Which steam pump would you build?

[KenG]

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

[Builder01]

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.

David

[VGC]

http://www.bremsenbude.de/bilder/lpu/015.jpg
As far as I know, the valve piston set has no mechanical contact with the piston set.

[Johnny O]

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.

[Bill Shields]

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.

[VGC]

@ all: Do you know what are the smallest steam pumps made by commercial manufacturers?
Are there some for gauge 1 (45 mm) anywhere, or even smaller ones?

[Pontiacguy1]

From what I have seen, most gauge 1 locomotives use either an axle pump or a hand pump to raise the water level in the boiler, or they have no means of raising the water level while under steam. I am sure that someone, somewhere, has built a 1/32 scale or 1/24 scale working steam pump, but in Gauge 1 I've never seen one. I've seen a few in Gauge 3, but that's about as small as I've seen them.

[VGC]

When I wrote "gauge 1", I meant the German expression "Spur 1" which is 45 mm gauge and 1/32 scale. Did you understand 1" (one Inch) ?

[Asteamhead]

Bill:
100 % agree to what you wrote!
Pontiacguy1, VGC :
There are lots of smaller single piston pumps. At least one I saw on a scale gauge 1 narrow gauge locomotive - may be 1 / 24!
Far the best such pumps are made by manufacturer Hans Link . They are proven, very reliable and not expensive. You may change them by adding some sort of housing which make them look like the prototype . Please see the photos.
It's very hard to build such small pumps as true models and still working reliable ! Knowing this from more than 40 years of experiance by building several of such pumps including a working air pump.
Look, the Worthington SA pumps had just one piston valve of genious construction . The single valve was moved and blocked by small steam chanals near the end positions of the main piston. No mechanical connection there. They worked (and still do f.e. on the J 611) absolutly reliable . Whish anybody would built one as model
In case you dare, please try to first understand and then start to build such a pump as a model! Now one else did, yet ...
Different sorts of pumps, being built for the German RR DB, got a sophisticated 3-valve-combination to avoid mechanical connections.
Best of them was an improved 2-piston valve solution for simple (not compound) steam cylinders as shown above. Absolut reliable, but may be still too complicated to build in model size.
Then there is the so called Peters - valve, which uses a standard main shuttle valve in combination with a pilot valve on top of the cylinder.
This is pushed to the uper position by the main piston while pushed down again by steam from a small chanal at the lower position of the main piston. Thus there is no direct mechanical connection to the main piston
This method works pretty fine with small models, too

But Bill is right, in case you want to avoid nightmares and endless trials on s t e a m by yourself!
Happy building!
Asteamhead

[Bill Shields]

that is a LOT of pieces for a water pump...probably more pieces than in one of my ENTIRE locomotives...

that fact that they ever run at all is beyond my Blacksmith mentality...

[ChipsAhoy]

Bill:
I have the castings and I have downloaded your plans dated 2008, for the Large BvB pump (actually downloaded several years ago) and haven't had the nerve to start working on it up until now (maybe). I am not a machinist but I do a little on a lathe and mill as needed and learn one function at a time.
Before I dive in, is there any text or narrative to accompany the drawings? I know that there is a lot of information in the 32 drawings, but I will take all the information and hints I can get.
Thx Scotty
By the way, thank you very much for providing all that work you have in those drawings!

[Bill Shields]

See the www site for docs to accompany drawings...they give a suggested order of operations.

As always...suggest you start with simplest parts first and gain experience as you go.

Built my first on a chinese desktop mill doing dykem layouts with a scribe and no drop. And honestly...if I can build one anyone can.