Live catenary

I've been toying with the idea electric traction but if I'm going to go to the effort of putting up catenary I don't want it to be just cosmetic.

In general, the model catenary duplicates one of the rails. This is fine until the loco is turned.

Another option is to follow the prototype - make both rails common and always take power from the overhead. This would require rewiring rollingstock, which isn't a big issue, but would prevent the electric stock from running on a normal 2-rail layout or running steam or diesel under the wires.

Is there any electronic trickery that would allow a vehicle to run off 2 rails or off overhead, whichever way it's facing? The idea would not be independent control of two trains off both power sources at the same time, but rather some sort of on board system that could make a circuit through the overhead and /either/ rail depending on which way it's facing.

This would be purely DC. I don't even want to think about how to do this with DCC!

Cheers David

Reply to
David Bromage
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A simple changeover switch on the control panel wired so:- Take the wire that you would connect to the track to the changeover connection. Take the two outputs of the changeover , one to each track. Leave the wire to the overhead permanently connected.

Reply to
turbo

I forgot the KISS principle. I was thinking of electronics on the loco to switch between rails depending on where it detected power!

Cheers David

Reply to
David Bromage

How would that meet the criteria of running two rail pickup stock?

Regards

Reply to
Peter Abraham

Easy; you have two DC controllers. Each with own supply (so no common earth), which for simplicity can be achieved with two mains transformers.

Controller 1 - wired to both rails in normal manner Controller 2 - wired to O/H wire and to the change-over switch. The outputs of the change-over switch go to each rail.

The switch means Controller 2 is connected to either rail, but not both.

The locos would need to be wired internally for either "track running" or "O/H plus one side". The O/H locos would not have any electrical connection to the "other running rail".

You could drive two DC locos simultaneously (one from track, one from O/H) on the same bit of rail using the above.

The scenario may complicate track sections used to isolate locomotives; one would either need to be ingenious, or use double-pole track isolation to break both rails.

- Nigel

Reply to
Nigel Cliffe

Yes, good idea. I have grown too used to HM 2000s which would not tolerate that application despite being apparently quite separate supplies.

Regards

Reply to
Peter Abraham

I would have thought it would be easier with DCC (all polarity switching being done in the loco chip), just make sure that all the near rail (from the front/control panel) are on the same ve+ as the catenary and use the all the far rails are ve-. Or have I missed something about DCC?

Reply to
:Jerry:

Yes :-) !

1) Many German suppliers of O/H electric locos advise against using live OH supply on a DCC equipped layout. I guess they have a good reason, which may just be complication ! 2) Its a completely unnecessary complication to a DCC system; DCC adequately addresses locos independently from the track. 3) If doing the O/H live, and supplying other locos via track, you still need the same change-over switch between LH and RH running rail for the O/H return path.

- Nigel

Reply to
Nigel Cliffe

David Bromage skriver:

2 words:

Forget it.

Klaus

Reply to
Klaus D. Mikkelsen

Hi David,

Quick first thoughts: Yes, it should be possible. What would the on board electronics detect:

- left rail to right rail: Traction current A.

- left rail to overhead: Traction current B.

- right rail to overhead: Nothing or A+B or A-B. (0v to 24v)

Obviously "common return" wiring isn't going to be feasible because no one of the three conductors is common. Both rails would have to be cut for each block and both would need to be switched . (Double pole switches rather than the normal single pole)

You'd need two in-loco modules/relays that connected the motor (to rail) when rail to overhead current was detected, probably a relay with a capacitor to give some delay to allow for intermitent current collection. A second relay contact would cut out the other relay coil so both relays couldn't be on together. The whole module would cost less than 5 pounds per loco, but you'd face the expense of the double pole switches compared to the single pole block switches normally used.

I think that covers it all.

Greg.P. NZ

Reply to
Greg Procter

I've got a Hornby class 86 locomotive with pantograph which can run from catenery or the rails. There's a slide switch in the roof to select which power source to use. I've never tried overhead power through as I could never find a supplier of a kit (and didn't fancy building it all myself from scratch!)

I'm sure you could do something clever with electronics to automatically detect which power source to use but as others have suggested much simpler solutions I wouldn't go down that route unless you fancy doing it for the sake of it.

peter

Reply to
naked_draughtsman

A small but vital point, I use PWM controllers, so there's always 12 volts available in combination with a capacitor for lights, or in this case the relays.

Reply to
Greg Procter

On Wed, 6 Feb 2008 20:34:22 +0000, naked_draughtsman wrote

Was this model comptemporaneous with Hornby's own catenary kits?

Reply to
Stimpy

I would keep the catenary cosmetic and go DCC much easier. I use Lenz and it is not reccomended to feed decoders via a pantograph and catenary as there could be a voltage spike resulting in a fried decoder. On the real railway current is returned via the running rails to the feeder or sub station. You cannot replicate this with variable polarised DC model railway current. regards, Steve

Reply to
Brush4

May I ask why not. The only benefit i can think of is having sparks flying off as loco goes round. May be better to work out how to get sparks seperately whilst using track for motive power.

Cheers, Simon

Reply to
simon

If you *only* have O/H powered locos, then things are real easy -- all fun and games with reverse loops and switch frog power switching vanish. The track (both rails) are one side and the catenary is the other. Period.

Reply to
Robert Heller

I agree.

Think about reliability. If lets say an 8-wheel loco is powered strictly to the track then it has 4 points of pickup on each track. If you use catenary then the same loco has 4 points of contact with the track and only 1 (or 2 at the most) with the catenary (the pantograph). So, IMO, it will not be as reliable as a track powered loco.

Peteski

Reply to
Peter W.

On 2/6/2008 9:32 PM Peter W. spake thus:

You folks oughta talk to Bob Hundman (former publisher of /Mainline Modeler/); he ran several articles showing detailed construction instructions for building working catenary. Stuff looked beautiful. Don't know if he has actually run any of it, but looks as if it could. (I have no doubt that making working catenary would require extreme care and diligence to pull off successfully.)

Reply to
David Nebenzahl

3 words:

Not very helpful.

Live catenary can be done, reliably, in model form. Take a look at what the N-Cat group are doing in N scale.

This is taking it one step further to get around the problem of not being able to turn a loco.

Cheers David

Reply to
David Bromage

I know that the trollies used two poles, one for each direction. You might be able to use the pantographs the same way. To go forward, raise the rear pantograph and reverse, the front one. Also, Marklin makes catenary and supplies for catenary. It is all german prototype in HO, but it does work. Vollmer also makes catenary

Walther's 2008 HO catalog, pages 306 & 308

Reply to
Frank A. Rosenbaum

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