A fix for the Air Pump

So, following some communication with the steam boating forum we are all agreed that the Edwards Air Pump as drawn is missing  anything to hold the valve-plate in place, or seal its contact with the pump body. This means that:

  1. The whole valve tends to move up and down with the piston rod, (and I think this needs to be a “good” fit to prevent leaking round the pump-rod, so this is unavoidable).
  2. There is nothing to seal the lower valve plate (the one with the holes) where it sits on the ledge of the pump body…

So, my solution is to:

  1. fit a gasket under the valve plate
  2. make and fit a nylon block to hold the plate down – made 10 thou too long, so that the top cover provides some “squishing pressure”

As other members suggested this may help pump performance by removing “deadspace” (but it is beyond the valves so I am not sure if this is correct), and secondly it needed to be made in a way that ensured the outlet port is not cut-off if the block rotates; so, as can be seen in the pics below, I have made it with an exhaust annulus and internal ports to the valve chamber cut in the bottom…

I think this approach will also prevent the valve opening too far….. a test in the kitchen sink proves that it all works!

Here are some pics of the block and completed pump assembly.

air pump stuffing block in situ

air pump stuffing block in situ

air pump valve chest stuffing block

air pump valve chest stuffing block

air pump valve chest stuffing block

air pump valve chest stuffing block

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3 thoughts on “A fix for the Air Pump

  1. The Severn Bore

    Hello Mal,
    I made the bottom of the valve chamber bore a few thou undersize so that the static valve plate was a press fit in the bottom of the bore. The moving plate has a neoprene rubber washer shaped gasket bonded to it with industrial adhesive, and I followed advice from a previous Leak builder to fit a light spring between it (the valve) and the top cover. Both bits are out of some free 316 that I managed to scrounge! It sort of seems to work by hand, but that is not a fair test. Note that the pump as designed pulls a vacuum on the downstroke, as there is no valve to back fill the piston bore until it gets low enough to uncover the ring of ports. From what I am told and read about, this is all part of the design….
    Col

    Reply
  2. Pingback: Gaskets and Unions | SY Befur

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