A long standing project revived

Entry posted by 2mmMark June 21, 2013

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I forget exactly when it was but at a 2mm Expo a few years ago, I was sitting next to Richard Wilson, each of us doing different demos. Richard was working on something that caught my eye. It was a little cast white metal traction engine which looked rather nice. However, cleaning up the wheel spokes was taking rather a long time. I recalled I had the same kit in my gloat box. If I recall correctly, it's a Fleetline Aveling & Porter. Thinking laterally, a good way to avoid the wheel refining chore would be to put it on rails. Once back home after the Expo, I dug out my kit, found some suitably sized wheels (10mm & 7mm disc) and cut out some frames from brass sheet, getting to the stage below.

Only the main boiler casting was used, sandwiched in some plasticard to insulate it from the split frames. The next question was how to motorise it. The intention was to have a battered RCH wagon behind as a sort of tender, as was done for some Scottish "pugs". This would contain the motor, driving the 10mm wheels via a UJ to a worm & wormwheel.

Well this was great in theory but after two or three abortive attempts, it became apparent that this was somewhat ambitious. The drive wasn't very smooth and tractive effort from a single brass driver with not much weight over it was limited. So it was put aside and dragged out from time to time while other ideas were considered.

Then at ExpoNG, a solution presented itself. Nigel Lawton had introduced his MPD18 drive unit for OO9, which had an 18mm wheelbase - perfect for a 9ft wheelbase wagon in 2mm scale. As a plus point, the wheels were fine enough to be used on 9.42mm gauge as they stood, making a small alteration to the back-to-back dimension.

Above is the basic chassis etch assembled. I did beef up the bearing surfaces by laminating bits of scrap etch as I felt that the axles running in the 10 thou nickel-silver frames might be a touch under-engineered. Next I sorted out a body. I had some 2mm Association RCH wagon kits but I'd put these away carefully in a safe place... They'll turn up one day! Instead I used a 2mm kit for a LMS van, teamed up with a Peco 9ft wheelbase underframe kit. The plastic body & underframe would avoid any shorting out, useful as the clearances are a bit tight.

This brought me to the stage below with everything fitting into place nicely.

The MPD18 chassis was completed and with a little bit of fettling, runs quite acceptably well. The rubber drive belt is definitely quieter than a pair of spur gears but there's still some noise from the final worms & wormwheels (which are Tenshodo products).

I did wire in the suggested 15 ohm resistor but found it to be unneccesary, so it's been bypassed. I made a rear buffer beam for the loco, fitted some couplers and the ensemble has been trundling up & down my test track nicely.

It's slightly wierd seeing a box van moving independently! Anyway, it's now functional and will hopefully be visiting one or two layouts at 2mm Expofest tomorrow & Sunday.

In the fullness of time, the van body will be replaced by the originally planned RCH wagon "tender". In the meantime, the loco crew will have to use big wing mirrors when running in reverse!