Air compressor location
From: "Richard Gagnon" richg_1998@yahoo.com
I model 1890 and I have noticed in photos of locomotives of the time that the air compressor moved from the engineers side to the fireman's side but I have never seen any discussion on why and how it happened. Engines from say 1900 on mostly had the compressors on the fireman's side. Any more information on this subject?
—Richard
posted from CPRR Discussion Group at 10:03 AM
7 Comments:
From: kylewyatt@aol.com
On the question of the air pump moving from the engineer's side to the fireman's side, I do not actually know for sure. But I suspect it had to do with who had mechanical responsibility for it. In the 19th century the fireman was responsible for throwing fuel into the firebox (coal or wood), and for wiping the loco and polishing the brass. Oh yes, and for tightening the hand brake on the tender when the engineer whistled for down brakes (there typically were no brakes on the loco in the days before air brakes). The engineer was responsible for all things mechanical, including running the loco, putting water in the boiler (crosshead pump or injector), and for the air brake system. Some time around the turn of the century (plus or minus) the fireman appears to have taken over responsibility for putting water in the boiler, and may also have assumed responsibility for the air pump – by this time a rather more reliable beast not in need of constant attention.
I can't prove all this, but have pieced it together based on a number of odd bits of information picked up over the years.
—Kyle Wyatt
From: Schuyler Larrabee
... that's all quite interesting, and makes sense, but there is another thing that might have been a motivating force: Air pumps and balance. It's obvious that until Mr Westinghouse had his idea with braking, there was no need for pressurized air on a locomotive. But then, you needed a Serious Air Pump along with a Serious Air Tank. Neither of these were weightless. I've always figured (and maybe have heard before, but I'm not sure) that the air pump and tanks were generally on the opposite side from the injector (which also became much larger in later years) so as to laterally balance a steam locomotive. ...
—SGL
[from the R&LHS Newsgroup.]
From: Ron Boham
Another factor in equalizing driver weight side-to-side was the application of power reverse cylinders, also pretty hefty. They were pretty much on anything built after 1930 or so if it was bigger than a Pacific, and applied to some older engines which had originally had "armstrong" reverse. Air compressors got larger also, up to a point, after which it was easier to add capacity by adding another compressor, instead of trying to make them larger yet.
—Ron Boham, Ralston, NE
[from the R&LHS Newsgroup.]
From: Schuyler Larrabee
Good point, Ron, I had not thought of that. They were applied to much smaller engines, too, such as 0-6-0s.
—SGL
[from the R&LHS Newsgroup.]
From: Dick Dawson
It's true that power reverse cylinders were rather heavy, but they were introduced some time after air compressors were typically located on the left side of the engine. Also, while injectors could be fairly heavy, locomotives had two, one on each side, in case one failed in service. It was definitely not a good thing to be unable replenish the water in the boiler.
—Dick Dawson
[from the R&LHS Newsgroup.]
From: kylewyatt@aol.com
I know that when a side-mounted feedwater system such as a Worthington was used, the feedwater pump was mounted on the opposite side from the air pumps for weight distribution. Not sure about injectors – usually there were two – one on each side, except if a feedwater heater was used. On the other hand, I see plenty of photos with feedwater pumps (both Worthington and Elesco) mounted on the same side as a cross-compound air pump (but I can't say what is on the other side). Of course there were such things as power reverses to fit into the weight equation.
—Kyle
[from the R&LHS Newsgroup.]
From: ANDREW DOW
I understand that feed water heaters played a role in this, too, on railroads such as the Norfolk & Western. This was certainly true on the later Y-class 2-8-8-2 locomotives, after the Y2 had had the pumps on the smoke box, and no feed water heater to need balancing.
—Andrew Dow
[from the R&LHS Newsgroup.]
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