Garratt question

[paulmartinsmith]

I’ve just found this thread and would like to make some comments concerning Garratt-type locomotives.
I worked on Garratts in Africa and I can confirm that their most attractive feature was the combination of a very large boiler and a short wheelbase.
This is particularly useful in Africa, which is a bloody big largely empty place with lots of room in the loading gauge but someone stuck the rails too close together and constructed bends rather than curves.
As a locomotives hauling power is directly related to steam generation rate, the ability to sling an unencumbered boiler between a pair of trucks resulted in a very powerful yet flexible locomotive. The firebox for instance could be of almost unlimited capacity with stoker or oil firing and some seemed big enough for a table, chairs and refrigerator.

I was always amazed at how much the boiler overhung on tight curves in the yard without toppling the whole contraption over.

Incidentally, I’ve never seen a Garratt boiler lifter from its trucks by crane. I think most workshops lacked the capacity to lift a boiler free. If the bolsters needed attention, the boiler was jacked up a little at one end. Tubes and super heaters were replaced mostly by removing two plates in the “Frontâ€

[bjdick]

South African railways are narrower than the UK standard around 3.5 ft I think.

I had the pleasure of helping to assemble the three part power unit,of a preserved South African Garratt.It was pulled into position by traction engines.

The steam driving units are attatched to the boiler assembly by oil filled,rope sealed spherical thrust bearings.IE only gravity keeps it together.

The steam supply to the units passes through the centre of these bearings to the engines.This means you don't need flexible pipes for steam supply,as the driving units pivot on the bearings.The bearing also seals the steam from escaping