA recommended practices, set about designing a chassis and running gear from first principles – Sentinel side rods thus had spherical bearings while LAMA members stuck to top-hat bushes....

Anyway Andrew was playing taxi on Saturday so it was Sunday before he got home and we set off for Scunny. Toby and Stephen were already there and we started by taking a good look at the axleboxes. According to the book, there should be three-quarters of an inch clearance at top and bottom of the axleboxes, and in the book, a simple side-on drawing makes this look simple. .Looked at on the real loco, with flycranks and side rods obstructing the view, it is not quite so easy to get any sort of measuring tool in to check.

What did become apparent, however, was that there was little enough engagement with the spring pillar pin and the bottom of the spring on the front left axlebox and moving the loco up and down demonstrated that the axlebox moved happily up and down in the hornguides, that the spring pillar too was well greased and free but that there just wasn't any significant weight on the axle. What we did find, however, was a large cold chisel jammed behind the front left spring and the frame side, so this has been added to our tool box.

When Sentinel first developed the 0-6-0, they used a 12 leaf spring. That 0-6-0 was a 200hp steamer, and the first 0-6-0DH (Sentinel 10032 “Chris Moody” sadly no longer with us) was built on a steamer chassis, and is the reason why Sentinel 0-6-0s drive on the middle axle. Later, Sentinel were unhappy about the spring breakages on 0-6-0s and started fitting a 14 leaf spring, for which different length pillar pins and spring shackles are required. Up to now, my plans to go do some work on the 03 (viz change the drive pulley for the charge pumps) had been put to one side as Andrew declared that he had scoured the cab and could not find the pulley. Thus I was on hand to think through the situation and call for a detailed check of what length pins and shackle bolts we had. From the dimensions, and comparing to the drawings subsequently at home, it seems like we might have a loco where some clever dick has put two 12 leaf shackle pins on the leading side of the middle springs, although Tom as 14 leaf springs throughout.

In an attempt to try to get more weight on the front spring, Andrew decided to slacken the shackle bolts on the left side middle, so dug out the requisite spanner from the van. Although 1.5” BSWhit, the modern nylocs fitted do not comply with Sir James' spanner-size formula and in the end Andrew found the best fit was a 2.25” A/F Lion Brand. A big old traditional forged open ended spanner, some 20” long.

But starting the big nuts is not like car maintenance, and eventually I looked on as with a 6ft length of stout vacuum pipe slotted over the spanner, these three stout lads applied significant force. Ping! Suddenly all 3 were on the floor: actually two were on top of Stephen. They picked themselves up confident that the nut had turned.

“No, its slipped” says one

“No, the spanner's broke,” said another, and sure enough the Lion has roared its last and a fresh metal crack, a sixteenth of an inch at its widest, now starts from the corner of the flats. We could, at a pinch, force it back shut and weld it up, but would we ever trust it again?

On an 0-4-0, if one end of the loco is low, you wind up the spring shackles of the other end to force it to take more weight, but with an 0-6-0, everything starts pivoting over the middle axle. Thus with around 50mm difference in buffer beam clearance front to rear, I think we need to wind up the rear shackles to get it to transfer more weight to the front, but it would help if first we had all the right, correct and compatible bits to go with the springs. If all else fails I'll have to get some made – I have known people fabricate them from machined eyes and threaded bar welded together, but sooner or later they'll snap.

I managed to escape to the 03 for a while. Sure enough, the pulley was in a box in the cab, but of the 2 belts needed to go with it only one was still present, and as it was late in the afternoon it seemed pointless squeezing under the front to make a start. Instead I squatted under the desk, and played with the position of the third limit switch, which, if you've been studying this blog intently, you might recall wasn't quite running properly against the cam. The switch is for the moment clamped tight in its new position with one bolt and it won't take long to back-mark and drill further holes to locate it permanently.

Monday, and once Andrew had surfaced we headed down to Rowsley. With me I had an oil pressure switch, a solid-state AVR for the dynamo, a coolant temperature gauge to go with the sender fitted last week and an LED to give us an oil pressure warning in the cab. Andrew was planning to get back on to painting and preparing Libby for reassembly of casings, etc. But he was willing first to head into the bowels of Ashdown and remove the old temperature gauge and aid fitting its replacement and the LED from the inside while I held them in the cab panel. There was also a long length of mains 2-wire running along the inside of the casing, heading from the batteries to the panel, but not connected at either. This we removed between us.

Andrew is quite adamant that the monstrous box on the side of Ashdown must go, and that therefore the exhauster must relocate inside the old casing line. After all, Hudswell did it on the versions built for BR and anything Mr Hudswell and Mr Clarke can do, Messrs Briddon and Briddon can match or surpass. And when you get down to it this should be possible. At present the exhauster is driven by 3 ludicrously long belts which connect the compressor on the far side and the exhauster on this with the crank at the bottom. In so doing the belts are scraping the tube that contains the fan shaft, and the wrap-around at the crank, which dictates how much power can be transferred, is uncomfortably low. Ironically, despite the size of the exhauster, the amount of power it requires is quite small, and 3 C belts are overkill. So a new bracket that carries the dynamo at the bottom and the exhauster above, and utilising the 2 grooves that run from crank at present only to the fan, will in due course be created.

In the meantime, I had an AVR to change and the old electro-mechanical control box was mounted at the front left of the old casings, where before that box was added, it was readily accessible. Now to get at it one must remove the rubber suction hose from the exhauster, insinuate oneself between Gardner and exhauster tower, manoeuvre around a copper pipe and work with one's head in close proximity to drive belts, coolant pipes and casing struts with one's bum on the Garner timing case and legs twisted around pieces of sharp edged RSJs. Having achieved the impossible of getting in, one then either drops some vital part or realises that an essential tool is still in the van and reversing the process will be essential in order to proceed. All the parts at this end of the loco have not seen such a things as a steam cleaner in many years, and were covered in black, oily sludge, though thanks to the on-going contact with parts of my anatomy, are considerably cleaner tonight. But if progress is slow and tortuous, it can be achieved and the old control box has been stripped out, the new AVR enclosure installed and connected to the dynamo and the oil pressure switch that trips the relay and brings in the field on this particular incarnation of the circuit board. All being well tomorrow, I can work in the comparative comfort balancing on the fluid coupling as I cable up the panel end of the shebang.

Now, I was expecting that this edition of the blog would be appearing first in the new-look version of Weekend Rails. But sadly I had not anticipated the attention of some little oik who succeeded in loading an unwanted file into Andrew's site during the week and which damaged part of it, preventing me from accessing. Thus my site hoster has had to switch his time to repairing the damage on ABL rather than finishing the upgrade to WR. No pictures this week – one because I've been too hot and dirty to take any, and two to ensure that when the WR upgrade resumes, this entry will not take long to transfer. Normal service will be resumed next week.


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