I had saved this from an old post. Glenn is a very sharp guy.
Bill
----- Original Message ----- From: "Glenn Ashmore" Newsgroups: rec.boats.building Sent: Monday, October 20, 2003 2:07 PM Subject: Re: cheap vacuum bagging
The problem is lubrication. Refrigerators circulate oil with the
> refrigerant to keep the compressor lubricated. When you use it as a
> vacuum pump there is no oil. You can extend the life a little by
> squirting a little WD40 in the intake before each session but that is of
> limited value when the compressor runs 4 or 5 hours at a time.
>
> I suspect that the older compressors last longer because they are built
> "looser". As refrigerators got more energy efficient the compressors
> have been built to closer and closer tolerances so constant lubrication
> became more critical.
>
> I made a high vacuum system back in science fair days out of an old
> pre-WWII Kenvinator compressor and used it for several projects. When I
> started doing woodwork I used it to bag veneers for several years. When
> it finally died I tried several newer compressors but none lasted more
> than a couple of sessions. They would run for 10 or 15 minutes and then
> the thermal switch would kick them off. Ruined a lot of expensive
> veneer trying to figure a way to keep them running.
>
> There are at least 50 vacuum pumps on eBay right now that would be ideal
> for vacuum bagging. All under $100 and many under $50. Not a bad price
> considering that if a refrigerator compressor craps out in the middle of
> a session you could ruin that much material or more.
>
> Here are a few that would work.
>
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Here is a perfect setup complete with flow guages and tank:
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>>> William R. Watt wrote:
> From what GA wrote it would be better to look for an older unit than a
> > later one as I assumed. It could be tested with a car vacuum guage. A
> > vaccum guage costs about $15 at Canadian Tire. I found one at a garage
> > sale last summer for $4 which included a timing light and a remote starter > > switch.
> >
> > As for burnout maybe the compressor doesn't have to run at full power.
> > Perhaps a light dimmer switch could be used to set it at the speed needed
> > to maintain the vacuum for the particular application. Or 2-3
compressors
> could be hooked up together and run at lower power off the same dimmer switch. > > > >
> >
> > --
>
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