About Comments

Comments are enabled on all postings. Click a posting to find the comment box. Comments are moderated and appear after my review.

Friday, 12 October 2018

A Model Railway - Track Laying

The track plan is for a fictitious BR(S) branch line terminus, although some aspects are taken from real locations. The platform accommodates two roads. Road 1 can hold a pacific class locomotive with two MK 1 coaches and includes a run around loop. Road 2 is a bay that accommodates a tank locomotive and two pull-push coaches. It also doubles as a loading dock and cattle dock. An engine shed is served from the run around loop. A separate goods siding branches off  before the station.

Track is Peco code 100. Turnouts are medium radius insulfrog and manually operated. Track is pinned to the foam board with 31mm dress making pins. This is not a firm fixing in foam but when the ballast is glued in place it should hold the track firm.

Three tracks span the baseboard joins. Since the baseboards can be separated for transportation some means of electrical connection is necessary and consideration given to a more robust means of track fixing at the baseboard joins.

For simplicity no special treatment of the track at baseboard joins was undertaken. I may live to regret this. A robust method I have used before is to replace the last sleeper with a copper clad sleeper that is glued to the baseboard and the rails soldered to this.

I had given no thought to electrical connection whilst building the baseboard. Since the boards are solid then any plug and socket arrangement, wire connections or any other gubbins below track level cannot easily be contained within the baseboards unless chunks of  foam are cut away. With hindsight it would have been useful to extend the hardboard side panels to give a void beneath the foam board to retain such items. Happily, this omission has so far not manifest as a problem.

At the board track joins I soldered bare wires to cut down Peco fish plates that slipped over the end of the rail. Wire runs were easily embedded in grooves cut in the top of the foam board *. Where a wire has to run beneath rails an insulated sleeve over the wire stops short circuits.

The existing metal board connecting hinges serve as electrical connection simply by using a board hinge fixing screw to hold the wire as well. Of course, only two wires can be connected this way - the feed and common return, and yet there are three tracks spanning the baseboards requiring six connections. The workaround was to wire the feed and return to all three tracks. No problem for DCC but for DC there are sections of goods siding and run around loop that are always live where a train cannot be held isolated whilst another is run. For my track plan this is unlikely to cause operational problems. The elegant solution is to use a multi-pin connector with the six rails connected to their mating rails through it. But, I wanted to keep things simple for this model railway. Hence the compromise.

*Postscript - Short Circuit

A modellers nightmare, worst still is an intermittent one. I had tested the track with powered locomotive and for a week or so no problem. Then, the locomotive came to a grinding halt. The electrical meter confirmed a short circuit between feed and return. I started to desolder wires from the rails but no cause of the short could be found and it eventually cleared itself. I put the wires back and locomotives ran again - for a while, and then the short returned. I could not fathom how the short arose and even suspected a faulty turnout. So I desoldered all the wires from the rails again, which cleared the short from the tracks. But there was still a short between feed and return and yet the two were now physically isolated. It then dawned on me where the fault lay.

I deliberately used bare wire (except between rails) to be unobtrusive to the eye above ground and buried it in grooves cut in the foam board where appropriate.

What I did not account for was the aluminium foil board covering. Somewhere along the wire run the bare feed and return momentarily touched the conductive aluminium foil causing a connection (short circuit). To correct the problem I re-cut the grooves a little wider taking care to strip the foil from the area. If I used this burying method again I would ensure the wire is sleeved with insulation where it is buried.

To Part 5.

To Part 1.

No comments:

Post a Comment

Related Posts Plugin for WordPress, Blogger...