Hi All,
Bob here from Timboon near Warrnambool in South West Vic.
Michael,
Have seen online pics of old refrigerator motor\pump units used as vacuum pumps. Dunno about longevity as I have a feeling they normally have some oil in the refrigerant for lubrication. Probably got info filed somewhere in my puter.
As well as a normal pump there are other 2 other options depending on just how high a vacuum you need.
1. A venturi setup powered by compressed air.
2. Old household vacuum cleaner will work in the lower ranges but a bleeder inlet is essential as the air most flow thru the motor to keep it cool so it doesnt burn out.