DCC and running locos from overhead traction wiring

Hi,

I've got a couple of loco models that have live overhead traction wiring support through their pantographs and one question which I've raised in forums at my site in these two threads:

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is whether there is any standard for whether the left-hand or the right-hand rail is connected to the pantograph(s) for power collection using DCC.

I haven't come across a standard for this, but someone who's more savvy with the NMRA standards may well know what the answer is.

Failing that, I will ask the folks on the NMRA DCC working group list since I'm still a member of that list.

With the Modelling the Railways of NSW convention coming up, I'm hoping to fathom out what's going on with electric loco and passenger train models. I still have one of Ian Storrie's excellent 86 class kits (unfinished), but wouldn't it be fantastic to have high-quality brass models of the 85 and 86 class NSW electric locos, and perhaps even of the Victorian E-class locos, since that's an ideal medium for modelling electric locomotives in HO scale.

Thanks if you can provide a definitive answer to the question. Feel free to comment in the forums at my site too if you'd like to. I'll transfer any information from here to there otherwise.

Regards,

Craig.

Reply to
C. Dewick
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Craig

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Section 4 provides the answer. In a nutshell appying positive voltage to the overhead should make the model go forward. The negative would be the left hand running rail, as per normal 2 rail practice. A switch (if fitted) would switch the positive connections between RH rail & overhead. Any DCC changes would have to reflect this.

Reply to
Kevin Martin

With DCC , this is my personal opinion, I see NO NEED to use the overhead, as there is no advantage. Under DC yes, it's a great way to have a seperatly controlled lcoo on a layout. But DCC where you have total control of the individual locos, I would model the overhead, ensure the pantographs spring and do not fould, and leave it unpowered.

-unless you really really really want the spark of the panto to be replicated !

You can do it, lets say all powerfeeds on the track are a red and a green wire. You could make the overhead wired say for the red wire and connect the overhead to the red track pickups. Won't achieve anything really control wise at all.

My two cents. David Head

Reply to
dthead

Thanks for the info. It doesn't really help much with DCC since there is no such thing as a 'positive voltage' and 'negative voltage' with DCC. It's a pulse-width modulated square wave with an amplitude of between 15 and 20 volts.

It could be something that's much more difficult to solve in reality because if the pantographs are connection to one specific power pickup side of the loco, changing direction would require either a shift in 'polarity' of the power feed to the overhead wiring or a device in the loco itself to change which side of the power pick-ups it is connected to. Does that make sense? I'm not sure if it does to me but maybe this is something that's been largely ignored in terms of DCC development.

Craig.

Reply to
C. Dewick

There's something to be said for the 'arcing and sparking' aspect of electric traction, but I wonder how good that is for long-term operation. After all model overhead wiring is nowhere near the physical and electrical capabilities of the real thing.

True, but it's an extension of DCC which doesn't seem to have been given much attention.

In reality there may be RFI/EMI issues relating to doubling up of one 'rail' of the power feed from the booster which may affect decoder performance. I'm not an RF expert though so it's all speculative at the moment.

Regards,

Craig.

Reply to
C. Dewick

Not really, I can't see why DCC is any different WRT pantographs/pickups. Just liven the overhead so that it is equilavent to the RH rail. If you turn it around you might have an issue though, I haven't thought too much about that.

Reply to
Kevin Martin

"C. Dewick" skriver:

It depends on, how you turn the loco around. But standard is right-hand, since left is "common".

There is really no idea of using the overhead wire when running DCC. It will only cause you more problems. You have to make sure that the loco is placed correctly, Otherwise tho loco will not run. The current pickup from overhead wire is not as effective af from many wheels. You can off course use _both_ track and wire, but then a loco on the track, that is turned around, will cause a short circuit.

Using overhead wire for supply makes it impossiple to do a reverse loop.

Klaus

Reply to
Klaus D. Mikkelsen

In message , C. Dewick writes

Craig, the standard answer to using DCC fed through the Catenary is "Don't". It's unnecessary as you have already wired your track up and it exposes you to a variety of additional and unnecessary complications. Keep the overhead as a scenic extra and stay on the track feed.

Reply to
Ian Birchenough

What scale are you modeling? DCC on my HO club's layout is 14VAC at the booster (with the Digitrax Chief system) with a RMS meter, Tony's RRamp meter. And on my home HO layout, it's more like 12VAC (with my Digitrax Zephyr system).

To do that so the power pick up doesn't matter, the solution is simple... Wire both rails to the same polarity and use the catenary for the other polarity, just like the prototype. It's what my old club did for 45 years on our trolley trackage, and it worked very well, considering it was live overhead. It also meant that we never had to isolate diamonds and rail frogs.

Paul A. Cutler III

************* Weather Or No Go New Haven *************
Reply to
Pac Man

Have you ever run a trolley? There's a darn good reason to use the live overhead if you are going to put the poles and pans up: What happens to a pan or a pole that falls off the wire? It snaps straight into the air as high as it will go. If you have dead overhead, it will now hit every catenary bridge, tunnel, guy wire, signal bridge, RR or highway bridge, etc. and either stop the whole thing in it's tracks, break the obstruction, or break off the pan/pole. This gets expensive as poles and pans ain't cheap. If you have live overhead, the trolley will stop...probably instantly as few trolley models that I've seen have flywheels. This is a great safety device and allows one to run a trolley with confidence that if a pole or pan falls off the wire, you're not going to have to fix it all the fricken' time.

Control is not the point at all with live overhead. Most trolleys that I've ever seen are seperate RoW's from the mainline anyways, and at my old club, both trolley rails were the same polarity.

Paul A. Cutler III

************* Weather Or No Go New Haven *************
Reply to
Pac Man

But it won't matter if both rails are the same polarity, which is what my club's old trolley layout was like.

Again, wire both rails the same polarity, and it won't matter which way the loco is pointing. Certainly, a pole or pan is not as good as 4 wheels, but then that is why one models trolleys anyways...to have that wire, to watch that pole run in and out, to watch that pan go up and down. It's what makes trolley modeling different from the rest. And if you don't use the overhead for power, be prepared to fix a lot of pans and poles over the years as they will hit obstruction after obstruction when they fall off the wire.

Shows what you know. If both rails are the same polarity, there is no reverse loop wiring at all!

Paul A. Cutler III

************* Weather Or No Go New Haven *************
Reply to
Pac Man

If you have a dead overhead, and you run with the pans and poles up, then what do you do when they fall off the wire? I'd be watching them get slammed into all kinds of obstructions and getting damaged. If I use the overhead as power, I'd be watching my trolley stop instantly and not be damaged.

Paul A. Cutler III

************* Weather Or No Go New Haven *************
Reply to
Pac Man

Pac Man skriver:

Yes, but the DCC system runs with square wave and not sine wave current.

Correct - until you want to run a diesel/steam loco...

Klaus

Reply to
Klaus D. Mikkelsen

Pac Man skriver:

Shows what you don't know.

If you have read what Craig wrote here:

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Qoute: "Hi everyone,

My new layout design is coming along well. Something I've decided to do is make it an industrial setting with lots of general industry serviced mostly by rail, and I'd like to have the 'main line' feeding into the area electrified so that I can run my electric locos (Ian Lindsay 86's and brass 46's) as well as diesels." Unqoute

How do you want to run diesels, with both rails beeing the same polarity ?

Klaus

Reply to
Klaus D. Mikkelsen

According to Lenz (who developed DCC), several more European modelers, and myself, the reason not to run with live overhead is fairly simple and has been referred to indirectly in some of the answers. The small contact area of the pan/wiper as compared to the contact points of the wheels. Also, in our experience, more arcing takes place with pans and pantograph wipers which the highly sensitive control unit interprets as a short and then shuts down. Unless your layout will receive fairly heavy use to keep the overhead wire clean and arc free, I would suggest running normal rail to rail. It can be done, as I have done it (European prototype), however, it was found that the rail to rail solution was more reliable.

Reply to
+GF+

"Klaus D. Mikkelsen" wrote in message news: snipped-for-privacy@du.kan.finde.den...

I'd put in a toggle to switch between live overhead and normal 2-rail operation for each track so equipped...unless you are going to be running eletrics AND diesels on the same train (most times when that happened on the prototype, at least in the USA, it was for pulling trains through long tunnels...not something that one would normally need reverse loops to accomplish). In which case, you would be out of luck if you wanted reverse loops, too. If it was a case where you'd never switch the electric around, you could rely on only picking up one rail with the wire for the other polarity. I don't know much if anything about Austrailia rail (other than they got some New Haven G-4a 4-6-0's during the war) and how they operated their electric service. But on the New Haven, in the electified zone, diesels (and steam) were the exception, not the rule...unless one counts New Haven, CT where they changed locos. But, if I wanted to model an electrified mainline, a toggle switch or relays based on occupancy would be my answer for solving the problems of live overhead. Either way, it is not "impossible" to have a reverse loop with live overhead. My club, the South Shore Model Railway Club

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had two reverse loops for 45 years...and there were no gaps, no toggles, not much of anything, really. Just rail and wire and a bunch of scenery. In fact, in one of our loops that was under the scenery, the trolley wire was replaced with a brass trough (or "C" section beam) which made it nigh impossible for the pole to lose contact while in the tunnel. Worked well, too. It even had a ramp on each end for pans...

Paul A. Cutler III

************* Weather Or No Go New Haven *************
Reply to
Pac Man

Ok...but I have to tell you that our transformers powering our boosters are using the 14VAC taps. Are you saying that the voltage is higher than that after it goes through the booster?

You could simply use a toggle to switch between the two (live overhead vs. normal 2-rail)...unless you want to run diesels/steam with the electrics. Was that common in Austrailia?

Paul A. Cutler III

************* Weather Or No Go New Haven *************
Reply to
Pac Man

Pac Man skriver:

But why all the extra work, when all locos can run without modifications on simple 2 rail ?

I guess you didn't run DCC and mixed diesel/electrics.

Klaus

Reply to
Klaus D. Mikkelsen

Pac Man skriver:

14 volts AC becomes 18VDC when it is rectified.

After that is is beeing chopped into squares.

I don't have a clue. But I can tell you that here in Denmark a lot of diesels rund undeneath overhead wire.....

Klaus

Reply to
Klaus D. Mikkelsen

On Thu, 22 Jun 2006 05:03:23 GMT, I said, "Pick a card, any card" and "Pac Man" instead replied:

And then?

-- Ray

Reply to
Ray Haddad

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