vehicle air compressor, 12V

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Old 07-13-13, 09:41 PM
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vehicle air compressor, 12V

I do not know enough about compressors to know what I should buy. I want to go cheap, say no more than 200 and the cheaper the better. I want to have an air compressor in my truck to run my 3/8" and 1/2" air hammers, guns, ratchets, impacts, die griners, ect. I want to run nail guns and inflate my tires.

I also would use this to power my diff lockers and air horns.

what I don't know is what kind of pump I would need and what kind of tank I would need? can anyone tell me what I should look for?

im open to a belt driven mount on the engine or a 12V connection. I have room for up to a 40 gallon air tank under the bed.

I would use air tools for light to medium duty I think, maybe no more than a couple minutes at a time. that said if im trying to cut off some rust or undo a stuck on bolt I don't want ot run out of air.
 
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Old 07-13-13, 11:38 PM
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confused

ok so im looking at a York a/c compressor that came on AMC cars in the 70's. I cant find any 12V system that can deliver above 2.8CFM and the York does 9.6 so what would stop me from taking this A/C compressor, hooking it to a tank with a regulator and mounting an electric lawn mower engine or golf cart engine to a chain driven wheel on the compressor and placing this under my bed?

I want to build an air compressor setup for under 250 if I can but I don't want to have a poor system, I want to be able to use it and these 400.00 12V systems that deliver 1.4cfm are absoulty useless to me when my air tools require 5.5-8.2cfm@90psi.

thoughts?
 
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Old 07-14-13, 02:11 AM
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Nope, you won't find any battery-operated compressor to even come close to what you desire.

In the 1980s I installed a foreign air conditioning compressor on my Dodge (Mitsubishi) D-50 pick up. It was a fairly easy install as all I needed to do was to use a piece of angle steel that held the compressor and bolted to the engine using some threaded bosses that were obviously for something like adding an A/C compressor. There was an extra groove on the front pulley just for this. I added an inexpensive pressure switch to actuate the electric clutch and a "bail out" bottle for a receiver. It worked great for an air horn, little steam whistle and for small air tools used intermittently. No way would it have been sufficient to run a pneumatic grinder or sander.

I used it to supply air to a nail gun when I re-did my bedroom floor and about half way through the job the compressor threw a rod. Most likely it simply ran out of lubricating oil because refrigeration compressors have a tendency to pump oil through the system. It doesn't hurt anything in a closed refrigeration system but when using it as an air compressor you will actually lose the oil.

I had considered getting another compressor but finding a good one at a price I could afford was not successful. If I had been lucky and found one I would have modified it so that it would take a tap off the engine oil to maintain a minimum level and drain the rest back to the engine oil pan.

Forget about using a chain drive or any 12 volt electric motor. If you cannot belt it off the main engine then you will need to use a separate gasoline engine. At that point it is probably better to get a real air compressor with a gasoline engine. Be mindful of the pulley ratios so that the compressor doesn't turn more RPMs than it did as an automotive A/C compressor.
 
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Old 07-14-13, 03:21 AM
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You may be able to find something like what you need at a tractor-trailer supply house. Not sure what size truck you will be mounting this on, but a third air tank and an engine mounted compressor should power enough reserve for intermittent use. Grinders and sanders, doubtful. Not enough volume unless you go with a 40 gallon tank.

Is your truck diesel? Is it turbo? Turbo diesel engines are positive pressure engines and have no vacuum, so a small amount of compressed air can be derived from the engine directly, but it would involve precise piping and regulation.
 
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Old 07-14-13, 08:51 AM
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I am going to order this compressor today: York 210 A C Compressor and Clutch on Board Air Compressor 4x4 AC | eBay

from the specs I found it does about 10.4 CFM at 90psi at 3K rpm. the compressor is rated up to 6K rpm so I would think I could change pully sizes to give it a higher rpm.

I would like to power this with a 12V motor, what would stop me from using a 12V drill motor and change up pully sizes to give the desired RPM? I would think that it would have the torque to turn the compressor no?
 
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Old 07-14-13, 09:01 AM
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the truck is a diesel, I am open to engine mounted but I don't have a factory alternator and the room under the hood is limited by twin turbos and such. so I kinda wanted to take advantage of the 4 group 31 batteries and 400A alternator by electrically driving the compressor.

so ive got a 5 gallon air tank right now but cant seem to find inexpensive air tanks anywhere. they are like 500.00 to get a 20 gallon and more for a 35 or so. how large of a tank would I really need here?
 
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Old 07-14-13, 12:16 PM
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Just passing thru here.

You need the BIGGEST air tank you can fit. You need to store up the air while you can make it.

You can not run that compressor on a 12 VDC motor...... it just isn't going to happen. The amount of torque needed to turn that compressor will be incredible. Increasing the pulley sizes .... not likely..... as you spin the compressor faster you require more motor torque.

Companies like Viair and Oasis specialize in 12 vdc air compressors.

You will probably need to find a smaller belt driven compressor.
 
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Old 07-14-13, 03:32 PM
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You won't be able to run it at 3k RPM on a diesel at 1:1. Mine begins to red line at 3500. You'll need a different pulley system to increase RPMs at the compressor. Even if you could, a 12v drill will run about 10 minutes WAO. Just not enough torque and not enough run time.
 
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Old 07-14-13, 07:02 PM
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10 CFM would require about 2-1/2 to 3 horsepower. To get that from a 12 volt motor would require at minimum 200 Amperes. Finding a motor would be difficult and expensive.

The bigger the air receiver the better. If all you have room for is a 5 gallon then that is it. The smaller the tank the more cycling the compressor and the less "burst" airflow that you will have.
 
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Old 07-14-13, 08:21 PM
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ok so ill try to find a 35 gallon tank then, I just don't want to drop 500.00 on a tank... id spend up to 80.00 on a tank. the compressor I suppose ill mount on the engine then and just run with that. my thoughts on the 12V drill was to run the drill directly to the trucks batteries so it could run for a longer time. I have no issue with pulling 200A from my batteries, I can pull 5KW @ 450A for 5 hours before I need to charge the batteries again.

so if I find a mount for a Vpully at the alternator then I can run that to the pully on the A/C compressor and work from there.

my engine red lines at 3200 and maxes at 3500. I am replacing the valve springs, rockers, push rods, and injectors to turn the engine into a 4000RPM max and 3600 red line.

if push came to shove I could fit maybe a 60 or 65 gallon tank under the bed but do I really need that much air? I would think a 20 gallon would be enough wouldn't it?
 
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Old 07-15-13, 12:58 AM
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How big a receiver is dependent upon the CFM consumption of the tool(s) you are going to use. If the compressor puts out 10 CFM and your largest tool only requires 8CFM then you can get away with a minimally sized receiver. Be VERY careful that you consider the true CFM requirements of the tool and not the advertised consumption. As an example, a 1/2 inch impact wrench is rated at about 4 CFM average consumption but in reality it draws more like 24 CFM when running. Definitely use a pressure regulator on the receiver outlet to control the pressure at the tool to 90 psi. Run the compressor with a 100 psi cut in and 120 cut out and you should be okay.
 
 

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