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[Non-preserva.] Why two air pumps on this loco?
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Author:  rock island lines [ Tue Apr 22, 2014 9:31 pm ]
Post subject:  [Non-preserva.] Why two air pumps on this loco?
Steam student here. Your patience requested.

I stumbled onto photos of C&O 701 yesterday and immediately noticed the double air compressors. I wondered why a modest-sized locomotive would need two. Reading more, I learned that 701 hauled trains over some grades. So can we assume the extra air pump was spec'ed out to ensure safe train handling over tough terrain? Or could it be some other reason? I'm lost.

Pics of 701:
http://www.rgusrail.com/vaco701.html (Pics on this site can be clicked to enlarge.)

Also attached is a still shot from a video of 701.

A similar loco, C&O 711, has just one air compressor:
http://www.northamericanrails.com/yahoo ... _large.jpg

[Edited to delete a comment about the Hocking Valley Ry, and to add photo].
Author:  Robby Peartree [ Tue Apr 22, 2014 10:49 pm ]
Post subject:  History shows itself in unusual ways
Actually reason the two air pumps may be sitting in an archive somewhere and the story behind this “unusual feature” may have quite a story to it.

SP 3420 was converted to grease cakes in December 1918 due to the melon season rush. The shipment of Imperial Valley Cantaloupes and other fruits were a hot commodity and freight speeds on the El Paso & Southwestern were increased from 30 to 40 mph for these trains. At those speeds the C-19s were cutting axles and the grease lubrication was seen as a way to reduce if not eliminate the problem. Researching the history of SP 3420 gave us the reason for this change on 3420 and a view into the relationship between the SP, EP&SW and even the Rock Island as the Rock Island was the railroad that actually pushed this trade. “Unusual” things or certain set ups can actually tell you a lot about a locomotive’s operational past if one chooses to look.

Respectfully,

Robby Peartree.
Author:  Overmod [ Wed Apr 23, 2014 11:10 am ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
IIRC, double compressors are used when there are long consists and/or cold weather that make pumping down the air on a train too long a process with only one compressor.

For example, if this locomotive were used to handle strings of empties, in typical C&O mountain winter conditions (see Wardale's account of the ACE 614T testing if you need some details about these!) the double compressors might be very useful...
Author:  Frisco1522 [ Wed Apr 23, 2014 11:13 am ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
You'll find variations like this on many roads. Due to assignment to a hilly division, perhaps it was to recover from applications quicker or maybe longer trains required too long for a single pump to charge.
Nothing unusual here.
Author:  Les Beckman [ Wed Apr 23, 2014 11:16 am ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
C&O 701 sure doesn't look very good in these photos. But perhaps they are old shots, and the engine has been given some recent TLC. Anyone know for sure?

Les
Author:  Dave [ Wed Apr 23, 2014 11:32 am ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
Has nobody asked why there aren't two air pumps on 711?

dave
Author:  Lincoln Penn [ Wed Apr 23, 2014 11:43 am ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
Dave wrote:
Has nobody asked why there aren't two air pumps on 711?

dave


Or if there is a second pump on the other side?
Author:  Dave [ Wed Apr 23, 2014 12:39 pm ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
My point is, that if you consider the differences in the service to which they were assigned, it would probably explain the difference. Two pumps were not unusual on some entire classes of locomotive.

The oddest I have worked on was a little 0-4-0T with two pumps hanging off the front end. It had worked at a power plant, and had been part of a dam and railway construction contractors fleet before that, so the probability was that it had been used as a portable air compressor to power tools and air dump cars besides moving them around.

dave
Author:  Loco112 [ Wed Apr 23, 2014 10:00 pm ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
All roads with grades had in thier time table handbooks a max number or cars that can be pulled over certain track sections depending on the number of workgin pumps on a locomotive.

If the power you were running only had one pump, or you had two, but only one pump was operational, you might not be able to haul as many cars as there were to haul, or you would be in violation of your handbook.

Who can tell us what model pumps those are, or might be?
Author:  Russ Fischer [ Thu Apr 24, 2014 7:32 pm ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
I would guess they are 8 1/2 150s. Hard to tell for certain from the angle the photo was taken. They might be 120s. I wonder about the pipes that appear to be attached to the air cylinders on the left pump. I haven't seen anything quite like that before and wonder what their purpose might be.

Russ
Author:  rock island lines [ Thu Apr 24, 2014 7:49 pm ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
A close-up photo of the pumps is here (scroll down a bit).
viewtopic.php?f=1&t=11884
Author:  NYCRRson [ Thu Apr 24, 2014 10:28 pm ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
I believe that all of the later NYCRR passenger steam loco's had two air compressors. The latest Hudson's (J3's) and the Niagara's had two compressors on the front "deck" above the pilot and behind "guards" to keep them safe. The metal guard screen on the Niagara's had an "after cooler" (loops of steel pipe) to cool off the compressed air.

Reasons for multiple compressors;

1) Pump up the train air line faster
2) Quicker recovery of the train air line after a large brake application
3) Redundant systems, if one compressor fails you still got some air to work with
4) In train signalling systems on passenger trains used air; the conductors valve in each car could signal the locomotive using a separate air line that ran the length of the train
5) The water system in the passenger cars was pressurized with air from the brake system, there was no water pump in each car. A tank with fresh water was pressurized from the air line, when you opened the faucet in your sleeper the air pressure forced the water out of the tank into your sink
6) It's a lot easier to dump extra air than it is to get more pressurized air if the compressor is at it's limit

And the NYCRR was not a "mountain railroad", they where the "Water Level Route".

Just the preferences of the motive power departments I guess, a ~$250,000 loco had two ~ $1000 air compressors, the second one must have been worth the money or they would have skipped it. Kind of like having two coffee cup holders in your SUV, it doesn't cost that much more and the second one comes in handy some times.

Just my opinion, Kevin.
Author:  Loco112 [ Fri Apr 25, 2014 1:33 am ]
Post subject:  Re: [Non-preserva.] Why two air pumps on this loco?
Russ Fischer wrote:
I would guess they are 8 1/2 150s. Hard to tell for certain from the angle the photo was taken. They might be 120s. I wonder about the pipes that appear to be attached to the air cylinders on the left pump. I haven't seen anything quite like that before and wonder what their purpose might be.

Russ

You are right, its hard to tell the 120's from the 150's visually. They are most likely 150's because of the high boiler pressure of the locomotive. The 120 and 150 in the designation for the CC pumps stand for; "cubic feet of output per minute". The 120 is designed to put out 120 cu ft per minute on 160 psi steam and run at 131 strokes per minute, while the 150 is rated at 150 cu ft per minute output at 131 stroke per minute on 200 psi steam.

The pump on the left has the cast in boss and bolts for a lubricator, probably the version prior to the F1-A, so the left pump its probably the newest.

The head on both these pumps was new with the special PENNSYLVANIA RR Only; "S" and an "E" type (I think) type that the Pennsylvania RR worked on and with, but its nearly the same as the "D" model that saw huge production for 15 years, and were used post 1940 at the same time as thePENN's "S" and "E", but on every other RR in the world. So think of these PN RR S and E pumps as developmental "D" models.

The "D" model was the super superheated pump that was supposed to be the end of development and was to take any pressure and temp a locomotive could feed it. It was the last model built, and sold well into the 1950's untill the end of steam, so maybe it was the best and last and solved all the earlier problems.

The earlier A & B versions were good for some serious superheat, but had slide reversing vavles and needed a lot of oil. They could be over worked with a really high pressure dry steam that came along after these were getting used up. The A & B were still installed OEM as of 1925 on the D&RGW K-36 that had a 200psi BP and a great superheater, so they could still do the job, while the "D" was in development to solve the lubrication problems that the A & B's were experiencing with the newer locomotives.

WABCO pushed the "D" as the replacment for the A & B. As soon as the "D" came out, it was soon the standard OEM mounted CC pump. This was around the year 1939+/- a couple of years. Those old A & B CC compressors worked a long time with some hot temps and high pressures, so they were still good pumps even for big modern locos.

The head on these compressors is just what and where you'd think it would be. It sits on top of the pump and covers the left and right side air and steam cylinders. Visually, the head on the A & B models had a slightly larger diameter round cover plate, that has a popped up center area about the size of a silver dollar, its bolted to the end of the "shuttel valve" (that is cast into the middle of the top head). The "shuttle valve" on the D head has a flat cover plate, that is smaller than the A & B models, it too is visible from the side view in the attached photos.

To avoid confusion with the CC designation there was no "C" model 120 or 150 CC pump.

Here is a photo of a cc pump with the A & B top head;

http://www.google.com/imgres?imgurl=htt ... 42&ndsp=52
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