Overhead Wire Circuit

Mobi

Mobi

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I read in another forum that for overhead catenary, one power source is connected to catenary and another one to one of the rails!

This sounds an overly complex way! Why the loco can't get power from overhead wire alone like real railways?

Is it because circuit is not completed as rails are placed on plastic sleepers? But how does it work in real railways then?

If catenary still requires power thru rails, then it sounds like worse of both worlds - you not only need to clean tracks but overhead wires as well.
 
004.JPG If you have an Analogue ( NOT DCC) layout then you have the capability to run 2 locos on one track!!

You need 2 seperate controllers, one for the RAIL powered loco & 1 for the ELECTRIC loco ie 1 with a Pantograph!

LGB locos with pantographs have a red dot underneath this indicates which SIDE the wheels return the current from the motor back to the controller

SO you connect 1 wire from controller 1 to overhead wire the other wire from controller goes to the Rail on which the RED dot wheels will run
Controller 2 is connected to the 2 running rails in the normal way
Its realy quite simple

Overhead wire does not actually need much cleaning the pantos see to that

A lot of this info is contained in reference books on Model Railways for example i recommend RAILWAY MODELLING BY NORMAN SIMMONDS
usually avail s/h from Amazon
 
'Real; railways also use the track as 'ground' or return. One wire wont make much work!
 
So you can't have the loco running the other way, i.e. no return loops? Ouch, never had that problem with Maerklin 3-rail!
 
Beddhist said:
So you can't have the loco running the other way, i.e. no return loops? Ouch, never had that problem with Maerklin 3-rail!
Click to expand...
Yes true no reverse loops possible, unless of course you run solely from the overhead and bond the 2 running rails as common return,

I suspect then that with Marklin Stud contact system you cannot run 2 locos independantly then ? As you could with the TRIX Twin system, but even with the TTR system reverse loops were not possible
 
Two circuits to allow two individually controlled locos Mobi, you don't need both circuits on the one loco. Same thing can/is done on indoor railways small scale model railways if you want to go to the trouble. Bound to be plenty to read about how to do it. Just don't get you polarities mixed!
 
No problem: the centre studs are always positive and the rails negative. Catenary is positive. That was Maerklin's big argument: the electrics are dead simple. Just plug it all in. Same with switches and signals, they get ground from the track. The only thing virtually impossible is consisting, unless you never change direction.
 
Due to the inevitable short circuit (eventually) it is not recommended to run two rail and catenary together.
 
stockers said:
Due to the inevitable short circuit (eventually) it is not recommended to run two rail and catenary together.
Click to expand...
Cant see why! We are considering here analogue not digital control, so there for you would be using 2 independant analogue controllers one to control the catenary fed circuit the other to control the 2 rail circuit, so why would there be any more risk of a short circuit occuring?
Indeed LGB in their instruction books some years ago before the advent of Digital used to describe how to set up 2 train control as described
above.

I used such a set up on a couple of my garden lines in the 80s and did not suffer any short circuit problems.
 
So, let me get this right..
<warning! typing and thinking at the same time, here!> :eek:

The 'tram' (fed from overhead) can only be run in one direction? - That can't be right??

If the two controllers are totally separate, you must be able to run one loco on each supply in either direction at the same time?? - Yes that would work, it would not matter that the one rail had volts from one controller, as the other would still create a voltage on the second rail relative to that.

I do see you are not able to run a loco with the same feed in the opposite direction at the same time. - Unless you have a DPDT switch on the loco to control polarity to the motor. - But you would also need to swap the 'return' feed to the other side of the catenary-powered loco..


Think I have that right? - More coffee needed!
 
Yes PhilP, it's a variation of the standard common-return wiring used on many layouts for decades. If I remember correctly from school physics lessons regarding electric circuits, the two voltage sources must be completely separate for this to work properly - eg. mains controllers MUST have totally independent supplies - ie. separate transformer secondary windings.

I can do this with some of N gauge locos, but to be honest it's not worth the effort to wire up all over my fiddle yard, and in such a small scale the pantograph's single point of pickup isn't reliable enough. These days DCC gives you much more flexible independent operation on the same track.
 
004.JPG Lokk at this way and remember we are talking good old fashioned DC NOT DIGITAL

If you ha a loco with a pantograph ie electric outline and a layout with catenary which is powered from an independant controller.(power unit)

It can be controlled independantly to a 2nd loco*** which is powered from the track in the conventional way with a 2nd controller.

The proviso being that the loco being powered from the overhead supply has to be placde on the track with the pickup return side of the loco wheels (indicated by a red DOT on LGB pantograph locos) on the rail which is being used as the return to controller 1 +++

This then allows independant control of the 2 locos on the same track the locos can run in either direction so if the users wish thsy can hit each other!!
*** NOTE the 2nd loco could be a Pantograph loco with the control switch (LGB) set to track power
+++ when an LGB loco is set to pantograph power pickup the current return is arranged through wheels on one side only indicated by the red dot
Digital does away with all this in these modern times

OH dear its gettin late!
 
Thanks both..
I had sort-of sorted it by the time the brain had caught-up with the fingers!!
 
Mobi said:
I read in another forum that for overhead catenary, one power source is connected to catenary and another one to one of the rails!

This sounds an overly complex way! Why the loco can't get power from overhead wire alone like real railways?

Is it because circuit is not completed as rails are placed on plastic sleepers? But how does it work in real railways then?
Click to expand...

Real railway takes current (in UK a fixed voltage 25kV 50 Hz) from the cat wire and return is via the rails. The loco transforms and rectifies this to a voltage suitable for the traction motors and this is controlled by the driver in the cab.

On a model railway , analogue (DC) your controller is not in the cab, so you are controlling either the voltage to the rails or to the catenary, using your controller which also transforms and rectifies the current. You can only control one train at a time. If you have another loco on the same track, both will move.

So to have separate control of these locos, it is possible to power one loco from the cat, and one from the rails. One of the rails will be 'common return' to either the cat or the other rail, i.e. shared. This is a normal electrical convention and is quite usual, and saves on copper wiring.

The only physical way of isolating the catenary from the rails on a real railway, would be to have TWO wires with 2 very narrow pantographs side by side and is very much more complex! Usually only seen on Mountain Railways on more complex 3 phase systems where the extra power is needed for the slopes and rack rail.

It does seem complicated if you have no electrical knowledge, and it's not something that even I (An Electronic Engineer) can easily explain in words on the forum....
 
The only physical way of isolating the catenary from the rails on a real railway, would be to have TWO wires with 2 very narrow pantographs side by side
Click to expand...

I think that is what trolley buses use!

Why do people use overhead power wires in G scale? It is expensive (just like electrification in real railway) and offers so real advantage over track power.
 
Mobi said:
I think that is what trolley buses use!
Click to expand...

Correct, and that's because trolley buses run on rubber tyres (insulators) and not on rails (electrical conductors (as opposed to ticket collectors!)), so feed and return wires are necessary.

Trolley buses normally run on single routes with no junctions. It's the junctions where wiring can be complex because you have to cross over wires. So what usually happens if 2 trolley bus routes co-incide for a short part of their routes is that you have 4 wires, or 2 wires per route. Should you wish to move from one route to the other, you lower the trolley poles and move across to the other pair of wires....
 
Mobi said:
I think that is what trolley buses use!

Why do people use overhead power wires in G scale? It is expensive (just like electrification in real railway) and offers so real advantage over track power.
Click to expand...

I think the answer is because they can, because to them it seems more realistic to emulate the way the real railway does it, and because it does give you the ability to run two trains on the same track when set up correctly, without going over to DCC.

Personally I don't like to see locos with pantographs up but no wires, so I run with wires on the public visible parts of my N gauge layout even though not actually picking up power. I still get to see the pantos "riding the wire". When I took my layout to Germany a few years ago this was something many people picked up on, as it's still quite rare to see in N gauge.
 
Not that it matters at this point, but when I was operating my Lionel electrics, GG! and EP5 on three rail AC, I was also able to operate, at the same time, diesels and steam locos. The ZW transformer has four throttles. One throttle powered the catenary while another powered the rails. Since the ground or "U" post was common, it took care of the outside rails which all of the locomotives used as a return. So on the electrics, I simply disconnected the rollers that picked up power from the center rail and soldered that wire to the pantograph lug.
 
I use it for my analoque tram, to run two trams at the same time. Of course it has 2 power supplies. I use the switches inside the original LGB tram to tell them to use overhead lines, or track power.


In that small movie you see, how it.works. You see two trams runnig. The yelloow and red original LGB trams are with overhead power. The track on both sides, where the other tram waitiong in isolated track sections.
 
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