|HR Jones Tank No. 58 after her repairs|
At the February Running Day on the CDOGG layout in Carlisle my Jones Tank, which was built some time ago did not run at all well, in fact she failed to negotiate the circuit at all. I thought it was partly a problem with the front bogie and partly due to the vagaries of the track, particularly where the lifting flap provides a testing unevenness, which has been the ruin of the pretensions of many a poor engine. My misgivings about the track were however unjustified in this case as examination of the offending bogie running on my test track at home highlighted the fact that the rear wheels were not even revolving! The problem proved to be entirely a bogie malfunction. Closer investigation showed that the frames had somehow expanded and were actually breaking away from the horizontal stretcher and locking the back wheels. There was a good deal of lead weight glued into the bogie between the frames and I could only surmise that, depite my using Araldite epoxy glue, expansion of the adhesive was somehow to blame.
The engine started life as an aged Jidenko/Shedmaster kit, described by Laurie Griffin himself as "a difficult kit" and difficult it is, nearly impossible actually, without a great deal of modification and improvisation. The bogie frames were, on examination, found to be only 0.45mm thick, too flimsy for frames really. In addition, the mudguards on the front bogie wheels had always been a problem, the restricted clearance causing them to foul the cylinders and front buffer beam. Though this did not result in an electrical short circuit, as the wheels are insulated from the mudguards, it did not improve the engine's running characteristics. I resolved to simply scrap the old bogie and build a better one and see if I could improve clearances at the same time.
|The mudguards are clear of the cylinders now though it's still tight.|
I cut the new bogie side frames from 0.7mm nickle silver and built the bogie solid, without compensation. The earlier version had enjoyed the complication of hornblocks for the rear wheels to slide in, which I decided to scrap in favour of simplicity, relying on the central pivot of the bogie to provide articulation in all planes. I omitted most of the lead weight, adding only a modest amount this time. I was able to re-use the mudguards, though I remodelled them as tight to the arc of the wheel as possible and though I probably managed to pinch less that a millimetre, it made all the difference and the rebuilt bogie ran visibly clear of the buffer beam and the bottom of the cylinders. I made new guard irons, bending them and their support from a single strip to replace the earlier multi-part lash-up, not only providing a more robust solution but also an improved appearance.
The engine runs well now, at least it does on my own test track in the studio, taking the 6ft radius curves in her stride. An ABC Gears' Mini Gooch gearbox with an 1833 motor and flywheel, which I deem essential if space allows, ensures smooth running.
My aim when building a locomotive is that it should perform well in a "club layout situation" and these repairs should ensure that it does just that. However, due to the ongoing deadly virus crisis, her test run on the club layout in Carlisle is postponed indefinitely...
|Rebuilt mudguards and guard irons, note clearance under buffer beam is tight.|