The pump I got from CST 22 years ago isn't pulling the vacuum it used to, so I got me one from Harbor Freight for $80, part number 98076, http://www.harborfreight.com/25-cfm-vacuum-pump-98076.html .  I could say that the Harbor Freight pump really sucks, but that is ambiguous for a vacuum pump.  It seems to work a treat: it makes a pretty complete vacuum according to my ancient gauges, anyhow, and it moves a lot of air when air is there, so it looks like it can keep up with little leaks.  It is intended for evacuating air conditioning systems, so I don't know how it will fare with continuous operation like all-night vacuum bagging.  I'll report when I find out. 

   Every try a refrigerator pump?  Those tend to be bulletproof and will run continuously for years.

    Brett

Howard how much of a vac do you need?  I run my pumps 24 hours at a time. I just change the oil a lot because of the thing I pull thru mine. I dont know how long the oil is good for useing it like you are.

I operated the pump about 20 hours making a cowl.  The cowl stuck to the mold, but the pump worked fine.

Thanks, Don.  Some places came loose, but those that stuck would have taken a heap of pressure to blow off.  I keep coming up with new methods to stick parts to molds.  The most effective so far has been to use Frekote 700 mold release on a doped balsa plug.  It acted as a super bonding agent to affix the dope to the casting epoxy.  In that case I was able to chip and sand the balsa out.  This time I used 35-year-old K&B Superpoxy to bond the casting epoxy to the carbon-epoxy cowl.  I had hefty layers of Frekote and Johnson's wax between the ancient Superpoxy and the cowl.  I have sanded off the Superpoxy and brushed on a couple of coats of PVA for the next round. 

No, but I got the cowl out of the mold

Thanks, Don.  Some places came loose, but those that stuck would have taken a heap of pressure to blow off.  I keep coming up with new methods to stick parts to molds.  The most effective so far has been to use Frekote 700 mold release on a doped balsa plug.  It acted as a super bonding agent to affix the dope to the casting epoxy.  In that case I was able to chip and sand the balsa out.  This time I used 35-year-old K&B Superpoxy to bond the casting epoxy to the carbon-epoxy cowl.  I had hefty layers of Frekote and Johnson's wax between the ancient Superpoxy and the cowl.  I have sanded off the Superpoxy and brushed on a couple of coats of PVA for the next round. 

Is this an epoxy thing?  I don't remember having that much trouble with polyester parts.  Sometimes we did, but it mostly involved people being stupid (or, in one case, malicious).

PVA was just for spraying onto a part that you wanted to cure out thoroughly, because polyester doesn't go 100% in the presence of air.  I never saw it used as a release agent in my dad's shop -- and I did plenty of mold work.  It seems like it'd mess up your nice finish.

Tim, Polyester releases well typically because it shrinks as it cures,, another issue is the first few parts out of a molde tend to be really prone to sticking,, IMHO,, and limited experience on our aircraft parts.. and if you spray the PVA like it was paint, you can lay it down with minimal affect on the finish,,,

We certainly experienced the "first few parts out of the mold" problem -- one of the ways to @#$% up a nice new mold was to not be attentive about waxing it every time for the first few parts.

After a mold had some mileage, though, you could pull half a dozen parts out of it.  You paid attention to how easily it pulled and the surface finish, and waxed as necessary.

Man, all of this is reminding me of how happy I am that the last time I had to take care of a mold was over half a lifetime away...

I've used a freezer compressor for 20+ years.  When the freezer of refrig goes its generally has lost its freon due to a pinhole leak in the lines.  Its cheaper to buy a new one.  But the compressor is still good, it'll run for another 50 years.  I have mine connected to an adjustable vaccuum switch and an empty freon bottle to act as a plenum to keep it from cycling too often.

I guess so.  It seems to have a finite shelf life.  The problem may have been with the old Superpoxy, too.