I do a fair amount in a small blast cabinet, had to upgrade the compressor just for that alone.
I mentioned in Gregski's post, scour craigslist. There are some great deals out there. Picked up this unit that was never installed for $650. 17 CFM @ 175PSI with 100% duty cycle.

 

Does your compressor have a water separator/trap? Even if it does the compressor working continually will generate a lot more condensation and that may lead the sand binding up.

 

I have the same problem with mine. My compressor is a large enough and media is dry. I also used a water sperator. Its a Harbor Freight one. I have to take mine an either jiggle lower control or shake the pot. what a pain in the butt. Fustrating enough job as it is.

 

Just an FYI,

Search a blasting equipment manufacturer. On their website you should find a chart that tells you how much air you need dependent upon the size of the tip. Big tips get a lot done but need big air. Even a small tip say 5/16 needs something like 12 hp of air compressor. Blasting yourself is a pain in the ***.

tips to research
-Pay attention to your tip as they often wear larger in a short amount of time
-research your blasting material, heavy material hits hard and can warp
-research you pressure at the tip, light material at high pressures hits hard
-research the regulator and volume, you need a big *** reg to move a lot of cfm at low pressures
-try to aim the material at an angle, not perpendicular to the work
-you can warp a panel in short order if you screw up

I used a big 3 phase electric compressor with 2 5 hp gas guys and still couldn't maintain enough cfm with a 3/8 tip.

I think the only way to go is to rent a big gas/diesel powered compressor. Make sure it comes with a reg that goes low enough for your work.

I was told with copper slag 20/50 or 30/60 to blast with about 40 psi at the tip. CFM will be dependent on tip size. This was a safe setting for a rookie blaster as long as they didn't do anything stupid. It worked well enough for me. Truth be told I stayed away from large flat panels, just in case.

 

Well i finished out the first 50 lbs of the heavy grit, tried the 30-60 grit glass and it flowed like a charm, but i was very careful to close and open the media valve at the start and end of each compressor cycle...which was obviously not very long but i think ill just do the car in 4 parts, right now im working on the engine compartment and front rails, next ill do the trunk, then ill do the interrior and last ill do the bottom.........that being said, it does suck to wait but i guess patience is a virtue, hahaha i can do about a square foot or so per cycle so its not terrible, but ya if i was trying to make money on the project or cared to get it done right away then ya i would steal my old mans compressor (or rent one)
I did notice a bit of moisture in the line however, so i will be investing in an inline water seperator for at the compressor outlet (theres one on the blast tank inlet but not too sure how good it works) any suggestions on a seperator?
thanks for all the great input guys
oh and just one last question....why do they use the rubber tips that wear away quickly, why not use a steal tip? im sure there is a good reason, just curious.
Nick

 

a water trap at the compressor isn't going to do much of anything but waste your money.

the separator needs to be placed in a location that will allow the air enough time to cool (i.e. long black pipe). if you setup your plumbing correctly, you will get more water out of the pipe than the separator.

rubber tip? are you talking about the stopper?

 

Kinda like my pic above? I get most of my water out on the first loop. I was looking for hot water base board to really cool the air but with the 80 gallon tank and the intercooler between stages its not too bad.

Corzy, steal the compressor. You're going to want it when you start painting. HVLP guns use a lot of air. You'll have the same moisture problems in your paint.

Steel tips don't last very long either, you want to go ceramic....just never drop your gun.

 

well i do have 100 feet of black air hose, and its all reeled up in the corner, i only pull out maby 15 feet, so most of the water im sure gets knocked down there, but ya maby ill have to hard pipe a few copper loops into a seperator, thanks for the tip.
ya the gun i have came with 4 ceramic tips, i was just wondering why ceramic.

 

You'll just fill your hose with water then you'll really have problems when you paint. You need drip legs so the water has somewhere to collect and most importantly give you a way to drain it. At the bottom of the each loop put a T and then just a 4" piece of pipe and cap it. Every couple of days pop the cap and let it drain, especially before you paint. Water has been a problem for me but I finally have it solved with the copper loops and 3 filters for paint (each is different and serves a different purpose). Most recently I added an auto drain to the tank, every 30 minutes it open for 10 minutes to get any water that may have collected out of the tank. Sometimes I forget to unplug it and you can hear it fire off in the middle of the night. My tank pressure is 175 so its a pretty good blast

I have a hose I only use for paint, its only about 20' but its 1/2 hose that I have a 6' piece of 3/8th on just to make it lighter at the gun. It's amazing how much pressure you'll drop even in a 20' length of hose. When it comes time to paint make yourself one of these, attach it to the gun, pull the trigger and set the pressure. It will probably be 10 - 15 lbs lower than the pressure at your regulator. Learned this the hard was after shooting really crappy only to find that my one desiccant filter was almost clogged. Had 50 psi at the regulator and only about 2 at the gun. Then got the tip about setting the pressure with a gauge at the gun.

You'll like the ceramic tips, just don't drop the gun. Eastwood sells them too, about $18 for 3, although buy them from eastwood on ebay and save $5 on shipping. They last a long time.

 

OK great advise velocity...just wondering how big copper tubeing i should use? and wouldn't it be easier to do a zig zag back and forth angled so the water all will drain back to the tank and place just 1 trap at the tank outlet, or the loop inlet (same difference) instead of on each loop??
thanks