Kit Building Chassis - Isolating for DCC

[ianLMS]

Good morning all,

I have recently acquired (from a felow RMWebber) a Craftsman Midland 0-4-4T 1P loco kit complete with high level gearbox, motor and Romford wheels. I intend to commence building it in the next few weeks and am starting to plan it out and make sure I have everything I need before I get started (Poppy's chassis jig, wheel tool, B2B guage etc).

 

I watched a You-Tube video by "the loco builder" and he mentioned having to isolate the chassis from the wheels as he uses DCC. I intend to fit a chip into the loco and run it DCC as well.

 

Question: I have the Romford driving wheels but the seller believes they are one pair insulated and one pair non-insulated. Does this make a difference? Do I need to isolate the non-insulated wheels from the chassis and if so, can you recommend the best option? or do I need to buy a new set of Insulated wheels?

 

I have posted this in the kitbuilding section as well just in case!

 

Thank you

Ian

Edited May 25, 2018 by ianLMS

[34theletterbetweenB&D]

For DCC, I would always suggest insulated wheelsets so that the loco frame is isolated from the rails, and especially when a metal body is to be mounted on it. Primarily because if the frame is live to one rail, then any contact with a wheel rim on the other rail will trip the system, and clearances were tight on Craftsman kits, my long ago Craftsman C12 was known as 'old sparky' in DC operation despite all wheels insulated. The latter because a metal body will be live to the frame unless special effort is made with insulating attachment points. Two such models with this construction are then a short waiting to happen.

Edited May 25, 2018 by 34theletterbetweenB&D

[Phil S]

You may have noticed how ALL manufacturers changed to having plastic (insulating) coupling assemblies once Zero-1 (and partly 2rail) and the like were launched - instead of a live-metal extension beyond the chassis which MIGHT be of the opposite polarity to the vehicle they have just coupled to !

(Although MOST model manufacturers standardised on which side of the chassis was common to the track, Tri-angHornby were the opposite --- this showed up with Zero-1 and its 3wire connections when Triang/Hornby locos initially ran backwards !  - to  the dismay of the MD (apparently)  - so within weeks of launch, Red labels reversing Forward/Reverse were supplied and then the panels re printed for new production   (This is how I gained much early experience in digitising locos - having 32 at launch, and then a few weeks later having to re-do them all - which ranged from a simple swap of insulating sleeve  (Xo4) to complete reconvert (Mainline white motors using screws into the chassis for connections)  and rotating magnets on Wrenn/ Hornby Dublo W/Country  locos)

 

Once double-heading and piloting/banking becomes a feasibility, then it helps if the locos don't short circuit as soon as they touch 8-)

The Secondary effect - and already mentioned - is the preference NOT to use the body as a conductor when a derailment occurs - because it is very likely to cause a short.  (and one reason why I prefer isolated lamps/LEDs -NOT using the common chassis return as in the Fleischmann Railcar conversion thread - for which I would ALSO ADD a1N4148diode in series with the LED/resistor to avoid reverse voltage breakdown risks if using the chassis path ... which can occur above 5Vwith some LEDs (0.5V with 'flashing LEDs')

 

As a comparison  - would you accept  mains wiring around your house which RELIED on or even used metal window frames, radiators and pipework for the return path** ??? ....  especially with decoders in close proximity to the bodywork -the risk of accidental contact is 'high' - and if that contact is then directly connected to (supply) rail ...maximum current may flow....

[Please do not confuse this analogy with the use of an earth-path with protective fuse in mains circuitry, or RCCB's or assuming (falsely) that copper plumbing can or should be used as an earth return. [Although BBC engineering policy was that ALL exposed pieces of metalwork should have an earth connection]

 

**I worked at a school once, over 30 years ago,where SOMEONE HAD wired many of the stage lights to use the earth as return ,and the lighting bars used common returns internally ....positively shocking 8-)

[ianLMS]

I have contacted Markits with the same picture hoping they can advise on a good solution or even better they will tell me the wheels in the set are already insulated

[ianLMS]

I tested the wheels with a continuity tester and i have one pair non insulated and one pair insulated so have ordered another pair of insulated wheels from Markits. That should sort it

Thanks

Ian