GMAM Boiler Data

[Ian Roberts]

I have the data tabulated in Dusty Durrant's book on the Garratt Locos, but need the following:

Length between tube plates:
Size and number of tubes:
Size and number of flues:

If anyone has a link to SAR or Manufacturors diagrams for th class a link would also be appreciated.

In this case Google was not my friend

Many thanks in advance

[John Ashworth]

Frank Holland's The Steam Locomotives of the South African Railways Vol 2 (p 113) gives:

• the length between tube plates as 13' - 6 1/2".
• 282 tubes 2" external diameter.
• 50 tubes 5 1/2" external diameter.

Can't find any reference to flues.

[Ian Roberts]

Appreciate the info John, Flues are an alternate name for the Large Tubes

[Ian Roberts]

Another question on the GMAM and, for that matter, the other minimum water capacity garrets such as the GO

At the end of the run

Was the water tanker always kept at one end of the loco and the whole assembly turned on a wye or did the loco run round the tank when changing directions?

Ian

[John Ashworth]

I don't know the answer to that one, Ian, but no doubt someone will.

Are you aware of the new Garratt Yahoo group? See here

[Martin Coombs]

I have a digital version of SAR drawing 5/15883 in front of me as we speak. This shows the general arrangements of the GMA/M boilers. The dimensions given by Holland are indeed correct.

Ian wrote:

Another question on the GMAM and, for that matter, the other minimum water capacity garrets such as the GO

At the end of the run

Was the water tanker always kept at one end of the loco and the whole assembly turned on a wye or did the loco run round the tank when changing directions?

GMs, GMA/Ms and GOs all had auxiliary water tenders. The front water tank on the loco (there was no rear tank) was treated as for emergency use only. It was checked at the beginning of a duty and filled if necessary but was normally left shut off.

The water tenders were as far as possible left coupled to one end of the loco, rather than being uncoupled and moved to the other end of the loco. Some were even fitted with headlamps. The whole combination would be turned when possible on a triangle to put the loco in front of the tender. Others may be able to think of exceptions to this practice, maybe when a triangle was not available and the curvature of the line made tender first working impracticable.

On the Greytown line from Pietermaritzburg, and on the Cape Natal when appropriate, pairs of GMAs were semi-permanently coupled together, bunkers outwards and with the two tenders in between the locos. This was the equivalent of setting up a pair of diesel hood units with the cabs outward to improve visibility in either direction.

I did have a few days in late 1974 firing from Vryheid on ballast trains down the new Richards Bay coal line. In this case the lack of watering facilities made extra water supplies essential. The pair of double headed GMAMs were set up as described but in this case two tenders were needed for each loco, all in a row between the loco fronts. There was some joking from the crews about the fireman having to walk almost the entire new route in order to uncouple and run round for the return trip!

Martin Coombs

[Ian Roberts]

Many thanks for the answers so far, I always regret not persuing the big garratts when I was working in Durban for a couple of months around 1975.

No internet in those days and it was at the time of the extreme petrol shortages with none available after about 1800 weekdays and none at all at weekends.

Since I had very little time off I was limited to the NG garratts on the coast.

It seems that the preferred make up was coal bunker unit first with the water tanker following the water tank on the loco.

This then leads to the question of signal sighting on what had become a left had drive loco.

Were there any duplicate controls as were provided on the Australian NSW AD60 garratts for bunker first running?

I have joined the new garratt site although it seems to be more restoration and minuature focussed at present.

Ian

[John Ashworth]

Sounds as if Martin has had a lot more experience of them than me as I only fired GMAM 4079 a few times in preservation, but let me try to answer and he and others can correct or add.

Bunker first gives better visibility generally as it is shorter than the boiler. Signals in South Africa are generally on the left (fireman's side), even though the driver's position is on the right, and one of the duties of the fireman is to confirm the signals with the driver. So when any loco rides bunker first the driver is actually in a better position to see the signals. The GMAM has no duplicate controls (and I don't think any other South African Garratts have either).

[Ian Roberts]

I have read in various publications that the coal used on South African Railways was of lower quality than, for example, that supplied in the UK. This was the reason for the early adoption of lare grate area fireboxes on South African Railways.
Does any one have any record of what the fuel consumption was per drawbar horsepower hour for the GMAM and the calorific value of the coal in BTU's?

Ian

[John Ashworth]

Ian, I don't have my books with me at the moment so I can't check, but I seem to recall that David Wardale's The Red Devil and other tales from the age of steam had a lot of general technical data which might include the stuff on coal.

[Ian Roberts]

Thats one book I don't have, but you are right, its just where you would coal issues would be discussed.
It may be something to order but in the mean time if anybody has the info it would be appreciated.

Ian