Does any one know if its possible, and not terribly stupid, to start with an air compressor that delivers 3.7/2.7 SCFM at 40/90 PSI with 135 max pressure, add extra air storage with PVC and end up with 4.8 CFM at 80 psi?
I am looking at building the joewoodworker venturi without having to buy an bigger air compressor.
Uhmmm - you’re thinking of building a helluva big vacccum storage tank? To work with http://www.joewoodworker.com/veneering/v2-about.htm ?
Okay, what you want to think about might be this:
Your compressor can deliver ( if it has a storage tank of some kind ) 4.8 CFM at 80 PSI…it just won’t do it for very long before the compressor kicks on once the pressure in your compressor air tanks gets down there some. If you have, for instance, a small-ish compressor with a great big tank, you might be fine as is.
There are other venturi vaccum setups out there that use less air- http://www.vacuumclamping.com/shop/showProd.asp?prod=176 for one, and you can doubtless find others. http://www.teknocraft.com/products/vacuums/venturi_generator.asp was another I ran across. You just use a different venturi vaccum generator, all the other components can be pretty much the same.
While the venturi vaccum setup described there is capable of pulling a certain amount of vaccum in a certain amount of time, is it really all that bad if it takes a little longer? This might, by the way, include longer time required to pull enough vaccum in an enlarged vaccum storage manifold or tank.
Especially if , say, you were to put a tee and a valve in there so that you could take out a lot of the air with a shop-vac and then finish up to final pressure with the venturi setup. And seal your vaccum bag and the rest of the assembly really well.
The bigger diameter the vaccum storage manifold, the thicker your tank walls will have to be to hold out under pressure. You might want to look into things like water tanks for home water systems, especially those fiberglass types with a diaphragm in 'em. They get tossed when the diaphragm goes and they would still hold a vaccum pretty well. Or, just deal with the comressor running more often and longer.
hope that’s of use
doc…
What is “extra air storage with PVC”? Tanks are steel, and pressure rated.
You can add storage, but you can’t increase the output rate of the compressor. The best you can get is additional delivery while the stored air is expended, then when that’s depleted you’ll be back to the capacity of the compressor as if there were no storage.
I think the answer to your somewhat oddly posed question is NO.
I sent you a PM about an air compressor I have for sale.
Thanks, this did help a lot and I am looking at a different vacuum generator.
Although it was a stupid idea, I was thinking if I added enough extra storage between the compressor w/ 6 gallon tank and the vacuum setup, I could trick the vacuum generator into getting a good vacuum that would give the compressor time to fill up the extra tanks again.
The jww set up uses pressure rated PVC so thats what I was thinking. Pretty stupid huh. A bunch of PVC pipe in my garage at ~125 psi just waiting to explode.
Uhmmm - if you use the additional PVC ( schedule 80 pipe in anything over 3" diameter might be a move, make 'em fairly long) as vaccum storage, then it shouldn’t be a problem. That and another tank or two in paralell with your compressor ( like http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=40057 ) plus another inexpensive air pressure regulator and you should be good to go. You will wind up running your compressor a lot, but… hopefully not for long.
Now, this is probably overkill - we are not talking about a humongeous tabletop with a leaky vaccum bag here, especially if you get the majority of the air out with a shop vac before firing up your venturi setup. The tee for that isn’t shown, but it’d be in the vaccum line to the vac bag. The solenoid valve/vaccum sensor only opens if the pressure drops, after all, and you’re not drawing a whole heckuva lot of vaccum, lest you squash the foam with too much vaccum.
What I’d do is go with the basic system and test it on some scrap foam with a little bit of resin and cloth and maybe a couple long pieces of 2x12 in the bag ( to simulate the volume of a 9’ board ) and see if it does an acceptable job. Building much larger vaccum tanks is cheap, as is adding a pressure tank. But, after all, you may well not need to do any of that. Try it and see.
hope that’s of use
doc…