Nostalgia & History > Yosemite Valley Railway

Found this photo of Yosemite Valley #28 in my files. Location is Merced, Calif. Photographer unknown and date unknown.

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SOMEBODY liked air pumps!

Why the duplicate pumps?

Single-phase compressors usually do not have the capacity that the 8 1/2" cross-compounds do, but they are simpler to work on. There is the added luxury of having a spare too in case one fails on the road. Some roads liked it this way. That's why you'll frequently see a pair of single-phase compressors on a locomotive where you'd usually see just one cross-compound.
Look at pics of smaller NdeM power & other roads in Mexico & you'll see quite a few of them have a pair of single-phase compressors.

Nitehostler, this engine has FOUR 11" air pumps!

Maybe because it's all downhill from El Portal to Merced? and they didn't want to sit around all day waiting for 2 pumps to get the air back. Lot's of big steam had pairs of cross compounds.

MTMEngineer...
I sure missed that one & have no other good answer for this oddity other than what was posted here. Very strange indeed.
I did look through Hank Johnston's book on the YV this morning & engines 28 and 29 are the only ones that I can see having 4 compressors. Some photos show engine 29 with 2 and others with 4 compressors. Most of their power had the pumps mounted on the firemans' side of the boiler, but some were pilot-mounted too.
I can only guess that their thinking was to use a pair of them at a time, leaving the other pair as back-ups. If these were as big as 11", they would consume a large amount of steam compared to what most roads would be using, cross-compounds.
Very strange.

A couple of years ago I took a picture of ex-YV 29 on display in Veracruz, Mexico. All traces of the airpumps on the pilot beam had vanished, and I asked Jack Burgess about their absence when I sent him a print. He said the extra pumps on the pilot were to supply air to air-operated side-dump cars during the big line relocation for the dam construction, late 20's/early 30's, and were removed about 1940; five years before the YV was abandoned. Regards, Arturo