PTO driven air compressor

[Ideehoan]

I'm thinking of building a PTO driven air compressor for sand blasting. My shop unit puts out about 10 cfm at 90 and its slow.

Harbor Freight sells this:
145 PSI 5 Horsepower Twin Cylinder Air Compressor Pump

If I manifold it with my shop unit I should have decent cfm.

Anyone set something like this up? I guess I need a pto stub shaft for a pillow block setup? Any tips appreciated.

(Tractor is a Kubota B7610)

 

[Ideehoan]

http://www.tractorbynet.com/forums/build-yourself/87592-power-take-off-air-compresser.html

Did some more searching and sure enough someone has done exactly what I was thinking. I had thought too of connecting direct to the flywheel but was unsure how that would work. He did not provide much follow-up to indicate how it functioned and its durability. Seems like a sensible setup. It would however be nice to find a higher capacity pump.

 

[strum456]

I have considered doing the same thing. I think RPMs might be a problem for you. According to the specs for that pump, a standard PTO would be roughly half speed.

My plan was to use a much bigger Gardner Denver pump that I have laying around and run it off my 841 Ford that has a Sherman transmission. This would allow me to run my PTO near 1000 RPMs, which is what most compressors need.

 

[BHD]

this is what I came up with, I have a 540 and a 1000 pto shaft, I do not rember but some where between 50 to 75 cfm at 125 psi,

 

[Ideehoan]

this is what I came up with, I have a 540 and a 1000 pto shaft, I do not rember but some where between 50 to 75 cfm at 125 psi,

I checked yours out when searching. Awesome setup!

strum456
Re: PTO driven air compressor
I have considered doing the same thing. I think RPMs might be a problem for you. According to the specs for that pump, a standard PTO would be roughly half speed.

My plan was to use a much bigger Gardner Denver pump that I have laying around and run it off my 841 Ford that has a Sherman transmission. This would allow me to run my PTO near 1000 RPMs, which is what most compressors need.

I have the 2 speed pto so high speed is in the 900s. I'm going to see if I can luck onto a higher capacity pump but I could get by with the HF unit. High capacity would certainly speed up blasting by allowing larger nozzles.

 

[BHD]

you could start with one pump and if that was not enough add a second and belt drive it off your first pump, I would suggest you add a unloader valve on it some where, (an unloader valve is different than a pressure dump or a safety relief valve) in that it stops letting air in to the tank and diverts it to the atmosphere some (on mine it works internal of the pump) but there are those who just exhaust the pump air separate from the pump,

and example in URL Unloader, Load Genie - Compressor Valves - Air Compressor Accessories - 4TK14 : Grainger Industrial Supply

 

[Ideehoan]

I'm looking at unloader valves. As I understand it, there are different types, the most common being one used to "unload" pressure off an electric motor driven compressor piston when it shuts off, and has a check to prevent tank discharge by reverse flow. In this setting the valve is triggered by air directed to the valve by the pressure actuated switch when it shuts down the compressor. Its function is not pressure control, but easier starts.

Another type is the "pilot unloader" which directs air to an actuator which "unloads" the compressor by idling down a gas engine, or other mechanism. Here it controls pressure by regulating the motor (idling it or actuating valves to prevent compression).

Neither of these applications are intended to control pressure by exhausting air.

I would think a pilot type could be used in that fashion. I'm not sure however, what advantage there is over an ordinary pressure relief valve.

One issue might be service life? I'm not sure a relief valve is intended for repetetive use. Perhaps another thing is noise as a pressure relief valve makes shrill discharge noise. The pilot valve could be directed through tubing to subdue the sound.

Anyone know the answers?

 

[zzvyb6]

A really good idea ! I like this approach because for me it would be for intermittent use only. My shop compressor can run the other stuff, ok.

I had been thinking about a mid-pto compressor, but then I got a rotary 540 air compressor made in Italy to use out in the field for tire service, etc.

So what do you need to complete the sandblaster system ? A blast cabinet (obviously), and a shop vac, but what else? Would you need a reservoir tank and pressure regulator, dryer, etc?

I'm all ears !:thumbsup:

 

[Groo]

While I like the simplicity of a direct drive, based on the low power requirements of the compressor compared tot eh tractor's PTO rating, having the tractor near idle and gearing up the compressor would made more sense. You could also incorporate an electronic clutch easier that way too.

I guess its just a matter of how much time do you want to put into it vs. how much will you use it.

 

[dynasim]

I have purchased the equipment to make a hydraulically driven compressor using the harbor freight 2 cylinder compressor, and a surplus center hydraulic motor.

I am a bit worried about the pressure cycling on the motor, but the power on a 10 gpm flow circuit works out just right. I want to use a pilot driven hydraulic diverter, but will have to see if I can find or make one. The goal is make a compressor that only needs a very small tank(I can adjust the tractor speed to get the compressor capacity I need).

The all in(with a pneumatic unloader) is about 500$ for a 20 cfm, 150 psig, compressor.

The hydraulic part of it should make it safer and easier to use.

Chris

 

[BHD]

the unit I listed above is a vent unloader self contained, I have used one on a smaller compressor,
Compressor Components
more info
http://www.rossbrownsales.com.au/files/continuous_run_vent_unloaders.pdf


Load Genies & Unloader Valves

there are diffnret sizes depending on CFM requirments

a saftey valve will not close untill your considerable lower psi than what your wanting they may blow at say 125 or what ever they are rated for but my not reseal untill 40 psi, they will work the way you would want them to for that pourpose,

my compressor uses a a head unloader, the unloader works the valves in the compressor and so it does not pump,

 

[Groo]

big truck valves close at about 110 I think. They must be cheap since they are so plentiful.

 

[Ideehoan]

the unit I listed above is a vent unloader self contained, I have used one on a smaller compressor,
Compressor Components
more info
http://www.rossbrownsales.com.au/files/continuous_run_vent_unloaders.pdf


Load Genies & Unloader Valves

there are diffnret sizes depending on CFM requirments

a saftey valve will not close untill your considerable lower psi than what your wanting they may blow at say 125 or what ever they are rated for but my not reseal untill 40 psi, they will work the way you would want them to for that pourpose,

my compressor uses a a head unloader, the unloader works the valves in the compressor and so it does not pump,

I see the Load Genie is indeed designed to control pressure by exhaust flow, and your explanation of the relief valve limitation makes good sense. Thanks!

dynasim
Re: PTO driven air compressor
I have purchased the equipment to make a hydraulically driven compressor using the harbor freight 2 cylinder compressor, and a surplus center hydraulic motor.

I am a bit worried about the pressure cycling on the motor, but the power on a 10 gpm flow circuit works out just right. I want to use a pilot driven hydraulic diverter, but will have to see if I can find or make one. The goal is make a compressor that only needs a very small tank(I can adjust the tractor speed to get the compressor capacity I need).

The all in(with a pneumatic unloader) is about 500$ for a 20 cfm, 150 psig, compressor.

The hydraulic part of it should make it safer and easier to use.

Chris

That should be a nice setup. Are you planning to use two compressor units to get 20 cfm?

Groo
Re: PTO driven air compressor
While I like the simplicity of a direct drive, based on the low power requirements of the compressor compared tot eh tractor's PTO rating, having the tractor near idle and gearing up the compressor would made more sense. You could also incorporate an electronic clutch easier that way too.

I guess its just a matter of how much time do you want to put into it vs. how much will you use it.

I agree and if I wind up using it a lot, I will do exactly that.

zzvyb6
Re: PTO driven air compressor
A really good idea ! I like this approach because for me it would be for intermittent use only. My shop compressor can run the other stuff, ok.

I had been thinking about a mid-pto compressor, but then I got a rotary 540 air compressor made in Italy to use out in the field for tire service, etc.

So what do you need to complete the sandblaster system ? A blast cabinet (obviously), and a shop vac, but what else? Would you need a reservoir tank and pressure regulator, dryer, etc?

I'm all ears !

This will be for blasting outdoors with a pressurized blaster (also from HF ) although I do use a blaster cabinet (also from HF ) in the shop. Dust is managed with a 1 HP dust collector (also from HF ). I run the air through a copper coil inside an old fridge (freezer section) then a long section of copper pipe to cut down moisture as it helps keeping the sand dry (also important for painting).

One key often overlooked, is nozzle size. The newer deadman valve from HF is a big improvement with 4 nozzle sizes. With 10 cfm I can almost keep up to the 2nd smallest. Blasting speed with improve greatly with larger nozzle size allowed by more cfm.

I will put a reservoir tank on the pto unit since I have an extra, but this is optional as I'll be feeding it into the shop system which has a 60 gal tank. It will provide portability.

I got lucky and found one of the HF 2 cyl units, NIB on Craigslist last night so I'm going with that for now. I'm having a 4 1/2" circle laser cut from 1/4" plate steel and will weld on a pto adapter I found today. I'll drill a 7/8" hole in the end of the adapter for access to the flywheel bolt. 4 1/2" is the size of the flywheel hub. It will be drilled and bolted on (3 holes). I chose 4 1/2" to make centering easy, and laser cutting to minimize imbalance.

 

[Ideehoan]

Here's the blasting project.
The white hood is provided with fresh air by a used CPAP unit (used for sleep apnea).

 

[dynasim]

What I bought is this:

145 PSI 5 Horsepower Twin Cylinder Air Compressor Pump

and this

Surplus Center - 2.5 cu in WHITE 255040F3DD22AAAA HYDRAULIC MOTOR

along with a bunch of hydraulic connections, a tank, and an unloader.

I haven't figured out the motor to compressor connections, and want to retain the pulley(for the flywheel effect). I just got the stuff, so I really haven't worked on it yet.

It looks like it will be about 15 cfm@40 psi, with a 145 psig max pressure. This is, by far, the most economical motor, so I won't fine tune it. I am pretty sure a bit smaller motor(volume wise) would work(torque wise), and could get the cfm up, but I don't want to spend the extra 200$.


Good luck.
Chris

 

[PHILIP8N]

A right angle belt drive pto gearbox like this would make a nice driver. I have an extra one of these, and I always thought about taking the flat belt pulley off, adding a v-belt pulley, and driving an air compressor with it. With the pulley arrangement, you can match pump speed as required. Plus, I have a 3 speed pto, so that helps as well. Mount everything on a carry all and off you go. I have a 18 scfm 175 psig in the shop, so I have all the air I need there. I also have a 10K generator, so if I work away, I have enough electricity to power all my saws, drills, battery charger, and even a small 15A compressor. Philip.

 

[Ideehoan]

Looks like some nice restoration work there.

I'm puzzled by this fitting. It's a flared fitting like hydraulic hose but with a nut kinda like a copper compression fitting would use. Anyone know what this is?

The other pic is the pto adapter ready to be welded onto the 1/4" plate which is bolted to the flywheel.

Edit: OK so its just a flare nut fitting. Never seen such a large one and don't have a 3/4 flaring tool. Another challenge...

 

[Ideehoan]

Here's some shots of the assembled unit. The tank was free from a friend. I think it is off a large truck but not sure. The tank saddle was bent out of 1/8" x 4" steel.

The compressor output fitting is 3/4" OD flared copper. A nuisance to track down as this is not used in general plumbing. I finally found it at a compressor shop :ashamed: :laughing:

I installed a 150 psi blow off valve and have an overload valve waiting to be added before I put it to work. I wound up taking it to my local tractor repair shop to get an opinion on a PTO rattle when down at idle at higher psi. We decided it's due to a combination of straight cut gears driving the pto, and the on/off rotational forces of compressor function. I was advised not to worry. It won't be running at idle anyway.

I'll paint it Kubota orange after it has proven itself.

 

[PHILIP8N]

Nice unit. Just a few comments from my experience. The vertical tank is not well supported, and will put stress on your piping. Laying the tank horizontal will be much more stable. Philip.

 

[Ideehoan]

Thanks for the input.

I chose vertical so it's more compact for storage. It also gives the option of adding a second compressor mounted above. The drain fitting on the bottom is set up so it contacts the ground providing tank support and balance when not connected to the tractor. I may add something there so it does not sink on soft ground.

The mount is actually quite solid. There is no movement of the tank during operation. It might be a concern if it were being transported long distances on rough ground but such is not the case. The compressor does bounce somewhat while running. The piping has a flexible connection so the solid pipe is not affected.