Overhead wire layouts

[danny]

A slightly obscure question but does anyone have any experience of building a layout with working overhead electrification? I know Jim Owers' Lochsanda used this system but am not sure whether he's on this forum. It would work very well for a project I'm currently looking at (where it has several advantages over 2 rail with cosmetic overhead lines). I've worked out what to do in theory, now I'm wondering about the best sources of copper wire, masts etc. I realise there are a number of items in 4mm scale intended for tramway modelling which would probably be very suitable, but I'm not sure what height they all are, which would be best to use etc. I think Lochsanda used Sommerfeldt masts and bow collectors or pantographs (as opposed to trolley poles). I would probably like to do the same but the Sommerfeldt masts may be a bit too low for what I have in mind.

I'd also be interested to know if anyone who has built or used such a system has found it to be reliable, and whether reliability is particularly likely to be worse on a shunting layout than on a continuous run. Any thoughts?

[engerth399]

Only a brief reply.  I have built two tram layouts with power collected from the traction wire.  I used 4mm scale steel poles which have a threaded base (I'm not sure now if it was 5 BA or 7 BA).  I sleeved these with brass tube to give them some profile.  For the wire I used 0.3 mm nickel silver wire.  These items were obtained from East Lance model Tramwas Supplies.

Peter

[danny]

Only a brief reply.  I have built two tram layouts with power collected from the traction wire.  I used 4mm scale steel poles which have a threaded base (I'm not sure now if it was 5 BA or 7 BA).  I sleeved these with brass tube to give them some profile.  For the wire I used 0.3 mm nickel silver wire.  These items were obtained from East Lance model Tramwas Supplies.

Peter

That's very useful information, thank you. Do you find that it runs reasonably reliably, compared to 2 rail?

[engerth399]

A bogie car is wired so that power is returned thru' all eight wheels - but pick up is thru' a very small stationary wheel rubbing on the wire.  This is very susceptible to even small amounts of dirt.  However it is very satisfying when you can four cars running automatically, two in each direction!!

[danny]

A bogie car is wired so that power is returned thru' all eight wheels - but pick up is thru' a very small stationary wheel rubbing on the wire.  This is very susceptible to even small amounts of dirt.  However it is very satisfying when you can four cars running automatically, two in each direction!!

I was hoping to use sprung bow collectors/pantographs rather than trolley poles, as it seems these would be more reliable and also they would not need to be reversed at the end of the line.

[engerth399]

Bow collectors would not need to be reversed ( though there are such things as automatic trolley reversers involving a trianguler wire layout - there's one at Crich) but you have to be more careful to see that the wire is centrally positioned above the track.

[danny]

Bow collectors would not need to be reversed ( though there are such things as automatic trolley reversers involving a trianguler wire layout - there's one at Crich) but you have to be more careful to see that the wire is centrally positioned above the track.

Don't some prototype systems have the wire zig zagging between posts to even wear? Although I'm not sure this would be so necessary on a model.

[engerth399]

The theory is the wire meanders about a bit to prevent a groove wearing in the bow collector (or pantograph).  I'm pretty sure no one will get the wire that well-centred in a model.

[danny]

Only a brief reply.  I have built two tram layouts with power collected from the traction wire.  I used 4mm scale steel poles which have a threaded base (I'm not sure now if it was 5 BA or 7 BA).  I sleeved these with brass tube to give them some profile.  For the wire I used 0.3 mm nickel silver wire.  These items were obtained from East Lance model Tramwas Supplies.

Peter

Just to come back to this, is there a need to insulate the actual contact wire from the traction poles/masts? It seems like this would be sensible but I'm wondering how it would be achieved, as most of the equipment I've seen has the masts made out of metal and everything soldered together.

[Ian McAulay]

My understanding is that for either pantographs or bow collectors, the wire zigzags over the track centre line or on curves a series of straight chords have the same effect. The actual pickup on these is a carbon strip on top of the metal structure and the zigzagging is to avoid wearing a groove in the carbon.

Pantographs (eg Blackpool trams and most modern tramway systems) work in either direction. Diamond pantographs are symmetrical anyway and single arm designs (much like railway pantographs) work with the elbow either leading or trailing.

Bow collectors (eg Glasgow trams) always lean away from the direction of travel. I remember watching the tram conductor flipping the collector over at the end of the tram route near where I lived in Glasgow 1959-61. This involved pulling on a rope to do it and presumably there was a fairly slack span of contact wire to make this possible. I don't know if this can be done automatically when the tram changes direction.

Ian

PS Talking of trams. Does anyone know of a supplier of OO or HO scale tram rail? ie with the flangeway included in the cross-section.

[danny]

My understanding is that for either pantographs or bow collectors, the wire zigzags over the track centre line or on curves a series of straight chords have the same effect. The actual pickup on these is a carbon strip on top of the metal structure and the zigzagging is to avoid wearing a groove in the carbon.

Pantographs (eg Blackpool trams and most modern tramway systems) work in either direction. Diamond pantographs are symmetrical anyway and single arm designs (much like railway pantographs) work with the elbow either leading or trailing.

Bow collectors (eg Glasgow trams) always lean away from the direction of travel. I remember watching the tram conductor flipping the collector over at the end of the tram route near where I lived in Glasgow 1959-61. This involved pulling on a rope to do it and presumably there was a fairly slack span of contact wire to make this possible. I don't know if this can be done automatically when the tram changes direction.

Ian

PS Talking of trams. Does anyone know of a supplier of OO or HO scale tram rail? ie with the flangeway included in the cross-section.

But in model form, does the live contact wire need to somehow be insulated from the structure supporting it, even if the latter is also made of metal? It seems as though this might be a good idea to avoid shorts or making the resistance too high, but I'm not sure how to do it as most model tramway wiring that I've seen appears to have the wire either soldered to or wrapped round the supports.

In terms of the locomotives, I'm thinking of using diamond pantographs - a compromise between not looking too modern but also not having to be reversed, which would be a bit of a pain on a shunting layout.

I'm not sure whether the wire needs to zig zag on a model although I was under the impression that this was less of an issue than on the real thing, especially at low speeds.

[Ian McAulay]

Speaking totally theoretically here, as I have no experience of building model OHLE, live or dummy...

I don't see any problem with having the masts 'live' as well as the contact wire. The baseboard is likely to be a good insulator and the track base is probably insulated anyway, as it would be for ordinary 2-rail operation, so a short circuit between them is very unlikely. I would also expect that all-soldered construction for masts and contact wire is going to be more robust than a construction with insulation. If the masts are live, that also gives an opportunity for completely invisible power feeds, by having some or all overlength so they poke through the bottom of the baseboard and connecting the electrical feed there.

My 2p worth!

Ian

[danny]

Speaking totally theoretically here, as I have no experience of building model OHLE, live or dummy...

I don't see any problem with having the masts 'live' as well as the contact wire. The baseboard is likely to be a good insulator and the track base is probably insulated anyway, as it would be for ordinary 2-rail operation, so a short circuit between them is very unlikely. I would also expect that all-soldered construction for masts and contact wire is going to be more robust than a construction with insulation. If the masts are live, that also gives an opportunity for completely invisible power feeds, by having some or all overlength so they poke through the bottom of the baseboard and connecting the electrical feed there.

My 2p worth!

Ian

A good idea with the suggestion of poking through to an under board power feed, the only issue could be that that space probably needs to be used for connections between the tracks (electrically, a complex track layout is the same as a straight line with overhead wire, unless isolating sections are specifically needed, which they won't be, so it makes sense for me to common all the rails and connect them up to provide the return side).

I'm concerned about the high resistance that might be introduced if cast metal etc., that the overhead wire supports could be made from, is live (in contrast to good conductors like copper wire, which might be used for the actual contact wire). I also don't know if the electric current would cause any damage to paint applied on the outside. While brass tube is actually used successfully as a conductor in other parts of this project, it's in much, much shorter lengths so perhaps not quite the same thing.

However, I definitely agree on the question of how robust it would be - insulation would seem to involve supergluing bits of plastruct into the mast assembly at what are, from a structural point of view, fairly awkward points.

[Ian McAulay]

Electric current passing through something is only going to affect paint on the surface if it gets hot. Hopefully we're talking about much lower currents than that!

It might be easier to common the overhead. My reasoning is that it's fairly easy to put insulated rail joiners in track but much less so in the overhead wiring. (The previous discussion about robustness also applies here.) If there's an issue with poor conductivity of the masts, then putting the feed through several of them will improve the situation. (Think of them as resistors in parallel.)

As I said before, this ios all very theoretical for me - I've never built model OHLE. I hope it's helping anyway.

Ian

[Paul Alliet]

Back a good many years ago, I built several HO American trolley (tram) layouts with overhead wire--simple suspension, not catenary.  It's standard procedure to use the masts (poles over here) for power feed, and it doesn't cause any problems.  The small gauge wire used for contact wire does have relatively high resistance, especially if it's nickle silver, so fairly closely spaced feeders are desirable.  Whether to gap the trolley wire or the rail for sections was a hotly debated topic.  I usually gapped the rails for the reasons Ian suggested, but either one will work and neither one is right in an absolute sense. In the early 2000s there was an article in the 009 News about the Isle of Dhoon Railway, which used overhead wire; you may want to look it up.

Paul