The great thing about the Roy Link Bagnall kit chassis is that it works just as well for a 1:32 Bagnall Sipat as it does for a 7mm scale 7" Bagnall. That is to say that the wheel diameters and spacing, the length and width and the positioning of things like cylinders, smokebox and cab are the same, give or take a millimetre for both. However, as with the 7" Bagnall, the valve gear is a little bit of a mystery. Bagnall's had their own patented valve gears, first the Baguley gear, and then the Bagnall-Price valve gear. What's supplied in the kit doesn't appear to be either but as part of the gear is an eccentric which was often fitted inside the frames it could be a representation of either. This is something for a later blog because so far I haven't cracked it.

The modifications I have done so far are purely for model railway reasons. As mentioned before, I wanted to make this model locomotive battery powered and radio controlled. The radio control is by means of a Deltang receiver supplied by Micron Radio Control. The power comes from a 3v LiPo battery, also supplied by Micron, as were various sundries such as a charger driven from a USB port and various plugs and cables. The other important item is the control box, which is like a standard model railway controller except it communicates to the loco receiver over WiFi.

At the moment all those pieces are in their packets, awaiting the time to install them. The first thing that needed doing on the control side was to make sure the loco body work could accommodate them.

As the radio control kit and the battery are 3v rather than 12v a different motor would be needed. The choice fell on the now ubiquitous N20 motor which can be acquired in 3v, 6v and 12v versions. The reason for choosing this is that in the 3mm Society we have the benefit of Geoff Helliwell's work with these motors and Geoff has also designed motor bogies and loco gearboxes around these motors. As 3mm finescale is 14.2mm gauge and my 1:32 18" gauge project is 14mm gauge then Geoff's designs should fit nicely.

The N20 motor is about the same size as a small Tenshodo or Mashima motor. The main difference is that the N20 is provided with a spur gear train to provide the gear reduction. It is for that reason that the motors are offered not just for different voltages but also with different speed ratings. Geoff recommends the 300RPM version for slow locos and 600RPM for mainline stuff. 300RPM it was then. Data sheets for the N20 can be found on the internet quite easily

Geoff Helliwell provides kits to mount these motors to 3mm Society members and I acquired one of these from him. This 3mm scale 0-6-0 mechanism built by Geoff illustrates how suitable these motors and gear trains are as a replacement for a Mashima or similar (photo: G. Helliwell, reproduced from Mixed Traffic)

The actual drive to the wheels is via crown and pinion gearing, which is much more efficient than a worm and wheel. It is possible to put the pinion directly on the motor and drive the crown wheel directly but that requires more space inside the frames that 14.2/14mm gauge permits, never mind the 12mm gauge of TT. Hence the need for some idler gears. The bits Geoff supplies to 3mm Society members include an etched nickel silver mounting on which a stub axle for an idler gear can be soldered - the idler gear held in place by a circlip - and holes etched in the right places for the motor and drive gears. Geoff also supplies a small brass jig piece for positioning the motor mounting at the correct distance from the driven axle (photo: G. Helliwell).

This all makes for a very straightforward assembly (photo: Geoff Helliwell).

On my 1:32 scale Bagnall the Roy Link design has the motor mounted vertically so it fits inside the firebox. The same can be done with the N20. As the motor does not have to sit across the frames as it does for a 12mm gauge chassis the idler is not required. Unfortunately it is still not possible to drive the crown wheel directly because of the limitations of gauge and back to back, so an indirect drive is still required as this detail shot shows.

The only small problem is that the final drive pinion requires a length of axle mounted inside a long bearing and that also goes up into the firebox but then fouls the white metal casting. Some of this had to be cut away, but fortunately that could be done internally without showing anything outside. The N20 is also slightly longer overall, thanks to the spur gearing, than a Mashima but as the boiler and firebox on the 1:32 model need to be placed a couple of millimetres higher than on the 7mm scale model, that can be accommodated.

So I have the mechanism built and working. Next up, sort out the valve gear and add stuff like the brakes.