The Stovebolt Site Forums The Shop Area Paint and Body Shop Air compressor Question

I've done a couple searches on this but got no results, so I am going to ask. What kind of difference is there when going from a 3HP motor to a 5 HP motor on a 60 gallon air tank. And what or is there an advantage to having more than one cylinder. I want to get a compressor to run a sandblaster. I read on a thread I can't find that someone was using a 60 gal. and it worked well. I sort of understand the PSI at pressure concept, but the motor capacity relationship makes a big difference in cost.

Thanks

A bigger motor will be more efficient as well as being able to keep up with the air demand better. Same goes for having a 2 cylinder dual stage pump. If you're going to run a sanblaster, you want to get the biggest HP motor, pump, and CFM you can, as blasting is a high airflow demand job. You'll also want to consider one that can be run on 220 instead of 110, again, they run more efficient that way. You'll also want to avoid oilless compressors. The dont hold up very well under 100% duty cycle jobs like sandblasting or hig air consumption equipment like die grinders.

I agree with everything that Bill posted.

I just came in from using my large blast cabinet that is suppled air by a Harbor Freight 5-year old 60 gal 16 cfm 5 hp 2 stage 240v air compressor. It works fine, but it is about as small as I would suggest to use for a blast cabinet.

Check the TP Tools website for a tech tip on plumbing the air compressor for relatively dry air supply.

http://www.tptools.com/StaticText/airline-piping-diagram.pdf

Bill and Tim,

Thanks for the guidance. Now I have to decide on the best local deal I can find on a compressor.

Thanks again

To add just a smidgen more info you need to pay more attention to the CFM/PSI rating of any compressor you buy more than just the PSI. Look at the requirements of the blast cabinet you will buy and make that the "minimum" continuous output requirement of the compressor you buy. For example if your blast cabinet requires 16 CFM @ 90 PSI you'd be wasting your money buying a compressor with a 12 CFM @ 90 PSI rating.

There is no such thing as having too much compressor when you're sandblasting. A friend who was in business as a professional sandblaster had a trailer-mounted mobile rig that used a Ford flathead V-8 engine as a compressor- - - -running on 4 cylinders and compressing air with the other 4. Obviously, some major engine modifications had to be done to make that system work. I helped him install a '51 Mercury crankshaft with a 4" stroke to replace the 3 3/4" stroke Ford shaft to get a little more air volume. I think his rig used a 250 gallon Propane tank for compressed air storage and the working air pressure was around 100 PSI. He could move a lot of air (and sand) with that rig!
Jerry

Read up on what to look for when buying a compressor at eatoncompressor.com

Jerry,

I would pay admission to watch that thing work! Ingenious, but I think I will go a more traditional route.

Builder, the Eatons look great and I will read more on the site.

Again Thanks All

Mike, the concept is pretty old- - - -lots of Model A's got converted into jackhammer compressors by cutting the frame off just behind the cowling, and mounting a tank where the front floorboards would normally be. The hood, radiator, and cowl-mounted gas tank stayed put, while the engine ran on cylinders 1 and 4, and 2 and 3 did the air compressing. The front axle got welded into a straight-ahead position, and a tow bar replaced the front bumper.

More recently, I saw a Ford 302 V-8 converted into a compressor when a construction crew replaced the fuel storage tanks at a truck stop where I managed the Diesel shop and wrecker service.
Jerry

So how did that work? Block off the intake and exhaust ports and hook an air-line up to the spark-plug hole? How would you profile the cam to actually keep the engine running?

Any engine will run on half its cylinders without a lot of modification- - - -just disconnect the spark plug wires to every other cylinder in the firing order. No camshaft modifications are required. On the compressor conversions, it was necessary to keep the gas/air mixture out of the cylinders used to compress the air. The valves are blocked shut on the cylinders that do the compressing, and the lifters are removed. The spark plug hole is enlarged for a bigger thread, and a fitting is installed with a one-way poppet valve with a very weak spring and an exhaust port, so air can be drawn into the cylinder, compressed, and sent through another one-way valve to a storage tank. Every downstroke of the piston draws air into the cylinder, and every upstroke compresses. Some of the more sophisticated rigs had a custom-cast cylinder head with bigger ports for the cylinders that were doing the compressing. A smaller carburetor was fitted to handle the reduced airflow to the cylinders that are still running. I think the modern unit that uses the 302 Ford as a base engine uses custom cylinder heads. I don't remember which company sells that one.

With a little tinkering, I believe a modern 4-cylinder engine from a compact car could be converted into a pretty effective compressor, using the same methods that the Model A conversion used.
Jerry