Hang on a minute "a PMU" - the photo clearly shows one set of etchings and a semi-built up unit. So this is either a little bit of clever photoshop trickery or there is more than one in the pipeline. That said I would be interested in knowing what the power train arrangement will be.chap needs a PMU!
Adrian, could you show us what you have put together? The 6mm motor should work but you do need to have as little friction as possible in the drive train. If you look at any of the commercial N mechanisms they are all loose and sloppy. Quite different to a 7mm scale mechanism.Thanks for the explanation - I hadn't realised it was a two car unit as I guessed PMU as Personal Motor Unit. I've just been trying to put together a motor unit for a rail motor and I used the 6mm motor from Nigel Lawton. Unfortunately the motor hasn't got enough umph to get the wheels turning. So I'm going to have to go through checking everything is free as possible, plus try a slightly larger motor to get the mechanism run in. If it loosens up then I may try putting the 6mm motor back in. Hence my interest is seeing what solution you come up with.
Adrian, could you show us what you have put together? The 6mm motor should work but you do need to have as little friction as possible in the drive train. If you look at any of the commercial N mechanisms they are all loose and sloppy. Quite different to a 7mm scale mechanism.
Hi, thanks for the interest. I will post where I have got to but rather than clutter up Jerry's thread I will start my own 2mm workbench thread for it. I've tried to make the mechanism free running rather than sloppy - there's very little spare room to have it loose and sloppy!Adrian, could you show us what you have put together? The 6mm motor should work but you do need to have as little friction as possible in the drive train. If you look at any of the commercial N mechanisms they are all loose and sloppy.
Yes, I didn't express that too well. The N gauge comment was to illustrate how the mass producers make things work while dealing with their manufacturing tolerances. Trying to replicate this with proper gears and bearings from the 2mmSA would lead to tears and rapid wear. The aim should be to have nearly no perceptible resistance when revolving the gear chain as the small motors have very little torque at low revs but are ok once running.Whilst I would agree that you want as little friction in the drive train as possible "all loose and sloppy" is likely to cause more problems than it solves. In N this is generally to allow locos to go round silly tight curves and has very little to do with good running.
Jerry