Which steam pump would you build?

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Re: Which steam pump would you build?

Post by KenG » Sat Oct 26, 2019 7:45 pm

Are you asking about single cylinder steam pumps with shuttle valves? See nelsonlocomotive.com/shay

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Re: Which steam pump would you build?

Post by Builder01 » Sat Oct 26, 2019 7:49 pm

VGC wrote:
Sat Oct 26, 2019 8:53 am
Just a question in between: Is there anybody (I mean any forum user) who has developed and /or built a steam pump without mechanical contact between valve piston(s) and steam piston set?
I think I understand what you are asking. The problem is, the steam valve must be set, or moved, according to the position of the steam piston. There must be some sort of connection between the steam piston and the steam valve so the valve can be set, or moved, correctly in relation to where the steam piston is. I cannot think of any steam engine that has a mechanism other than mechanical, to move the steam valve.

Is there a different way to sense the position of a steam piston and then correctly position or move the steam valve ? Electrical, pneumatic, magic?

Most steam engines have a part that rotates, so a simple eccentric, or return crank (which really an eccentric) is most often used to position the valve. When there is no rotating part, like in a reciprocating feed water pump, the only simple way to move the steam valve is by a mechanism connected to the reciprocating part, such as the piston rod, or, even through the piston itself.


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Re: Which steam pump would you build?

Post by VGC » Sun Jul 12, 2020 3:43 am

As far as I know, the valve piston set has no mechanical contact with the piston set.

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Re: Which steam pump would you build?

Post by Johnny O » Sun Jul 12, 2020 12:46 pm

I built the Van Brocklin in 1.5” scale. Its the duplex style, I believe its a Bill Shields drawing. I only needed to loosen up some of my o-ring fits but it ran very well in bench testing. I plan on mounting it on my 0-4-0 A3. There was an interesting article in Live Steam recently on modifications made to it with PEEK material used for the valve block and a modular design with ease of machining in mind. The author did leave off the mounting ears in favor of a more complicated bracket. I liked the rest of what he did though. This is the one I built, great project.

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Re: Which steam pump would you build?

Post by Bill Shields » Sun Jul 12, 2020 7:49 pm

The answer to the question about control valve position is yes

There are pumps with no mechanical connection between valve and piston...but the concept really will not scale well.

Position sensing by mechanical means is the easiest..but electro sensors will work. Again scaling down is really not practical.
The duplex pump may seem like a lot more work than a single cylinder...but in the long run is the easiest to build and keep running.

The single cylinder pumps tend to be more finicky with respect to construction and long term operation....unless you are looking for a realistic model from a time before the duplex pump was generally not used...ot is a no brainer... build the duplex.

The concept of using PEEK is interesting and valid . However I have yet to have a BvB stainless on bronze pump wear out or fail as a result of the material choice.
Too many things going on to bother listing them.

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