The motors of most shop vacuums are cooled by the air that flows through the vacuum parts. If there's no
flow of air through the hose, there's none through the motor and the motors burn out quickly. A very few
shop vacuums (Fein and ?) have 'bypass' fans which cool the motor even if there's no flow through the hose.

Ed Askew wrote:

I just use 2 shop vacuums. Actually, one is a vacuum cleaner for
cleaning out pellet stoves. I've done small things with just one
regular shop vac I bought at Wal-Mart. The thing is to get a good
seal from your bag. You need lots of duct tape.

Ed.

(William R. Watt) wrote in message ...
There is a website describing how to use a discarded 'fridge compressor
for vacuum bagging. The fellow who tried it used a vaccum gauge from an
automobile in his configuration and claims he got 25 psi vacuum for his
project. He just used standard plumbing fittings to connect the vacuum bag.

I do not have the website address. I was browsing on a computer at the
public library at the time and did not write it down. However you can
find it by going to www.boat-links.com, clicking on "The Mother of All
Boat Links", clicking on the first box "amateur boatbuildign and repair"
and scrolling down untill you find the link about vacuum bagging.

Nowadays all discarded 'fridges go to a recyling depot where they "vacuum
bag" the freon gas to protect the ozone layer of the atmosphere. It should
be easy to get a compressor by telephoning the miniciapl garbage
department. Since compressors do wear out it would be a good idea to look
for ones off later model 'fridges (the date of manufacure should be on a
label on the 'fridge) bring home 2 or 3 to try.