Hi Tim,

A few thoughts:

How about using multiple (3 or 4) shafts with springs on each. You could avoid some of the binding/alignment problems.

What about a side exit. You could run the exhaust port directly out the side of the pump and out the side of the boat. No constrictions, no elbows, straight water flow. I think the tee would be a bit too much of a constriction (even if large enough, but then you'd have to add a strum box to pump the water level low enough).

Make your breather holes larger than your inlet and exhaust ports, so there would never be more back pressure in the pump than positive pressure that is moving water.

I am still leaning toward a diaphragm pump, which would alleviate the foot entrapment hazard, no need for breather holes, and a lower mounting profile. However, I'm still searching for that perfect diaphragm material that will allow me to put the rest of my ideas into action. I think I need to check out Dean's latex idea.

Here's a sketch of my ideas for the piston-type pump: I think your pump design is highly durable and reliable, though.

Shawn

: (Sorry, I messed up the title on that previous post.)

: Intrepid Pump Builders,

: Shawn's diagram and instructions for constructing a hand operated bilge pump
: inspired me to design a plunger-type foot pump. Below is my sketch of what
: such a pump would look like. I envision mounting it in the center of the
: front bulkhead on the cockpit side with a big friendly foot pad the size
: of a automobile break pedal. The main pump housing and plunger is simple
: with the oneway valves located in a tee below the pump. I thought that the
: tee could be made to be removable for field service of the valves, and
: having it at the lowest point would reduce the amount of water left in the
: pump housing after the pump starts sucking air. As for dimensions, they
: are totally flexible and can be tuned to get a comfortable size and gpm
: (gal per minute) rating. I imagine the housing being ~8" in diameter
: with 4-6" of plunger travel. The plunger would be smaller than the ID
: of the housing with rubber flappers on both sides of a rigid disk in order
: to get a high tolerance design. There should probably be a sleeve around
: the plunger rod at the end cap to help the plunger move straight in and
: out, but maybe not...

: This is the first pump of any kind that I've designed. Any and all comments
: are welcome and appreciated.

: Thanks alot,

: Tim.