Southworth Engines Boiler Feed Pump

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alanfrost:
Thanks for the compliment. I suspect the degree of surface finish on a valve face my be dependent on the pressure and viscosity of the fluid being contained as well as the dimensions of the transfer passage. You would certainly grind the valve faces for an internal combustion engine where pressures and temperatures are high but the viscosity of the intake air and exhaust gases are low. The water pump valves I made did hold air pressure but in practice any backflow on the intake side probably offers more resistance to flow than the output pressure needed to feed the boiler.

alanfrost:
My pump is up and running but I have only run it on air so far. I made liberal changes to thread sizes from those in the design substituting #2-56 for many of the 10 BA locations. Getting BA taps and dies is not easy in the USA with many sizes not being available on this side of the pond. Fortunately I inherited a good collection of BA taps and dies from my father but am still missing some from my collection. Getting the exhaust valve timing adjusted is certainly a labor of love and start up was initially erratic but I traced that to having been too energetic with polishing the shuttle valve spindle and creating too much clearance for it to hold pressure and move the valve body. I also had problems with the valves seating and made some changes to the height of the valve body to making it the same thickness as the valve chest with the gasket material providing the working clearance. As other have commented the exhaust valves floating cross head seemed a trifle sloppy and I extended the 1/16 inch rod through the top of the valve chest to provide better control of the cross head's movement, Thanks to Bob Potter for providing two 1/16 ID O rings with the casting kit. :clap:

I increased the thickness of the valve chest top and bottom cover to better allow even compression of the gaskets in those locations. I also modified the cross head design to accommodate a #2-56 cap screw making it stand proud of the valve chest face and used a thicker back plate with a slot milled to provide a track for the cap screw head to run in.

Steam Geek:
When you are machining the castings what tollerances are you aiming to achieve ? 2 thou ?

alanfrost:
Posted video of pump working on air on YouTube. Use "alan frost steam boiler pump" as search string to locate.

dsquire:
Alan

Here is the link to your video. This will save the members from having to search for it. Hope you don't mind me putting it in here.

[ Invalid YouTube link ]

Cheers :beer:

Don

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