Suitable chassis for overhead wire conversion

[engerth399]

The Light Railway part of the name is often forgotten but as I enjoy modelling electric street tramways (picking up from the traction wire) as well as French metre gauge it has been useful for me.

[danny]

The Light Railway part of the name is often forgotten but as I enjoy modelling electric street tramways (picking up from the traction wire) as well as French metre gauge it has been useful for me.

I always assumed (partly based on the paragraph about this on their website) that the light railway part referred to things like the Burton & Ashby Light Railway (which actually was an electric tram line) or the modern sense of the term 'light rail'.

'Note: the light railways covered by the TLRS are those which predominately run tramway type vehicles, rather than, for example narrow gauge steam railways.'

https://tlrs.info/about-us/

[engerth399]

That is the case but there is a lot of modelling info there.

[danny]

On the Roco idea, is there any way when looking at one of identifying whether it is one of the ones with the overhead power switch built in?

I'm not sure what it would look like on other locos (or other manufacturers) but the 'switch' is a small slotted screw head, and on that EBay loco is visible towards the left hand end in the 1st photo (about ⅓ the way along from that end with the fine brown 'wires' routed around it). Unfortunately I can't recall from my own Roco BR 144.5 (I used the chassis under a railcar...).

From the description it sounds like the switch is in the 'wrong' position - loco does not work on the track but the motor works with current applied direct, but it's up to you to decide if £30 (+£4 p&p) is worth the gamble or not.

So as a bit of an update the BR 144.5 has now arrived. I've managed to get it working off both the overhead (well, a bit of brass tube with the lead from the controller held against it for now anyway) and 2-rail though it seems to be a bit unreliable if the body is not pushed down. I think this is due to the loose body meaning that the switch is not in proper contact with the circuit board on top of the motor (which it needs to be to complete the circuit, regardless of whether it's running in 2-rail or overhead mode. This is perhaps something I can actually fix more easily when I make the new body, rather than trying to repair the original switch.

However, it does appear that when in overhead wire mode the loco is only returning current through one rail (which I assume is how it's designed to work, for 2-rail layouts with additional overhead wire and common return). I don't think there would be a problem trying to run this on a system that returns through both rails (as I intend to do) but obviously it means that one side of the chassis is not being used, increasing the risk of dead spots. Is it likely to be possible to alter the chassis to return through both rails? It looks as though this could be a bit complicated as the pickups on the bogies are not particularly easy to access. It would obviously be nice to retain the ability to run off either overhead or normal 2-rail as then I could run it on my other layouts as well, but it's not essential to have this.

In terms of actual running qualities (as far as I can tell so far anyway) it seems perfect - relatively slow and smooth, and crucially with the ability to actually push the transporters and heavy motorised wagons on top.

[JulienW]

So as a bit of an update the BR 144.5 has now arrived. I've managed to get it working off both the overhead (well, a bit of brass tube with the lead from the controller held against it for now anyway) and 2-rail though it seems to be a bit unreliable if the body is not pushed down. I think this is due to the loose body meaning that the switch is not in proper contact with the circuit board on top of the motor (which it needs to be to complete the circuit, regardless of whether it's running in 2-rail or overhead mode. This is perhaps something I can actually fix more easily when I make the new body, rather than trying to repair the original switch.

From memory the brass screw on the roof is attached to a rotating brass contact on the underside of the roof. This contact presses against tracks in the circuit board fixed to the top of the chassis, and the relationship of rotating contact and tracks dictates whether it picks up from the rails or the overhead.

With the body lifted off the brass rotation contact isn't in the circuit, so neither system will work - as you have discovered!

As you say it may be easier to fix the situation when you've sorted out what the new 4mm scale body will look like.  One thought is to (carefully) solder wires to the contacts on the circuit board and run them to a miniature slide switch attached to the body somewhere.

However, it does appear that when in overhead wire mode the loco is only returning current through one rail (which I assume is how it's designed to work, for 2-rail layouts with additional overhead wire and common return). I don't think there would be a problem trying to run this on a system that returns through both rails (as I intend to do) but obviously it means that one side of the chassis is not being used, increasing the risk of dead spots. Is it likely to be possible to alter the chassis to return through both rails? It looks as though this could be a bit complicated as the pickups on the bogies are not particularly easy to access. It would obviously be nice to retain the ability to run off either overhead or normal 2-rail as then I could run it on my other layouts as well, but it's not essential to have this.

I suspect that's because it's easier to switch on of the feeds to the motor between one rail and the overhead, rather than (in effect) have one switch to do that whilst the other switches both rails together for a '2 rail pick up + OHW'.

It would also mean that if the loco in OHW mode was placed on track in 'normal' mode (pick up from one rail & return current though the other) it would not create a short, whereas if the wheels on both sides are wired together it will. Given the way these models may have been used - on layouts with caternery equipment but also running diesel (& steam?) locos - this is probably the better (or 'least worst') option, and would work better if the rails were wired for 'common return' (one rail common to both the other rail and the OHW).

To be honest I'd leave the system on the Roco loco alone, as with it's heavy metal chassis block and 8 wheel pick up (or 4 wheels on one side & the wire) it's going to take a lot to stop it.

[danny]

From memory the brass screw on the roof is attached to a rotating brass contact on the underside of the roof. This contact presses against tracks in the circuit board fixed to the top of the chassis, and the relationship of rotating contact and tracks dictates whether it picks up from the rails or the overhead.

With the body lifted off the brass rotation contact isn't in the circuit, so neither system will work - as you have discovered!

As you say it may be easier to fix the situation when you've sorted out what the new 4mm scale body will look like.  One thought is to (carefully) solder wires to the contacts on the circuit board and run them to a miniature slide switch attached to the body somewhere.

I was thinking of having some kind of rotating switch still, but actually located in the hole on the chassis circuit board, rather than just pressing down on it from the body. This has the advantage that it won't be dependent on how tight or loose the body is (the contact with the pantograph will probably still be dependent on this, but the way that is done is a bit more robust and reliable anyway). The disadvantage is that I'll have to take the body off to switch between overhead wire and 2-rail mode, but I'm not really bothered about this and it seems inevitable anyway, given the increased height of the new body.

I suspect that's because it's easier to switch on of the feeds to the motor between one rail and the overhead, rather than (in effect) have one switch to do that whilst the other switches both rails together for a '2 rail pick up + OHW'.

It would also mean that if the loco in OHW mode was placed on track in 'normal' mode (pick up from one rail & return current though the other) it would not create a short, whereas if the wheels on both sides are wired together it will. Given the way these models may have been used - on layouts with caternery equipment but also running diesel (& steam?) locos - this is probably the better (or 'least worst') option, and would work better if the rails were wired for 'common return' (one rail common to both the other rail and the OHW).

To be honest I'd leave the system on the Roco loco alone, as with it's heavy metal chassis block and 8 wheel pick up (or 4 wheels on one side & the wire) it's going to take a lot to stop it.

I agree and am increasingly inclined to leave it basically as it is. With the existing design of this loco it will still be able to run on a system where both rails are bonded together to form the return, it just means one side of the wheels won't form part of the circuit, but the re-wiring necessary to change to 'both-rail return' seems potentially quite complex. I'm also starting to realise how useful it would be if the loco was still 'dual-equipped' (to borrow a term from prototype railways) as at present I don't have any overhead wire layouts on which to test the loco and run it in. This would, as you point out, effectively need another switch somewhere to switch the polarity of the wheels on one side.