Model Catenary Issues

Model Catenary Issues

By Roger Heid

Comments by Ernest Robl

 

Catenaries are the wires which electric locomotives are suspended from.  On the roof of an Electric Locomotive you can see some kind of lattice work, called a Pantograph. This device holds on to the catenary wires. This setup does not require constructions of elaborate bridges across deep valleys, on electrified lines.

Oops! I am not writing a script for ‘Looney Tunes’. I think I caught that, just in time.

Anyway and regardless, you just learned the nomenclature of associated equipment. Below are pictures of what I am talking about.

70228

Example of a Catenary Section

74101

74103

Examples of Catenary Support Masts

36334

36600

Examples of Pantograph Styles

There is a distinct difference between the real world and the model world. I will not cover the real world. This I leave up to Ernest, he knows all about those challenges and the ins and outs; I don’t. I do know that these overhead wires, the catenaries, provide the electricity to feed the locomotive motors. That seems to be quite obvious.

Now I want you to take a sheet of paper and draw a half circle, resembling curved tracks. Now put three dots on that, evenly spaced, and connect the dots with straight lines. You see what I am getting at? These straight lines do not follow the curve. Each dot resembles a mast from which the catenary wires are suspended from.

It does not require rocket science to figure out the dilemma. If the curve radius is very tight, it will require a forest of support masts to enable the pantograph to stay connected. Got it?

In the real world, the catenaries are just thick wires, behaving like a rope.

Now, in the model world, more often than not, the track curve radii are quite a bit smaller than encountered in the real world. Now you will face two choices to make. Are you going to install too many masts, or are you using a catenary system which is stiff and bendable and keeps its shape? Just think.

If you wish your layout to resemble the real world, you obviously need to avoid tight curves. It seems you can’t win this one if the overall size of your layout is too small. That’s all I can say, period. This decision is up to you alone. Confused? Read over all this again, slowly.

In the old analogue days, there was a switch on an ‘Electric Locomotive’. It allowed you the choice between picking up the power from either the tracks or the catenaries. You could run an ‘Electric’ without the actual need of catenaries. Been there, done it.

Now enter the world of Digital Command Control (DCC).

The following information may be a cold shower to some, a relief to others. Among serious model railroaders, there appears to be an established consensus: Don’t power the catenaries. They are only for aesthetics and show.

Why would that be, you ask. Well, without going into lengthy technical and scientific explanations, I will tell you that much. There are too many mechanical and electrical connectivity issues. No reliability. You may try this yourself, but don’t blame me if, most of the time, it doesn’t work. I told you so! Savvy?

On the upside, this allows you to use any catenary associated equipment of your choice, from any maker, to suit your personal fancy. Just be very careful and conscientious about catenary installation into tunnels or inaccessible places on your layout. Don’t paint yourself into a corner. Think twice before you do it. It will save you from some unwanted frustration.

That’s all, folks!

Please, do not post questions in the Blog System. Go to the Forum under an appropriate topic.

Thank you.

 

 

 

 

5 Responses to Model Catenary Issues

  1. Ernest Robl says:

    Since Roger has mentioned my name in the above post: While I am far from being an expert on catenary, I’ll do my best to answer any questions related to prototype catenary in the Forum. (I have talked about catenary with both Austrian railroad officials and locomotive engineers.)

    As Roger has indicated above, prototype catenary essentially behaves as a thick heavy rope (made of wire, of course) and needs to be tensioned. Due to limitations of scale, model catenary is mostly made of stiff wire or in some cases stamped metal shapes. So, some of the features of prototype catenary can only be indicated, rather than being exactly duplicated. (This is actually a good thing for modelers.)

    One little-known feature is that most switch (turnout) heaters in electrified territory are powered off the catenary. Switch heaters are used to stop the accumulation of ice and snow in the switches, which would keep them from operating propery. In the U.S. and on non-electrified European lines, such heaters are usually operated with propane or other types of gas.

    But, as indicated above, most switch heaters on European main lines are electric. This can be seen by small transformers mounted on the catenary masts near switches, from which a cable leads to the heater. Most makers of model catenary offer replicas of these transformers.

    In larger modern station installations, the electric switch heaters would probably be fed off a single larger transformer in a trackside enclosure.

    I model Austrian prototype, but want to include some Swiss motive power on through freight trains on my planned layout. As the Austrian and Swiss catenary standards are different, only Swiss (including BLS) locomotives with multiple pantographs of the two different types would correctly fit in. This would also give me an excuse to include modern German electric locomotives with four pantographs, two of which are designed for Swiss catenary.

    – Ernest

    P.S.: There’s also an earlier Blog by me on electrification issues. Search the Blog system under “electrification.”

  2. Ernest Robl says:

    Oh, and one important terminology point:

    Not all overhead wire is catenary. Catenary is actually the term for a specific type of overhead wire configuration that consists of both a contact wire and a suspension wire, with the two connected by vertical wires. This helps the wire span a greater distance between masts without sagging too much. The term catenary comes from the curve of the suspension wire.

    The German term Oberleitung is a more generic term for overhead wire and does not automatically equate to catenary.

    Many streetcar systems and some electrified industrial tracks do not use actual catenary, but rather a more simplified construction that only uses a single wire. Most manufacturers of model railroad overhead wires also offer models of the more simplified construction.

    Of course, some streetcar systems use simple wire — often anchored to buildings on either side of the street into which the track is set — in developed urban areas and actual catenary on suburban lines where the tracks are on a dedicated right of way.

    And, there are also several types of provisions of overhead electric supply in tunnels, some of which do not use actual catenary.

    – Ernest

  3. peter martin says:

    Modellers who install catenary are special people, the kind you want in the lifeboat! I have a fellow train lover who installed almost 110 feet of HO catenary and the time and patience required is amazing, there again he is a surgeon. I had a large G Scale out door layout that had close to 300 feet of catenary but that is much easier to install. I am not going to install catenary until the model designs for HO improve. There should be a medal for people who can install catenary and remain sane, of course it should be functional and over 50 feet in length.

  4. Gareth Pearce says:

    I would like to make a simple correction to misinformation in one of the entries that reads “Among serious model railroaders, there appears to be an established consensus: Don’t power the catenaries.”

    This is completely wrong and shows just how un “serious”…that so called serious railroaders actually are! They are expressing just prejudice that reflects solely their own lack of cleverness in assembling and operating their systems. I have operated an n guage swiss prototype catenary powered DCC model railway flawlessly for many years, there is absolutely not a word of accuracy in the opinion expressed.

    I note that the reason given “There are too many mechanical and electrical connectivity issues. No reliability” My answer is where are the mechanical issues and what electrical connectivity issues? A basic course in soldering may be a good start and make sure your pantographs are in proper working order. Most spring pantographs offer entirely sufficient pressure against the underside of the contact wire for excellent continuous digital signal transmission. Maybe the “serious” railroaders operate out of fdilthy old garden sheds or dont know how to maintain their catenary contact wires.

    The main material for catenary wires for over the counter bought systems is either copper plated mild steel wires (0.5mm) or nickle silver. I use a mixture of both that have been painted with enamel… but abraded on the underside to expose the metal for current collection. Maintaining the underside in a non oxidised condition is a matter of simple maintenance with a maintenance vehicle fashionned from a weighted cargo vehicle on top of which is mounted a pair of box type pantographs that can be raised and lowered as necessary for the kind of maintenance being undertaken. One pantograph has a thin strip of the finest wet and dry abrassive paper and the other has a fine strip of felt super glued across the bow collector. If the layout hasn’t been operated for a few months, an electric locomotive with a pair of pantographs raised is used to haul the maintenance vehicle with its felt pad raised to which is applied a minute drop of ATF (automatic transmission fluid). ATF is a non drying conductive lubricant with a high level of detergent that reduces surface tension allowing the underside of the catenary to be well coated so that oxygen is kept well away from the surface.

    I also lubricate the articulation arms of both box type and single arm pantographs and also across the surface of the collector pan. One run around the layout with the cleaning vehicle and you can revert to single pantograph current collection for all locomotives with 100% reliability in DCC operation for single locomotive and consist locomotive configuration. Both rails are fused electrically so current collection across even the most complex point switchwork is effortlessly reliable with of course the advantage that there is no possibility of any track short circuiting on return loops. Overhead conductor rails in tunnels are made from upturned nickel silver rail and regular power supply to these rails ensures there is no voltage drop across the layout.

    I have found this is the best way to operate a railway if you run electric prorotype. Switzerland is 100% electrified and I don’t operate any diesel.

  5. Ernest Robl says:

    Different modelers have different approaches as to how they build and operate their layouts. That doesn’t necessarily make one approach right and all the others wrong.

    If you have succeeded in operating your digital layout totally from catenary, good for you.

    But, the vast majority of people I have encountered have come to the conclusion that it’s best to operate digitally off the tracks and to leave the catenary unpowered. It certainly makes life simpler if you are operating a mix of electric, diesel, and steam motive power. I’ve visited several European club layouts and do not remember a single one that used powered catenary.

    There are any number of things on our model railroad layouts that do not operate exactly as on the prototype. For most of us, the main idea is to have fun, and not necessarily replicate everything on a prototype railroad to the final degree.

    As I’ve pointed out elsewhere, a growing feature among high-end electric locomotive models is to be able to raise and lower the pantographs remotely. (Right new this feature is only available on a very small number of models, but the technology to make this possible is advancing quickly.) If you power your locos only from the catenary, you will not be able to raise a lowered pantograph — because the model has no power or connection to receive digital commands.

    Again, I’m not saying there is anything wrong with your approach, if it works for you.

    By the way, Switzerland’s railways are not 100 per cent electrified, though Switzerland is one of most electrified countries in the world. Switzerland has 4,424 km of standard gauge track; of those, 3,654 km are electrified.

    These are 2014 figures from the CIA World Factbook, which is available both in print and on the Internet.

    So, Switzerland does indeed have diesels, primarily to work non-electrified industrial tracks. If the SBB did not have diesels, it would not be able to rescue stranded trains during electrical and catenary problems.

    – Ernest

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