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steam feed pump

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Michael S.:
Hello,

I was able to purchase this steam pump together with a material set for a Stuart steam engine.
It was cleaned and oiled and tested with compressed air. It looks very similar to the Stuart feed pump but is larger. No castings were used. It has a bore of 35 mm but the piston of the pump is only 6 mm in diameter.
She's running quite well.

Michael


http://www.youtube.com/watch?v=Qj_17aubhLg

crueby:
Great find, it runs great!

Kim:
Very nice, Michael!  Great pump, and the Stuart engine will be a fun project too!  :popcorn: :popcorn:

So, just a general question - I've seen many pumps with this kind of valve actuation - the slider-type thing that bumps the valve over at either end.  But why don't any engines use that type of valve?  They all seem to use the eccentric.  Is there an advantage to the eccentric for engines that the bump type lacks?

Just curious.

Thanks,
Kim

crueby:

--- Quote from: Kim on November 07, 2023, 06:09:40 PM ---Very nice, Michael!  Great pump, and the Stuart engine will be a fun project too!  :popcorn: :popcorn:

So, just a general question - I've seen many pumps with this kind of valve actuation - the slider-type thing that bumps the valve over at either end.  But why don't any engines use that type of valve?  They all seem to use the eccentric.  Is there an advantage to the eccentric for engines that the bump type lacks?

Just curious.

Thanks,
Kim

--- End quote ---
The bump type is great when there is no crankshaft, but if there was a crankshaft, then the bump needs to be really tightly timed to the crank web, otherwise it would either try to reverse before getting to top/bottom dead center, or it would keep pushing even when that point is reached, and never reverse.
The pump type like this had a number of variations, common version would have the bump rod move a slider internally to move the actual D valve. That way, if you are just starting up, and the throw is near the end, the D valve is still driven hard one way or the other, and not just barely closed or open. That lets it have full power to either finish the stroke or start the next one in the other direction - very important if you are pumping water into a boiler, and have to start with full load.
Hope that helps?

Kim:

--- Quote from: crueby on November 07, 2023, 06:14:44 PM ---
--- Quote from: Kim on November 07, 2023, 06:09:40 PM ---Very nice, Michael!  Great pump, and the Stuart engine will be a fun project too!  :popcorn: :popcorn:

So, just a general question - I've seen many pumps with this kind of valve actuation - the slider-type thing that bumps the valve over at either end.  But why don't any engines use that type of valve?  They all seem to use the eccentric.  Is there an advantage to the eccentric for engines that the bump type lacks?

Just curious.

Thanks,
Kim

--- End quote ---
The bump type is great when there is no crankshaft, but if there was a crankshaft, then the bump needs to be really tightly timed to the crank web, otherwise it would either try to reverse before getting to top/bottom dead center, or it would keep pushing even when that point is reached, and never reverse.
The pump type like this had a number of variations, common version would have the bump rod move a slider internally to move the actual D valve. That way, if you are just starting up, and the throw is near the end, the D valve is still driven hard one way or the other, and not just barely closed or open. That lets it have full power to either finish the stroke or start the next one in the other direction - very important if you are pumping water into a boiler, and have to start with full load.
Hope that helps?


--- End quote ---

Interesting!  Yeah, I can see how that makes sense.  Thanks for the reply, Chris.  ;D

Kim

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