Stuart triple - types of metals to get

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rhankey

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Thanks Simon. You will need a heeping dose of patience, as other than a couple other loose parts, that is all I have accomplished in the little spare time I have had in the last six months or so. At this rate, it will be another year before it is likely to be complete.
 

steamer

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That is coming along nicely Robin!

Keep it coming!

Dave

 

rhankey

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I've made a bunch of parts since the last update.

Today, I decided it was time to tackle the 2-start 3/16"X20 TPI threads for the reversing handle shaft and corresponding nut. I feared this more than making the crankshaft, and it sounds like others who have made the triple have also feared making these threads. This was the first threads I've cut on my lathe, and it was roughly 35 years ago since I cut one or two single start threads on a lathe in a high school metal working class. It went without a hitch.

I gotta say, thread cutting is almost too easy to do on my 50 year old Hardinge HLV, and you gotta wonder why more lathe manufactures haven't copied some of Hardinge’s very thoughtful but simple lathe cutting features.

In short, once I had everything setup it took less than 5 minutes to completely cut the external threads. The process was as follows:
  • Set right and left automatic carriage feed stops so it automatically stops the carriage at the shoulder on the left, and just before the 3 jaw jacobs chuck on the right that I was using as a steady rest.
  • Set gear box to 10TPI (20TPI / 2, since it's a two start)
  • Set compound to 59deg, and zeroed both the compound and cross slide to zero with the bit just touching the piece.
  • Cut first start thread. The HLV automatically stops the feed when it hits the carriage stop, so all I have to pay attention to is flipping a lever to retract the compound at end of cut (which does not upset the dial settings). I then fed the carriage to the right until it automatically stops at the right carriage stop. Then I reset the lever that retracted the compound, dial in the new depth of cut on the compound, and repeated the process again. The carriage stops work so well, that you can actually cut at up to 1000RPM, though being my first threading experience, I took it slower.
  • Once the first thread start was complete, I disengaged the threading gear box from the main headstock spindle, rotated the spindle exactly 180 deg, and re-engaged the threading gearbox. I learned this trick by accident from a Hardinge forum a few days ago, and takes all the hartache out of cutting multi-start threads. The headstock is attached to the gearbox with a 48T gear, so 1, 2, 3, 4, 6, 12 or 24 start threads can be done with ease.
  • Cut the second start thread just the same as the first start.

The internal thread was the exact same process, but I had to use a miniature carbide boring bar that was about as stout as a paperclip. and only about 1/16" longer than hole I had to cut. I had to be very careful retracting the compound so the bar did not scrape or cut as I withdrew it from the hole. As a result, it took me about 20 minutes to cut this thread. I broke the cutting bar on the very last cut - I was just chasing the cut I made, so it wasn’t really necessary. Fortunately, the two parts fit perfectly so I don't need to get another cutter and remake the nut.

Here is a picture of the finsihed threads (still oily from coming straight off the lathe). I still have to machine the reest of the shaft.

Robin


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Swede

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Excellent write-up. I have to agree, threading with the HLV feels like cheating. It's almost too easy. The Hardinge methods works especially well for internal threads. You can cut a thread relief groove only 0.062" wide in the ID, and set up the lathe to kick out when the tool enters that 0.062" relief groove. I've noticed that the kick-out mechanism is good to within maybe 0.020, meaning the lead screw disengages plus or minus 0.010" every time.

Good tip with the multi-start thread, BTW.
 

rhankey

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Swede, I agree, compared to my distant memory of cutting a couple threads on a SB 9" and a large tool room lathe 35 or so years ago, threading on an HLV is like cheating.

I found that I had to set the spindle speed before setting the carriage stops. The stops kick out very predictably for any given spindle speed. But if I changed the speed, then the carriage stops needed readjusting. A slower spindle speed seems to allow the carriage to travel futher beyond the stops than a higher spindle speed.

Robin
 

rhankey

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I have finally finished the reversing gear and piston guide bar assembly. the only deviation from plans is with the reversing handle, as I did not really care for the look of the reverse handle shown in the plans. I am starting to feel rather comfortable with using the rotary table for profiling now, as can be seen with the guide bar bracket. That part required 30 seconds of minor file clean-up work after it came off the rotary table. I was a little disappointed that the castings for guide bar bracket and one of the four reversing rod brackets was a little light on metal, no matter how I positioned the part for machining, which made life a little more difficult.

At this point, I believe I have about 50% of all the parts completed. I think the next parts on the agenda will be the connecting rods and their associated bearings. Then I think I will have to start on the cylinders.

Robin


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Swede

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Looking great!! You are obviously experienced at hand finishing metal. I'm seeing crisp edges, no tool marks, and a nice finish overall.

I love the crank handle in the first picture. What is the size of that base casting?
 

rhankey

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Thanks Swede,

The sole plate is 3.5" x 6", not including the bump outs for where the two pumps mount on the rear. The columns are about 4" tall, and I made the crank about 11" long. Some of the parts, like the undulating gunmetal guideplate bracket required essentially no cleanup (about 1 minute of filing and sanding). Some of the parts have required hardly any sanding or cleanup.

Robin
 

Blogwitch

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I hadn’t considered the clock making world as a possible source of smaller sized broaches or tapered reams.
Last year, I started again to use castings, and so wanted to gear myself up to use tapered pins for a lot of the joints (I like to be able to get things apart easily, but retain perfect alignment).

I purchased a set of these tapered reamers, and although there is no picture of them, I can attest that they are very good quality indeed, and at a fraction of the cost of buying single units. They only come in a very small package, so postage to the US should be relatively little.

http://www.tracytools.com/index.php?route=product/product&path=20&product_id=567


John
 

Swede

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A late reply, but I can vouch for those taper pins being superb at what they are designed for. I used them to assemble the crankshaft components for my large radial engine, and once driven in, using a hydraulic shop press, they are NOT coming out.

It can be a bit tricky to ream to a correct dimension/depth. Like any slow taper, if you ream too much, the pin drops in with no force; too little, and even under severe press load, they'll only go 2/3 of the way. Experimentation with scrap of similar metal is a good way to figure out how much to ream. Then, a little tape on the reamer marks the spot.

A good goal is perhaps just a few percent of the fat end of the pin standing proud of the hole... the excess can then be ground off.
 

rhankey

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It has seems like a long time since providing some update pictures. There have been a lot of little parts to make and not quite as much time to spend in the basement lately. Other than the air and water pumps, I think I have now completed the bottom end. Like the eccentric straps, I decided to add some oil cups for the connecting rod bearings. Since there was no space to add the cups directly to the bearings, I opted to attach the cups to connecting rods. So far everything seems to align perfectly with mating parts. The real acid test will be when it comes time to attach the cylinder head to the bottom end.

So far I have only found a couple minor mistakes on the plans. The supplied bolts for the drag links were too short, as it would appear Stuart changed a couple dimensions for the drag lings at some point but forgot to update the affected bolts, so I had to make my own drag link bolts. I also found that they forgot to specify or include the nuts for where the valve rods attach to the expansion links, so I will need to get into the nut making business too.

I have not decided whether to make the pumps next or get started on the cylinder head and the rest of the top end. The cylinder head scares me a bit, as there are roughly 150 - 200 holes, many of which need to be tapped.

Your comments John & Swede on taper pins will prove useful, as I need to make and install taper pins to fix all the parts to the reversing shaft. I am waiting to do this until I have completed the top end, so I can be sure to align the eccentric rods perfectly with the valve rods. I will definitely practice with some scrap metal first.

Also, since I posted my last update, I got a complete and un-started Stuart twin launch casting set with reversing gear from the late 1950's or very early 1960's, which will be my next project after completing the triple. It is much simpler to that of the triple, but should look good when done. The twin launch castings are of such amazing quality. Many of the castings almost look like completed parts ready for buffing (other than not having holes drilled). What a difference compared to the triple, in which the castings are very crude looking, requiring a fair bit of filing clean-up before I dare take a cutter to them, and many of the gunmetal castings have been very tight on metal, and even short on metal (it is almost like they did not allow sufficiently for shrink), resulting in some very careful work to make the part to specs.

Robin


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Blogwitch

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Robin,

I have been saying this for a few years now, ever since ST were taken over, it looks like they are using castings as the patterns for some of their production rather than specially made patterns. If you can get hold of earlier casting sets, then do so, they should be much better.

There has been a lot of complaints about the quality and tight on machining dimensions, in some cases they are unable to be machined to plans because the castings are so under size.

I suppose they will get even worse now that they have been taken over yet again, unless the new owners invest some money in getting new patterns made.


John
 

Charles Lamont

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Bogstandard said:
I have been saying this for a few years now, ever since ST were taken over, it looks like they are using castings as the patterns for some of their production rather than specially made patterns.

I suppose they will get even worse now that they have been taken over yet again, unless the new owners invest some money in getting new patterns made.
The castings used to be made by shell moulding, not quite the same as conventional sand casting.The mould half is a flat plate with a half pattern on it with core prints, locating pegs & sockets, runners and risers, all in one, in steel. This is covered in a sand/resin mix which forms an accurate 'shell' over the mould. This is all done in a machine. When removed from the mould, two half shells are clamped face to face to form a flask into which the metal is poured. ST catalogues used to illustrate the process. I have not seen any recent castings so I don't know what they are doing now.
 

rhankey

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Speaking of castings. How should I go about cleaning out the steam passageways that go between the valve chests to the cylinders? The passage ways have quite abrupt curves. Only one of the 6 passageways seems to be clear enough to blow air through. The other 5 are completely plugged somewhere in the middle. I'm not sure if I can disolve whatever Stuart would have used as a core with some sort of solution, or if I can poke a small diameter wire through. I figure I should probably deal with this before I start machining.

Any ideas?

Robin
 

rhankey

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Here's a long overdue update. I have had little time in the basement over the last 3 or 4 months. The cylinders, valve chests and cylinder covers also required much more work than I anticipated. This being my first engine, I am still falling victim to thinking parts will be easier to make than they actually are. I have now almost completed the top end. I still need to make and fit the pistons, lagging and pipework, then pin the reverse shaft, and then make the two pumps. Oh, and I guess I need to make a base to set the engine on.

Attached below are two photos showing the first time I attempted to mate the top and bottom halves. It was the first time I assembled the top end too. I wanted to see if everything aligned and to ensure there was no binding. The two halves slid together perfectly, and all seems to move just fine. What a relief.

The top and bottom LP and IP cylinder covers set a new level of crappy castings for me. They had large areas of thick cold spots. And the LP covers have some rather visible voids that I could not avoid. The HP covers were wonderful to work with, and appeared to be cast using a different process - perhaps they come from an older batch. There were no cold spots or voids in the cylinder castings, but it was quite a challange positioning the finished part in the rough casting to get the best comprimises for all the valve ports and the like. Hopefully the piston castings will be fine, as they are thicker chunks of CI.

I deviated slightly from the plans, and opted to use screw in valve tail rod guides (the semi-circular domes on the top of the cylinders) for all three valve rods, rather than just the IP valve. I figured this would look better, and allow me greater mchining accuracy.

I think the end is in sight.

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Rivergypsy

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I'm not quite sure how I missed this thread for so long, but what beautiful work - very, very nice!!

I'll tag along for sure, and I may just have to get cracking on my compound again after seeing this ;)
 

rhankey

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I'm not quite sure how I missed this thread for so long, but what beautiful work - very, very nice!!

I'll tag along for sure, and I may just have to get cracking on my compound again after seeing this ;)
Thanks for the praise.

You will need to excuse the slow progress and less frequent updates, as I have been distracted with a lot of travel lately so am not getting much time in the shop. The pistons and lagging are now done and I am making a couple tube bending jigs to form the steam pipes to the very tight angles Stuart specifies. This project has been quite a fun learning curve.

Robin
 

RCW

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.. and keep filing reports, with pictures! Beautiful workmanship.

--Bob
 

rhankey

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Other than mounting a brass name plate to the front of the base, I have completed my first engine. What a fun and expensive learning curve that engine was. At the start of this project I didn't own a lathe, mill or any other tooling and had only done a little metal working in high school more than 35 years ago.

I apologize for the shallow depth of focus, as our camera doesn't do well with taking photos of small objects.

I am now starting on a Stuart twin launch, which I'll document in a new thread. The castings for the twin launch were produced in the early 1960's and appear to be night and day better than the castings I received for the triple (which I purchased from Stuart about 2.5 years ago prior to the change of ownership). I'm keen to get the twin launch completed, as I am keen to get started on a Stuart (H.A. Taylor) Undertype engine with integral boiler, which is also from some old castings.

With that, I think this thread has drawn to a close. Thank to those in this forum who provided wisdom and along the way when I had questions. Much appreciated.

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