Motorise a turntable, kit

[AyJay]

Prompted by the article in February’s issue of BRM on motorising a Peco Turntable, I would like to add my findings on this subject for the benefit of anyone considering this useful addition to their layout.  

I purchased and fitted the Peco Turntable, LK-55, several years ago, along with the motor kit by Expo. For the first couple of years, it worked fine.  But then I found that the movement began to get worse and as of yesterday, refused to move at all.

 

Slight digression first.  If you have not seen the motor kit, it comprises of the motor itself, gearbox and selection of gears from which you can select a range of ratios. There is also a smooth round metal rod about 15cm long that engages with the underside of the turntable bridge, a large red gear wheel to fit on it, a worm to fit on the gearbox output and engage with the red gearwheel. Lastly, there is a coil of wire, Double Pole Double Throw switch, batteries and battery holder.

 

Thinking that the gears had probably jammed, I placed the baseboard on its side to access the mechanism and taking it apart, discovered that it was not the gearbox at all.

Underneath the centre of the bridge, around which it rotates, is a protrusion into which fits the metal rod. This protrusion itself slides inside a bush that fits into the turntable well and the one rotates inside the other. Well I had found that this originally snug fit had become seized and needed some ‘encouragement’ to come apart. Perhaps the pressure of the metal rod had caused its holder to expand, or perhaps the cold had made the bush contract?  Anyway, the remedy was in the use of a needle file and fine glasspaper to ease the connection a little.

 

I should have left it there.  I feel that what I did next was a step backwards that I may regret.

When fitting originally, I used the whole of the metal rod, with the turntable bridge at one end and the red gear near the other.  To secure the bottom end of the rod in place, I had a piece of ply mounted horizontally and fixed to the internal bracing of the baseboard, the rod end rotating in a small hole.  The motor assembly was fixed to the upper surface of this sheet and engaged with the gear.  I decided to change this and follow what was done in the article by remounting the motor directly under the turntable well and re-site the red gear accordingly. What I found was that the pressure of the worm was now forcing the gear sideways a little, causing the bridge not to sit flatly, but to lift up away from this force.  I may try to put it back the way it was, but the use of superglue on the rod may mean that I have ‘burned my bridges’ in that regard.

 

Other observations include:

It does not take much encouragement for the contact springs to lift the bridge.  It may be helpful to glue some weight to the underside.

The motor is noisy and could resonate; some damping may help.

The rod end is round and smooth, fortunately it is a tight fit into the bridge and the gear.  I would have preferred if it  was an ‘interference fit’ e.g. squared, splined or threaded.

The worm does not engage very well into the teeth of the gear and only catches the top of the teeth; the teeth are of a different profile, they also lie perpendicular across the gear.  I may try to see if I can wedge one side of the motor so that the axis of the worm is not in the same plane as the gear, about 5 to 10 degrees should help improve the engaging of worm to gear.

Lastly, I dispensed with the battery and repurposed an old phone charger.

 

Can I recommend buying this turntable and motor?  Yes! I would also have no reservations about buying another if I wanted one.  I own my mistakes and everything we do is a constant learning exercise.

 

I also now have to do something about the appearance of my turntable, I think I’ll apply brick paper round the inside wall of the well.  But I’m not sure what to do with the well floor?  Perhaps paint it black and sprinkle coaldust, something to represent moss and then dribble in some patches of Deluxe Instant Water to represent puddles? But what do I do with the exposed ledge at the top of the wall and the immediate ground surrounding it?  Think I’ll have to take another look at the Didcot Turntable…   Suggestions anyone?