A Question About Garratt-Type Locomotives...

Hey guys,

Got a question about Garratt-type locomotives. Those, large, boxy structures that look like tenders on the front and back of the locomotive... are those water tanks, or what other function do they serve? Just currious. I have the crazy idea of building one in On30 scale for my next model railroading project, something along the lines of this beast here...

http://users.powernet.co.uk/hamilton/bg ... arratt.jpg


(Well, that, and I'm genuinely interested in these things!)


Appreciate any info. you guys have on these things.

The one at the smokestack end of the boiler was a water tank: the one at the cab end was a "full service" tender, with some waterr tankage and a coal bunker.

(I have a book (A.E. Durrant, "Garratt Locomotives of the World," 1981) on these critters: no scale drawings, but lots of information: I'll try to answer questions. Garratts came in many sizes and configurations, from 040+040 to 484+484, and were built over a period of about half a century: there are lots of prototypes to model, either exactly or as inspirations for plausible freelancing!)

I also have a book on Garratts by D. Trevor Rowe and Manuel Alvarez (who sent it to me), with some great black-and-white and color photos of Garratts around the world. No elevations, but specs for many types. Oh, I should add that the book is in Spanish: "Locomotoras Garratt de España y del mundo," published in Barcelona in 2000.

the British LMS railway operated a fleet Garratts designed by Fowler and built by Beyer Peackock.
I cant lay hands on it right now, but the LMS Garratts are the subject of one of Essery's books on the history of LMS locomotives, with many pictures and drawings.
here's a bit of inspiration for the modelling that google turned up...
http://members.westnet.com.au/locoman/garrettpage.html

Thanks for the info, guys! It is very much appreciated!!!


Allen,

Yeah, I thought that's what the arangement was, but the technical drawings I've found online only show a hollow space (no coal bunker) with what appear to be receivers for the water hoses from the towers. Just wanted to make sure I was interpreting them correctly.

No Garratt's were everr built for use in North America (Antarctica is the only other Garratt-less continent!), though I have a vague memory of seeing that someone was importing a small one for ?? a tourist railway ??. Alco bought U.S. rights from Beyer-Peacocke (the patent-holder and main British builder of the type), but didn't make any sales: U.S. railroads preferred Mallet-style articulated. I'm not sure whether this was just prejudice, or whether there was some technical justification for it. South African Railways sampled Mallet's and then went for a large number of Garratts, in several classes. PERHAPS the Mallet-style is better at the sizes of U.S. mainline steam and Garratt's better for smaller, lighter-weight, designs, though I can't think of any convincing reason why that should be so.

Many-- by no means all-- Garratt locomotives were built for narrower-than-standard gauge: they are characteristic of third-world railroads. So perhaps something like Colorado narrow-gauge would be the most plausible place for an "alternative history" U.S. Garratt-- except for having a longer boiler than typical Garratt's, the "Rio Grande" Garratt in the photo you linked to in your first post, Komachi, looks like about as plausible an American Garratt as anything I can think of. If I get a chance tomorrow, I'll skim through the book and see if I can find a (metre- or 3'6"- gauge) Garratt that would have suited Colorado with a bit of modification.

(Hmm... I think there were two-foot gauge Garratts, if you want to imagine one in the Maine woods....)

Two more books worth looking for -
"Articulated Locomotives" Leonard Wiener, London 1930, + Kalmbach reprint New York 1970
"Steam Locomotives of Rhodesia Railways" E.D.Hamer, Malmo 1983

A few scans from these two here http://s894.photobucket.com/albums/ac14 ... p/Garratt/

As to gauge, Wiener states that the very first Garratt engine, an 040+040, built in 1909 was provided to the Tasmanian Rly which was 2 foot gauge. This engine differed from all other subsequent Garretts in having the engine cylinders on the inboard ends of the bogies, and in being a compound. A photo and write up of that engine can be found in "Locomotives of Australia", Leon Oberg, Kenthurst, Aus. 1996.
There were also 600mm gauge Garratts in Brazil, and on the Darjeeling-Himalayan.
At the other end of the spectrum, dozens of large Garretts were built for the Indian broad gauge (5'6").
Photos of various Indian classes can be found in "Eisenbahnen in Indien" Frohn et al., Wien 1983.

The sole example of a Garratt on the LNER was built in 1925 and spent its life pushing trains up the steep banks in the north of England. It was designed around the LNER three cylinder 2-8-0 class O2, it is thus a six cylinder steam engine. numerous photos and details can be found in the RCTS "Locomotives of the LNER" volume 9B, Leicester, 1971.

Allen,

Your speculation is pretty much what I've come across while I've been researching Garrats. Popular beliefs seem to follow the idea that the Garrat's failed in the North American market because...

* The opposed piston design of the Garrat was "too radical," whereas the Mallet design was essentially two locomotives cobbled together, facing the same direction. A silly reason, yes, but it just didn't appeal to "the powers that be."
* As a steam locomotive operates, it consumes coal and... water. Water and coal not only equal fuel, but weight and therefore tractive effort... which is lost as said fuel is consumed. With the Mallet, the weight of the boiler is more-or-less constant over the driving wheels and therefore, you don't experience the loss of traction.
* As for the whole standard/narrow gauge bias... I can't honestly tell you if the Garrat is better suited for standard or narrow gauges, various writers have also noted the fact that the majority of Garrat's are found on narrow gauge lines and may be better suited for said application.


However, as I'm not intimately familiar with the intricacies of steam locomotives (Garrat or otherwise... I've been a "diesel man" up until fairly recently), I can't really comment on the pros and/or cons of the Garrat over the Mallet, or "standard" steam locomotive design. Mayhapse those who are better versed in the world of steam are willing to offer their knowlege/opinions on the subject?

The "opposed piston" issue may have been a factor inhibiting the use of Garratts in North America, but it also inhibited the development of duplex-drive locomotives. As I understand the issue, a cylinder-and-drivers unit running "backwards" was more subject to wear due to dust, etc. kicked up by the front unit. I believe that was part of the problem with the B&O's "Emerson" and the PRR Q1. Garratts may have been more successful in other countries, and less subject to the wear issue, for several reasons: (a) track speed might have averaged lower than in North America -- though there were some fast passenger Garratts -- reducing the kickup of corrosive matter; (b) the two engines were further apart than on a duplex-drive locomotive; (c) the locomotives ran in both directions, equalizing the wear on the crossheads and piston rods, etc., and (d) labor costs for maintenance were lower than in North America.

Furthermore, part of the reason for the use of Garratts was to get a more powerful locomotive without appreciably increasing the pressure on the track and roadbed, by spreading out the locomotive weight. Trackage tended to be more heavy-duty in North America (as reflected in heavier rolling stock as well as locomotives) than in other parts of the world, so the weight issue was less significant. The reason most Garratts were narrow-gauge engines was that railways in other parts of the world were often built to narrower and lighter specifications. Given the typically lighter weights tolerable by track structure in other parts of the world, the adhesion factor affected by the reduction in water or fuel supply at each end of the locomotive nay have been less significant than would have been the case in North America.

I am no expert on these issues and stand to be corrected by those more knowledgeable.

Garratts seem to have been treated as bi-directional, which very few (non-switcher) North American steam locomotives were. Advantage for a third-world country (and Colorado Narrow Gauge was, perhaps, economically more like a Third world country than it was like the New York Central!): cheaper infrastructure, with fewer or no turntables and wyes.

If the "backwards" cylinders on one of Garatt's engines were the big worry, and if you were willing to sacrifice bidirectionality, there is no reason in principle why you couldn't have the cylinders at the inboard engine of the rear (in normal operation) engine unit: after all, most Garratts had the cylinders at the outboard ends of both units, but at least one had them at the inboard end of each unit, so ... why not one of each? (Of course, a Garratt has a long wheelbase, so if you are NOT going to use it bidirectionally you might need extra-long turntables!)

But is the direction a rear-mounted cylinder faces a big problem? On the PRR Q-1 and the George H. Emerson, the rear cylinders were right next to the fire-box, which was apparently a bad thing, but would the dust (etc) problems with a "backward" cylinder that WASN'T next to the firebox be all that bad? After all, Souther Pacific lived with that orientation for cylinders on its Cab Forwards!

(Sorry. Just speculation there. Will try to be more informative.)

Allen, speculation is really all we have hear as there is no definitive answer why no US roads bought garratts.

Another possible factor MIGHT be an overhang issue.... Where as a mallet-type articulated overhangs to the OUTSIDE of a curve, a Garratt would overhang to the inside of a curve. This could be a factor in a myriad of ways: 1) Clearances were built to account for the outside overhang, perhaps there was concern that certain clearances on the inside would be too small? 2) With the super-elevation on many of the curves, it may have been considered that the inside overhang might throw the CoG too far to the inside causing a slow-moving garratt to roll into the curve, where as the mallet's overhang would help counterbalance such a tendancy.

All of these have a counter point... diesels overhang to the inside also.

A Lima-designed garratt likely would have been a 2-8-x+x-8-2 using many of the superpower principals, and the boiler of an Allegheny. Hmmm... sounds like an interesting investigatory project.

A number of the speculations lean toward why Garratts were preferable to Mallets on remote, narrow gauge lines but dont seem to help with the opposite case.
I'm going to go with the "conservative practice" case, of US engineering - simply that Mallets were already established practice in the States decades before the Garratt was commercially successful.
One other point worth mentioning, Mallets were almost universally compound engines, whereas (almost) all Garretts were single expansion. That distinction suggests Mallets' better thermal efficiency would benefit larger more advanced railroads where economies of scale would overcome the (implied) additional maintenance cost of the more complex machinery, and conversely would never pay off for the smaller, lower margin roads.

edit to add: According to Wiener, the variance in weight on drivers from full tanks and bunker to empty is on the order of 10%.

Two major differences between the Garratt and the Mallet (compound and simple):

1. The Garratt has twice as many flexible steam joints as the Mallet. As a result the maintenance costs on the Garrat will be higher;

2. The Garratt has much longer steam runs from the boiler to the cylinders. This results in greater drops in pressure and heat when the steam reaches the cylinders, thus reducing power and efficiency.

Stuart

In South Africa Garratts tended to run hauling an auxiliary water tank. Use of water from this tank car reduced (but did not eliminate) the variance in weight over the driving wheels.