The air powered locomotive
The air powered locomotive
(OP)
http://www.aircaraccess.com/images/3stage%201.jpg
The compressed air powered locomotive has had a long, if quiet, career. The setup shown above is one of the later and more succesful designs.
I am very interested to know why they reduced the pressure from 150 to 30 atmospheres before using it in the engine. My only thought was that the 30 atm holding tank allowed the air to warm up a bit before hitting the piston, and perhaps 30 atm was as much as they wanted in the engine itself - 450 psi is a fair pressure.
Of course one thing worth pointing out is that they probably weren't worried overmuch about efficiency.
The compressed air powered locomotive has had a long, if quiet, career. The setup shown above is one of the later and more succesful designs.
I am very interested to know why they reduced the pressure from 150 to 30 atmospheres before using it in the engine. My only thought was that the 30 atm holding tank allowed the air to warm up a bit before hitting the piston, and perhaps 30 atm was as much as they wanted in the engine itself - 450 psi is a fair pressure.
Of course one thing worth pointing out is that they probably weren't worried overmuch about efficiency.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.





RE: The air powered locomotive
Its pure speculation, but I would imagine that 30 atm air is a lot easier to control than 150 atm air.
Here is another link to that engine.
http://ww
B.E.
RE: The air powered locomotive
Assuming it was, it was probably easier to stick a reducer in than than to uprate all the engine components and fiddle around with cylinder volumes at TDC.
A.
RE: The air powered locomotive
It was more of a put-put than a train. Probably a 2" gage.
It hauled ore and tailings.
The tailings went to a big dump that is now a site targeted for clean-up. They didn't get all the mercury out of the rock and now its being leached into the creek, the river and ocean.
RE: The air powered locomotive
Although 450 psi is not very high compared with peak pressures seen in an IC engine, the pressure is sustained for much of the cycle (depending on the cutoff ratio) and that has a big effect on the strength required for each part.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: The air powered locomotive
I tried to search their archives but for some reason was unable.
http://www.compressedairmagazine.com/index.asp
There were quite a few of these locomotive in mines near my home. They were nearly all gone by the 1960's.
RE: The air powered locomotive
Isn't it easier to design a compressed gas engine to run on a fixed pressure than on a constantly decreasing pressure?
The displacement must be great enough for the engine to still work at the end of the day when the storage tank pressure is low. That much displacement may tend to over-perform in the morning if full tank pressure was applied.
Bill
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"Why not the best?"
Jimmy Carter
RE: The air powered locomotive
If you run with the intake valve open for the entire power stroke you run at the full reservoir pressure. If you close the intake valve just after the start of the power stroke then the air that is in the cylinder expands adiabatically. The latter is far more efficient. That's what you do on a steam engine, when you are cruising along you change the cutoff to minimise the steam consumption.
Cheers
Greg Locock
SIG:Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips.
RE: The air powered locomotive
Additionally, stepping down the pressure after the tank means all the engine plumbing and controls can be made to a lower pressure rating.
RE: The air powered locomotive
B.E.
RE: The air powered locomotive
Mike Halloran
Pembroke Pines, FL, USA
RE: The air powered locomotive
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I remember seeing a locomotive on display in New Orleans with three tanks. I think this is it at the bottom of this page:
http://www.cdmrr.com/other_porters.html