Power Options

While I've not had lots of time for modelling recently I've been pondering a number of locos that, given the time, I would like to model. As with a lot of the other locos I've modelled in the past these tend to be quite small engines leaving me with few, if any, options for powering them. When I hit this problem with the Hudson Hunslet 24hp diesel I ended up designing a custom chassis for it, and I might still take this route, but in the interim I've been looking to see what existing chassis I might be able to adapt.

The KATO chassis from Japan have a good reputation for reliability even if they can run a bit fast; I've used one in the past when I built my first OO9 loco. Most of their chassis are, however, quite a bit bigger than I'm currently looking for. Or at least that was what I thought until I read a short article by Roger Lycett-Smith in issue 263 of Model Railway Journal (MRJ).

Roger had built a model of a tiny open-cab 4 wheeled Ruston using a KATO 11-107 chassis which starts out looking like this.

Clearly as it arrives, it's not going to be much use for building a 4 wheeled loco. It turns out though, that inside the white casing the motor sits above one of the bogies (which isn't driven) and is connected via shaft and universal joints to the gear train on the other bogie. What Roger had done was to rearrange this setup so that the motor was directly connected to the gear train. My attempt at replicating this resulted in...

Having now done this myself, I've discovered that the instructions in MRJ don't quite make sense. Roger states that...

The power bogie, worm removed from it's carrier and fitted direct to motor shaft, which has been slightly shortened and a brass strip made to secure the motor to the bogie

Unfortunately the shaft on the motor is no where near long enough to pass through the worm, and certainly not long enough to need shortening. In fact if you only attach the worm to the motor shaft it wobbles around quite loose in the housing; this might be partly due to me not having permanently fixed the motor in place but even so I would imagine it might lead to unnecessary wear of the gears if they are moving around too much. My solution, has been to fix the worm to the motor shaft and then insert the original pin the worm was on from the other end. This means the worm is now supported at both ends as before. It also means I have a rotating shaft onto which I'm wondering if I could fit a small flywheel; a job for the lathe next time I have enough desk space to turn it on.

I've not soldered wires onto the pickups yet as I'm considering some more radical butchering to fit the loco I want to model, but I have tested that it runs nicely like this by attaching power direct to the motor terminals.

While it's certainly not the smallest chassis, it has the advantage of being made from reasonably high quality parts which are known to be reliable, and it uses a proper 12v motor. Plus the chassis are cheap; you can buy them in the UK for about £24, although if you are happy to wait you can get them direct from Japan for around £14.