Kit built metal locomotives electrical insulation

[ardbealach]

I have a DJH kit built tank locomotive which runs well in analogue.  I want to DCC it, and I am told that the metal body and metal chassis can be a bit of a disaster with potential electrical shorts when it is DCC'ed.  As a way of reducing the potential of wiring contact with bare metal, and the possibility of shorts, does anyone have any thoughts on how I could seal the inside of the boiler etc to provide an electrically insulated internal skin?  I am aware of the need to cover all the soldered joints in the wiring with flexible insulating sleeves.  Thank you in anticipation. (AM)

[jpendle]

Why not seal the decoder with Kapton tape? That will prevent it shorting to the body of the loco.

 

Regards,

 

John P

[RobjUK]

I use Tygaflor tape - it's just about indestructible, for both mechanical protection and insulation.

It's not cheap but I've never seen anything that compares to it; I know some companies use it on packaging machines to stop the steel wearing away...

 

From a very quick search, this is the cheapest place I've found:

https://www.eldertapesandrubber.co.uk/ptfe-glass-cloth-with-adhesive

 

(And I've been using the same roll for something like 15 years; it still seems the same).

 

Insulate the metal surfaces with that rather than the decoder - that allows better cooling.

 

Edited October 11, 2019 by RobjUK
typos

[34theletterbetweenB&D]

On good ground putting shrink on insulation on all soldered wire joints and lining the decoder void with an insulating tape. However, that's not the problem in my experience.

 

14 hours ago, ardbealach said:

I have a DJH kit built tank locomotive which runs well in analogue.  I want to DCC it, and I am told that the metal body and metal chassis can be a bit of a disaster with potential electrical shorts when it is DCC'ed...

My best advice. Run the loco on DC around the layout in the dark, and watch closely. Turn it round and run it again. Did you see any sparks on the loco? Those will be a problem.

 

Important question. Is the loco frame and thus body live to one rail by intention? That is 'inadvisable' for DCC. Not impossible, but if it can be converted to have frame - and thus body - fully isolated from track power, the problem set is much reduced. That may be enough to eliminate any sparking seen on the test run, check again.

 

If there is still sparking, then it is a patient slog to find all the shorting points and eliminate. (This even affects RTR OO. Bachmann have used cast metal for the footplates of many of their steam locos. Once carrying wheel flanges have cut through the paint, see those sparks. Cutting arches to provide clearance cures.)

 

Finally will there be more than one kit built loco operating, live to one rail? If so insulation of all buffers and couplers is advisable.

 

It is possible, I have several metal kit builds running on DCC, but all of them relatively small inside cylinder types. Mighty happy to leave the large outside valve gear types to the RTR mfrs....

[RexAshton]

I believe the problem is with earlier DJH kits as the motor is earthed directly through the non-insulated wheels on one side via the chassis. This also means that by default the body is also live to one side. As far as I know if the loco has insulated wheels on both sides there should be no problem. Beware of putting extra heat shrink around the decoder as it could cause it to overheat.

[ardbealach]

Thank you all for your helpful comments which have been most useful in understanding this DJH kit. (AM)