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Nick Mitchell

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  • Location
    Earby
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    2mm Finescale
    1950s ex-Lancashire & Yorkshire Railway / LMS Central Division

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  1. At the ZAG this morning, I was playing with a new product which hit Shop 3 a few days ago and popped through my letterbox yesterday - a milled brass 30:1 gearbox. I'm very impressed with it. The worm shaft has standard phosphor bronze frame bushes soldered into the brass frame. When properly assembled in a chassis, the gear will be fitted to a muff, and the muff will rotate in the large hole, ensuring the gearbox is electrically isolated from the frames. Instructions are on the Association website. Here I'm using a 1/8" drill bit so I can slip a skew-cut gear in and out for testing the mesh... in this instance a not-quite-perfect gear from a batch I recently made. The perfect ones were all delivered to the shop earlier this week...
  2. I rolled up a Raithby etched 8F boiler barrel to see what it was like. That had been my Plan A (I think?) as well. It came out as a section of a true cone, which is not quite right. It needs to be oblique. The bottom of the boiler should be horizontal - it is quite noticeable in photos of 8Fs taken side-on, because the boiler bottom is just above the top of the frames. I think Peter Whitehead and David Eveleigh had an article in the Magazine many years ago about turning such a shape form solid brass for a Great Western engine.
  3. That's looking very nice. What are your plans for the sawn-up Black 5 boiler/smokebox casting with this kit? I've been looking at mine and wondering what the best way forward is. I don't think I could simply glue them together.
  4. That's correct, Simon. At first I tried 603 retaining compound, but I had a 50% failure rate. I really don't understand why. 243 threadlock gave much more reliable results. In theory, the bond shouldn't be as secure, but the forces it will be subject to are miniscule. Don't forget the tyres are held on the wheels with retainer, as are the axles on the Mark V wheels. I'd be much more worried (if indeed I were worried at all!) about soldering the crankpin into the wheels than soldering the retaining washer onto a glued-in crankpin. I have had soldered-in crank pins fail and start rotating on brass wheel centres due to not heating them up enough (through a surfeit of caution), but touch wood I have never had a tyre come loose. You need special flux to solder successfully to stainless steel. While it is fine to have your crankpins retained with a plug of solder and able to rotate in the wheels on an 0-6-0, if you have a return crank fitted to the crank-pin, you would have a disaster on your hands... guess how I know?
  5. The worm sets we got from KKPMO in Poland had a 3.0mm bore. Yours must be one of these. The current gears have 3.2mm (1/8") bore like the Ultrascale ones the Association supplied even longer ago. The last batch we had from Poland were problematic in that the skew was cut the wrong way so they didn't mesh at all with the worms! As long as you haven't got one of those(!), you need to fit it to a 3-102b metric gear muff. The stepped muffs (3-102a like your unused one) are designed to take a 1/8" worm wheel and a 3.0mm spur gear. You can't fit a metric worm wheel to them, since the 3.0mm section is on the short section. I don't think you'd be able to fit a 3.0mm bore gear onto a 1/8" muff without noticing, however brutal you were!
  6. It is no illusion. The firehole door is below the level of the footplate. It is actually quite easy to fire with the world's smallest shovel - once you get used to the idea that the grate is circular! There are no dampers, so you have no control over the rate of combustion other than with the blower. The ash pan (a flat, round tray) is almost touching the floor.
  7. It is an absolutely awesome machine. I want one! I'm really hoping Paul "Piglet" Middleton will allow it to stay at Embsay for a while, or visit us again soon. For anyone who doesn't know what Chris is talking about, Joining Beatrice and the resident NER Autocar at Embsay last weekend were three visiting locomotives. On Monday I spent the day firing No.8 "Lucie", a Cockerill Type IV 0-4-0 tram loco as she hauled our set of Victorian and Edwardian 6-wheelers. I was pleased to get the text on Sunday night saying Lucie was replacing visiting Terrier "Knowle" on the roster (firing the Terrier had nearly killed me on Saturday), and I couldn't stop grinning all day. She has Walschaerts' valve gear, but unusually the return rods are driven by eccentrics inside the frames. I'd never fired anything with a vertical boiler before, but it steamed brilliantly and thought nothing of our 2 miles of 1:100 out of Bolton Abbey, thrashing along at 15-20mph while sounding like a Black 5 on an express... A model would certainly be a challenge, but do-able I think. The water tank is fairly large (basically the whole of one end) and the boiler has room to conceal a motor.
  8. He was indeed witness to this ritual... just once... though I believe the madness had already taken him by then.
  9. The central piece folds into a U shape. The arms of the U form the top and bottom flat sliding surfaces of the crosshead. Each of these arms has a tab which fits into a slot in the front and rear plates. The piston rod pin then solders to the flat base of the U in-between projections on the front and rear plates. The tabs on the U only fit into both slots nicely if it has been folded square and parallel. I soldered mine from the outside, introducing the solder where the tabs protrude through the slots. That way there is practically no cleaning up required inside the sliding channels. The other advantage of this style of construction is the amount of space inside the body of the crosshead for the little end of the connecting rod. The only scope for error is in soldering the piston rod either off-centre vertically or at a jaunty angle - but that is a potential pitfall with any fabricated crosshead. I check the alignment by holding the crosshead in a pair of parallel jaw pliers and eyeballing the piston rod.
  10. I've been working on some valve gear over the last few days. Outside Walschaerts to be precise (my favourite kind!) This is for a Fowler 2-6-4T which I haven't looked at for over a year since finishing writing the instructions for Nigel to supply with the etches. Those instructions (and the kit design) have the loco in mid gear, but I am building an "enhanced" version in forward gear just for fun. Don't worry - it won't reverse itself... A bit of forward planning was required when making the cylinder block for the loco. As well a as tube to guide the piston rod, a smaller tube was built into each side to guide the valve spindle. The piston guide tubes are 1mm o/d 0.5mm i/d, drilled out to 0.7mm once in situ. The valve guide tubes are 0.8mm o/d 0.45mm i/d. Eventually a tuned cover will fit over the protruding valve guide tubes to represent the end of the valve chest. In the photo above, the slide bars have been fitted, and quite a bit of time was spent filing and polishing them to ensure the crossheads can move very freely. The crossheads themselves are a 3-part fully etched version which come as part of the kit - very cleverly designed to be self-jigging, and incredibly effective. An alternative with a cast back/centre and etched front is available (and equally effective), but I really like the all etched version: In the picture above, the right hand cross head and connecting rod can be seen. A 0.65mm plated dressmakers' pin has been used as the piston rod, and has already been cut to length and domed off at the end. Once the crossheads have been tested in the slide bars with things temporarily lashed together on the chassis, the adaptations to the valve gear can properly begin... Here is the radius rod freshly cut from the fret, with a nice fold-up valve crosshead guide on the end of it: You can see in the picture above I have opened out the hole in one of the rods where the lifting arm is designed to locate. This is the first stage of clearing out the slot. The next stage will be to cut the webs with a scalpel. The slot, btw, is 0.5mm wide. Below, the slots in both rods are nearly there. A thin strip of wet'n'dry pulled through the slots will finish them off. The little crosshead guides have gone too, but will be saved safely for later. Next my attention turned to the combination levers. Nigel has made life easy here by etching two holes at the top end: one for the valve spindle and one for the radius rod. For robust-ness, these parts (and the union links which join to them at the bottom end) are quite reasonably made a bit thicker than scale. The prototype ones also have a slight taper, so it was into the vice to thin them down a bit... there's plenty of metal either side of the fluting to play with. In the vice I've got 0.3mm rod through the holes at either end of the parts. These hold the part a consistent height above the vice jaws. Being a watchmaker's vice, it is capable of gripping the very thin edge of the metal. A bit of scrap 0.45mm thick acts as a guide to file down to for the union links (one of which I am attacking in the picture below). The combination levers were done free-hand, as they didn't need to be thinned quite so much. I am using a #6 cut swiss file which is very fine. This procedure is repeated on both edges of each part. Here's a comparison shot between a set of parts after thinning and the originals: Next the expansion links need some attention. The position of the gear will be set by pinning the radius rod to a different location on the link. Below the pivot for forward gear, above for reverse in the case of an outside admission valve. In the picture below, an additional hole to set the gear has been drilled in each link. I decided to add the equivalent of a half-etched overlay to give a bit more 3D relief to these links. They were soldered to a scrap of 5 thou. shim (being careful to do one left and one right hand!) before drilling through the holes and cutting them out: Here are the modified left-hand parts laid out in roughly their final arrangement with the cross head. A valve spindle needs to be fabricated. This is a bit of 0.45m brass rod (a sliding fit in the 0.8mm tube), squashed flat at one end. A valve-gear washer is soldered onto the flat, and then frilled through to form an "eye" at the end. More of these washers and short lengths of 0.3mm rod are used to form pivot joints between all the parts. For the top end of the combination lever, I made a special double washer (filed from a bit of scrap etch, using the holes in the combination lever as a drilling template). In the photo below you can see the double washer just having been soldered, with a scrap of oiled cigarette paper in place below it as a solder barrier. At this stage, with the valve rod and piston rod joined together, the two need to be tested in the cylinders. The important bit us to make sure the leading edge of the cross head doesn't catch on the back of the combination lever as it passes behind it. If it does, the combination lever will need to be cranked outwards. This one, however, is just perfect! The rest of the valve components can then continue to be added to the lengthening chain. Below I have added the expansion link and return rod. The conn. rod is temporarily held in place for effect. This is as far as I have got this afternoon. My eyes need a rest before I do any more!
  11. I found this video on YouTube showing the preserved Compound 1000 double heading with Jubilee Leander over the S&C in the early 80s. At the start of the clip, you can only hear the Compound's exhaust, which sounds just like an ordinary 2 cylinder engine. One of the left hand cylinder drain taps is blowing through once per revolution of the wheels. After about 18 seconds, Leander is opened up, and her 6/8 beat becomes audible, drowning out the Compound somewhat.
  12. Hi John. The short answer is no. The main reason is that I've posted details and photos of everything I've done since that first draft on this thread. The other reason is that the fold-up etched radial truck I used is not available commercially, so it wouldn't really be appropriate as part of a set of notes for other people to follow. If you are using the chassis Chris Higgs produced to go with the body etches, I suspect you will need to make different modifications. Nick.
  13. A good phrase to add to your search for Farish chassis on ebay is "spares or repair"
  14. Not necessarily. There is a great little article by John Whitehead in the December 1980 Magazine on his Expanda-Link close couplings. He reports these will work down to 7" radius curves!
  15. You'd need to contact David Varley directly (or via the Association). He hasn't visited RMWeb since August, so may not see messages posted here.
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