I saw the photo of the Erie Triplex in the February issue. The third set of pistons were mounted beneath the cab with rods connecting to drivers on the tender. I’ve never seen this type of a wheel arrangement on any other type of locomotive, was this a unique design or was it tried on other smaller locomotives as well? A Consolidation locomotive (for example) would have room for pistons under the cab. By powering the wheels under the tender you would have some of the advantages of an articulated locomotive but on a rigid, shorter, frame… a more powerful compact locomotive.
Virginian had Triplexes too, but they aren’t significantly different from the Erie locomotive to ‘count’.
Actually, though, what you have is a ‘third engine’ with cylinders and drivers in rigid alignment, with the cab and tender body happening to be located above it. It isn’t so much that there is ‘room for the pistons under the cab’ as that you have three eight-drivered engines in a row (the forward one hinged to the middle a la Mallet, and the rear one articulated to the middle one) with a guiding truck at each end of the chassis.
There was some experimentation with just the kind of ‘enhancement’ you describe, as early as Archie Sturrock’s steam tenders (described in Fryer’s book on experimental British steam), with the most famous American examples probably being the ‘tractor’ or ‘motor’ tenders used on the Southern Railway (shown here, in Parker Lamb’s book.
The more ‘tried’ version of this approach was the ‘auxiliary locomotive’ (in four-wheel and six-wheel versions) tried by Bethlehem et al. – these had the not unimportant characteristic of fitting underneath a tender of normal capacity, not one with a high deck and limited water capacity. While a conventional engine wouldn’t have the severe augment-balance issues the auxiliary locomotives did, they still represented ‘too many legs and not enough steam’ when tried in practical service.
Were a Consolidation chassis, or perhaps a Mastodon/12-wheeler chassis (to get a bit better weight-bearing capacity), built with a Really Big Boiler, or with all the thermodyn
Southern had some locomotives (Mikados, I think) with steam engine running gear under their tenders. I think they used frames & cylinders & drivers from old Consolidations. As I understand it, they weren’t too successful & didn’t last long. I think they called them Tractor engines or some similar name. A Southern fan might give you info.
There’s a picture of a Southern engine with a 4-4-0 engine under the tender in the October 1917 issue of Popular Science, which is available on Google Books.
- Erik
Don’r forget Garetts!
There were thousands of Garratts built, with driving wheels under each tender and nothing under the boiler. Also consider three and four-truck Shays, Sturrock steam tenders and a host of other designs.
In addition to Shays, there were Heiselers and Climaxes with trucks under the tender.
One of the problems with putting power under the tender is that weight on divers changes considerably as fuel and water are consumed. Virginian’s lone triplex was not particularly successful due to inadequate boiler capacity, but it also had a reputaion for being slippery on the back end. IT was ulimately rebuilt into an AF class 2-8-8-0, with a new boiler and cab used to build an essentialy new MD class 2-8-2., both of which were considered successful.
Thanks to all of you for the responses… more questions to follow!
Tank engines also have the disadvantage of varied weight and thus adhesion.
While I will concede that the weight of the tenders will vary as fuel and water are consumed, Wiener noted in “Articulated Locomotives” that the factor of adhesion for Garratts, Shays and other such articulated locomotives was calculated based on empty tenders and water tanks.
And the tender weight problem (if that was indeed a concern) could be resolved by keeping the tender near full or by enlarging the tender’s capacity, or even by constructing the tender with a heavier frame.
This would restrict range, however, but probably isn’t a problem for helper service.
One possibility is to use a “canteen” water car with a pump to keep the water tanks full longer, although the coal would still be consumed.
The front tender truck of some Indiana Harbor Belt 0-8-0 switchers had a steam booster built into them. The two sets of wheels were connected by siderods.I believe they were similar to the boosters some steam engines had in their rear trucks, like New York Central Hudsons had.
This is what I meant by ‘auxiliary locomotive’ (Bethlehem’s trade name for the idea) in my post on the 8th, in order to differentiate it from what Ulrich was discussing.
The auxiliary locomotive was generally even more ‘adaptable’ than a typical booster (which normally acted on only one axle of a trailing truck, and used wheels of greater diameter than on typical tender or freight trucks). It would fit nicely under a conventionally-dimensioned tender and allow some proportion of the tender’s mass to add to adhesive weight at starting and low speeds… usually more restricted speeds than an equivalent booster would be able to use.
For more on the difference between the Franklin and Bethlehem boosters, go here for some additional information.
The ‘fastest’ road locomotive I’m aware of that had these was a class of LV 4-8-4; my understanding was that they were often in the shop, and were replaced with more conventional trailing-truck boosters at a relatively early date. It’s possible that these have falsely acquired a ‘bad name’ as track-wreckers, in the same way that the PRR T1 was wrongly supposed to be hopelessly slippery… but it does appear that almost everywhere the auxiliary locomotives were used, they were either removed or modified to remove the ou
Nice to see the picture of the IHB U-4a, the “grandest 0-8-0 of all”. David P. Morgan was right, the boiler would do justice to a heavy 2-8-2. I would opine that the auxiliary engine on the tender was used to make better use of the boiler’s steam-making capabilities.
Isn’t the C&O 614 equipped with a “booster” engine? The wheels under the tender can be steam driven? I seem to recall reading that Ross blew the gears off of it on a hard start, many years ago while he was doing his ACE trials. (American Coal Enterprises?)
SAR had one class of Bayer-Garratt which ran with an auxiliary water tender. The over-the-driver cisterns were kept full until the auxiliary tank was drained completely.
Chuck
This was the usual sort of (Franklin) trailing-truck booster. Wardale recounts the booster damage in the chapter on ACE in the Red Devil book.
[8D]uncle pete[UNION PACIFIC] tried “boosters” I. E. traction moters under the fuel tender on there big double engine diesels. I believe they were the ones from GE with the airplane engines . they were called big blows