Weekend Rails

what we do for our kids

Of spherilastik magic

20th May 2018

I know, I shouldn't moan about the sun after all the rain and snow we've had, but I got this dashcam for Christmas and the self-adhesive pad that is supposed to hold it to the windscreen goes soft after an hour or so parked in direct sunshine and I come back to find the camera ready to take close-ups of the passenger side floor. I'm getting tired of trying to get it to stick again and prodding the cable back into the trim around the screen. Another fall or two and it's out with the epoxy.

So, I took a slightly circumventory route last Monday to avoid the traffic in Bakewell: it only added a mile and got me to Tunstead for 09.00 to find Andy H, Paul, Alan, Liam and Jack were there or arrived shortly after. I had brought up another pallet of parts which Alan duly unloaded, and with subtle comments from Pete C that we were in the spotlight and must be seen to make progress, we made yet another effort to clean that RF25 gearbox.

That gearbox has been a swine. It was pressure-washed before it left Darley. Me, Liam and Jack have spent most of a day in the quarry workshops with scrapers and de-greasant but still it looked as though it hadn't been cleaned at all. Thus first real task of the day was to attack it once again with scrapers, wire brushes and de-greaser and after what must have been an hour or so take the decision to paint over anything remaining(!). Out came the paint brushes and red oxide primer and the gearbox duly became presentable.


RS8 has a wheelbase of 5 feet, quite short for a shunter nowadays but I suppose common in the days when the plain 9 foot wheelbase timber bodied wagon held sway. Anyway, we rolled the other wheelset up, chocked it at 5 feet from the drive axle, and after lunch set about putting the frame onto the axles.

I had, of course, checked that the gearbox drive axle was the right way round (fortunately I can recognise the right hand side by the replacement crankpin) and that the driven axle was also in the correct orientation.You do feel such a fool when you come to present side rods to crankpins and find that the second side is 180 degres adrift! Thus in theory, it should have been a doddle, though I was a little apprehensive since I am more used to doing this with the finesse of the Mattersons, not the clumsiness of an old electro-mechanical crane. In theory, the frame being slightly out of level ought to make things easier, enabling one pair of axleboxes to be guided in before the second pair contact, but RS8's frame is significantly rear end heavy and our first attempt - well actually our first two attempts - had the drive axle boxes jam. In the end Paul re-rigged it so as to be much nearer level and this way we got it on to its wheels, with some wooden blocks between boxes and hornguides as the springs are not in yet.


For the moment, the gearbox is still sat on wooden blocks and Pete C had concerns about somebody being too inqusitive and having the box topple over on to them. What prevents this normally is the torque reaction arm, which inevitably is about as unconventional on RS8 as is the rest of the loco.

To recap, on jackshaft driven locomotives like 03s and 04s or their industrial counterparts, the final drive gearbox is rigid in the frames and ought not to move at all. (A tip for 03s and 04s. lift the cab floor and see if the wing nut on the oil filler panel is scraping the underside. If it has been then the fitted bolts and dowels are fretting). On locomotives where there is no jackshaft, then the gearbox is mounted on an axle and to keep it notionally upright, a link shaped like a dumbell spans the gap between a bracket on the gearbox and a bracket on the loco frame. Each end of the dumbell is bored out to accept a large spherilastik bush, that is one where the centre section is shaped like a ball, and the outer is similarly spherical, and the two are bonded together with rubber to allow it to twist - a little - in almost any direction. BUT (and I am sure someone will come on and say 'ah, but on the such-and-such locos built for the Outer Mongolia Mass Transit it wasn't...') these links are almost invariably horizontal with the loco at rest and springs set up correctly. Not on RS8. Although, looking at the drawings, a 'conventional' torque arm was perfectly possible (and if this project was just Andrew and me together I would have been tempted to re-engineer it) Tunstead's designers not only created a torque arm on a 15 degree or so slope but put the two bushes in different axes and in the brackets at each end not the arm itself. Anyway, these bushes are almost certainly the originals from 1959 so it was arranged for the complete assembly (which was in 'as received' condition still) to be taken back to the quarry workshops and be stripped on their press.

In the meantime, we finished the afternoon by cleaning and painting a cross stretcher, which originally was right beind the rear axle in its steam loco days, but Tunstead moved back and angled to provide a support for the handbrake linkage. It is not far back from the gearbox so getting it installed will prevent the latter falling far should anyone disturb it before the torque arm is back.

I came away from Tunstead with a list of bits to organise, but on Wednesday had another call so on Thursday morning paid a visit to the quarry workshops. The pins that pass through the spherilastik bushes had moved, they told me, at 35 tons and a helluva bang that had scared the ... out of everyone in the workshops. The pins themselves were scrap.(they were only ever mild steel hex bar) but a look at the bush itself revealed as I feared that they were well past their 'use by' date. Components like these go hard with age and the rubber 'spalls', cracks and deforms on the outside. You can see the outline of the bush itself in the picture below. I left them to press these out (and they decided to 'warm it a bit' first - goodness knows what sort of a bang it would make otherwise!) having checked everything against drawing. Sadly the Tunstead drawings quote a Tunstead sketch number for the bush (which drawing no longer exists) and a Tunstead Order Number on Metalastik (ditto) but not the manufacturers part number.


I was under no illusions that this was going to be easy. Metalastik changed hands and rationalised its products years ago, and here was a bush made to imperial dimensions in 1958-9 and I was hoping for a near replacement that might involve the minimum of re-machining. I passed the details on to my regular supplier and pondered whether a non-spherical bush, a parallel one often called a silentbloc could be substituted. Late Thursday afternoon however the answer came back that it was still available, although the 3.5625 inch OD was now masquerading as 90.5 mm. So two were ordered Friday morning and will be taken up to Tunstead as soon as they arrive.

Another thing that has been vexing me is a replacement shim for the gearbox. The axle bearings are held in place by bolted caps and shims for adjustment. That at one side was a single 15thou brass and somewhere along the way it got broken.and was on the list of things to be sorted fror months. Two weeks ago the problem got passed back to me. Discovery number one, you can have any thickness you like of brass shim provided it's 6 imches wide. But my piece needs to be 10.75 inches and two half circles would drive you potty trying to fit them. Last week I spoke to two suppliers, neither of whom came back to me. This week I found another supplier in Mansfield and whether it was for local interest, they did quote me, for 15thou brass or 0.1mm stainless - although they were at little embarrassed when I pointed out they'd quoted me 10.75mm not inches, and said it was 0.1mm think, not thick! But at least I had a price and once sorted, got an order placed.

Work on the revised engine mount designs both for RS8 and Adolf are nearly finished. RS8's rear set is the more complicated for having the clutch air cylinder bracketted off it. Indeed, while I'm used to a cylinder of 3 inch or 80mm bore driving the clutch at a radius of about 12.5 inches, RS8 has a cylinder of only 2.5 inches bore on a radius of 5.25 inches. It must be working a lot harder and I am not going to attempt to get the old cylinder reconditioned: instead a new ISO standard cylinder of 63mm bore will be installed.

On Saturday Andrew was away but I had the pleasure of Stephen, Toby and Charles from the IDRPG and two visitors from Holland, plus a regular reader from nearer home, the latter re-visiting Peak Rail for the first time in about 20 years. Steph too was away at our daughters, leaving me to be head host and caterer, so the IDRPG three had to provide their own lunches and the microwave was inaugurated. They spent their time (apart from when I sought assistance) in cutting open the silencer from 1382 before welding it back up again. Presumably satisfied, the silencer and adjacent pipework were fixed into the top of the casings.


The bushes for the brake hangers are due shortly, so they can see themselves nearing the time of being able to test run it properly.

I was back today and joined by Jagger, and after numerous mugs of tea to offset the dehydrating effects of all this sun, he made a start on the Wickham from where we'd left off. Meanwhile I was overseeing some batteries that had caused problems yesterday: one which yesterday was charged up around 12.3 Volts had dropped back to 6 overnight. Andrew when he arrived was peeved to see all the batteries which have been breeding around the workshops and declared he was going to start manufacture of a battery rack, and set about drawing up a design on squared paper. I meanwhile, set about investigating converter base pressure on Charlie.

I do not like the long-established practice of bringing oil pressure and converter fluid pressure lines up to the instrument panel. Small bore copper or plastic is all very well but sooner or later they begin to weep and a cocktail of oil, fuel and whatever dust and dirt was prevalent in the atmosphere gets mixed in the desk, and if, like we did at Hills, the relays and electrical gubbins are underneath the instruments, then your entire electrical control system gets the benefit.So as each loco comes through our tender hands, it gets electrical gauges for temperatures and pressures.

Of these, the pressure senders appear the most fragile. Charlie's converter pressure gauge had been concerning me for weeks. Each time I ran it I saw less and less pressure and wondered whether the charge pump was dieing. But a loco with no base pressure needs revving much higher and shows a marked lack of enthusiasm to pull things, yet Charlie was as controllable as always. So I decided to try changing the sender, and today was when I went looking.

Charlie is a compact loco. The converter is halfway in the cab and access is through the doors under the desk or the lift off panels at the sides. The sender is right at the back of the converter so reaching it meant working at arms length, kneeling on the edge of the metal cupboard surround, not recommended for long periods. But it was worth it: I fiired Charlie up and back came the indicated pressure, so all it seems is well.

With a little help with gas from Andrew, Jagger wrapped up with most of the frame parts removed and only the power unit to come out before de-wheeling. Unfortunately our regular sand-blasting contractor fell off a ladder recently and cracked 3 ribs, so is not taking bookings. Still, it gives us more time to ensure his day with us is fully utilised with more components ready and waiting.


Both days the 2HAP has had its doors open to get air flow through and I am sure the musty smell is reducing, or maybe I'm kidding myself.

OK, so another week over and not a mention of the Royal Wedding. (This doesn't count). Andrew tells me next weekend is a further bank holiday weekend. Didn't we just have one of them? When I was young Bank Holidays were few and far between, to be savoured in anticipation and enjoyed at the time like a dry wine. (Exit stage left, muttering).

This site runs on a system that employs Cookies to establish a link between your web browser and our site. This link is required to deliver to you the page you requested, let you see any photos or videos or to use the contact form. The Cookies that allow this to happen are automatically downloaded to your device (pc, mobile, laptop etc) when you click onto our site. If you set your web browser not to accept Cookies then its probable you will be unable to use Weekend Rails properly. Click to Accept (or the message stays visible). To find out more about the cookies we use and how to delete them, see our Privacy Policy.

I accept cookies from this site