Inside a Vacuum Pump

I had hoped this was going to be a fixed it but as I now believe it to be a burnt out motor it's a simple show and tell

When I spotted this in the junk heap I thought it was a small compressor, I checked it wasn't wanted and wombled it.

(Wombles were a 1970 TV creature that collected rubbish and made it into useful stuff) It turned out to be a small vacuum pump that someone had already had an investigative nose at and not fully reassembled. The case screws were missing as was the fuse holder and the contacts looked badly burnt that should have been holding the fuse. As the screws were already missing the back just pulled off removing the 2 fixing screws that held the circuit board with the fuse holder revealed a rectifier and smoothing capacitor, the pump may be mains operated but the motor its self runs on DC not AC. A fuse having blown and burnt out its contacts suggests the pump might be seized as there is a slot in the end of the motor shaft I tried turning it with a large screw driver to my surprise not only did it move freely the motor casing did as well at this point I noticed that there were no case screws so I tried to pries the pump body off the motor as it seemed quite firm I decided to start at the other end with the pump and see if there were ant fixing screws inside the other end

As there was no oil visible in the level window and one of the fixing screws for the housing was missing a washer under it I concluded the housing had been removed before, on removal of the cover about a table spoon of light oil spilt every where. No fixing screws were evident in the back plate but it did look as if 3 fixing bolts passed all the way through the pump body so I removed these first, they were very tight and I had to resort to hitting the allen key with a small hammer to get them to start moving. With these 3 long bolts removed the pump body remained firmly fixed in position, I removed a further 2 smaller allen screws(hex socket head bolts) and the end plate then lifted off along with the first pump rotor. The vanes of the rotor appear to be glass and free moving. luckily I didn't disturb them as the will be lapped by use to the profile of the pump cavity whilst these look unworn there will be some wear and refitting them the same way round will maintain the efficiency of the pump and not have to wait for them to bed in again. each plate of the pump body was fixed to the next by 2 more blots. even once fully removed the motor body stayed where it was with no evidence of any further fixing bolts.

gentle prising this time caused movement a little rotation a little more leverage and repeated a few times the motor support bearing came out of the housing the motor case with the field magnets lifted off and left the armature fitted to the back plate. A further surprise awaited the motor bearing didn't double as the back bearing for the pump a second sealed ball-race remained in the housing for that. the threads for the missing motor fixing bolts proved to be the same as the bolts for the casing of the pump by using die nuts to check the thread size I've established they are M5, careful measuring of the thread diameter and pitch the checking with reference table would also show this. I'm sure these tables are available on line, but a little flip book is to me more convenient.

Time and space constraints associated with a move of house meant that somethings had to go, I could probably have replaced or maybe fixed the motor but having no where to work or store potential projects this went into the waste electrical and electronic recycling bag (WEEE)