Christmas Day and having watched SCD I had the greater pleasure of seeing the steam railmotor work under its' own power. There have been times though when the chassis nearly ended up in the bin.

Following on from my last entry, having done the basic chassis it was time to set up the motor and gearbox. Unusually the High Level gearbox was not as smooth as they normally are when I fitted the brass final drive. The motor was a Mashima 1624 which fitted neatly in the brass frame I had constructed that would carry the central bearing locating in the body and thus bear the weight. The fit was a little too neat as I found the motor and gearbox would only fit if separated and I had to fix the motor afterwards. I do find one of the great advantage of the High Level gearbox is the ability to fix the motor in place without having to remove the gearwheel, the screws can be fitted at the side. Once I had the gearbox and motor in their correct position I smeared Araldite over the joint between the two sections of the Road Runner gearbox to prevent torque movement. Soldering would be easier but I had visions of melting the idler gears. The Alan Gibson wheels were then fitted and the interminable job of quartering began. Eventually I had the wheels running freely with coupling rods fitted and was able to solder the crankpin nuts on the leading pair of wheels. This was where the problems started. I wanted a good solder join as once the valve gear is fitted the front wheels are virtually invisible, let alone accessible. If the nut came loose it would mean having to dismantle the valve gear. Of course trying to get a good join meant the plastic on one of the wheels softened slightly, I thought though I had got away with it as the crankpin was still firm.

Having done a brief test run without valve gear I was a little perplexed that the quartering seemed to have gone out. Correcting this I turned my attention to the valve gear and cylinders. My big problem here was that there was no way of checking clearances etc., the whole assembly had to be fitted in place first and hopfully everything would be OK. I therefore Araldited the cylinders to the frame with the front flush with the stretcher as per the example at Didcot. The valve gear assembly then had to be fitted; I had decided to lightly tin the slide bars, apply some LMP solder to them and fix them in the cylinders by applying a soldering iron to the slidebars and gently push them in ensuring that the white metal crosshead was well to the rear away from the soldering iron. At the same time I had to coat the motion bracket with Araldite to fix that to the frame and then this had to be threaded through the coupling rod. Seems very complicated but it did work and I had the chassis runnning well for a brief time. Well after I eliminated a dreadful screeching noise, the end of the motor shaft was fouling the bulkhead in the body. I simply removed part of the bulkhead as it can't be seen.

Unfortunately the quartering problem arose again and on closer inspection I realised that one of the front drivers was, if not loose, not tight on the axle. It was clearly slipping and having thought about it I realised that that the softening caused by the soldering iron had done more damage than I thought. There was nothing for it but to dismantle the valve gear and take the wheels off.

Having giving it some thought I decided that because of the inaccessibility I would use Romford wheels which were far more durable and wouldn't melt. The quartering was an added bonus. These wheels are now made by Markits and having looked at their website found a 4ft wheel that fitted the bill. I have to say that I was a little reluctant to use the old Romford wheels as whilst they were good in their day the coarse flanges and fixed balance weight don't bear comparison with more modern offerings. However I was pleasantly surprised, the wheel profile is to RP25 standard and there are no balance weights cast in. I also thought that the wheels seemed to fit better than before in that I didn't notice the wobble you would get once fitted and the nut secured due to inaccuracies in the casting. In the old days the only way to eliminate this was to use Romford wheels turned on the axle. The crankpin hole is now threaded to take Romford crankpins, I opted for the de luxe version which has a threaded shaft to take the bush also threaded 14BA. The bush is the same thickness as that on the Gibson crankpin which avoided any potential problems with the coupling rods already drilled. The Markits website is well worth a look as amongst other useful bits they do the old Romford screw couplings which I always thought were the best you could get. They may be slightly overscale but this means they are easier to use and most importantly are pre-assembled. I don't see the point in spending the best part of an evening making up a pair of screw couplings. The only slight disappointment with the couplings was that they were not blackened as they were back in the old days.

The wheels arrived promptly and I began to reassemble the chassis. It was a lot easier to use spacing washers with the Romford wheels (the washers were another good find in the Markits website) as I could fit and take off the wheels to insert the correct number and thickness of washers without fear of the wheel loosening on the axle. I'm not sure that with the straight cut gears it is absolutely imperative to have no play in the driving axle but my problem was the limited clearance behind the valve gear. Any sideways movement would have meant the wheel or crankpin hitting the crosshead. I did find the wheels were a tighter fit on the axle than I recalled when I last used Romfords but then that is probably better. Unfortunately I had to remove the cylinders as the wheels were behind them but I was pleased to see that the Araldite really held them on and it required a lot of effort to break the bond. Basically from then on it was a case of reassembling the valve gear as I had done earlier. Before fixing the cylinders though I had a very close look at them and found that I had to pack one of them out from the frame with a piece of etch scrap. It was impossible to have done an accurate saw cut when I separated them from the original cast stretcher.

I did one side first and found that the crankpin fouled the crosshead very slightly. I was able to sand down the crankpin which did the trick. The Gibson crankpin bush has a thin flange adjoining the wheel to give some clearance and is secured by a nut. The Markits crankpin has a thicker flange adjoing the wheel as this is part of the pin assembly whilst the bush is threaded with the retaining flange on the outside replacing the nut used to secure the Gibson bush. Overall the Markits crankpin protruded fractionally more than the Gibson one, not normally a problem unless clearances are critical as in this case. Having set this side up I did the other side, again I had clearance problems and had to sand down the crankpin bush. I also found that the tiny nut holding the connecting rod to the crosshead just fouled the coupling rod so I cheated and bent the rod very slightly which solved the problem. There was no way I could have reached the small screw fixing the con rod so this was the only option.

I always try turning the wheels with the final drive nut loose to see just how free running the chasis is. It wasn't perhaps as free as I would have liked but there was not the tight spot that indicated incorrect quartering of the wheels, I think with so much of the valve gear being driven the various joints imposed a slight additional load. Anyway after some tweaking of the current collectors the chassis ran very well.

I had looked again at the fixing to the body, the nut at the top that engages in the hole in he roof and felt this could be improved. I soldered a washer to a nut that I fitted to the screw protruding into the hole and by running the nut up and down the thread meant I could get the correct clearance as the body rested on the washer. The body seems to sit a little high if a wagon is coupled to it but if any lower then the solebars fould the valve gear.

After all this effort the completed railmotor was running well and packed away as a "finished job." I've attached a photo of the chassis as completed, apologies for the quality but it was testing the close focusing qualities of the camera.

I certainly learnt a few lessons and I hope recounting my mistakes enable others to avoid them. It was certainly a challenge to incorporate parts of a Nu Cast chassis with an Alan Gibson chassis but if a proper etched kit with all the fittings becomes available then I'll certainly replace this one.