The Australian AD60 class Garratts were the heaviest, I think at 260 long tons, say 286 US tons or 572 000 lbs. These were 4-8-4+4-8-4 and were introduced with an axle load of 15 tons (150kN, say 33000lb) for use on light rail. They were the most powerful steam locomotives in the country, with a TE of 59000 lb, later raised to 63000lb by increasing the cylinder diameter and increasing the weight on drivers by unloading the trucks.
Some contemporary locomotives in South Africa the classes GM, GMA and GMAM had relatively little water on board, and hauled a cylindrical tank car with water when on a train. They could run around a locomotive depot without this, but not far outside. This reduces the effect on adhesion of using up the water supply.
I’ve watched videos of them, they are as impressive as any steam power, but those tanks on the front and the empty space in the middle just looks funny, lol. I remember the first one I saw I wondered where the fuel tank was in middle.
According to “Articulated Locomotives”, which should be required reading for any steam fan, the tractive effort and factor of adhesion for Garratt locomotives was calculated with empty tenders and water tanks. Another advantage for Garratts over Mallets was the way the locomotive tracked on curves. On a Garratt, the mid-line of the boiler was on a chord inside of the curve in which the chord intersected the curve at the hinge points. On a Mallet, the mid-line of the boiler was on a tangent which extended outside the curve.
to which one might add that Garrats (in the smaller sizes) were also found on some perfectly ridiculously crooked track, here and there around the world. Not only did they not have clearance problems, but overall they were phenomenally flexible, both laterally and vertically.[:D]
No matter how you calculate the Garratt’s tractive effort (and with empty tanks and fuel bunkers, you’re figuring on some percentage of what the engine weighs on drivers, and unless that percentage is ridiculously low . . .) it will diminish as the consumables are used. It is true that it will be greater than that calculated when you have full fuel bunkers and water tanks. But what tractive effort is available, no matter how it’s calculated, is going to be less and less the farther up the mountain you get.
If you consider a long mountain like UP’s Wahsatch or some other western biggies, you’d have to set the tonnage rating for a Garratt not much more than what it would be with empty tanks and coal bunkers to make sure you had enough tractive effort to get you all the way to the top. But Big Boy’s tender (and thus his trailing load) actually got lighter the closer to the top he got. Not much, considered as a percentage of his total train tonnage, but some. But the Garratt will lose weight where it will hurt him.
The D57 class was the most powerful locomotive in Australia. Tractive effort was 64,325. They were called the Lazy Lizzies, because of their ablility to heavy loads seem effortless. Don’t confuse them with the D58, as they were not as powerful as the D57.
Most people even in Australia alway put the AD60, as the most powerful locomotives, even that it was the most powerful in the Southern Hemisphere, but there is at least 6 African locos that are more powerful, the GL’s [SAR] were the most powerful of all of them, then the RR 59 class was next, even the GMAM [SAR], were more powerful than the AD60.
Peter indicated as early as 2006 that the ‘quoted’ values for D57 tractive effort were not correct; although I do not know what the “right” value would be, it would certainly seem from his comments that it was below that for the late AD60s.
I would also like to see the actual horsepower curve for both locomotives; the D57 having the advantage of three-cylinder balance, so should be able to develop somewhat better speed and therefore HP than an AD60’s two-cylinder engine might permit. (Were the AD60s equipped with proper adjusted lateral on the trucks, and lateral-motion devices on the end driver pairs, to give better control of yaw and hunting?)
I’d also like to see the result of a ‘proper’ D58 with the revised conjugating gear actually constructed to reduce shaft whip, and cylinder bore and stroke set properly to achieve the comparable performance that NSWGR personnel seemed to like fibbing about. But the amount of work needed to make a truly workable three-cylinder simple out of the locomotives as built (including the need to put the conjugating shaftwork behind the cylinder block, or else install some kind of lever or rocker system to get all the valve-stem expansions in the right direction) was ‘too much’ in the age of dieselization, and I can’t imagine anyone doing T1-Trust levels of work replicating a ‘corrected’ one just to prove how the design would have worked out if Young had had 20/20 hindsight.
Perhaps if 5711 is fully restored, and given a running tender with proper axle loads, we could run dynamometer testing in comparison with 6029 and get a better answer than just consternation.
You can see right in this thread (May 18 2005), with reference to Dusty Durrant’s book, that various Garratt TEs were, and are, adequately documented and known.
And humor me, please, in one thing: stop using TE numbers to characterize how ‘powerful’ a class of locomotives is.