Gast Vacuum Question

[Charles Drake]

I have already asked Steve Schlumpf this question and he suggested I submit it to a larger audience. I'm in the process of setting up a vacuum system as he has described--unfortunately, Surplus Center no longer has the Gast pump he has described but I found one on ebay. Perhaps those of you who have a new or relatively new pump can answer this question. When I hook a vacuum gauge directly to the inlet of the pump, the vacuum oscillates rapidly between 23 and 26 inches (oscillations occur every second or so and are very repeatable). Has anyone else noticed such operation directly at the pump (Steve suggested it might be because it is at the pump--he says his system where the gauge is located somewhat away from the pump is steady). I guess another question I might ask would be if anyone has installed a repair kit in one of these pumps and their experience with the results. Advice/info would be welcome and thanks.

[Bill Arnold]

Charles,

The best resource I've ever found for vacuum system info is Joe Woodworker (http://joewoodworker.com/veneering/welcome.htm). My system is built around a RobinAire pump and I got most of the peripheral items from Joe.

[Tom Klass]

Don't take this wrong but is it running in the right direction? When you put the gauge on is it in a tee or plumbed right into the pump housing? If it is a vane style going in the wrong direction will sometimes cause this and yes you can get rebuild kits. I got mine through Grainger usually all it is is the vanes. They are made of a carbon type of material and break easily. Make sure you put them in the right way too the leading edge should be the chisel shape. Hope this helps.
Tom

[Mike Null]

If you haven't bought one yet these people had 4 used lightly used ones for sale a week ago for $100 each. http://www.newing-hall.com/Docs/MovingSale.pdf

[Phillip Bogle]

I might be heading you in the wrong direction but.... I owned a printing and graphic design company for 20+ years. We had Gast pumps in every press and half of the plating equipment. Every used press company had some sort of Gast pump laying around. I have an old vac frame for my plate burner that I have set aside for a vac chuck. You might want to see if you could get a used pump for a very low cost. Not the vac pumps on a small duplicator press. Tell the press supplier or repair house what size you are looking for and I would bet they have one around. In 30+ years working for myself or others I never remember a pump wearing out.

It might be worth a shot?

[Don Kondra]

I have already asked Steve Schlumpf this question and he suggested I submit it to a larger audience. I'm in the process of setting up a vacuum system as he has described--unfortunately, Surplus Center no longer has the Gast pump he has described but I found one on ebay. Perhaps those of you who have a new or relatively new pump can answer this question. When I hook a vacuum gauge directly to the inlet of the pump, the vacuum oscillates rapidly between 23 and 26 inches (oscillations occur every second or so and are very repeatable). Has anyone else noticed such operation directly at the pump (Steve suggested it might be because it is at the pump--he says his system where the gauge is located somewhat away from the pump is steady). I guess another question I might ask would be if anyone has installed a repair kit in one of these pumps and their experience with the results. Advice/info would be welcome and thanks.

Greetings,

The oscillation is due to the nature of the way the pump works and would be steady if you tried it farther away from the pump.

The interior shaft is off set from the center of the cylinder, the vanes sit inside slots in the shaft and as it turns, the vanes slide in and out of their slots and ride against the outside wall of the cylinder. In effect this causes a "scooping" action with the air...

Installing a repair kit is no different than changing bearings in any other machine, the only thing to watch for is the end cap bolts need to be torqued exactly the same.

FYI the Gast pumps are rated for 25".

Cheers, Don