Vacuum Assistance

[Cartierusm]

Ok so I've been using my Surplus Center Vacuum Pump for a while now and I've just started to actually think about it's operation and wanted to know if I'm getting the most out of it.

This is the model I have http://www.surpluscenter.com/item.as...4-1540&catname=

and I'm using 1/4" NPT Air Compressor Couplings to a 15' 3/8" air hose. Now it doesn't colapse and does pull vacuum, no I don't have a gauge on it, but I just built a new jig and when I put my finger over the hole it doesn't seem to be very strong. It's not weak but I figured with all I've read about how strong it is I assumed it would suck my finger off. I also don't leave it covering the hole for more that a second or two as I'm afraid it would suck my finger off.

Any suggestions, or should I just do the smart thing and get a vacuum gauge? I'm just starting to think of the straw effect. If I have a really long straw for soda, the longer and more narrow it is the harder it is going to be to suck the liquid through. So if that's my problem what kind of hose should I be using that flexible so I can put it on various attachments? Also where should the gauge go at the pump side or near the jig side?

[ger21]

I'd build a reservoir to give you some rom for leakage. Check out the www.joewoodworker.com site for info.

I have the same pump, but haven't had time to do anything with it yet.

[Cartierusm]

I read joes site originally but didn't see the need for the reservois as this is a dedicated pump and has it's own thermal protection, but I will browse through it again.

Does the amount of air space in jig have any affect on actual holding power? Meaning if I just had a few small gooves as air channels as opposed to 1/4" wide by 1/4" deep channels?

[nonubbins]

Originally Posted by Cartierusm Does the amount of air space in jig have any affect on actual holding power? Meaning if I just had a few small gooves as air channels as opposed to 1/4" wide by 1/4" deep channels?

No. The grooves act as a reservoir, just takes longer to pull a vacuum. Leaks can kill a vac system,check well for leaks. Try it without the fittings, they're built for pressure. At 20 in.Hg your pump is pulling about 9.8 psi. If you don't have a vac gauge, test your system by using a part that's a specific size and see if you can move it. A 10"x10" part will have 980 lbs. of down force on it.

http://www.engineeringtoolbox.com/pr...ter-d_569.html

[Cartierusm]

Thanks, I'm not sure how to test for leaks, I know if it's a pressure system using test leak. I figure since I'm using an air compressor hose I can just pump like 10 psi through the system and use leak liquid.

Thanks for the suggestions. I just figured maybe I was getting restriction from the small long hose or the lack of air space in my jig.

I will test for leaks and then I will put a vacuum gauge on so I can see if it's pulling the right amount of air.

[ksubenny]

Originally Posted by Cartierusm Thanks, I'm not sure how to test for leaks, I know if it's a pressure system using test leak. I figure since I'm using an air compressor hose I can just pump like 10 psi through the system and use leak liquid. Thanks for the suggestions. I just figured maybe I was getting restriction from the small long hose or the lack of air space in my jig. I will test for leaks and then I will put a vacuum gauge on so I can see if it's pulling the right amount of air.

When I was in college I frequently cursed vacuum setups as the R&D shop I worked in supported DOT testing and we had quite a vacuum pumps. To diagnosis a leak we would start from the fittings at the pump and work outwards. We had gauges permanently installed in the lines and we would slowly unhook the downstream hoses and plug them, check the gauge for the reading, if there was no/very minor change we would hook up the next hose and repeat the process until you saw a major drop in the readings from one fitting to the next and we would then we would start looking at those hose ends/fittings much closer.

If that doesn't find it you can use the soap/water trick and lightly spray the fittings and see where its bubbling/removing liquid, but be careful as you don't want to get too much water sucked into the pump. Another suggestion would be to use only vacuum rated lines/fittings with your system. You can pull a vac with non-vac rated fittings, but the vac rated lines made a big improvement in our systems when we switched from non rated components.

[Cartierusm]

I called All Star Adhesives and Gaskets, where I bought my Gasket Material. They said the channel in between the gasket material is critical because it's the only area that is actually doing the clamping. So I'm going chuck it up again and cut some more grooves. They said depth doesn't matter it's the amount of surface area that matters.

[ger21]

Originally Posted by Cartierusm I read joes site originally but didn't see the need for the reservois as this is a dedicated pump and has it's own thermal protection, but I will browse through it again. Does the amount of air space in jig have any affect on actual holding power? Meaning if I just had a few small gooves as air channels as opposed to 1/4" wide by 1/4" deep channels?

Holding power is a function of the surface area of the vacuum. Ideally you want the vacuum pulling on the entire surface of the jig. You can accomplish this by having a channel around the perimeter and having small "bumps" inside the perimeter to hold the part slightly off the jig, but allowing vacuum to pull virtually the entire surface. All Star adhesives sells a thin rubber tape that works well for this, called Z grabber. www.allstaradhesives.com

[Cartierusm]

I cut a whole mess more channels in my jig and changed some of the plumbing fittings used to connect the hose to the jig and the vacuum pump and added a vacuum gauge. Now it works excellent. I'm pulling 25 Hg. Thanks for all the help.

[ger21]

Since the pump is only rated for 26", Id say that 25"HG is pretty good.