CF MRC

The connecting rods for Lord President are, of course, tapered and fluted. I had thought about milling them out, but the taper makes life tricky. In the end I simply made a skinny rod and then silver soldered two sides to it to make the webbed casting. These additions were then filed back until they almost disappeared. The little end pin was initially a drill shank silver soldered in place. I subsequently learnt that this would not accept soft solder for the securing collar, so it was replaced with a bit of watchmakers pivot steel. Clearances are tight, but seem to be working out OK. Looking at the unkind photo, I will take the top web off, thin the rod down and soft solder a new web in place. Tim

Sorry for the dental stuff, I do use a lot of watchmaking stuff as well. The technique for casting with a potato is that the alloy is heated in the cone of the investment ring until molten. A wet half potato is then firmly placed on top. The flash steam from the potato drives the metal into the mould space. Other techniques that used to be used are a stirrup and chain (a better engineered version of Jim's string), swinging the casting ring in the stirrup around by hand, once the metal is molten. Tim

At Guy's, as students, we had centrifugal casting machines that were wound up: effectively clockwork powered. They required a choreographed action of placing the hot casting ring in the arm, heating the gold in the crucible with a gas torch and letting go the centrifugal arm at the correct moment. We did our phantom head course with real gold and it was quite easy to harvest splattered gold from around the casting machine, if you followed the less savvy students who put the ring in back to front. In this way I collected enough material for my first gold safety valve. Students nowadays don't have half as much fun! Tim

Two crossheads & pistons These little devils were quite fiddly. I made the first one on the left hand side by dead reckoning and serendipity. The second one was, of course, much easier as I knew what was needed; so I photographed it's construction The slipper and socket for the piston rear end was cut out of sheet steel with a bit of excess material for filing back later. This was then bent up with the piston socket going backwards and the slipper folding forwards. The metal was scored with a slitting file to ensure that it bent predictably. The piston was made from a broken twist drill (I have plenty from this project!) and the socket was augmented by a small length of syringe needle towards the front. The whole lot was then silver soldered up. Following the article on silver soldering in the latest MRJ I got some 'Silver Solder Paste Easy 15gm Syringe' from Palmers metals. This is really much easier than separate flux and solder for these very small jobs. The long tag hanging down was subsequently scored to allow it to bend right back on itself to form the basis of the arm which will be surrounded by the forked union link. This was then silver soldered again, to make the whole assembly very strong. Finally, the two holes for the little end and the union link were drilled. At the moment, the crossheads can slip back towards the wheels, but the connecting rod will hold them out, as will the union link and combination lever. The connecting rod will have the little end pin silver soldered to it, pass through the crosshead, and then the big round boss and castle nut will be represented by a piece of syringe needle and the pin slightly poking through. Not quite prototypical, but I don't think I'll loose any sleep over it. Tim (P.S. Do you like my new avatar? LNER publicity sticker from the era)

You could always use a half potato for driving the molten alloy into the investment cavity, Jim. Bits of string could be risky! Tim

A cast backhead. As intimated in previous posts, I intended to make a cast backhead for 2003. So the pattern was made from styrene - a little thickened in some areas to allow for metal flow. The details were broadly derived from an A4 backhead. This pattern was sprued with wax into the bottom corner and mounted onto a casting cone. The spherical swelling on the sprue acts as a metal reservoir close to the pattern. The casting ring is lined with a thick card-like material to allow swelling of the investment (not sure why these images are horizontal). The vacuum-mixed gypsum investment was poured onto the pattern in the casting ring, making sure that there were no air bubbles. Once set, the investment is taken up to a high temperature (700 dec C) that burns out the plastic and wax, leaving a space for the incoming molten metal. At the same time, the investment expands to compensate for the shrinkage of the molten metal as it freezes. The casting was made using an induction-heated vacuum casting machine with 1030 deg C melting point alloy: "Phantom Metall NF". Once cool, the student's alloy casting (brass) was divested and then bead blasted to remove the remnants of investment. The casting was then fettled and bolted into the cab. It needs the fire screens fitting to protect the driver and fireman's legs. At least they won't have to worry about a dangerous drive shaft on this engine! Tim (P.S. I expect this has stimulated a few of Jim's memories from his dental undergraduate education)

Don't forget that there are lathes at the MRC that you could use, if required, Justin. Or alternatively, in another Roman City messed up by Boudicca. Tim

I have fitted the motion support brackets for 2003. These are soldered onto two brass bars that are, in turn, bolted through the PCB frame spacer. I also soldered on a small web around the edge of the casting: this is quite conspicuous on the real thing and makes the whole assembly look businesslike. Don't know why, but the cylinder looks a little whimsical / sad in the first photo. Second photo shows the bracket sitting under the running plate. The width has come out about right as can be seen with the body in place. This will need some insulating tape or fag paper and Araldite on it to maintain insulation. Need to finish off the pattern for the backhead (it was started at the MEE at Ally Pally) & then the crossheads and pistons. Tim

Presidential motion support. I have been making the two brackets at the distal end of the slidebars. Our clever etching chaps would probably have had a few flicks of a mouse and hey presto all done! However, these ones were cut out of two sheets of 10 thou nickel silver well tinned together. The first photo shows the Macor blocks I use for holding items whilst soldering: they save the finger tips! The design for the brackets was sketched out in my notebook, as can be seen in the second photo. They are quite complicated and will need to look like a heavy casting when complete. The pair of brackets were fretted out with a piercing saw, as can be seen in the third photo, with bits to cut out marked by cross hatching. The two brackets can be seen in the fourth photo, ready for bending. The bending lines were pre grooved with a fine slotting file (some of the design bits proved to be superfluous). Once bent up into shape, the brackets were silver soldered on to the slide bars. They were spiked into a charcoal block and the slide bars rested against the end and then held down with some bent dress making pins shoved into the charcoal. The valve guide end was draped in wet tissue to prevent the soft soldered piston stuffing box from coming adrift. Very small pieces of solder and flux were placed on the ends of the bar and the whole lot heated to red heat, with the solder flashing nicely. This also served to stiffen up the bracket by filleting the corners. Final photo shows the two sub assemblies. They have now been roughly fitted to the engine and I'll show the mounting when complete. The beauty of using silver solder is that it is very strong and soft soldered details can be put on without everything falling apart. Tim

They would make a nice train on CF! Tim

Maybe John modelled the Lickey, but I also modelled a 1:37 incline on my N gauge layout Gouldby for Caldecote. It featured a Big Bertha converted from a Minitrix 2-10-0, or more precisely, the goodwill of a Minitrix 2-10-0. It featured in the last issue of Model Railways edited by Roy Dock in the mid 70's. The layout was also used to illustrate the Graham Farish range. Tim

The heavy gang made a trip to deepest Somerset yesterday. Lord President flattened out some dodgy track. A surprise guest also came from Canada, just fresh from overhaul at the Blackburn works. The CME in charge of the building of the P2 was heard to say: "thank goodness the buffer beams look like they will be the same height!" The driver of Dominion of Canada was less impressed, however, as the front bogie wheel had just hopped off the possibly permanent way.

Why was 6 scared? Because 7, 8, 9. Tim (from Hertfirdshire)

The engine will perform much better with finescale wheels Valentin. My Johnosn single was originally made with n gauge wheels and spent more time going sideways than forwards. I think that the better fit of wheel to rail gives better traction in a small awkward engine. Tim

Justin Takes a look at model aircraft ailoron pivots and cranks for any mechanism. It's what we used fir the front turnout on the NLR electric lines. Pretty cheap and very reliable & adjustable. Tim

I packed out the cylinders with an L shaped shim. The cylinders are now a bit taller and have the characteristic and conspicuous brake lever arm supporting bracket underneath. There is now just clearance, even with the overlong front coupling rod pins. One thing I have only noticed today is that there should be a very slight downward - backward slope on the cylinders: fortunately, this was easily accommodated by the slack on the fixing screws. The motion support bracket will be next. It hangs over the front drivers and will be quite a large chunk of metal. I will soon need to bend out the front guard irons, otherwise Lord Prasident will plough up Jerry's track on Saturday! Tim

Looks like you are having fun there Gareth. Where is the motor going? Tim

With the mileages that our locos do, I am not convinced that Simpson springs would last long enough. However, we have used skids under our 0-6-0s for years. They work very well and are hard to spot if chemically blacked. The running gets better and better of course as the track gets cleaner and cleaner. The only down side is that they are bit vulnerable in storage, but can be easily tweaked. Axles need a bit of slack in their bearings, but over do it and CF will soon wear them out! Tim

Stuart, point well taken: the photo was obviously staged, otherwise I couldn't have taken the photo! However, you will observe that the blade is below the metal sheet and so could not jump over the top towards my thumb. Also I only use such powered instruments with very significant finger rests to lock one hand against the other, limiting any potential run away, as shown in earlier posts with hand instruments. Tim

Looks like your engines like peaty water Jim! Tim

A star ship. Having sweated on the piston rod stuffing box I have now ended up with two mini starships. I have left the slidebars closed together for mutual support- the motion support bracket will sort this out when it's made. Once on the engine it is evident that a little bit more side clearance would be useful. I can easily pack out the cylinders by 10-15 thou and still be well within prototype loading gauge. This will also allow a representation of the brake operating pivots and levers between the frames. The front coupling rod pin will not have a collar on it. I think I have worked out how to make the crosshead: it will involve some metal origami. Tim

Silver soldering For strength and convenience, the slidebars / lug joint needs to be silver soldered, as the piston stuffing box will be soft soldered to the bottom of the lug. For silver soldering I use a borax flux, easyflo silver solder and a small gas torch - as can be seen in the first photo. The components are held by pins in a heat resisting mica block with other carbon blocks to also act as heat shields. The assembly photo shows the components held in place with a pin, running through the valve guide. The area is fluxed with the borax paste and a very small piece of solder cut and placed in the flux near the joint, out of sight at the back. The components are then heated up with a flame and the solder flashes into the cracks - simples! The secret with silver soldering is just using the right amount of solder. The final photos show the assembly after cleaning up. The slidebars are currently very delicate and desperately need support at the back. Next job will be to make the piston stuffing boxes and then the cross heads and piston rods. As always, the camera is rather cruel. Tim

P2 rear valve spindle guide and slidebars. These are quite tricky pieces, as they are fixed to each other. For construction purposes they needed to be removable from the cylinder. I therefore turned up some brass bits to give me enough meat to whittle out the correct shape for the valve stuffing box and guides as well as a lug into which the slidebars would be soldered. I made three - the second one was a tad too small and was not an interference fit in the cylinder. The slidebars were made from thick steel sheet, with the slot cut out using a fine diamond disc, as can be seen in the second photo. The slidebars were filed down to shape and slotted into the lug at the bottom of the valve spindle stuffing box (third photo). Tim

Seeing a realistic train move through a realistic scene as a three-dimensional painting has always been what floats my boat. Fortunately, we all live in a very broad church! Tim

It depends on scale. We used to run very long trains on Chiltern Green and the scenic scope of the model easily accommodated them, as you could stand back and see them in context. It is more difficult to do this in the larger scales because you can't stand back far enough (unless outdoors). Tim