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Sort of an air compressor spin-off

JNHEscher

JNHEscher

Red Skull Member
Joined
Jun 7, 2020
Member Number
1892
Messages
2,999
Loc
Dogwood, MO.
Anybody ever try the belt-driven compressors at low RPM? They all state their max RPM and PSI. I've considered mechanically driving one of these off a decent sized wind turbine with enough reduction to not need 100MPH wind to turn it. Just let it continually pump at low speed to fill lots of tank volume and maybe put some mechanical, pressure-activated brake on it.

I know these have reed valves. A ball check valve would be necessary as the reeds probably bleed pressure off to quickly. I've never seen one run slowly and am curious if they will still build up pressure at something arbitrary like 25RPM.

20210501_192521.jpg

Currently have a Craftsman 120v 33gal that's loud and adds plenty to our electric bill. Thought about hooking up my super quiet 12v Viair to solar, but the overall cost added up too much.
 
Most compressors have a minimum rpm for the splash lubrication to work.
 
JNHEscher said:
Anybody ever try the belt-driven compressors at low RPM? They all state their max RPM and PSI. I've considered mechanically driving one of these off a decent sized wind turbine with enough reduction to not need 100MPH wind to turn it. Just let it continually pump at low speed to fill lots of tank volume and maybe put some mechanical, pressure-activated brake on it.

I know these have reed valves. A ball check valve would be necessary as the reeds probably bleed pressure off to quickly. I've never seen one run slowly and am curious if they will still build up pressure at something arbitrary like 25RPM.

20210501_192521.jpg

Currently have a Craftsman 120v 33gal that's loud and adds plenty to our electric bill. Thought about hooking up my super quiet 12v Viair to solar, but the overall cost added up too much.
Click to expand...
{Puts on wizard hat}...

My educated WAG says you will stop building pressure at some rpm where leaky parts (reeds, rings) start to leak down at the same rate as the pumping parts are pumping.

25rpm may get you 20psi where 50rpm may get you 45 and 75 may get you 100, etc...
 
Firstram said:
Most compressors have a minimum rpm for the splash lubrication to work.
Click to expand...
That should be a minor issue, the OP can also rig an oil pump to the imput shaft and design nozzles to mimic a splash and spray oil setup or better yet engineer a pressure lub oil system for the compressor. Add several filters and a large oil sump tank and it sounds like a great way to make shop air. Get several 2500 gal used propane tanks so you can build up extra air for when you outdraw your compressor. Design a complicated manifold system so you can draw from one tank at a time.Stack the tanks on a trailer and you will have a mobile air setup Seems like a great idea. Consult the New 4 stroke guy for technical help
 
Firstram said:
Most compressors have a minimum rpm for the splash lubrication to work.
Click to expand...
I don't see how over-filling to the bottom of the mains wouldn't solve that as long as you don't also turn it at normal RPM and cause windage issues.
 
Just about every compressor I've seen has a check valve at the tank. You can get those in whatever flavor you want. I assumed they were all ball valves, but
1620043057241.png


I would almost think you'd wan the reeds in the head leaking down a bit to help keep it unloaded when the wind is very low. You wont be spinning fast enough for a centrifugal unloader so when you have, say, a gusty day where it's running at speed for a few seconds, then slowing or stopping, and then gusting again, you're going to be fighting all that pressure in the head on each restart.
 
Instead of super slow speeds, use a smaller compressor. Same result.
 
ChiScouter said:
That should be a minor issue, the OP can also rig an oil pump to the imput shaft and design nozzles to mimic a splash and spray oil setup or better yet engineer a pressure lub oil system for the compressor. Add several filters and a large oil sump tank and it sounds like a great way to make shop air. Get several 2500 gal used propane tanks so you can build up extra air for when you outdraw your compressor. Design a complicated manifold system so you can draw from one tank at a time.Stack the tanks on a trailer and you will have a mobile air setup Seems like a great idea. Consult the New 4 stroke guy for technical help
Click to expand...

This is more or less what I've wanted to do for a long time. Grab a propane tank or two for some major compressed air volume. And yeah, the oiling is a no-brainer.

Dethmachinefab said:
Instead of super slow speeds, use a smaller compressor. Same result.
Click to expand...

This cute little guy is the smallest that Surplus Center offers. Know of any belt-driven compressors smaller than this? I was searching for the smallest available to do exactly what you suggest. If I were to drive this with a wind mill, I'd still have to put some reduction in the equation.
 

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JNHEscher said:
This cute little guy is the smallest that Surplus Center offers. Know of any belt-driven compressors smaller than this? I was searching for the smallest available to do exactly what you suggest. If I were to drive this with a wind mill, I'd still have to put some reduction in the equation.
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Find an automotive compressor off something that turns 6500-8000rpm from the factory. That should get you a nice low displacement that a windmill can turn without gear reduction. Stick an oiler inline and an oil seperator after it.
 
arse_sidewards said:
Find an automotive compressor off something that turns 6500-8000rpm from the factory. That should get you a nice low displacement that a windmill can turn without gear reduction. Stick an oiler inline and an oil seperator after it.
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Like the little electric motor-driven buggers?
 
JNHEscher said:
This cute little guy is the smallest that Surplus Center offers. Know of any belt-driven compressors smaller than this? I was searching for the smallest available to do exactly what you suggest. If I were to drive this with a wind mill, I'd still have to put some reduction in the equation.
Click to expand...

there's about a zillion old cast iron compressor heads out there sitting atop rusted out tanks with 1/4hp 115v motors on them
they're always on the side of the road for free up here
get one of those, they've got a smaller bore than a lawn mower
 
[486] said:
there's about a zillion old cast iron compressor heads out there sitting atop rusted out tanks with 1/4hp 115v motors on them
they're always on the side of the road for free up here
get one of those, they've got a smaller bore than a lawn mower
Click to expand...
I'm in Colorado where everyone thinks their junk is worth gold. When I get enough time, I'm going to check out the A/C compressors I have.
 
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