Water Pump valve question

[DickInOhio]

I started planning and building a different kind of engine about a month ago. This is the first engine Ive built that is water cooled. I need to make a reciprocating water pump and am not sure what makes a good check valve for water. The pump bore and stroke will be .375 x 1.000. The water piping is .188 id brass. The pump will be mounted horizontal and powered by the back and forth motion of the arm at the rear of the engine in the pic. Any help, advise, suggestions will be appreciated.
Thanks
Dick

 

[Charles Lamont]

If the speed is low you could use stainless balls. For your 3/16" pipe bore size
you could use 3/16" passages, 1/4" balls in 5/16" chambers, with ball lift limited to 3/64". For slightly higher speed a winged valve can be used - like a short poppet valve but with 3 or 4 radial fins on the stem to guide it in the hole, cut in the axial direction with a slot drill.

Reciprocating pumps need careful design if they are to run at any speed. Personally, I would be want to gear the pump down if the the engine is meant to run at more than a few hundred rpm.

Some use an o-ring as a valve seat.

 

[Jasonb]

That sounds a very big pump displacement if its just to circulate cooling water on what looks to be a fairly slow reving engine. Unles sthat engine is making a lot of power I think you will have a job forcing that amount of water through 3/16 pipe

Last watercooled that I made with a pump was 1" cylinder and 1.5" stroke, the pump on that was 1/8" bore x 3/16" stroke. As Charles says it used balls as valves. 3/16" OD pipes.

J

 

[DickInOhio]

Thanks guys. I agree with all your comments. I have reduced the pump chamber to 1/4" and the stroke is optional. Speed of the engine is as slow as possible, 200 maybe. I need to gear it down more. Maybe run the pump off the cam shaft. Still time to make improvements.

 

[gbritnell]

The natural tendency for hot water is to rise, therefore you have the thermo-syphon type of cooling. Some old hit and miss engines had this type where the water would rise to the top of a screen and the process of transferring the heat to the air cooled the water and it dripped back into the reservoir and was recirculated. If you wanted to add a pump to this type of setup a simple vane type pump would be more than enough to help move the water. It could be powered by a small belt from the crankshaft. This way you could avoid links and levers.
gbritnell

 

[Jasonb]

The one I did was also driven off the cam shaft, its the one on the right, the other is the fuel pump.

 

[DickInOhio]

The natural tendency for hot water is to rise, therefore you have the thermo-syphon type of cooling. Some old hit and miss engines had this type where the water would rise to the top of a screen and the process of transferring the heat to the air cooled the water and it dripped back into the reservoir and was recirculated. If you wanted to add a pump to this type of setup a simple vane type pump would be more than enough to help move the water. It could be powered by a small belt from the crankshaft. This way you could avoid links and levers.
gbritnell

Thanks George for your input, your experience is always welcome. I almost went with the thermo-siphon method but then changed my mind for two reasons. #1 I have never made a water pump and #2 the more gizmos adds more intrest
Iv decided to go with an excentric of the camshaft. Pump will be .25 bore X .5 stroke. Now to make the pump valves ?

 

[DickInOhio]

The one I did was also driven off the cam shaft, its the one on the right, the other is the fuel pump.

Thanks Jason. similar to what Im going to do. What you check valve setup?

 

[Jasonb]

I'll see if I can find my sketches, I made it based on photos of the original rather than the one shown on the plans

 

[DickInOhio]

Dont go to a lot of trouble Jason. I just like to see how others do things.

 

[Jasonb]

Looks like I got it slightly wrong, the fuel pump was 1/8" bore and the water pump ram 3/16. Passage in the pump is 3/32" and would have used 1/8" balls

 

[MachineTom]

While a positive displacement pump is simple enough to build, when hooked to a fixed drive like the camshaft locks you into, a difficult to tune system. If the pump volume is to much you can not restrict it, and if its not enough you can not increase it.

Since most of our engine run time is no load, cooling is a small consideration. It does not need much flow to be effective. Just figure your engine displacement, your volumetric efficiency (no load maybe 10%) rpm, fuel/air ratio, allow that 20% of the fuel heat needs to be cooled, then size the pump accordingly.

A belt drive pump gives the ability to change ratios to need the final engine needs.

 

[Jasonb]

Its just as easy to make another eccentric with teh hole drilled at a different offset than it is to make a new pair of pullies.

Or better still put a bypass on the pump so you can adjust the flow as you would a boiler feed pump..