I've got a really old AERASPRAY, "made in Birmingham" compressor, at least 45 years in our family. I am would like to know the output of it (no labels showing) anyone know the calculation to measure cfm or free air delivery etc. How do the various bits relate, bore size/stroke, motor Hp and revs, receiver capacity? thanks.
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rtbcomp
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Assuming we are talking about a piston compressors.
The swept volume is pi*r^2 * s (pi radius squared times stroke), so FAD would be swept volume * rpm * no of cylinders.
You will need more power the quicker you drive the pump, expect 2hp to roughly equate to 9 cfm, 3 to 14 cfm.
Receiver capacity doesn't affect these figures. The bigger the tank the longer the periods between the pump switching on and off.
The swept volume is pi*r^2 * s (pi radius squared times stroke), so FAD would be swept volume * rpm * no of cylinders.
You will need more power the quicker you drive the pump, expect 2hp to roughly equate to 9 cfm, 3 to 14 cfm.
Receiver capacity doesn't affect these figures. The bigger the tank the longer the periods between the pump switching on and off.
blimey Tigler how do you up load pics? What do you reckon the output of yours is? Mine's very similar, got same air filter, no oiler, I've got a beautiful little receiver/air cooler, about 6" dia. 12" high alloy pot with fins, looks like an old british bike engine. The air pressure gauge was/is a 5" dia brass thing looks like from an old railway loco. The motor recently pack up, a machine mart one just won't look the same!! The actual compressor pot is 4" dia (fins) and about 2.5" high, not including fined head. Poppet valves in head.
Regards
Regards
rtbcomp
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Look here for instructions how to load pics.
http://www.mig-welding.co.uk/forum/showthread.php?t=5340
http://www.mig-welding.co.uk/forum/showthread.php?t=5340
From memory mine is a 5HP 3PH motor so 15 to 20 CFM. Although it looks as scruffy as hell it runs and works perfectly ! It came my way by pure chance, I happened to see the guy in a unit near to a business we once had, getting a new compressor so I went up for a nose. During our chat he mentioned that the old one was being skipped when the forklift was free so I asked for a look. As soon as I saw it I realised what a fine old piece of machinery it was and immediately asked if I could have it, he replied that as long as it was out of his way within the hour I was welcome to it ! It took me 10 mins !!
The shear weight of it is immense and I reckon it will outlive me ! I plan to strip it down, clean it up and repaint so it returns to it's former glory. Imagine if it had been scrapped !
The shear weight of it is immense and I reckon it will outlive me ! I plan to strip it down, clean it up and repaint so it returns to it's former glory. Imagine if it had been scrapped !
shenion
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On my 20+year old compressor, i did a test. I emptied the tank and measured the time it took to fill.
Filled to 8 bar in 5 minutes, so that is 8 times the volume. It is a 60 gallon tank. 8*60=480 gallons of air.
480 gallons * 0.13368cf/gal=64.166 cf per 5 min
64.166/5 = 12.83 CFM.
It is rated at 10.9CFM@90PSI. I tried it measuring the change from 90 to 120PSI (2 bar change) and got just a bit less.
This calculates the free-air-displacement. What the compressor actually achives, not the displacement. Here, compressors are rated in FAD, displacement is not given (I think mine is about 14.)
Filled to 8 bar in 5 minutes, so that is 8 times the volume. It is a 60 gallon tank. 8*60=480 gallons of air.
480 gallons * 0.13368cf/gal=64.166 cf per 5 min
64.166/5 = 12.83 CFM.
It is rated at 10.9CFM@90PSI. I tried it measuring the change from 90 to 120PSI (2 bar change) and got just a bit less.
This calculates the free-air-displacement. What the compressor actually achives, not the displacement. Here, compressors are rated in FAD, displacement is not given (I think mine is about 14.)
rtbcomp
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There seems to be quite a bit of confusion over FAD. One definition says it's the volume of air drawn in at the inlet, which will be the same as that at the outlet if it exhausts back into the atmosphere. This would be the displacement x the speed, per cylinder.
Once you start compressing it the outlet volume decreases (the mass stays the same) so when you start quoting CFM you should specify at what pressure.
The very phrase "free air displacement" suggest the air displaced at zero compression.
Once you start compressing it the outlet volume decreases (the mass stays the same) so when you start quoting CFM you should specify at what pressure.
The very phrase "free air displacement" suggest the air displaced at zero compression.
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