Air Tank question

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Gra2472
Posts: 273
Joined: Sat Jan 25, 2020 8:02 pm
Location: Monte Rio California

Air Tank question

Post by Gra2472 »

Good morning all.

I am working on installing an air brake system on my mogul. The old steam brakes worked fine, but I added brakes to the tender, and I intend to add brakes to my freight train. Besides, every time I released the brakes, my right ankle got scalded from the exhaust.

I am wondering what general rule of thumb you might have for air tank sizes. I am planning on installing two 1-1/2" x 8" tanks and wondering if they will be sufficient with a Main Reservoir pressure of about 90psi. What size tanks do you have? What pressure do you run?

Merry Christmas


Garrett
Troublemaker extraordinaire
7.5" Allen Mogul
3 x 7.5" West Valley Baldwin Westinghouse Electrics
The railroad is almost done.
G. Augustus
Monte Rio, Ca.
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ChuckHackett-844
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Joined: Wed May 03, 2017 3:54 pm
Location: Tampa, Florida

Re: Air Tank question

Post by ChuckHackett-844 »

Are you charging them with an electric compressor with pressure switch? If so, the only thing the tank size determines is how often and how long the compressor comes on. Small tank: compressor cycles often, runs for short time. Large tank: compressor comes on less often but runs longer. If you have a leak, a small to mid-size is better because you will probably notice it cycling when you are not using air. 40 psi is fairly common but it depends on the cylinders you use (larger piston, lower pressure) and the linkage (force multiplier).
Regards,

Chuck Hackett, UP Northern 844, Mich-Cal Shay #2
Owner, MiniRail Solutions, LLC, RR Signal Systems (http://www.MiniRailSolutions.com)
"By the work, One knows the workman"
Gra2472
Posts: 273
Joined: Sat Jan 25, 2020 8:02 pm
Location: Monte Rio California

Re: Air Tank question

Post by Gra2472 »

That’s a good point, though I forgot to mention that I’m using a steam driven air pump.
7.5" Allen Mogul
3 x 7.5" West Valley Baldwin Westinghouse Electrics
The railroad is almost done.
G. Augustus
Monte Rio, Ca.
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ChuckHackett-844
Posts: 232
Joined: Wed May 03, 2017 3:54 pm
Location: Tampa, Florida

Re: Air Tank question

Post by ChuckHackett-844 »

In that case, I assume that the pump just runs until the steam times steam piston area equals the air pressure times the air piston area and it stalls. I guess then you want the reservoir to be large enough for a couple of applications to allow the steam pump to recover the reservoir. Hard to say, depends on the air requirements of a brake application (total system volume times pressure ... total volume depends on train length and the brake cylinders, etc.) and how often you want to be able to make those applications before you have to stop and let the reservoir recover. I don't think anyone can be much help there other than giving you examples and you doing some trial and error. My train is 12 cars and about 120 feet long. I run 40 psi train line pressure. I have about a 2-3 gallon tank (actually too big) at about 75 psi and I can do at least 5-6 applications ... but ... mine are automatic air brakes (pressure reduction applies the brakes). When my reservoir drops (leak or compressor not running) my brakes come on ... better than finding out that you do not have brakes :-)
Regards,

Chuck Hackett, UP Northern 844, Mich-Cal Shay #2
Owner, MiniRail Solutions, LLC, RR Signal Systems (http://www.MiniRailSolutions.com)
"By the work, One knows the workman"
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cbrew
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Joined: Sat Jan 04, 2003 12:17 pm
Location: Vancouver Wa

Re: Air Tank question

Post by cbrew »

I am running a pair of copper tanks on the tender that are 6" long and 2" dia. then like Chuck, I run auto air,, each passenger car has a alum paint ball tank that supplies the cars twin cylinders. when the system is pumped up, the viair 444 compressor will have a 30 to 45 sec cycle.
I run the tender tanks at 125 psi and all the car tanks run at 40 psi.

Engine and tender are straight air, cars are auto air.
If it is not live steam. its not worth it.
Gra2472
Posts: 273
Joined: Sat Jan 25, 2020 8:02 pm
Location: Monte Rio California

Re: Air Tank question

Post by Gra2472 »

Thanks guys. As a certified locomotive engineer I’m well acquainted with automatic air.

I once had a 120 car train cut in two by a motorist that was not pleased that was blocking the crossing. Boy was he unhappy when the conductor took his time walking 80 cars to the cut.

Automatic air for the train would be ideal, but I’m not sure I can do that with the railroad supply brake stand I have. It seems that it’s set up for straight air, which should be sufficient for my needs.

It seems from your description Chris, that my two tanks should be enough to supply my 5 car freight train.
Last edited by Harold_V on Thu Dec 24, 2020 3:00 am, edited 1 time in total.
Reason: to remove undesirable comments
7.5" Allen Mogul
3 x 7.5" West Valley Baldwin Westinghouse Electrics
The railroad is almost done.
G. Augustus
Monte Rio, Ca.
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