Electricity and steam engines

[Derek Walker]

This one has been bugging me. How does a steam engine generate electricity to run the lights and services for a train? or does each coach make its own via a generator running off the wheels? Are there battery banks in each coach because those lights will go out if the train stops. Do they (or did they) use 220VAC in the coaches?

[John Ashworth]

Derek, first, welcome to the FOTR forum. We hope to see many more posts from you.

In South Africa the coaches have generators underneath which are run by belts from the axles. Each coach has batteries to keep the lights (and in certain coaches the water pumps) going when the coach is stationary. They have varying voltages for different equipment as far as we can make out. Underneath FOTR's main line coaches there is a puzzling array of transformers and inverters.

In Kenya I once travelled on a coach where obviously the generator was working but the batteries weren't, as the lights would go off every time we stopped.

On South African steam locos the dynamo only powers the lights on the loco, not the train. Most steam locos in UK didn't have electricity at all.

I'm sure there are experts out there who can give you a more detailed answer and correct me where I'm inaccurate.

[Steve Appleton]

Hi Derek,
John's answer is spot on. What he didn't mention however is that the dynamo on the loco is powered by a steam-driven turbine located on the left-hand running board alongside the bolier. The dynamo's speed is regulated by a governor.
Many local passenger train operators have fitted 220/380V 50Hz diesel generators into "power cars" (usually converted from guards' vans) to power the train through an AC bus run down its length. This either augments or totally replaces the axle-driven generators. In the past, the aircon in the Slosh Meyl lounge cars was also powered from a large axle-driven generator (and batteries), leading to it having to be shut down if the train was stationary for more than a short length of time. Subject to correction, I believe that Slosh Meyl has or is fitting their tourist class trains with generators and electric train heating/aircon, replacing the old, increasingly unreliable steam-generating wagons.
To date, the Blue Train, the Premier Classe, Rovos Rail, Reefsteamers and other private tour trains are fitted with diesel generators. Most FOTR coaches have been retro-fitted with a 220V power bus for lighting (this was used on the 2007 Witbank Marathon, powered from the Reefsteamers' generator, and is now regularly used, connected to shore power, at night during coach cleaning). As yet FOTR does not have a generator (or power car); that has been on the wish list for a couple of years now, there are many other higher priorities needing the money. If you know of a fairy godmother...

[Derek Walker]

Thanks guys, it cleared up a few things in my head. By "steam-generating wagons" I assume you are referring to those tanks with a cab in the middle that were always behind the units on a main line train? if so, what was inside of those anyway? I seem to recall they lived at the "vapour depot" in Braamfontein too.

[Steve Appleton]

Yes. Those were they. The ubiquitous Vapour-Clarkson steam heat wagons.
Pics at: http://www.geocities.com/kritzingerf/steamheat.html
They consist of water and diesel oil tanks with a steam generator. They were needed because no steam supply was available from the non-steam locos for train heating.
Les Pivnic writes:

"The Vapour-Clarkson steam heat wagons were attached to all mainline passenger trains during the winter season. I mean all electrically or diesel-hauled mainline trains. There was a period starting in 1963 when Union Carriage supplied the type C-35 mainline saloons that the steam heaters had to work all year round because these coaches did not have independent electric water heaters. The SAR soon realized the shortcomings of these saloons and their successors supplied from 1969 - the C-36 - were fitted with electric water heaters. This allowed steam heaters to be overhauled during the summer season."

Wikipedia article here: http://en.wikipedia.org/wiki/Steam_generator_(railroad)
Incidently, if I am correct, the electric water heaters in the later saloons are supplied from a second, separate axle-driven alternator which, unlike the one used for lighting and water pumps, is not battery backed-up.