Overhead DC electrification - a potential solution to the conundrum of EMUs on heritage railways?

[eldomtom2]

I originally posted this on NatPres, but I thought this forum would be interested in it as well.
The topic of EMUs operating on preserved railways has long been discussed, but most of the discussion has focused on the possibility of a preserved railway installing third rail DC or overhead AC electrification. I would like to bring up a third possibility - that of installing overhead DC electrification. Unlike other forms of electrification, overhead DC wires are already in operation at multiple heritage tramways, and the ORR has not had problems with modern-day tramways extending their lines despite that meaning the installation of overhead DC wires on public roads. So in theory at least there should be no regulatory issues. A more obvious problem is the question of rolling stock, as I believe no overhead DC EMUs survive. However converting third rail DC stock to run on overhead power is perfectly possible - it has been done in America. Therefore, the primary question to me is this: could preserved third rail EMUs be converted to run on overhead DC power in a sympathetic and ideally reversible manner, and would that be acceptable to preservationists? There are also of course issues of finance, clearances, etc. which would also have to be met for any railway considering this.

 

[edwin_m]

Installing a pantograph to a unit not designed for one would involve some significant alterations to the roof - it may not be strong enough. Also, either some fairly drastic changes will be needed to create a lower section of roof, or the pantograph would have to sit on top of the existing roofline, which would probably put it out of gauge and the overhead line and any overbridges would need to be higher than otherwise.

The easiest option might be a dual-voltage 313 or 319 where in principle it ought to be possible to re-wire the existing pantograph directly to the DC side of the traction system. Older AC units would need a new control system, as they have tap changer or phase angle control that won't work on DC.

 

[AlastairFraser]

The problem is I think it's uneconomic, because DC systems have quite a lot of voltage drop over distance, if I remember correctly. The best solution for lines that the ORR won't permit 3rd rail on is battery, for which acceleration of development of a shortlist of technologies should be invested in.

 

[edwin_m]

The problem is I think it's uneconomic, because DC systems have quite a lot of voltage drop over distance, if I remember correctly.

They do, but that might not be a problem on a heritage railway where speeds and therefore electric currents are low and distances are short.

 

[AlastairFraser]

They do, but that might not be a problem on a heritage railway where speeds and therefore electric currents are low and distances are short.

Surely purchase of a substation or 2, conforming to modern safety requirements, and the OHLE itself wouldn't be cheap though? Unless you salvaged kit from upgrade projects.
Something like the Byron Bay heritage railway in Australia might be a better solution (although with charged batteries from the mains, not solar due to our climate hahaha).

 

[RobShipway]

It maybe me, but it maybe better to convert the preserved DC units to push/pull capability with any diesel loco's the preserved railways might have in stock. Those diesel engines, possibly in the future be converted to use either battery or Hydrogen power possibly?

 

[ac6000cw]

Given that the ORR is happy to let heritage railways operate large, high temperature pressure vessels on wheels, fueled by a human shoveling coal into a red-hot furnace, which if not maintained and operated correctly can cause serious injury (and worse), I think operating relatively low-voltage overhead electrification shouldn't be a major safety issue (in comparison).

But I doubt the economics of installing and maintaining the OHLE system for a small number of trains that might use it would stack up (versus steam haulage, which is a major draw for customers as it's something out of the ordinary). If we get to a stage where fuel for steam locos gets impossibly expensive or unavailable, then vintage electric loco haulage of suitably vintage carriages would probably be a viable tourist heritage operation in the right place.

But operating fairly ordinary looking (and boring sounding) EMUs - where's the attraction?

 

[Ashley Hill]

The class 71 has a pantograph .

 

[eldomtom2]

Installing a pantograph to a unit not designed for one would involve some significant alterations to the roof - it may not be strong enough. Also, either some fairly drastic changes will be needed to create a lower section of roof, or the pantograph would have to sit on top of the existing roofline, which would probably put it out of gauge and the overhead line and any overbridges would need to be higher than otherwise.

How heavy are trolley poles? That seems to be the method of choice for the few existing heritage third rail-to-overhead conversions.

 

[SynthD]

It would be cheaper to have a bottom contact third rail, DLR style.

 

[edwin_m]

It would be cheaper to have a bottom contact third rail, DLR style.

It's still possible to touch the live parts, just not so easy. Also, bottom contact third rail has to be raised well above rail level, and if it is to stay outside the gauge of other stock it needs the pickups of stock that uses it to project outside the gauge. As the several pickups are electrically linked, that means a live pickup protruding from the other side of the train. A railway with suitable layout might partly get round this by having the third rail (either top or bottom contact) one one side only and pickups similarly only on one side.

 

[DerekC]

A heritage railway has to have sufficient income to meet its operating costs, and it's hard to see how this could be achieved with an electric line. I know that old southern third rail stock has its aficionados who love it to bits (sorry, wrong phrase) but face it, EMUs are an efficient but pretty boring mode of transport for most people.

 

[randyrippley]

The class 71 has a pantograph .

I thought it was more like a trolley pole?

 

[ac6000cw]

I thought it was more like a trolley pole?

AFAIK it's a pantograph, of a design similar to the ones used on old 1500V DC traction (so that lowered and flat in the roof well it looks quite long and thin). I can't find a picture of a 71 with it raised, though (other than model versions).

EMUs are an efficient but pretty boring mode of transport for most people.

Quite.

A re-creation of something like a centre-cab NER EF1 pulling some suitably vintage coaches might have more appeal to the average customer. An old side-rod/jackshaft drive electric loco would be much more interesting fun though - more bits going round and up-and-down as it wheezes, whirs and grinds about - a British 'Crocodile' . How about an electric 08 to start with?