Roy,

In some cases, lower vacuum can give all the flattening and air removal needed while preventing excess resin loss. In that case it applies before the resin gels. Of course, if you need to prevent crushing the core or tooling, that might pose a problem for infusion. Test samples will help you figure it out.

The only other advice I'd give about pumps is to use an oil-less rotary vane or diaphragm pump. Pumps designed to go into the low vacuum range use oil to seal the vanes, and that oil will come out the exhaust in a fine mist. My first pump was a cast-off (free) Welch roughing pump from a high vacuum system. Working away at 25 in-hg, the exhaust looked like thin smoke. As for the vacuum capacity, pick up a couple of cheap gages from McMaster-Carr, put one on the pump and see how much vacuum it'll pull.

Regarding the switch, I bought the cheapest one that Omega had. I'm sure a few bucks more would have been well spent. I'm no electrician, but it wasn't a big deal to figure out how to wire up the switch, and valve.

I've included the link to an on-line magazine that I've found interesting and helpful. It has a number of good articles on vacuum bagging and infusion. I'm glad you've found my comments helpful. Keep us posted on your work - I look forward to learning from your experience.

Sam

: Thanks Sam

: I'm in the process of setting up a vacuum system and keep reading some
: conflicting numbers so am glad to hear what You've found to work.

: some of the stuff has to do with crushing the core/mold when using foam and
: some of the backing off of vacuum methods seem to be counter to my
: thinking.

: I can't really see how reducing the vacuum after the project has kicked, does
: any good since it's still about keeping the layers flattened and bubble
: free.

: I still have a little time to devise my system before the weather is
: conducive to using ...so I'm glad you posted while I've been in the search
: for components.

: as of now I do have a pump, but am also having dificulties finding specs
: since it's an older Sargent Welch pump and nothing seems to be given on
: line as far as specs....interesting how they can stamp a serial number and
: a model number, but don't seem to be able to stamp anything about
: capacities on the pump frame.

: I'll end up just doing the testing with it to find out it's capacity and
: capibilities.....would be nice to have read that it would pull 29 or 30
: Hg.

: I like your switch system...do you know of a less picky adjustiable switch?

: since I would rather go that route than the strict bleader valve method and
: need to buy whatever ....might as well get something that works up to 29
: or 30 Hg and gives me more options for vacuum settings.

: Thank You very much for the posting

: Best Wishes
: Roy