Atomic Systems

I was just doing a little reading on the Garratt. Unfortunately I have not been able to find out WHY a locomotive such as this was designed.

I know it was first used in britain and that it was a powerful loco but why would you design a loco to carry the water/coal on the engine chassis instead of in a seperate tender?

Doesn't the tractive effort of the Garratt decrease as water/coal is used up?

I suppose they used the particular articulated arrangement to allow it to be used on routes with tight corners. I heard it was used extensively in Africa.

Was it possible to 'uncouple' the Garratt boiler section from the water and coal bunker and perhaps replace it with a larger boiler or was the Garratt built as a single articulated unit?

The Garratt is an interesting design.

An answer is to avoid double heading.

At some stage, trains became so long that it was impossible to avoid assigning two locomotives to each train. This meant that two crews were also needed, and that was seen as an added expense.

The Garratt design, being effectively two locos in one, eliminated the need for a second train crew, thus saving money (in theory).

There may be other answers, but that's a start.

Mike

ortegus wrote:Was it possible to 'uncouple' the Garratt boiler section from the water and coal bunker and perhaps replace it with a larger boiler or was the Garratt built as a single articulated unit?

I don't know much about Garratts but I suspect they were built as 1 unit.

The first Garratt was built by Beyer, Peacock at the turn of the last Century (1900) she was an 0-6-0+0-6-0 and was exported to Africa, South, i think. Yes, they were designed to eliminate double heading, but they were also designed because the Railway in question had tight curves, so couldn't take any lon locos. The coal bunker and water tank were placed there for convenience, and yes, tractive effort did decrease as fuel was used. They were built as three units, not one as widely thought, semi-permanantly coupled, to split the unit, steam pipes etc had to be disconnected. Hope this helps.
Spearmint

Thanks again. Its interesting how they developed this particular design of loco. But for tight curves it makes sense.

I imagine they would have known that tractive effort would decrease as coal and water was used up and therefore planned for it or adjusted the length of the consist accordingly.

The worlds first Garratt was built in 1909 by Beyer Peacock. It was designated K1.
K1 is an 0-4-0+0-4-0 articulated Garratt, built for use on the North-East Dundas Tramway, Tasmania.

It is currently being restored at the Ffestiniog Railway's Boston Lodge works for use on the new Welsh Highland Railway.

The whr website at :- http://www.bangor.ac.uk/ml/whr/whrstock.htm

has more details about this.

Cheers
Kevin

Well, once the shortcomings were realised many other branches of the design appeared, the most famous was the Mallet, which was ounted on bogies rather like a diesel loco, this design, having it's boiler over it's drivers, eradicated the aforementioned tractive weight problem. Hope this helps.
Spearmint

I was under the impression that Garrets were designed primarily for narrower gauge lines,and to keep the wheel loading down on inferior rails.South Africa,Australia etc.

Thanks for the link. Alot of good information there.

Well, once the shortcomings were realised many other branches of the design appeared, the most famous was the Mallet, which was ounted on bogies rather like a diesel loco, this design, having its boiler over its drivers, eradicated the aforementioned tractive weight problem.


Are you sure the mallet is/was mounted on bogies? I thought it had a rigid/fixed pair of rear drivers with the front set articulating from a pivot under the boiler. What separated a mallet from being just another articulated locomotive (eg Big boy) was the fact that exhaust steam from high pressure rear drivers was used to power the front drivers: ie the definition of mallet encompasses compound steam usage (thus the big boy is NOT a mallet, though the Americans call anything articulated mallets)?

In fact the major advantage of the garratt was that its total weight was placed over the drivers (much more like a diseasel than a mallet): boiler, coal/oil, water, everything. With a mallet, the boiler sits over the driving wheels and the coal/oil and water is dragged along behind in a tender as a dead weight not contributing to tractive weight. A further advantage of the garratt design was its high tractive effort for low axle load enabling its use on lightly built or poorly maintained railway lines. I seem to recall that Ing L D Porta was at one time planning a massive garratt for the Rio Turbio railway in southern Argentina (2-10-2+2-10-2 or similar).

I stand to be corrected but the mallets were also generally low speed luggers because of their compound design whereas the garratts were capable of quite respectable mainline speeds enabling their use on passenger trains.

Yuri, I'm pretty sure your description of the mallet is right.

The first successful articulated locomotives were, I think, the Fairlie type, as designed by Robert Fairlie. These had an articulated bogie at each end of the locomotive and were known as double fairlies. Very similar to modern day diesel layout.

The first successful one was called "Little Wonder" that was built for the Ffestiniog Railway in 1869. There was also a type known as a single fairlie that had one articulated bogie with a normal unpowered trailing bogie.
Examples of both type can be seen running today on the Ffestiniog Railway.
The Ffestiniog Rly website ( http://www.festrail.co.uk ) has more info on these type of loco

Cheers
Kevin

Here in Queensland Australia, we still have the last QR Garret still running.
Here a pic of it http://www.sunsteam.org.au/T60a.htm
Its out of service at the moment for repairs.
But this is a fine example of one of Beyer, Peacock's creations.
Mstnoodle

There is an excellent Garratt site at http://users.powernet.co.uk/hamilton/source.html
Where he lists details of the 1600 plus Garratts ever built.

Apart from the overseas exports (the majority), some were used in the UK, the LNER had 1 and LMS about 40, I can remember when there was a derelict one in the old town station at Cheltenham, around 1960 I think it would have been.

blackfour wrote:The first Garratt was built by Beyer, Peacock at the turn of the last Century (1900) she was an 0-6-0+0-6-0 and was exported to Africa, South, i think. Yes, they were designed to eliminate double heading, but they were also designed because the Railway in question had tight curves, so couldn't take any lon locos. The coal bunker and water tank were placed there for convenience, and yes, tractive effort did decrease as fuel was used. They were built as three units, not one as widely thought, semi-permanantly coupled, to split the unit, steam pipes etc had to be disconnected. Hope this helps.
Spearmint

Wrong.

The true first garrat was built as a 0-4-0+0-4-0 for a little railway in Tasmania. The number was (and still is) K1, and is under restoration to operational condition at the Ffestniog Railway

someone has probably already said this

The impression is being given that they were used only on narrow gauge railways. The LMS had a fleet and used them to and from Toton sidings, and no doubt other places, to haul freights.

Zambian Railways was still using them in the mid-60s to haul copper from Ndola to the coast via Lusaka, Victoria Falls and the then Rhodesia and finally South Africa. They were also used on passenger services in Zambia.

John

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