Author Topic: Stuart Boiler Feed Pump  (Read 40563 times)

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #30 on: November 12, 2013, 10:30:20 PM »
Thanks guys for all those wishes and congratulations!  :)

After face turning the second side of the cylinder, I machined the fastening threads and steam ports of the cylinder casting
Then face milling the valve bearing surface (how is this suface actually called!?)and drilling holes to cut threads afterwards.
Milling steering ports took quite a while and had to be executed really carefully since there is not much room for the endmill to move when disengaging the cut.

All the steering ports finished. Also the cylinder is almost finished, only the drain cock threads are yet to be machined.

Then I cut two pieces of gun metal rod and milled them to size for the d-valves. The bigger one is the valve which is going to control the steam for the working piston. And the two finished d-valves. The smaller one will control the steam for the spool valve piston.

So much for today - Ill continue tomorrow.
« Last Edit: August 11, 2017, 09:33:48 PM by Florian Eberhard »

Offline Roger B

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Re: Stuart Boiler Feed Pump
« Reply #31 on: November 13, 2013, 11:09:08 AM »
Comgratulations on your degree  :cheers: and keep up the good work on the pump.
Best regards

Roger

Offline NickG

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Re: Stuart Boiler Feed Pump
« Reply #32 on: November 13, 2013, 01:21:58 PM »
Pump is looking excellent, great cad modelling and well done with the degree.

Offline smfr

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Re: Stuart Boiler Feed Pump
« Reply #33 on: November 13, 2013, 05:13:28 PM »
Nice going, Florian, and interesting to see your modifications to the original design.  :ThumbsUp: :ThumbsUp:

Simon

Online Tennessee Whiskey

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Re: Stuart Boiler Feed Pump
« Reply #34 on: November 13, 2013, 07:10:37 PM »
Nice work and great pics Florian. That degree is yours and it is never going anywhere now. Enjoy a little "life" mate. You are only young once, just ask most of us old farts :cheers:

Whiskey

Online Jo

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Re: Stuart Boiler Feed Pump
« Reply #35 on: November 13, 2013, 09:18:29 PM »
Then face milling the valve bearing surface (how is this suface actually called!?)and drilling holes to cut threads afterwards:


Florian,

In my Double Tangye articale Edgar Westbury referred to that as the "steam chest face".

Jo
Usus est optimum magister

Offline Don1966

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Re: Stuart Boiler Feed Pump
« Reply #36 on: November 14, 2013, 01:47:48 AM »
Congrats on your degree Florian and nice work on the pump. I have a concern with your D valves. Your cylinder is brass and you D valves are brass. Brass on brass will cause galling if rubbing for long periods. Stainless would be a better choice. Ask me how I know?  :facepalm:

Don

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #37 on: November 14, 2013, 10:22:34 AM »
Hi Don

Yes, I know that the material combination is far from ideal. I have been thinking about that problem aswell and what I have decided to do it anyway.

My thoughts were:

1. The castings are made from gun metal - I have used gunmetal as well for the valves. (though the cast gun metal may have slightly different material propertys.

2. There is a german locomotive manufacturer (Regner) who uses brass cylinders and brass valves. That also works for quite some time until there is wear which affects the functionality.

And if there was wear, I could fit a piece of stainless sheet (0.5mm thick) to prevent from furhter wear on the cylinder.


So, I will see what happens and then decide whether I have to modify it or just leave it the way it is.

Cheers Florian




Offline tel

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Re: Stuart Boiler Feed Pump
« Reply #38 on: November 14, 2013, 10:42:26 AM »
As an old friend and respected model engineer used to say - 'Slide valves wear IN, not OUT'

Nice work!
The older I get, the better I was.
Lacerta es reptiles quisnam mos non exsisto accuso nusquam

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #39 on: November 17, 2013, 10:19:30 PM »
So - I thought I'd write the next part earlier. But anyway, here it comes:


Next part to machine was the valve chest. I first face milled all the sides except the one opposite to the one with that little stub.
I used my wohlhaupter to machine the stub for the valve rod and to face the surface around the stub.
Next part was to mill the cavity. I did that after drilling the holes for the valve rod and the spool valve piston.

After that, I attached the chest to the cylinder and machined the backside of the cylinder after aligning the front sides. Also here, I was using my wohlhaupter and the horizontal feed. (You see - I love that tool :D ) The surface turned out quite nice.

So much for now, see ya ;)

« Last Edit: August 11, 2017, 09:39:17 PM by Florian Eberhard »

Offline K.B.C

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Re: Stuart Boiler Feed Pump
« Reply #40 on: November 18, 2013, 12:55:45 AM »
Hi Florian

I have just recently signed up to the forum but have been following your build of the Stuart pump and I do admire your workmanship.
I have over the years built and repaired about 9 - off these pumps but never considered converting to slide valve.

I have great reservations that your pump will not work.
Do you know that single cylinder double acting steam engines are not self starting and when running rely on the flywheel inertia to keep it going and if it stops at T.D.C. or B.D.C or the crank horizontal to the plain covering all ports it will not start.

In your pump like the single cylinder engine if the pump stops with the valve at Top or Bottom the inlet ports will be closed, likewise if it stops at mid stroke all the ports are covered  and no steam will get thro' to activate the shuttle valve, hence no self starting.

If you study the Stuart arrangement you will see that the auxiliary valve, the 5/32" dia one , always has a port open for steam to the shuttle valve and makes the pump self starting.

I may be off the mark here as you may have thought of a way to get steam to the shuttle valve if all the ports are closed, if so I will be very pleased to here how as you may have solved the age old problem of a single cylinder engine being non self starting.

George.
Your never too old to learn.

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #41 on: November 18, 2013, 10:53:16 AM »
I have great reservations that your pump will not work.

Hi George

Well, there could theoretically be a case where all the ports are closed. But the probability is very small because the auxiliary valve will have to get over the point where the ports are equally closed until the shuttle valve is going to move.

To describe it with an analogy: It is like having a pendulum stopping with the mass above the bearing point.
It is possible because of friction but the probability is very small and the stability at this state is very low.

I have attached a scheme of the principle of my pump:

If you look at it carefully you will find out that it wouldn't work that way, the piston would drive the auxiliary valve to the wrong direction.
But I have drawn the ports this way to make it clearer when looking at it.

If it should happen, that I am really gonna have problems, I will see what I can do.

Greetings Florian
« Last Edit: August 11, 2017, 09:41:35 PM by Florian Eberhard »

Offline K.B.C

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Re: Stuart Boiler Feed Pump
« Reply #42 on: November 18, 2013, 11:57:12 AM »
Florian ,
Thanks for the reply, it will be interesting to see the final result, I am still doubtful but only too willing to be proven wrong.
We all need you young guns to to experiment to change perceptions that us old hands have lived with for years.

Keep posting, I love your machining skills .

Regards
George.
Your never too old to learn.

Online steamer

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Re: Stuart Boiler Feed Pump
« Reply #43 on: November 18, 2013, 12:02:35 PM »
An excellent discussion Gentlemen....you both deserve credit for that.    :praise2: :praise2:


 I too am following along and although I haven't made one of these pumps, I have heard horror stories of their difficulty to get to run consistently.    That said...I give you great credit Florian, as if we always do what we've always done we will always get what we've always got.....

Let the chips fly!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Florian Eberhard

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Re: Stuart Boiler Feed Pump
« Reply #44 on: November 18, 2013, 12:23:43 PM »
Oh, George, when im already having such an old hand with those Pumps reading my thread:

How do you fix the water pump body to the cast iron base? The Stuart plans just "forget" about and I haven't seen any hints on how it was intended.
Am I just blind...?

Also on the internet, i wasn't able to find any hints.