Don’t think the air pump will work

I think there is a problem with the air pump design/drawings…

This looks like it’s not a problem with the drawings, so much as an oversight in the design…

The outlet flap valve assembly is not fixed/located by anything vertically within the outlet chamber… neither is the lower valve plate – part 3 on P20 of the book – (the one with the holes)  sealed against the lip it rests on above the cylinder….so (as I noticed when I completed a trial assembly) the whole valve (both plates and the rubber washer) move up and down with the piston rod, and even if the vacuum held it down, I feel sure any hard won pressure difference would be lost as the air leaked back into the pump round and under the valve plate.

My current plan is to make a nylon “block” which is a light push fit in the outlet chamber, has “ports” to let the air-water out to the  delivery port, and is slightly longer than the available space, so that when the top cover is fitted it will press the lower valve plate down onto a gasket I am fitting under the valve plate….

does anyone have any better ideas/opinions? am I missing something?

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