Another fine mess I've got myself into. I'm building a clock (which doesn't work yet) intending to run the pendulum in a vacuum. Years ago I bought an Edwards 3B vacuum/compressor from a nice man at a car boot sale who assured me it was a high-vacuum pump. Was he a naughty fibber?


Got it home, fired it up for a quick test, seemed to work but not good today. The motor runs but the compression and vacuum fail to impress. No manual or info on the web.
Suspected it needed oil and have the right sort. Sprayed myself & workshop, I think by filling the pump through the wrong hole at the top. Fortunately the big output filter was off and the oil came out without fuss. On second thoughts this type of pump may be medical, and not meant to be oily.
Opening it up revealed a rotor with four fibre vanes running in an offset circle – a vane pump.

The black nozzle top right photo above is for the vacuum hose. Below near the base is a plastic screw screw cap covering a felt pad with access to a chamber filled with coarse fibre: could be a filter, or an oil pad. Anyone know if this is the oiling point? The pump would have to be tipped sideways to use it.
Just underneath and to the right of the black vacuum connector is a big spring loaded slotted steel screw ending in a rod fitting into a hole. It probably communicates with the vacuum side – see below. I think it's a valve of some sort. Anyone know what it is?


The vanes don't seem worn and there's no physical damage inside to speak of.
As the pump is covered in cooling fins and has a 500W continuous motor I was expecting a more powerful vacuum and better compression. Have I bought the wrong pump and am I expecting too much?
All help and suggestions gratefully received!
Ta,
Dave
Edited By SillyOldDuffer on 24/09/2020 16:55:53