So I saw this little home made media blaster with the water bottle and the air blower that uses ground walnut shells. I'd like to make one but I'm not sure how much air capacity I would need to run it. Would a 4 gallon compressor/tank combo be sufficient or do I have to have the big old expensive 50 gallon deal?

 

For a small media blaster your 4 gallon compressor should be fine. Your limitation will be the amount of time you can blast for. 80-125 PSI should be plenty of pressure. But you air volume in your tank will limit your blast time along with how much blast media the water bottle can hold. You will be able to blast until the compressor tank runs low on air than you will have to wait for it to build up pressure again than you can continue blasting. With a small blaster you might run out of blast media before you run out of air. If you want to be able to blast continuously you will need a compressor pump that can match the SCFM requirements of the blaster. The tank will run low on pressure and the pump will kick in to supply the air you need to keep on blasting.

 

Ok thanks! I found one for $40 I think I'll buy it. I'll ket you know how it works out.

 

Ok so here's what I got.
An 8 gallon, 150 psi, Briggs and Stratton air compressor, a $5 blow gun from Harbor Freight, a box of ground walnut shells, and a 20 oz. Mountain Dew bottle. I carve a notch in the barrel of the blow gun, then drilled the hole in the bottle neck as shown in the YouTube video.
I can't stress enough how important it is to wear protective gear when using something like this. I had on leather gloves, a full face shield, a jacket, and jeans. Next time I will wear a heavy apron.
Here are the results.
This took almost two bottles of media, but only seconds to accomplish. This is a bumper I pulled from the boneyard to replace the one on my 02.

 

If you want to run a blaster continuously like that, you are usually going to need atleast 5-10 cfm minimum. I have a kobolt 30 gal oiled compressor that I love but even that with my media blaster, it needs to re-build air pressure every few minutes. All depends on the media blaster though.

 

Well, by the time the compressor needs to rebuild pressure, its time to refill my media bottle. Works ok if you're not in a big hurry.

 

If it works and gets the job done! I media blasted my entire frame so had a little bigger setup to do it all.