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Treatise on overhead construction
 Moderated by: Herb Kephart Page:    1  2  3  4  5  6  ...  Next Page Last Page  
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 Posted: Mon Nov 15th, 2010 07:47 pm
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Herb Kephart
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This will be presented in a series of short snippets. It certainly isn't the only way, and may not be the best way for some- but it is the way that I have refined with ideas of my own, and stolen from others (for which I will gladly take credit).

There is something that I should make clear, before starting. Many years ago, I did some trolley modeling in HO scale, but since then all my experience with trolleys has been 1/48 (US O scale) and full size- with too many years at a trolley museum. I have a very limited knowledge of systems in GB, and Europe, and I'm only slightly more familiar with modeling in those places. Also because I have been in the hobby for so long, I have not kept up with what is offered commercially. I have so much stuff squirreled away I don't remember half what I have. Being a scratch builder doesn't help either- because what little I buy is in the nature of materials.
So -- if that hasn't convinced you that I have no idea what I'm writing about---read on.

First, you should decide on the height your wire will be above the rail. Prototype practice was 14 to 22 foot- with city cars using the lower height, and the larger interurbans the higher. In cases (mainly in the Midwestern states) where interurbans came into town under the same wire used by the city cars, the wire was high to suit the larger cars, and in some instances the city cars, if they had low roofs, would have their poles mounted on 12"-18" high lattice work towers to get the angle of the pole where it intersects the wire the same for both cars. This angle can also be adjusted, to a limited extent by varying the length of the pole also. I have always gone with the lowest wire height consistent with being reasonable with the largest cars. If nothing else, the lower the wire- or rather the pole/wire angle, the easier it will be to back up with a pole, if the situation requires. There are two types of wire systems. Direct suspension is what nearly all trolley and interurban lines used-this is where a single copper conductor-between 3/8" and 7/16" in diameter (00 to 0000 Huw) was supported, and sagged to some extent, by poles beside the track approximately 100' apart. Another type called catenary was used, mostly by electrified railroads. In this system there is a suspension wire, which has a definite sag between supports, which are usually spaced farther apart. The contact wire is suspended from this by vertical wires of varing lengths (spaced abt. 10' apart) so that the contact wire is a constant height. This is much more involved to model, and since it is not typical trolley, will not be covered here.

The wire that I (and most other modelers) use is phosphor-bronze, .020" diameter.
It comes in coils, and is springy and resists efforts to straighten. Also, it will break if bent too severely (or bent and re-straightened) neither of which makes hanging the wire any easier. Here is what I have done for years. Although others continue to fight with the wire, (and lose) I remove some of the hardness, and end up with dead straight pieces to work with- so here is one of the secrets of my method. You need a source of low voltage with at least 10 amps. A large Lionel transformer will work (just), a big battery charger, or even a half dead car battery. Fasten one end of a piece of the wire to something solid- I have used a vise, and also a screw in the benchwork of the layout. Measure off and cut a length of wire- the length will depend on how big a power source you have, and experimentation will have to be done. Grab the free end with pliers. Now, with one wire from the power source connected to the fastened end, and a wire from the other terminal of the source in your free hand, pull 1-2 pounds force on the wire, and touch the second wire to the pliers. The wire should start to heat, possibly smoke a little from residual oil. Keep tension on the wire with the pliers. When the wire gets hot enough, you will feel the pliers start to move as the wire stretches. As soon as this happens, remove the electric connection from the pliers, but maintain the pulling force. The pliers will move a total of 4"-6" before the wire cools. When cool, the wire will be dead straight. and while not soft, will not be as hard and springy as it was when you started. If, with your power source you can't get the wire hot enough to lengthen, either shorten the length of wire that you are starting with, or get another larger supply of amps.
On the other hand, if everything happens too quickly -including the wire turning red and melting- go with longer wire, or less 'lectric. I use a 250 watt transformer, about 18 volts, and work with pieces 5-6 foot long wire.

Next time--Poles


Herb  :old dude:



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 Posted: Mon Nov 15th, 2010 10:08 pm
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W C Greene
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Herbie-I LOVE IT! Great info. When I first read this, I imagined the famous doctor raising the monster on the table and letting lightning hit it! "It's Alive!"...

Really, this is some good info and while I may not build overhead, it is very interesting and I learned something from your instruction. The day we don't learn something new is the day we don't wake up!

                       keep going, I'm with you....     Woodie



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 Posted: Mon Nov 15th, 2010 11:45 pm
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Paladin
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This could be the start of something a little bit different.

Like Woodie I am not into overhead stuff but the article makes for a good read. Can the wire be heated with gas torch or other means ?

Looking forward to the next episode

Don



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 Posted: Tue Nov 16th, 2010 08:26 am
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Sullivan
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Herb----

Great little article - so far. Looking forward to the next chapter. In the various overhead articles I've seen in the press I don't believe that any of them ever had anything to say about working with the wire - other than hanging it.

Woodie knows that I have always been drawn to this OTHER Dark Side of modeling.

This new forum is just another Communist plot!! REDS, REDS, EVERYWHERE!!

Love it!

Last edited on Tue Nov 16th, 2010 08:27 am by Sullivan



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 Posted: Tue Nov 16th, 2010 11:24 am
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Herb Kephart
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Thanks for the comments, my friends!

Don- you asked "Can the wire be heated with gas torch or other means ?"
Yes it can, but  unless it is to turn into a two man job, much shorter pieces than the 5-6 ft hunks that I work with will have to be used. Also the heat source (if a torch) will have to be moved up and down the wire rather quickly to prevent overheating one spot. I have seen fellows that work with the wire straight from the roll heat just the end with a cigarette lighter so they can bend it to connect it to the next piece without breaking- so the answer is yes--but the electric method is more uniform and (I think) more controllable.

James- got a chuckle from "This new forum is just another Communist plot!! REDS, REDS, EVERYWHERE!!" Certainly not a Commie, but early in my machining life, on the first day the foreman asked "What name do you go by- certainly not Herbert?". I said that it didn't matter to me- and he replied (because of my hair when younger)  "well here, you're going to be Reds" Am I posting too much? :us:

Woodie- See--you learned something today also! Fat lot of good it's going to do you though. :)


Herbie  :old dude:



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 Posted: Tue Nov 16th, 2010 11:33 am
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Sullivan
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More posts, Reds!!

There is so little info on proper construction of overhead lines and street trackage. The modeling press has darn few articles - maybe once in a blue moon - and only when they decide to do a little specialty layout series. I think it's been three or more years since MuddleRoadrailer did any.

I've pulled all those articles from the magazines and have them in a binder for that day in the future when I get the time, money, and wherewithall to do it. Like I said, I've always had a place in my heart for the trolleys and interurbans. It was just this past summer that my grandson and I road the Dallas (McKinney Ave.) streetcar line and we had a blast.

Last edited on Tue Nov 16th, 2010 12:15 pm by Sullivan



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 Posted: Wed Nov 17th, 2010 10:19 am
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Huw Griffiths
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Sullivan wrote: There is so little info on proper construction of overhead lines and street trackage. The modeling press has darn few articles - maybe once in a blue moon - and only when they decide to do a little specialty layout series.
I couldn't agree more.

The usual fare in the UK consists of occasional, very superficial, magazine articles - seemingly written on the basis that we already know what we're doing (so why the article?) - either that, or they effectively come up with a slightly more civilised way of saying "RTFM" (ditto).

This brings me to the "manual" - a Sommerfeldt "guide", which looks from the outside like a magazine - but it's very expensive and written in highly technical German, with a partial translation that serves only to confuse.

It's sometimes possible to find information on prototypes, or other scales. The Tramway & Light Railway Society website - http://www.tramwayinfo.com/ - has a section called modelling on line reference. If you go to their homepage, you're greeted by what looks like a card ticket - clicking on the flag marked modelling o-l reference, then scrolling down to the paragraph entitled general, leads you to a number of flags which lead to articles - the one about current collection makes interesting reading.


Of course, none of this tells you much about building model overhead - which is very different to the full size version. Let's face it - the distances between overhead supports are often "compressed" on model layouts - and the wire used on full size trams (and electric railways) won't always have a round profile. Also, even if the wire were the same profile, the diameter won't be exactly to scale (it would probably be too thin and snap in use).

In other words, compromises are called for - and we can only learn those from somebody who's been there before and is willing to explain. This is why I'm so glad to see this stuff appear here.


I don't want to hijack Herb's excellent "how to" thread - but one of the reasons why a number of tramway systems (especially on the European mainland) and electric railways use catenary is because trolley poles can't always be trusted to stay "on" the wires. This is particularly a problem at junctions - and led to the development of special "ears" for attaching wires and guiding poles etc through problem spots.

Basically, on systems that use catenary, cars don't have trolley poles - instead, they're fitted with pantographs (or sometimes bow collectors) which slide under the wire and are less likely to get "dewired". For this system to work properly, the wire needs to be taut - so catenary OHLE (overhead line equipment) often includes tensioning equipment (often weights on pulleys) fitted to some towers. The wire also needs to move from side to side (relative to the car and the pantograph), so it doesn't wear a hole in one spot on the pantograph head.

There's no doubt that pantograph / catenary set-ups work well (they're probably the only credible system with high speeds) - but designing them and setting them up involves a lot of skill and patience.


Saying that, trolley poles (as fitted to older tramcars - especially in the UK and USA) don't exactly have a reputation for being easy to set up. When the time comes, I'll be very interested in seeing how Herb has got them to work. In the past, I've tried and failed - judging by the number of exhibition layouts I've seen with "trolley pole style" "soft wire" OHLE and pantograph fitted cars, I don't think I'm alone.


Anyway, that's enough from me for now. I'm looking forward to seeing how this thread develops. I know it'll take time - that's fine by me. However long it takes, it means that I'm getting the chance to learn about this stuff - a chance that I haven't got elsewhere (and probably won't). Many thanks.


All the best,

Huw.

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 Posted: Wed Nov 17th, 2010 11:09 am
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Herb Kephart
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Huw--

Absolutely no problem about "hijacking" from me-- Your a major contributor to this thread, so far as I am concerned.

I intend to cover both wirework for pantographs, and poles--in fact on my layout most of the wire will accommodate either, although by rights the old style pantographs were seldom used on single suspension wire, and then only where very slow car movements were involved. The newer Flavely (sp?) single arm pans seem to be able to run on single suspension though--I suppose that it has to do with the amount of pressure, and/or the lighter linkage allowing better response.

Your comment about the real wire not being round, reminded me to hunt up a real "ear" used to fasten the wire to a support---



And the comment about deviations from absolutely scale are right on. I have heard that some folks are using Nickle Silver wire of a much smaller gauge, but I think that it is too soft, and if bumped, stretches--besides it has a much higher resistance--because of the material AND the smaller diameter.

So keep the comments flowing- you have provided some great links! 

Herb



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 Posted: Wed Nov 17th, 2010 01:44 pm
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Huw Griffiths
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Thanks for your kind comments.

Here's a link to the Faiveley website (with a number of PDF brochures - some more interesting than others - and most not related to current collection) - http://www.faiveley.com/uk/plandusite.php - and here's a direct link to the section about pantographs - http://www.faiveley.com/uk/categorie.php?ID=23#cat19.


Another major manufacturer of electrification equipment is the Chard (Somerset, UK) based Brecknell, Willis. A few years ago, David Hartland wrote a very interesting book, Collectors for Trains, Trams and Trolleys (ISBN 1-984474-292), which details the company history. The book also includes a number of photos of prototype OHLE and current collectors.

The Brecknell, Willis company website also includes some interesting literature - http://brecknell-willis.co.uk/bwdocs.htm. I particularly enjoyed the technical papers "good looking overhead wires" and "developments towards an active pantograph". (There's also some interesting stuff on their product specific pages.)


In case anyone is wondering, I believe the reason why pantographs are normally used with "stiff wire", catenary systems under tension is to prevent damage when the car reaches a wire support pole, or a junction. Without the tension, the pantograph would push the wire up - probably jumping, or causing a kink in the wire, the moment a support is reached. Apart from possible damage to wire and support, this could cause the pantograph head to break. In an extreme case, the pantograph could be ripped off the car.

To prevent this, the wire is always kept under tension. Also, the pantograph head doesn't actually contact the wire directly. Instead, contact is via a shaped carbon block, which slides along the wire. To stop the wire wearing a groove in the contact block, the wire also zigzags between supports, over a short range either side of the track centre line. This also allows the pantograph to continue collecting current on curves.

By the way, I'm aware that a lot of research has been done into working out the correct contact force between pantographs and wire on full size railways and tramways - it seems to vary according to the speed of trains (etc) using the lines and how much current they draw. There's also been a lot of research into how to achieve this ideal force.


Perhaps not strictly relevant here, I also enjoyed reading some of this material: http://www.old-dalby.com/Brecknell.htm

(Also of limited relevance, your comment about the high resistance of thin cross section wire reminds me of some gear I installed for a living, when I worked as a "university "labrat" - specifically, strain gauges. These work on the basis that, as a wire gets longer and narrower, its resistance goes up - and this change in resistance can be used to measure strain. I know there's also a lot of very OTT maths relating to this stuff - thankfully, I never needed to understand it!)


Anyway, I think I've said enough for now.


Regards,

Huw.

Last edited on Wed Nov 17th, 2010 01:55 pm by Huw Griffiths

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 Posted: Wed Nov 17th, 2010 02:03 pm
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Herb Kephart
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Anyone reading this thread- please see the second paragraph of the first post--an addition that I just made.

Working on the pole installment. I think that this is going to need some drawings, or rather sketches, or rather rough sketches, or rather VERY rough sketches, which I will have to do, and scan- but I'm hoping to post the pole bit this evening.

Herb  :old dude: 



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