|Kevan Shaw||26/10/2020 19:54:26|
|14 forum posts|
I just found this design for a small steam pump in 5 january 1973 Model Engineer. I would value some advice as to how viable this design is for an inexperienced model engineer like me and whether I could use aluminium for the cylinders and steam chests with brass pistons and valves.
|Simon Collier||26/10/2020 20:33:59|
404 forum posts
These sorts of pumps require great accuracy in the machining. Concentricity is critical and the holes for steam ports have to start and end in the right place. You don't want the piston packing to be too tight; I would use viton O-rings with about 5-10% squeeze. Personally I would use bronze preferably, or brass. I have no experience of aluminium in steam applications and don't know why you would choose it. Perhaps you just have some.
A friend just made a Westinghouse style pump for 5" gauge with internal pilot and shuttle valves. These are a real challenge and I am going to have a go very soon.
For demanding jobs like these pumps and injectors you have to start with the right attitude. If you think blunt drills, cheap blunt carbide boring bars and reversing work in the 3 jaw are OK, you can't expect success. If you are careful, patient and use the right tools and materials, it will work. Good luck!
|phil gardiner||26/10/2020 20:50:00|
|18 forum posts|
The Westinghouse pump internal pilot valve is the difficult part, it is so sensitive to adjustment but when you get it right it will start every time and will run on 20 pound pressure, i am delighted how mine runs.
|Paul Lousick||26/10/2020 23:14:55|
|1755 forum posts|
The pump shown does not have a shuttle valve to switch the steam from one end of the piston to the other, but a simple lever that operates a slide valve. The design is similar to the pump supplied from LSM for my Ruston Proctor traction engine.
A lever, connected to the piston rod operates the slide valve to reverse the flow of steam from one side of the piston to the other. This works OK when the pump is running fast with no restriction on the water outlet but when pumping under pressure (topping up the boiler). and the pump is running slowly, there is not enough inertia to carry the slide valve past the mid point and open the opposite steam port and the pump stops.
|roy entwistle||27/10/2020 09:15:56|
|1352 forum posts|
Stuart Turner used to supply a kit for one
|Rob McSweeney||27/10/2020 10:31:49|
|38 forum posts|
Kennions are listing drgs and castings for two LBSC designs, duplex and single cylinder Wiers pump.
|Henry Artist||30/10/2020 22:52:00|
121 forum posts
The thing with Westinghouse and similar pumps is that they are essentially a steam engine without a flywheel. Without the momentum of the flywheel to ensure the pump cycles completely your machining and valve timing must be perfect. This is why people get so excited when the things actually work.
A more achievable solution for a novice may be to go for an axle driven pump. If you are constructing a boiler to run a variety of engines the axle driven pump could be powered by a small donkey engine. It doesn't have to be anything fancy - even a single acting oscillating engine will do. While not as impressive in engineering terms as a Westinghouse pump it would be much easier to construct and can work just as well.
|Paul Lousick||11/11/2020 02:01:08|
|1755 forum posts|
Cut-away model of a duplex steam pump showing the internal working of linkages and valves.
Youtube video: **LINK**
1793 forum posts
Why has the d valve in the photo got two ports per stroke - not seen that before?
|Paul Lousick||11/11/2020 10:20:35|
|1755 forum posts|
Not sure Fizzy,
The inside ports are for the return steam and the passage is cut off as the piston nears the end of the stroke, possibly as a soft buffer, and slowing the piston so it does not slam into the end of the cylinder.
The outer ports are for the steam to enter the cylinder and has to be at the far end. But if you look closely (and stop and start the video), the timing of steam entering the cylinder is wrong. The steam enters on the exhaust stroke. Probably because the pump must be mechanically driven because of the cutouts and the operators got the sequence wrong.
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