Fiddle Fidd.. Fi...e

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Carrdo
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Joined: Thu Mar 06, 2003 2:20 pm
Location: Toronto, Canada

Fiddle Fidd.. Fi...e

Post by Carrdo »

About a weeks' work in the shop.

The lubricator for the LBSC steam operated duplex water pump in 1/2" scale. An untouched photo before final cleanup.

First described by LBSC, in the Model Engineer, in the fall of 1928. Still completely relevant today. Reproduced in his book Shop, Shed and Road.

You like drilling with a #80 drill - this has it. You like miniature silver soldering - this has it. You want to give all of your BA and ME taps and dies a workout - this has it.

And the 1/2" scale steam operated duplex water pump itself. Guaranteed to send one around the bend. LBSC says it is easy to construct (except for the steam passages drilling - even he admitted that).

Fortunately someone else made it - am just trying to finish it. Beautifully made. And it will work that way too if your machining is 100% perfect.
Attachments
266 The Pump Lubricator.jpg
265 The LBSC One Half Inch Scale Duplex Steam Operated Water Pump June 2020.jpg
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

Beautiful work on the pump rockers.
Attachments
269.jpg
271.jpg
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Bill Shields
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Re: Fiddle Fidd.. Fi...e

Post by Bill Shields »

i have one of those (partially complete) built by Jim Stuart from the same design.

It runs on compressed air => water end never finished.

Jim's worry was that it was futzy to get to run in the first place, and any wear on / in the rocker / pins driving the valves would render is non-functional in short order.
Too many things going on to bother listing them.
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

All of the steam side fittings made and installed.

Still more work on the water side fittings to make.

It may look simple but there was a lot of very concentrated and tense machine work involved. Like drilling a 1-1/4" long hole with a #52 drill. On the first attempt, the drill seized and snapped off. I then changed the bronze with an easier to drill alloy.

More miniature silver soldering...

... and the lubricator has to be aligned in two directions and end up straight to look correct when the header fitting is screwed home in the steam chest thread. Fiddle, Fidd.., Fi...e.
Attachments
272 All of the Steam Side Fittings Made and Installed.jpg
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

The water inlet fitting installed on the pump body.

The pump body had to be drilled and tapped first before the inlet fitting was made. It looks quite large as good engineering dictates that the inlet piping to the water pump (the pump suction side piping) has to be made larger than the pump discharge piping, at least one size larger and sometimes more as you do not want to restrict the water flow to the pump inlet in any way.

I found out the hard way that one has to be very careful with the tapping of the pump body here as I have never encountered any bronze material before which was so brittle. The water inlet thread on the pump body is shown on the drawings as being 1/8" long and threaded right to the bottom of a blind (cross drilled) hole which is impossible to thread that way.

I did have the correct size ME 7/32" - 40 TPI bottoming tap but the way some of the ME taps from the UK are made their "plug" tap is our "bottoming" tap (they use different nomenclature than in the USA which one should be aware of for many times they say taper, second and plug when we say taper, plug and bottoming and sometimes when they do say "bottom" taps their "bottom" taps look like our "plug" taps. Not all, but many are that way so one has to be extremely careful when ordering them.

I had to first modify the ME 7/32" - 40 TPI "plug" tap to grind the point off the end of the tap right down to where the first thread started to make it our "bottoming" type tap. One cannot start a thread easily or at all with such a tap so I had to employ a second "plug" tap to start the thread. And do not let the point on the end of the "plug" tap run into the bottom of the blind hole or a stripped thread will be the result. And guess what ...!!

I fixed it perfectly using (and modifying) the next larger size ME tap but another lesson learned the hard way. That bronze did not give any indication at all that it was about to let go and as well, there was no " feel" as to when the point of the tap hit the bottom of the blind hole.

On the second go round I just turned the tap(s) so carefully 1/4 turn, then backed the taps off and checked to see how close to the bottom of the hole I was.

The last operation is the water pump outlet to drill and tap (where the black dot is), install the outlet fitting and the pump will be ready for testing.
Attachments
273 The Water Inlet Fitting Installed on the Pump Body.jpg
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

Drilling and tapping the pump body for the water outlet. This would complete all of the steam and water inlet/outlets on the pump.

I chose to wait until the correct HSS "bottoming" tap arrived from the UK after the excursion with the pump water inlet tapping problem. It was sent over via air mail but it could have come by row boat, it took so long to arrive due to the current situation.

Anyway, this time I was not going, under any circumstances, to strip this thread which was a 3/16-40 ME and only 1/8" deep in a blind hole (as was the previous one).

The surprise was, the tap came with a pointed bevelled end (much like our plug taps) which I first carefully belt sanded away to make what we know as a true bottoming tap.

Careful layout, drilling and tapping followed - this time everything worked perfectly as I now knew how brittle the bronze body was.

I can now finally test the unit first on air and then on steam.
Attachments
266 Drilling and Tapping for the Water Outlet Fitting.jpg
268 The Finished Pump.jpg
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NP317
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Re: Fiddle Fidd.. Fi...e

Post by NP317 »

Nice to see it completed. I hope it works well and that you share your success with us!

This week I finally completed the body machining and porting on my Coles Worthington pump bronze casting. Quite the pain to do.
You have my sympathy on the threading job. I had similar shallow stud holes to tap. Nerve wracking to do.

(Off topic:
But tomorrow morning my steam launch goes into the Columbia River for its first post-restoration water testing!
I've been working on it the past 14 months and finally got the oil burner working well and consistently. Revision #3 was the charm.
I'm both excited and nervous. Full system test.)
RussN
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

The LBSC 2.5" gauge miniature steam operated duplex pump is now running on air. I am very, very happy to see it running but...

to get to this point, it has been a three week titanic struggle. I must have partially dismantled the pump 25 times to try and figure out why it wasn't working. I could write a book on what I learned. The first time that I hooked it up on air - nothing, just a hissing sound.

And this pump is complicated, there are dozens of parts involved and each and every one could have been the problem.

One general comment, this pump must have been constructed decades ago and then sat for decades before I got it. Sitting all that time produced a whole raft of sticking problems which I came to realize more by accident than by anything else. This pump has to be absolutely free to move without sticking anywhere and yet at the same time be air and steam tight. This means that the machining has to be perfect (square, straight and parallel, exact centre to centre distances and heights, no taper or distortion.. total perfection here and it was). After that, everything has to be lapped in place with gobs of light machine oil for hours and hours.

At the start,I was afraid that the steam passages drilling may have been in error causing the initial problem encountered as it is a nightmare to do it correctly (even LBSC says so) but all of the drilling turned out to be perfect. There is an absolute labyrinth of tiny steam passages to be drilled going in and around at all angles, crossing and internally intersecting within millimetres of each other everywhere. I tried to use a very fine copper wire and snake it through to see if anything was amiss but it is just too complicated so in the end either the pump works or it doesn't.

to be continued.
Attachments
269 The Pump Running on Air.jpg
270 The Duplex Steam Chest Valves Valve Spindles Valve Spindle Spigots Pistons and Piston Rods.jpg
271 The Duplex Steam Cylinder Ports.jpg
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

Round one - the first teardown.

In disassembling this pump I was afraid that, as the pump had sat for so long, some of the miniature threads and fasteners used in the pump had seized in some cases - and here I wasn't disappointed! One valve spindle which was threaded on its end into the valve spigot had seized and in trying to get it apart, it snapped off. It looked perfectly fine but it was so stuck, to get it apart I had to saw the entire valve spigot/valve spindle end apart.

Now there were two new parts to make before I even started! As I have said many times before, use an anti seize compound on all of your threads before final assembly. Where there is steam, water, repeated heating and cooling or just sitting with time, no matter what materials are employed, they will weld together under these conditions.

I won't go into all of the details but this took 3 days to repair. Every operation here involves making a special holding fixture and/or a collet. I have included only one photo of one special collet made to hold the valve spindle for machining the flats on it at exactly at 180 degrees in my spin index (the flats had to be exactly on size and length straight and parallel and exactly located lengthwise on the part). It looks like nothing but it took hours of work.

Every little detail had to be perfect. Just one little example. The brass valve spigots (seen in the previous post second photo) have 1/16" dia. pins and pin holes drilled through at right angles to the slots in the spigots where one end of the rocker arm fits. Well, the original pins were drilled and then pressed in never to come out again but some how they had to now. For the new pin, to avoid this situation in the future, I held the replacement pin wire in a 1/16" dia. collet (which is a special) in my lathe and filed a very slight taper on one end so that I could press the pin in with my thumb and pop it out again. If I didn't have that special collet well... I have been surprised at how many times it has been needed and used to date.

Another surprise was the end of the rockers where valve spigot pins go are slotted and not drilled holes. How the original builder produced such tiny miniature perfect slots perfectly centred in the end of each rocker...

end of round one.
Attachments
272 New Valve Spindle and Special Holding Collet.jpg
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

Round two through 15 or so.

With the hissing sound, I thought that the pump steam chest valves may be leaking or there was a leak through the steam chest cover or valve face not being lapped truly flat. This turned out to be wrong in both cases but more about that later.

The two steam chest valves are the two circular plugs as seen in the steam chest cavity of the second photo of the penultimate post to this one. The front face of each valve is precisely recessed in its centre and there is a projection on the rear of each valve having a very precise slot cut into it which fits over the flat machined into each valve spindle. There is no lead or lap on the valves as air or steam is admitted full piston stroke. The valves are machined so that the OD of the valve is made to a diameter equal to a distance over the extreme edges of the ports while the centre recess on the valves is machined to a size equal to the distance between the inside edges of the steam ports and is 1/32" deep. These two dimensions have to match exactly the port drilling size and spacing.

I initially thought that there might have been slight machining errors here but no they matched the above perfectly.

When screwed tight the hissing sound appeared to be coming through the steam chest cover so I thought the above and made a lousy paper gasket to take up any possible uneveness but again no! Elsewhere there were beautiful paper gaskets but not mine so if anyone knows how to do this properly, I am all ears.

What I finally realized was the the valve projection was ever so so slightly bottoming out on the valve cover internal face allowing the steam chest cover to leak. It took a long time to realize this as there was no visible gap anywhere between the valve port face and the closed cover. A few file strokes resolved that problem but the fun was not over. It also took a long time to realize that the valve spindles were bottoming out in the rear valve slots when the steam chest cover was screwed down tight which forced the face of the valve slightly hard against the port face. It was so slight that it just made things appear "sticky". Machining a thou or two from each valve face solved that problem as there needs to be a slight gap between the port face and the valve face equal to next to nothing but it has to be there. Setting up the valves holding them and facing them truly square was another fun problem.

Still not there. The next issue turned out to be the slot in the rear projection on each valve. The "fit" here has to be absolutely perfect in the sense that the valve has to be able to freely float very slightly up and down in the slot while being constrained by the valve spindle machined flat without any shake or end play whatsoever under its own weight only (which is next to nothing) leaving a perfect seal between the valve face and valve port so that any air or steam pressure in the steam chest presses the valve face against the port face. The valve slots were so narrow (LBSC knowingly doesn't give any dimension here) that my smallest Swiss pattern file would not enter the slot so I used some fine emery paper glued to a couple of thick feeler strips to lap the valve slots. In the end I got the free but constrained fit needed but after many, many trial fittings, concentration and nerves.

This ended the hissing and now when I pushed each rocker back and forth by hand I could hear and feel separate transfer and exhaust port openings and closings. This gave me some hope that all of the nightmarish steam passage drilling had been machined without error or mistake by the original builder.

I did give the port face and steam chest cover a slight lapping but it really wasn't necessary.

Now when air was applied the pump rockers seemed to want to move but didn't so something else was still wrong. It took days and days until I realized that the long piston rods attached to the steam cylinder pistons have to move up and down also but weren't as they were sticking due to the pump sitting for decades. The piston rods aren't solid but are partially hollow as they contain a trip rod which operate the piston/rod assembly to uncover another set of ports further down in the cylinders to allow the pistons to alternatively move up and down in the cylinders and also to act as a set of rams on the pump end.

At one point when I took out the pistons I messed up the graphited yarn piston packing (as seen in the second original photo) so I made myself another problem. I have never packed a piston this way and it was a devil of a problem to repack it with many more hours lost. All of the valve spindles, piston rods and pump rams have this type of packing complete with threaded stuffing boxes at both ends to add to the misery.
Carrdo
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Re: Fiddle Fidd.. Fi...e

Post by Carrdo »

To finish - parts 15 to 25 or so.

At this point I decided the bicycle pump wasn't going to get me anywhere so time to hook up the air compressor. I only had to make all of the adaptors and special fittings to transition from commercial to model engineering fittings which was another job not done all of these years.

Partially disassemble the pump, polish the pump rams with steel wool to remove any oxide layer, oil with a light machine oil, reassemble the pump, adjust (loosen or turn down) all of those pesky stuffing boxes with your fingernail (as they are so tiny the adjusting slots that it is the only way to get at them and to do it in place!), hand operate the rockers to see if things are getting a bit less sticky, repeat again and again until...

At about iteration 23, I had hooked up the air compressor and as the air pressure climbed past 40 psi, the pump began to move erratically, only on one side at first and then when the pressure reached 80 psi, the pump took off like a scared rabbit. Wow, success!

Disconnect the pump, re oil and repeat. The pump now runs on air but I would like to get the operating pressure down to about 20 psi if possible. It is going to be a long break in and once broken in don't touch anything. By the way, all threads and fasteners are BA and ME just as LBSC described.

Yes, there are probably easier pumps tp build and operate out there but to see this miniature jewel working - remember, it is only 1/2" scale or 2.5" gauge. I don't know how LBSC could come up with something like this but he did say somewhere that, in some respects, it is somewhat similar to the full size Westinghouse duplex.
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NP317
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Re: Fiddle Fidd.. Fi...e

Post by NP317 »

Wow! Quite the research project. Glad to hear you are winning.
RussN
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