DCC and running locos from overhead traction wiring

Your point is well taken with the older pantograph designs.... However, most modern pantographs have two or three contact points.

On the railway that Craig is modelling, yes - but mostly in an earlier period than he is probably interested in.

All the best,

Mark.

(Self-Confessed Rivet Counter)

And then, if you look at the web site, they're building a new layout.

J. Bright

Are you running electric only and honestly ? If YES make the panto one polarity, and the track the other so reverse loop should never be a problem after that. But you will have to alter your pickups etc.

You desire to protect the panto is admirable and it is your railway. Just pay attention to the reverse loop problems.

To me a train derailing takes litle time and if the panto get damaged, it would take a decent crash to do so, and if such force does occur, it will not matter if it is powerered or not - a derailment means wheels off the rails, and panto powered or not , the loco will stop and still cause that crash !!! So I would think it is still not needed, and will not protect your trains.

Regards, David Head

Thanks for bringing that up Klaus. I could of course decide to make the layout fully-electric traction based and since I'm in Sydney that's almost feasible, but I'm looking at using normal 2-rail power delivery (albeit using DCC instead of straight DC), and was wondering about using live overhead as well because it's sort of a waste of effort to make overhead wiring, etc. if it's just sitting there looking pretty and not doing anything functional. 8-)

Craig.

And regulated properly.

Sort of, but the duty cycle isn't fixed. It's a variable duty cycle signal. The timing of the voltage transitions is what conveys data to the decoders.

Same here. There are almost no electric locos now. Only about 4 are insured for live use but they're owned by a freight company (Silverton) which is partly-owned by the chairman of Pacific National and that company only runs diesel locos.

We've got many electric suburban and intercity passenger trains at CityRail running off the 1500 VDC overhead traction system system. The 46, 85 and 86 class electric locos ran off that as well. I was a trainee driver at Enfield in the early 1990's when all three classes of electric loco were still being used. I was rostered for the electric locomotive school the same week I had a call about transferring from freight over to CityRail in late 1994. 8-)

Craig.

"C. Dewick" skriver:

Do as the rest of us - leave it beeing pretty :-)

"My" model railroad is electrified allmost all over, except for shunting tracks and the harbour.

I you look at

you will on the left hand see a rough trackplan showing where the numbered photos are taken. Click on the photos to the right and see them in lager size.

Klaus

"C. Dewick" skriver:

Not allways. My Roco "lokmaus" just makes DC from the AC and chops is into squares.

It is a powerfull serial data transmission :-)

Only some lines i Denmark is electrified, so mainly all traffic is done by diesel. Except for transit trains between Swenden and Germany and a lot of local traffic on Sjælland (a large island, containing Copenhagen)

Klaus

On Wed, 21 Jun 2006 23:53:17 -0700, I said, "Pick a card, any card" and "jhbright" instead replied:

Thank goodness. I had this nasty feeling that they had been stolen or something. Close call, eh?

-- Ray

Well, yeah. I've done that several times, everything from a Bachmann LRV to a brass steeple cab. Just kinda goes with the territory.

Um, what reverse loop problems? There aren't any with both rails being the same polarity.

Have you ever run a trolley? I have, and trust me it doesn't take much to damage some pans and poles. For example, when a pole pops off the wire, it tends to spin a bit. It wouldn't take long for a pole to be flipped over backwards and wedged under a catenary bridge. When a pan pops off the wire, it will hit the next catenary bridge and crash stop the train if it keeps going. Since I've had to resolder a couple over the years, it's no fun. It actually got the point where we detached the roof of our brass steeple cab and applied it back on with a bit of velcro. When it snagged, it only popped the roof off (and this is with live overhead!). But that was when our overhead was built, it was built for poles only. We modified it for pans, but obviously we didn't modify it enough. LOL BTW, derailing was not really a problem. Oh, sure, we had a lot of them (street running and all), but the poles usually stayed on the wire during a derailment.

Paul A. Cutler III

************* Weather Or No Go New Haven *************

Pac Man skriver:

Or with DCC and dead overhead wire.

Klaus

I have to disagree with that. For starters, DCC is only rectified in the loco's decoder. After it comes from the transformer and goes through the booster, it's still AC. Digital square wave, but still AC. Secondly, I recently had to test exactly how much DC volatage was produced by a Digitrax DH123 decoder for a semaphore signal installation I was doing. Using our 14VAC booster and a Digitrax Chief for a "brain", my DH123 produced approx. 12.5VDC to the motor leads... So I don't know where you are getting 18VDC from.

It's also very common east of New Haven, CT today on the NEC. Connecticut runs diesel powered commuter trains called "Shore Line East" to Old Saybrook, and the MBTA runs diesel commuter trains between Providence, RI and Boston, MA...all under the wire. Historically, however, it was more the exception than the rule.

Paul A. Cutler III

************* Weather Or No Go New Haven *************

While it is a single point of contact for a pole, the shoe on the pole, IMHO, has a much bigger contact area than even 4 wheels. Think about it. How much surface area is a round wheel going to have on a piece of rail...even a flat head rail and a non-tapered wheel? Not much. A shoe, on the other hand, has a v-notch that slides along the wire. The main problem we'd have is dirt build up on the wire. What we'd usually do is run a trolley with both poles up to "scrub" the wire a bit, then drop the front pole. It'd usually run well, after that.

Paul A. Cutler III

************* Weather Or No Go New Haven *************

Because that's why you model trolley in the first place. Why do people insist on modeling narrow gauge? It's so much easier (and cheaper) to simply model standard gauge. But they do it *because* it's narrow gauge...because it's different. Same with trolley.

No, we didn't. Our old club was DC analog all the way. We did have a diesel under the wire, but it used a pole, as well, and yes, there's a prototype for it. On the real thing, the trolley used the wire for their signalling detection, so all diesels under the wire also needed poles to trip the signal detection system. On our new layout, we do plan to mix the two, but not at the same time. We plan to have a switch between overhead DC and 2-rail DCC...or maybe DCC with the overhead (we haven't figured that one out yet).

Paul A. Cutler III

************* Weather Or No Go New Haven *************

Well, the SSMRC was est. in 1938 as the Quincy Model Railway Club, and after a few moves during and after the war, moved to the basement of a small Weymouth, MA shopping plaza in 1953. We stayed there until 1998 (eventually, the layout grew to 2500 sq. ft.) when we moved to a former Naval Ammuntion Depot bunker in Hingham, MA. Our new layout will be over

6300 sq. ft., so one can see why we moved. Just like our old layout, we plan to have Eastern 3' narrow gauge, live overhead trolley, and, of course, standard gauge.

Paul A. Cutler III

************* Weather Or No Go New Haven *************

Pac Man skriver:

You just vrote that you had a 14VAC transformer. If you rectify that voltage (and you do that inside the booster) you get 18 volts DC. This voltage is chopped into squares by the booster.

Have you ever seen a circuit diagram of a bosster, or even looked at the components inside a booster ?

(been there done that - got the t-shirt) Klaus

Pac Man skriver:

And I'm rather sure that that is a common used system in Aussie ?

Klaus

Pac Man,

Thankyou for your discussion, I enjoy it. I also appriciate your experiance. You answered my questions proving to me you know what you are doing and not comming in bliond. So I expect your application of DCC will work.

I have a 4x8 tramway I were building with another person. It got to the platered street stage. It was to be overhead driven with both rails joined as the one polarity.

Buy we have drifted apart, the tramway stored. I have one 4-wheel tram for it, never used. So your situation is very interesting. Wiring this tramway would be easier under DCC.

The technical gurus may work out some sort of biased supply tied to the DCC that used the catenary and if you depole a relay cuts the loco's power ( but that adds alot of complexity to the layout, when it is fairly simple to switch the catenary as well as the track , as needed.

Wish you well, and do come back to tell us how it goes practically !!

Regards, David Head

Klaus D. Mikkelsen spake thus:

OK, OK: "chopped into squares" = converted to AC. The DCC signal is AC, just a square wave instead of a sine wave. Still AC.