I had never hear of tandem compounds until I happened to run across a photo of one on the following site: http://catskillarchive.com/rrextra/blatpg17.html Click on the first entry to see Santa Fe Decapod No. 940. Unlike Vauclains the tandem compound had the high pressure cylinder located in line with and immediately in front of the low pressure one. The two cylinders shared a common piston rod and valve gear. From what I've been able to gather, Baldwin pioneered this design. From the standpoint of maintenance accessibility it seems to me that the tandem would be superior to a Vauclain and I wonder why the former didn't become more widely accepted than it apparently was. Comments anyone?
Mark
Problems with valve timing was the biggest issue with tandems. The weight and especially the length of the duplexed cylinders also led to overloaded front trucks, especially two-wheel trucks. Accessibility of the packing was not as good as on the Vauclin compounds, where each piston could be pulled on its own. Superheating more or less did away with the value of compounding at a lower cost.
Even Vauclin compounds were hard to justify due to maintenance cost and complexity. Most engines built as compounds that survived past 1910 got superheaters and simple cylinders.
The only tandem compound with which I'm familiar is on an Armco Steel stern-wheel towboat on display in Keokuk IA. Of course, a lot of the issues involved with railroad compounds were less of an issue with marine compounds.
The Erie built a tandem compound in the 1860s that was not successful. Santa Fe's original 2-10-2's are teh only ones I could find in the US, though examples existed in South Africa, New Zealand and maybe Europe.
rcdrye The Erie built a tandem compound in the 1860s that was not successful. Santa Fe's original 2-10-2's are teh only ones I could find in the US, though examples existed in South Africa, New Zealand and maybe Europe.
I wonder if this thread prompted the selection of today's Photo of the Day. In addition to the 2-10-2's the Santa Fe had some 2-10-0 tandem compounds. Decapod No. 940 is pictured in the site linked in my original post. It does seem that the Santa Fe is the only US road that acquired any of these oddities.
CSSHEGEWISCH The only tandem compound with which I'm familiar is on an Armco Steel stern-wheel towboat on display in Keokuk IA. Of course, a lot of the issues involved with railroad compounds were less of an issue with marine compounds.
There were also a number of stationary tandem compounds.
About fifty years ago, I took a ride on the steamer the President, which was in excursion service at New Orleans. I went down to the deck with the engines--and I recall that they were triple expansion tandem compound engines., one for each side wheel.
Johnny
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