These are ‘motor tenders‘ as discussed in Charles Fryer’s book on experimental steam and, briefly, in Wiener’s Articulated Locomotives. They did not work very well by comparison with, say, Mallets and are not as flexible or good-guiding as a Garrett. Where they were valuable, IIRC, was in hump service where the additional full engine was the ‘moral equivalent of a slug’.
I don’t recall what arrangements the Southern used for ‘tender’ cutoff but the photos, especially the new one that resuscitated this thread (by the way a perfect example of when you DO revive a prior thread instead of starting a new one) should show the method that was used. I’m pretty sure there was a separate throttle or valve to the “tender” engine, but it may have been in series with the main throttle and therefore acted more as a ‘trim valve.’
Well, well. I had never heard of these engines. I, too, wonder how the "booster" was controlled; was it in operation only when its tractive effort was indeed an advantage, as when ascending Saluda, or was it in service continuously?
Johnny
I found a picture of the aforementioned 2-10-2-2-6-2.
http://southern.railfan.net/images/archive/southern/steam/2102/sou5046.jpg
Now I wonder...Did the locomotive have separate throttles and Johnson bars for each engine (one under the locomotive and another under the tender)? I'm curious how the engineer could control each engine so they would be in unison (requiring higher revolutions for the smaller diameter drivers under the tender) since the engines were so different in wheel diameter and cylinder size.
Mark
After perusing my copy of "Articulated Locomotives" last night, I found that the SR duplexes were indeed inspired by the Triplexes in the use of the tender's weight for adhesion.
The SR duplexes started out as standard 2-8-2's. SR was in need of bigger power to handle grades out of Asheville and at the same time had older 2-6-0's and 2-8-0's on the scrap line. The frame and running gear was saved and a new coal bunker and water tank was built and installed where the boiler once was. A brick arch was installed in the firebox of the 2-8-2 to improve steam generating capabilities for the demand of the additional cylinders. Nothing is mentioned regarding the number of such conversions or how long they lasted as duplexes.
Unlike the Triplexes, the steam tender on the duplexes was separable from the rest of the locomotive.
Here is the site:
http://southern.railfan.net/images/archive/southern/steam/282/282.html
Southern also had regular articulated locomotives, 2-8-8-2s I believe. There are pictures of those locomotives at a site adjacent to the above.
I just located pictures of two such duplex locomotives: #s 4537 and 4576. They were both classified as 2-8-2s despite also having the 2-8-0 under the tender. The steam pipe to the rear drivers came directly from the boiler, so they must have had all high-pressure steam boilers. The diameter of the rear drivers was smaller than those under the locomotive. They must have been a wonder to hear with the exhause continually going in and out of sinc.
On ebay there was a model listed as a Southern Railway sporting a 2-8-2-2-8-0 wheel arrangement. It looked like a standard 2-8-2 locomotive with a 2-8-0 under the tender. I checked a website on Southern's locomotive roster, and it did not list this wheel arrangement. Did the Southern Railway ever have such a locomotive? If so, when and where did it operate? Was the locomotive built this way originally or was it a modified 2-8-2 with a 2-8-0 frame added under the tender? How many of these locomotives did Southern have like this? (If I was to guess, I would say it was a one-of-a-kind. short-term, unsuccessful experiment where an older 2-8-0 frame had been added to an existing 2-8-2.) Thanks for your help.
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