My 2mmFS plans involve a small layout of Holywell Town, a North Wales LNWR branchline of which more details to be posted separately. Whilst researching for stock for the layout I looked at Worsley Works for some coaches and spotted a set of etches for a LNWR M7 Railmotor. Whilst I don’t think they ever managed to see duties at Holywell Town I thought it would be a nice little model to add a bit of variety so a set of etches were ordered.
I considered the most important part was to build some motive power for the Railmotor so wheels, bushes and gears were ordered from the 2mmFS shop and motor, pulleys and belts were ordered from Nigel Lawton.
Following the guide from Nigel Cliffe I had decided on using PCB for the frames and brass spacer blocks to make a split chassis design. I had some suitable brass square bar stock and to keep the frame width down I needed to source some thin PCB. A lot of the thin stuff seems to be copper on card but I managed to find some 0.5mm thick stuff on a fibreglass base courtesy of Rapid Electronics.
The frames were marked out and drilled and the brass blocks filed to size.
The bushes for the drive shaft and the wheel bushes are then soldered in. On the prototype the rear of the bogie has a water tank, this has been represented by the additional brass blocks soldered onto the outside of the frames. In addition to adding a bit of shame to the bogie it will add a little more weight as well.
I then used a couple of drill bits to align the axle bushes whilst I clamped the frames together for drilling. I’ve drilled and tapped 14BA throughout for fixing the frames to the spacers.
So this was the finished bogie with the motor hanging off a PCB mounting plate running on the idler shaft and gear drive on both axles. This was the setup I wanted as on the prototype it has a boiler mounted on the motor bogie just where the motor is situated. The intention was that I could then hide the motor in a tube to represent the boiler with a bit of detailing added. Whilst it looked good it was a complete failure, the motor just didn’t have enough grunt to turn the wheels.
After seeking advice from a couple of well known 2mmFS modellers I came up with a few suggested modifications. This basically boiled down to a) fit a bigger motor, b) drive one axle and c) fit ball bearings where possible.
Consequently a few modifications ensued. One worm gear was removed, although a small stub is visible in the photos the gears have been filed down so it doesn’t engage with the spur gear. I have left it on the shaft to stop the drive shaft moving backwards and forwards. A new end frame spacer was made so that a ball bearing could be fitted, it was also made taller so that I could mount the motor on this rather than the drive shaft.
Finally the motor, although the 8mm motor was recommended this is too long at 16mm and would have caught against the end of the rail motor so instead I opted for the slightly bigger 10mm motor being only 12mm in length and should fit. So this is the MK II version and this one runs!
There is still some detailing to finish off, e.g. brakes. Also the blocks for the water tank look a little small now so I think I will replace them with something slightly larger. The coupling rods need to be tidied up. They look a bit funny because there is the representation of the forked joint in them. This is because I used the etched rods from the 2mmFS Association, unfortunately the only set to meet the wheelbase requirements was for an 0-6-0 set of rods and this was the section that fitted. I reckon it would be easier to tidy these up with a bit of filing than making my own set of rods.