Live Versus Dead Overhead

[Torpedo]

Hi,

I've been perusing this forum and registered so that I could ask about the overhead. I don't model at present, due to time and other constraints, but I love the old traction railroads and really appreciate seeing the work done by those modelling them.

In one of the earliest posts here, Interurban wrote, "That means ALL the wheels ground out on the track and the overhead supplies the power. Well that also means we have great running abilities."

I don't understand how having a single contact point (pole or panny) on the 'hot' side and multiple contact points (the wheels) on the ground side could provide better running charateristics than multiple contact points on both the hot and ground (half the wheels for each polarity). It seems to be that the single contact point hot overhead would be much more likely to produce stalls than standard multiple point contact 2 rail operation.

For the future traction layout I have in my head, I have always envisioned 2 rail DCC with strictly cosmetic overhead for the best running characteristics and most versatile operation.

Can someone tell me what I am missing?

 

[interurban]

Hi Torpedo, good question, first let me say welcome to the gauge and we are so glad you like traction.

OK when you have two rail operation , the power can be interrupted by -

Dirty track you may not have seen.
The odd failing slide connector rail join, causing switch tracks to be dead.
With overhead power , you can put your negative to BOTH rails and also jump the power over in the yards to make sure all rails are powered, very important with DCC.
The overhead when a Pan is used gives very smooth operation, I am just now adding Frogs to my overhead so trolley poles can be used , the pole operation is also smooth, ( not as good as Pans though, simply because Pan`s are forgiving on the odd unclean wire

Now here is a link to Trolley nuts who run live overhead AND DCC.
http://2guyzandsumtrains.com/Forums/viewtopic/t=2220/postdays=0/postorder=asc/start=0.html

http://2guyzandsumtrains.com/Forums/viewtopic/t=2943.html

http://2guyzandsumtrains.com/Content/pa=showpage/pid=70.html


If you look at my sidings you will see I solder a rail across the two rails to jump the power over.
I do hope this helps.

Keep us posted with your modeling when you get the time.
:thumb:

 

[bill937ca]

There are just as many stalls with two rail operation as there are with overhead. The cleaniness of the tracks are a major issue on many model railroad layouts. For reliable operation it takes alot of time and effort to keep the rails clean. And if your rails aren't clean then you will probably get dirty wheels. Join any model railroad club with a good size layout and you'll find out the work involved.

The biggest draw back of dummy overhead is that if the pole or pantograph snags a fair amount of your overhead can come down before you can stop the car. The live overhead you stop if you de-wire, just like the prototype. Another draw back is that you don't get any of the sparks that set traction modelling apart. (In HO scale I suspect most of the "sparks" are actually static-electricity.)

 

[interurban]

There are just as many stalls with two rail operation as there are with overhead. The cleaniness of the tracks are a major issue on many model railroad layouts. For reliable operation it takes alot of time and effort to keep the rails clean. And if your rails aren't clean then you will probably get dirty wheels. Join any model railroad club with a good size layout and you'll find out the work involved.

The biggest draw back of dummy overhead is that if the pole or pantograph snags a fair amount of your overhead can come down before you can stop the car. The live overhead you stop if you de-wire, just like the prototype. Another draw back is that you don't get any of the sparks that set traction modelling apart. (In HO scale I suspect most of the "sparks" are actually static-electricity.)

Good points Bill , the pantograph just keeps going with no dewiring .
The sparks, I LOVE them,and are actually the pole / pan sparking over the odd bit of crap building up be it ever so small, same as the wheels flashing .
GREAT stuff, in a darkened room

 

[Torpedo]

Thanks for the quick replies, folks. They provide excellent food for thought.

I never considered the consequences of dewiring with dummy overhead. That in itself is reason enough to make me rethink things. ops:

I imagine too, that having all the trackage at ground potential makes for easier construction of turnouts in the street? I can't recall seeing that discussed anywhere, though.

I have some other questions, too, but they don't relate to dummy versus live overhead, so I will start another thread.

Thanks again for your replies.

 

[60103]

Torpedo: I think some of the good contact can be credited to the trolley pickup sliding along the overhead. You have to go to O gauge or larger to make an operating trolley wheel; most prototype systems went to shoes long ago.

 

[jetrock]

There are pros and cons. One argument in favor of not wiring common rail is that you can also run steam or diesel equipment on the same track. I know some traction fans have installed SPDT switches (one pole to the trolley pole, the other to the other set of wheels) in their equipment, allowing them to switch between overhead pickup and two-rail.

A major argument against two-rail wiring is that there is not really a way to wire Richard Orr single-point turnouts for two-rail operation. I suppose it could be done, but it would be a serious challenge. So if you want to do trolley-style single track, two-rail wouldn't be very practical. I may do a bit of each: I want to have both diesels and electric freight motors running side by side (as they did on the prototype I model) but I also want to model streetcars on certain areas of the model--where the diesels didn't go, thus freeing up an opportunity for overhead-only operation. I think an SPDT switch is the way to go.

 

[Torpedo]

Thanks, folks, more excellent input. I am planning on pantograph operation, so sliding it is.

 

[interurban]

One BIG advantage of live overhead and all rails grounded, is the elimination of continuity problems. So Loop away at the terminals

NO BLOCKS.

Which to me eye sounds good.