Author Topic: Stuart No 2 Centrifugal Pump  (Read 2833 times)

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Stuart No 2 Centrifugal Pump
« on: October 22, 2022, 12:39:16 AM »
Late last year one of our forum members posted a photo of a set of Stuart centrifugal pump castings he thought he might well never get to make up. I have hankered after one of these pumps for many years, but they have not been available since the 1970's. They occasionally appear on Ebay, but get snapped up for more than I have been prepared to bid.  So I sent him a PM. Quite soon, the castings were seasoning under my bench instead of his.

I expected them to sit there for a good number of years, but this spring I got them out for a good look, aka fondle. I like to have them somewhere in the far back of my mind for ideas about machining set-ups and sequences to marinate gently. I also like to carefully measure the castings and draw up them up in 2D CAD so that I can see how best to get the finished parts out of the castings. I make an assembly drawing and an 'ideas' drawing so that I can make any adjustments to the dimensions made necessary by the castings or that I think would be advantageous. Next, I do detail parts drawings of my own, and then redo the assembly. Sometimes I model in 3D CAD as well, often to help make aesthetic judgements.

Anyway, come June, and to my considerable surprise, one day I suddenly discovered the body casting was sitting in the 4-jaw chuck and nicely clocked-up to a good compromise on the ultimately unmachined surfaces. "Oh well", I thought, "why not."

Here are the parts in the kit: body, flange, impeller, bracket, brass for gland and nut, copper pipe, stainless shaft, stauffer, 9 2-BA set screws and a taper pin to hold the impeller to the shaft.

Offline crueby

  • Full Member
  • *****
  • Posts: 18554
  • Rochester NY
Re: Stuart No 2 Centrifugal Pump
« Reply #1 on: October 22, 2022, 01:47:42 AM »
Interesting looking project, will be watching along.  Where's that popcorn...

Offline john mills

  • Full Member
  • ****
  • Posts: 417
Re: Stuart No 2 Centrifugal Pump
« Reply #2 on: October 22, 2022, 10:04:07 AM »
Hi
i made the one i have in the early 70'S bought from stuart turner .it did not take long and was strait forward to machine.Itpumps very well i have it driven on a sirus
it is mounted on a base i made a pattern for and cast in cast iron.
   John

Offline Steamingandy

  • Full Member
  • ****
  • Posts: 51
Re: Stuart No 2 Centrifugal Pump
« Reply #3 on: October 22, 2022, 08:29:31 PM »
Made my no1 up last year it’s a nice little project

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #4 on: October 22, 2022, 11:08:50 PM »
Here we have the body in the 4-jaw, with first op. turning completed. It was clocked up with the periphery running as true as I could get it, as this will be an unmachined surface adjacent to the machined rim of the cover flange. No 1 jaw seems clear of the job, but there is a packing piece in there gripping the rim of the casting.

The machining is all pretty straightforward. I was able to make the bolting boss a bit thicker than standard, which will help with the rather shallow tapped mounting holes.
The chamfer at the edge of the bolting boss was rounded to blend in to the cast surface. I did not take the bore all the way through, and after drilling I bored it to reaming size. The bottom of the counterbore for the stuffing gland is drawn as a 120° cone which I turned with the top slide swung round.

The thread for the gland nut is specified as 1/2" gas, or 0.825" x 14 TPI. I felt this was coarser than I wanted, and after a fair amount of vacillation, I settled on 13/16 x 20 TPI. The thread was single point cut almost to depth and then finshed with my usual trick of using a hand chaser as a machine chaser. I have made a QC toolholder with an extra broad slot specificaly to hold chasers, which have had their tangs cut off.

The second picture shows the second op. finished.  Using the Griptru chuck adjustment to get the turned 'shank' running true was not easy, as I needed to get the dial gauge between the body and the chuck jaws. The outlet tube got in the way, but I was able to get a consistent reading covering about three quarters of a turn. The casting surveys and design verification allowed me to make the outer face further out than design, just managing to avoid an unsightly undercut at the outlet boss, while still having enough material on the cover flange casting to compensate.

For completing the shaft hole the drill wandered quite a bit this side, but there was just enough material to clean up on boring, and final reaming with plenty of RTD produced a hole that was a pleasing tight running fit on the shaft material.

At this stage I had not made a final decision about the treatment of the pipe connections, only being sure I did not want to just solder a pipe into a plain hole the casting, as the original drawing shows. This meant I had to put the body aside and get on with something else.
 
The next two photos show first op. turning of the gland and nut.  The piece of bar for the gland turned out to be bronze or gunmetal, not brass.

The brass hexagon stock for the nut was so accurate that I was able to clock all six flats to half a thou. For screwcutting a female Whitworth form thread I usually bore to a size that truncates the crest radii, and screwcut with a tool with very little tip radius. This should ensure the threads are mating on the flanks. For a thread like this I use the lathe mandrel crank handle, not power. In this case I had the tool upside down at the back, for better visibility. (This does not mean you have to turn the spindle backwards, or work from left to right, or get a left hand thread.) The thread was cut to a fit on the body.
   
« Last Edit: October 22, 2022, 11:18:17 PM by Charles Lamont »

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #5 on: October 22, 2022, 11:13:30 PM »
Yes, Steamingandy, I have been looking back at that write-up. At the moment this job is more likely to be a shelf queen than do anything.

Offline Dave Otto

  • Full Member
  • *****
  • Posts: 4693
  • Boise, Idaho USA
    • Photo Bucket
Re: Stuart No 2 Centrifugal Pump
« Reply #6 on: October 23, 2022, 01:12:50 AM »
Very nice work Charles, looking forward to more progress.

Dave

Offline Bearcar1

  • Full Member
  • ****
  • Posts: 829
  • Chicagoland Area, USA
Re: Stuart No 2 Centrifugal Pump
« Reply #7 on: October 23, 2022, 06:34:13 AM »
These castings are of good quality and results in a relaxing, and pleasurable finished project. Mine is still awaiting a power source and I too am thinking along the lines of Stuart's Sirius. Of course I am on the look out for that casting set ....  :thinking:


BC1
Jim

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #8 on: October 23, 2022, 11:14:13 PM »
The bracket casting had sufficient meat on it to allow me to make the ruling thickness 3/16" - to my mind an improvement on the frail looking 5/32" specified. If I was carefull.
It also allowed a distinction in level between the machined circular bolting face and the as-cast crescent below. To use the final unmachined faces as references it was set up for milling the foot with packers* under to ensure even foot thickness, and a round bar to clamp the outside face flat against the vice jaw. I also checked the sides for square. Approaching a full clean-up of the foot, I reduced to 0.005" cuts to ensure I machined off no more metal than necessary.

Using the milled foot as datum, I then set the bracket up on the faceplate for facing and boring. I set the curved top edge to run true. The face cleaned up with cuts of 10, 5 and 2 thou, to finish 3/16" thick. The bore hit finished size and a fit on the body with a small patch still untouched by the boring tool. It won't matter or be visible.

The next photo shows the mounting holes being drilled and spotfaced, again with the bottom surface as datum (so strictly speaking, it should have been set against the fixed jaw of the vice).

By this time I had finalised the design of the pipe fittings. These will fit into female threads in the pump body and flange, and will have the pipes soldered in to them. The proportions benefitted from doing a 3D CAD model. They are made from a piece of 1-1/4" brass bar won as payment for doing a half-hour job for a friend. I got to keep the remnant, the best part of a foot long. I don't know its composition, but it is particularly yellow. My shop notes say "Screwcut, bored, chamfered, photographed, parted off, and dropped on the bench, bruising the thread."       

* (The packers are from a set I made up long ago. They are 2-1/2" x 1/2" and there are pairs in 1/32" steps of thickness from 1/16" to 3/8". Some are gauge plate, some are mild steel. Each pair is within 0.0005" on thickness all over. They are not hardened.)
 

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #9 on: October 24, 2022, 11:27:25 PM »
With the pipe fittings completed, I now have gauges for the mating threads in the body and cover.

The set-up for the outlet hole in the body may look a bit wild, but the only thing I was a little concerned about was the single bolt holding the pump body to the angle plate. I don't like having just one bolt as things have a tendency to shift, especially when milling. In this case there wasn't much choice, and the relatively large radius of the flange face clamped to the angle plate meant it should be OK.

There is no dimension or datum to work from, so the body has to be set square on the angle plate pretty much by eye. Then the angle plate is shuffled about on the faceplate to get the outside of the outlet boss running true. Once set up, the machining was straightforward. The hole was bored to 9/16" deep, and a 1/16" wide undercut made at the bottom.  Again I screwcut with the tool inverted, cutting at the back. In screwcutting, I found I did not have enough clearance and had to put a broad chamfer on the shoulder at the bottom. The thread is 7/8" x 20 TPI.

For drilling the mounting holes I had to make an extended centre drill. This time the job could be set square by reference to the face of the outlet boss. Although I was able to get the tapping started in the pillar tool, it mostly had to be done by hand. By the time I had the holes finished, despite leaving at least 1/32" thickness of metal at the bottom of the holes, the points had telegraphed through as little pimples on the back face inside the pump chamber. 

       

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #10 on: October 25, 2022, 11:45:40 PM »
Before machining the impeller, the shaft needed to be dealt with, so that the impeller could be finished on the shaft. I decided on a Loctite assembly rather than using the taper pin supplied in the kit. No dimensions are given for the impeller mounting. The shaft is Ø 5/16", and I decided on a seating Ø 1/4" x 1/2" long. Having faced and chamfered the other end, I set it up in the Griptru as close to true as the roundness of the bar allowed. I was nearly an 1/8" into the final cut when I realised something was wrong. That bit is under size. The rest, which will be quite sufficient, I got to 0.2496" diameter. I finished it at bottom open speed (200rpm). The resulting the fine, even tool marks will be good for Loctite.

The impeller is a very nice casting, and it took some thinking as to how to do it justice. After going round in chicken and egg circles for a while, I came up with this sequence.
First, set the outer face against the chuck jaws, gripping on the blades with aluminium softening folded round the jaws, and not too tight. This first operation is intended to just clean up the back face parallel to the front, and to just clean up round the rim. This is tentative, as it is not yet centred.

In the second photo, it is set up with the business side out. In this setup I adjusted the chuck to get a good compromise on true running of the surfaces that will not be machined, primarily the central boss. Once satisfied I measured the amount of run-out at the periphery at 0.008" TIR, and marked the high spot. No machining at this setting.

Now with the back face outwards again, I could again adjust the chuck to reproduce the run-out measured at step two. This time, the back face, relief, and bore were all finished. I made the disk 1/64" thinner than drawing, partly through lack of metal, and partly to give better alignment with the cast-in outlet port in the body. With the impeller still in the chuck I Loctited the shaft in place, using the tailstock drill chuck to support the outboard end of the shaft while the Loctite cured.

Next, with the shaft again clocked true between the chuck and impeller, I finished the OD to 2 thou radial clearance in the body. Fortunately, by backing off the topslide some distance, I managed to get just enough clearance between top and cross slide handles to cut the 11° angle on the face of the blades. If I remember rightly I had to set
something up again for this photo, as the toolholder clamp handle is in the free position. The final job at this setting was to reduce the projection of the central boss, which
seemed to me to intrude too far into the inlet. I trimmed the length, turned a taper and then rounded the nose.

Offline crueby

  • Full Member
  • *****
  • Posts: 18554
  • Rochester NY
Re: Stuart No 2 Centrifugal Pump
« Reply #11 on: October 26, 2022, 12:55:53 AM »
Nice progress - looks like thats quite a tricky shape to hold.  Watching along!   :popcorn: :popcorn:

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #12 on: October 30, 2022, 11:57:27 AM »
Because of the increased depth of the main chamber in the pump body, required to avoid an undercut, I had to make the cover flange thicker than specified. I have only allowed about 1/64" on the faces. To be sure of cleaning up nicely, the first operation was to set the face against the chuck and just clean up the bolting face and shoulder enough to provide good true clamping surfaces. A rough trial splash of paint gives a clue to the final paint job.

Face out, with a coat of primer on, the second op was simple enough. Set up initially with packers under the bolting face, then removed to allow tool clearance for turning the rim. I set the outer end of the central boss running fairly true to match up with the fitting. To get a clean, concentric paint edge of the rebate, I chamfered the edge, again with light cuts at several angles to blend in to the cast surface. I drilled and bored though the same size as the pipe bore, then opened out and screwcut, as for the body. There is a small blow-hole on the face of the boss, and a tiny area of the periphery remains unmachined, but it is right at the bottom and on the inside, where it will not be seen. Any smaller might not have matched the body casting OD.

For the inside surfaces, it had to go in the 4-jaw, as the 3-jaw would not accommodate the boss. I set it true by the bore. First I turned the register diameter to plus a few thou and then the bolting face to clean up just. I could not get anything behind to measure the flange thickness accurately, but by rule measurement it was pretty close to the intended 5/32". I then turned the register to fit. I was left with a comfortable 0.045" to take off the coned face to clear the impeller, checking with the impeller in the body and a feeler gauge between the flange faces. The photo shows how far the topside had to be backed off to get the handles clear.

For the radiused entry I cut multiple angles by eye and blended them together by sanding. Because of the coned face, a radius gauge was not a lot of help. 
         
« Last Edit: January 19, 2023, 08:39:30 PM by Charles Lamont »

Offline steam guy willy

  • Full Member
  • *****
  • Posts: 3238
Re: Stuart No 2 Centrifugal Pump
« Reply #13 on: October 30, 2022, 05:06:46 PM »
Hi Charles,  good to see the progress with it , and so glad it found a good home ... :)

Willy

Online Charles Lamont

  • Full Member
  • ****
  • Posts: 321
Re: Stuart No 2 Centrifugal Pump
« Reply #14 on: November 01, 2022, 04:12:58 PM »
Thanks, Willy. As I said, it came out from under my bench a lot sooner than expected. It has been an enjoyable short diversion from other projects.

Without doing some modifications to my available arrangements, probably necessary in the long run, I did not have enough daylight above the rotary table chuck in the mill for the impeller holes, so it was quicker to set up the Myford dividing head in the lathe.

The same arrangement was also good for the body flange.

It was worth taking a bit of care to ensure the stauffer ended up central and vertical.

For the cover flange holes, setting the angular position of the lettering by eye was really the only option, and quite satisfactory. The holes were co-ordinate drilled, (using the dials as I have no DRO) with the positions sanity checked with a rule.

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal