steam feed pump

[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


<a href="https://www.youtube.com/watch?v=Qj_17aubhLg" target="_blank">http://www.youtube.com/watch?v=Qj_17aubhLg</a>

[crueby]

Great find, it runs great!

[Kim]

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

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]

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

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

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]

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

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

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?

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

Kim

[Michael S.]

I think the advantage of these pumps is that they don't need a crankshaft. And therefore you are always able to start in any position.
And they can be easily regulated. As Chris says, even with counter pressure. In the duplex pump version, the water flow is also very even. Almost like a rotating pump.

Michael

[Vixen]

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?
[/quote]

Hello Chris,

Could you apply this 'all or nothing', duplex pump, valve gear to get your Ransome Tree Feller working? 

Mike

[crueby]

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?

Hello Chris,

Could you apply this 'all or nothing', duplex pump, valve gear to get your Ransome Tree Feller working? 

Mike

You were peeking!  Yes, a few months ago I drew up the changes to the Feller to use this type of valve system, copying the parts from the pump I made a couple years ago. Should be a much better runner at model size than the twisted-rod version was.
 

[GRAUBELE]

Hello Michael

The pump is running great.
Is there a source for a drawing of this pump?
I'm still looking for a steam feed pump for my two 2-liter and 5-liter steam boilers. (see pictures)
I've already received information from Bruno about his steam pumps,
but you can never have enough different steam pump versions to choose from before deciding to build a replica.

Dieter

[Michael S.]

Hello Dieter,
The pump is built exactly according to the Stuart feed pump blueprint.
I didn't build the motor myself, though. It's just a bit larger than the original Stuart pump.

Michael

[GRAUBELE]

Hello Michael

Thank you very much, I can do something with this information.
I'm familiar with the Stuart drawing.

Dieter

[john mills]

is  there another valve the rod moves a pilot valve and the valves in the next bore that is the actual vale in the stuart  type pump
The steam cylinder for that size pump end would pump to a high pressure the steam on the stuart pump is 1/2"  to 1/4"for a feed pump
john

[crueby]

There are a number of different valve systems used in feed pumps. One of the other ones was used in the Worthington brand duplex pumps, where each cylinder moved the valve for the one next to it. Quite ingenious, and worked very well - they sold them for many decades and there are a lot still in use. One neat thing is that without a crankshaft keeping both pistons moving together, causing the pumps connected to each piston rod to move in a pair of offset Sine waves, the two pistons/pumps create more of a continuous output with square waves, as one piston reaches the end and slows down, the other is starting up. The old Worthington catalogs show diagrams comparing crankshaft driven pumps and this style duplex pump, and how the flow is more continuous. Recently I obtained some of the old catalogs and used the drawings in them to create a CAD model that will be used in a future build. Here is the animation created from that CAD model:
<a href="https://www.youtube.com/watch?v=_hctDgcSxO8" target="_blank">http://www.youtube.com/watch?v=_hctDgcSxO8</a>
Chris

[GRAUBELE]

Hello Chris
 
I wasn't familiar with the functionality of this pump in detail.
Thanks for showing me.

Dieter

[Zephyrin]

 
this a model of donkey pump for little live steam loco by LBSC from reprints of extinct model magazines...
the pdf file is too large to be an attached file...
just a simple picture

the advantage is that the pump is not continuously working, as is the case with a pump powered by a wheel axle, and for nothing when the bypass is open.