Author Topic: A Tandem Compound Mill Engine  (Read 2543 times)

Offline deltatango

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A Tandem Compound Mill Engine
« on: January 29, 2020, 01:46:20 AM »
In my former world of w##k the saying was "if it hasn't been written up, it hasn't happened" so I guess it's time that I started a build log for the current engine.

The choice of engine for this project is the result of my interactions with MEM so I hope you all like it, particularly Tug and Bob Potter who have played their parts in getting this one started. Tug has written of the origins of the Arnold Throp/Peter Southworth compound mill engine model in "Tug's Corliss Tandem Compound Project" build log so I won't duplicate too much of that here, just enough to set the scene.

Arnold Throp, who was an apprentice with Cole Marchent & Morley, engine builders in Bradford (Yorkshire, UK) described a model of a typical small-to-medium sized mill engine in "Model Engineer" in 1982 but didn't give any construction details and as far as I know no such details have been published. The design was worked on by Peter Southworth and he evolved five basic versions and made (or modified) patterns and was the original supplier of castings. Since then the availability of castings has been patchy. At the Forncett day out two years ago I saw Tug's progress with his all-Corliss valved tandem compound version and was impressed with it (both the design and the workmanship!). At that time Bob Potter was running "Southworth Engines" and supplying drawings and castings for boiler feed pumps and for the mill engine and he sent me a set of drawings.  The engine was, just, within what my machines could deal with and I was very taken with the idea of building one so parted with the money. Bob had given up on sending castings via the post/couriers but he, very kindly, delivered the 23 kg of metal to friends of ours "to await collection". Customer service indeed! Since then the Southworth range has been taken over by Blackgates Engineering and their 2019 catalogue only lists the feed pumps, I really hope that Arnold and Peter's legacy isn't going to be forgotten!

Of the five versions shown on the drawings my choice was the tandem compound with Corliss valve HP and slide valve LP cylinders and an "air pump" (spray condenser, really). The cross-compound versions were attractive but too bulky for easy storage, transport or display. The tandem is long but will at least fit on a shelf.

As I've done with previous projects I re-drew the design using the "Alibre" CAD package and here are three screen dumps of the results:







{Will edit these to fit soon!}

Next post I'll put in a drawing and make a start on the big bits i.e. the flywheel and crankshaft.

David
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Offline crueby

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Re: A Tandem Compound Mill Engine
« Reply #1 on: January 29, 2020, 01:59:10 AM »
Oh, now that is a real beauty of a design!!  How big will the model be?


Hey, shop elves, break out the popcorn!!   :popcorn: :popcorn: :popcorn:

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #2 on: January 29, 2020, 02:44:29 AM »
Great to have you watching and commenting Chris!

The baseboard as drawn is just over 1 m long and the flywheel is 250 mm OD. The Hercus "260" lathe swings, not too surprisingly, 260 mm. As you will see soon this is a tight fit.

Hope you have lots of popcorn on hand as this won't be a quick build!!

David
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Offline Larry

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Re: A Tandem Compound Mill Engine
« Reply #3 on: January 29, 2020, 03:13:49 AM »
Great looking design. Anxious to follow your MEM Corliss build.

Offline cnr6400

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Re: A Tandem Compound Mill Engine
« Reply #4 on: January 29, 2020, 03:30:52 AM »
"OK Chris, I'll back the dump truck full of   :popcorn:  into your cellarway now, and then go get another load for  me"    :Lol:

CAD looks great David, look forward to watching the build. Have you checked the workshop door to be sure you can get it out when finished?  :shrug: :Lol:

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #5 on: January 29, 2020, 03:40:04 AM »
Thanks, good to have you along Larry and cnr!

It will go through the door - endways on. I just hope I get it finished before I'm too old and feeble to lift the damn thing.

There is also the important question from the "local authorities" as to "where do you think you're going to put this one?".

David
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Offline JackPick

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Re: A Tandem Compound Mill Engine
« Reply #6 on: January 29, 2020, 05:12:14 AM »
Wow, there's some work in that one David. Nice CAD model too.
Best of luck.
John

Offline MJM460

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Re: A Tandem Compound Mill Engine
« Reply #7 on: January 29, 2020, 05:30:14 AM »
Hi David,

Looking forward to following along.  It will be an interesting build.

MJM460

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Offline john mills

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Re: A Tandem Compound Mill Engine
« Reply #8 on: January 29, 2020, 06:52:30 AM »
Hi David

  I  too will follow your build  it will be an interesting model in full size these engines must have been impressive machines to watch working and i am sure your model will be too.
     
       John







Offline Jo

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Re: A Tandem Compound Mill Engine
« Reply #9 on: January 29, 2020, 07:40:46 AM »
Nice to see the construction of another of Arnold's engines David.  :)

I am building his Cross Compound version ... its rather huge  ::)

Jo
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #10 on: January 29, 2020, 07:50:48 AM »
John, MJM, John and Jo, it's good to have you following.

Jo, what progress have you made with the cross-compound? It would be huge bordering on humongous...

John M these machines are indeed very impressive to watch and many of them ran for a century or more with only replacement of normal wearing bits.

OK, just been called for a meal, more later.

David
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Offline Jo

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Re: A Tandem Compound Mill Engine
« Reply #11 on: January 29, 2020, 08:28:42 AM »
Jo, what progress have you made with the cross-compound? It would be huge bordering on humongous...

I didn't get very far as having finally found a big enough board to sit it on I decided I needed to find a display/storage arrangement for it first. It is too wide to sit on a side board or in a display cabinet so I toyed with the idea of converting a coffee table to mount it in but got no where so there it sits  :disappointed:

Jo
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #12 on: January 29, 2020, 10:25:55 AM »
Jo, thanks for the picture. I've seen some pictures of completed cross-compounds and it was thinking about those, and where we could put them that convinced me to go for a tandem. However, it would be great to see yours restarted, could my efforts inspire you??

It wasn't just seeing Tug's model that set me off, I have family connections to NW England so a representation of an important part of the history of Lancashire has meaning for me.

The model is based on a design by Arnold Throp, published in Model Engineer, 20th August and 17th September 1982. Arnold T described it in general as “… representative of the smaller types which were made in great numbers from about 1860 onwards in this country for driving textile mills, …”.

As the model is not intended to represent any particular full size engine it can have an invented back-story. My mother’s family were all from Burnley (Lancashire, England) with her father’s family (Read) being road and general contractors (“Paviors and Contractors” in the trade directories of the time) and her mother’s (Easton) were brush makers. The Eastons made every sort of brush from ladies hair brushes to the rotary brushes for road sweeping machines but their main source of income was sweeping and specialised brushes for the cotton industry.

Based on that background I have invented the engine building firm of “Easton and Read, Engineers, Burnley”. As these engines were often given female names this one can be “Mary” for my maternal grandmother. An engine this size was quite likely to have driven a weaving mill in the Burnley area, spinning mills used much larger engines. All I have to do is get the model to the stage where a makers plate and name plate are needed...


After collecting the castings I re-packed them into a small trolley case and spread the smaller ones out among our other bags (the maximum weight for any single item of luggage is 23 kg, same as the total of the castings so we had to keep the case weight down). I don't think the person on the check-in desk had ever had a case that small that weighed so much but she accepted my explanation of the contents - without much idea of what they were, I suspect.

After unpacking the set looked like:



and, with an embryo crankshaft included:



Enough background, time to get on with cutting metal, there's a heck of a long way to go!

David
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Offline scc

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Re: A Tandem Compound Mill Engine
« Reply #13 on: January 29, 2020, 09:06:05 PM »
Great stuff.........I'm in  :popcorn: :popcorn: :popcorn:   Terry

Offline jadge

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Re: A Tandem Compound Mill Engine
« Reply #14 on: January 29, 2020, 10:24:12 PM »
Should be an interesting build. Wow, one metre, that's a pretty big model. The castings look rather nice with good definition.

Andrew

Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #15 on: January 31, 2020, 02:18:04 PM »
Hello David,

Good to see you are about to start  :) I'll try to remember to look in from time to time but been a bit noticeable by abscence lately due to other distractions. Love those drawings - were that I could do likewise - super job indeed  :ThumbsUp:

Hope your castings prove as easy to machine as mine were - good luck with the build.

Who knows - it might even have the effect of getting mine back on the agenda (let alone the top) ::)

Best Regards - Tug



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Offline Bobp

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Re: A Tandem Compound Mill Engine
« Reply #16 on: January 31, 2020, 06:38:43 PM »
Thank you for your kind words David. I am pleased you managed to sort out the final part of the journey for them. What a marathon. My Corliss build has been very spasmodic but I am sure your posts will spur me on. The drawings are superb and are certainly helpful in trying to get you head around the Arnold Throp / Peter Southworth plans.

Blackgates have sorted the pumps now and I am encouraging them to get on with the Corliss. They certainly have some castings and I have offered to help them if they need it to get sets together. The engines are far too important to be lost to the likes of us and there is not much around that is so impressive and big! You can save a fortune on gym membership by just moving them around!

Bob

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #17 on: February 01, 2020, 02:34:45 AM »
Terry and Andrew, it's good to have you along, thanks for looking in.

Bob, I'm pleased you like the drawings, thank you! I'll PM later.

OK, we have Jo, Tug and Bob (and maybe others yet to come out of the woodwork?)with part completed Throp-Southworth engines and me with one just started, some friendly competition might be just what I need in the future to keep me going.

I haven't made a full set of drawings as yet, just been creating them as needed. The CAD model is based on the original drawings that Bob emailed to me and I've just spotted one difference from the actual castings so there will be revisions. The first is for the crankshaft etc:



I started with the crankshaft because:
1) It looks to me to be the logical core of the engine

2) It can be used as a gauge for boring the flywheel and if I can machine that on the Hercus 260 then everything else is within the capacities of my machines.

The crankshaft started life as a shaft from an unknown gearbox that was left behind at our previous house so this bit of metal has been waiting for a need to pop up for over 40 years. Hoarding rules!!
A long time ago I put this into the wood heater when the fire was very hot and left it overnight in the hope of softening it but I don't think that worked. The outside still had a hard case on it that would have defeated HSS and made for some exciting hot chips down the front of the T-shirt:




and some intriguing patterns where the splines had been:



Once through the hard case the steel was tough but gave a reasonable finish:



even HSS worked well:



Which all got it looking like:



All this happened just before we went away for Christmas and I'd also part-machined the flywheel, just failing to to achieve the slight interference I was aiming for on the crankshaft. Interestingly, when I got back to it in January the fit was rattling - shrinkage? Or just my failing memory?? Anyway the boss that carries the flywheel was machined off and a sleeve bored then fitted with Loctite 638. You'll have to take my word for it that the central part of the shaft here is 0.001" down to give the glue somewhere to live:



Just how successful this will be when the keyway is cut through it remains to be seen.

Next the flywheel.

David
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Offline crueby

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Re: A Tandem Compound Mill Engine
« Reply #18 on: February 01, 2020, 03:01:26 AM »
Watching along - really like the shape of those flywheel castings.  Those chips from the shaft look like they were HOT!
 :popcorn: :popcorn: :popcorn:

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #19 on: February 01, 2020, 03:18:04 AM »
Chris, the rule-of-thumb for carbide tooling that I picked up somewhere is that if the chips aren't blue then you aren't driving the tools hard enough. The finish was "spikey" but usable:



The interrupted cut over the old splines really made the chips fly, full face shield worn for that one!

David
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Online sco

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Re: A Tandem Compound Mill Engine
« Reply #20 on: February 01, 2020, 08:44:16 AM »
Watching along quietly David.  Impressed by the colour of those chips!

Simon.
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Offline pgp001

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Re: A Tandem Compound Mill Engine
« Reply #21 on: February 01, 2020, 09:27:36 AM »
You can add me to the number of interested builders of Southworth engines.
Mine being a Pollit & Wigzel called "Agnes" is not quite the same, but it too was originally modelled by Peter Southworth.

Phil

Offline Jasonb

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Re: A Tandem Compound Mill Engine
« Reply #22 on: February 01, 2020, 10:08:20 AM »
I've got a set of drawings that I was given so do I count?

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #23 on: February 01, 2020, 11:35:06 AM »
Simon, I love the colours and textures in the chips image but I'll try not to use any more material that produces such colourful swarf, hopefully everything else will come out of kinder materials like CI, FCMS, GM etc.

Phil, How I wish my Lancastrian ancestors had names like Pollitt and Wigzell! (OK I know P&W were a Yorkshire firm). Building Agnes surely counts you in.

Jason, I think anyone with a set of drawings counts, although you probably should machine at least something from them to really qualify  :stickpoke:

Seriously, for Bob's purposes when he's talking to Blackgates then the more people he can cite as "building one" or "interested" the better. In fact anyone with a workshop and a copy of any of George Watkins' books could be included.

David
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #24 on: February 02, 2020, 01:38:07 AM »
The largest bits of the Corliss are the two halves of the flywheel. The nominal finished diameter of the wheel is 250 mm so that fits on the Hercus 260, just...

Before finding out how I was going to turn the outside of the flywheel the two halves had to be joined so the mating faces were cleaned up on the mill:



The castings were made so that the finished diameter should pass through the centre of spaces between barring teeth so I aimed to get these right and get both pairs of bolting flanges to an even thickness. These looked OK when I first had them finished but all was not quite right and this caused a lot of extra work.
With the bolting faces cleaned up - and the iron was very nice to machine - I printed out two copies of the bolt-hole drawing 1:1 and used these as templates for the holes. Each flywheel half was set up by clamping to angle plates and setting horizontal to drill holes for the studs:



The outer bolting flanges were filed flat and the central boss "spot-faced" sideways on in the mill:



When fixed together the halves of the bolting flanges and the central boss all lined up very well and close to size and I was, prematurely, very pleased with the result. With the studs made (never made 1BA nuts before!) and the flywheel assembled I centered the wheel under the drill, again relying on the bolting flanges and boss, so the rough hole could be started with a 16 mm end mill, part of the plan to ease setting up on the faceplate later:



and mounted in the lathe with the help of a centre for support:



A large tipped boring bar could just be made to reach across the outside of the rim but had to be upside-down and the lathe run in reverse, hence the threaded rod washers and nuts through the headstock to prevent the faceplate unscrewing - as I thought  :-[ :



With perfect hindsight it's clear that this could fail, I should have put the securing rod through the faceplate before mounting the casting then it could have been tightened up hard. Having it over the boss and therefore transmitting the clamping forces via the spokes meant that it couldn't be as tight as was needed and the faceplate unscrewed just a fraction. As a consequence the faces weren't mutually at right angles and this had to be corrected later when the crankshaft was finished to the correct size and used as a mandrel:



I'll come back to correcting more errors in the next post.

David
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Offline Johnmcc69

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Re: A Tandem Compound Mill Engine
« Reply #25 on: February 02, 2020, 01:52:51 AM »
Excellent work David!
 I love your drawings, very nice work!
 Going to be a big engine,  Bob did a really beautiful job with the MEM corliss design. I'll have to have a look at the others.

 Looking forward to this design take shape.

 John

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #26 on: February 02, 2020, 06:22:48 AM »
Thanks John!

All and any nice comments and encouragement are very welcome, particularly at the start of what will be a long project. I enjoy the CAD modelling and drawing almost as much as the workshop stuff.

David
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Offline Jasonb

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Re: A Tandem Compound Mill Engine
« Reply #27 on: February 02, 2020, 07:15:07 AM »
Looking good so far, I'm interested to see how concentric the barring teeth came out.

If you find you need to have the flywheel back on the faceplate for doing the grooves then you can run the lathe the normal way by making use of your rear toolpost with an upside down tool, may need to do that if it chatters mounted on the shaft.

Offline jadge

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Re: A Tandem Compound Mill Engine
« Reply #28 on: February 02, 2020, 10:51:03 AM »
Definitely agree that if one doesn't get blue swarf when turning and milling steel then you're not pushing hard enough. I call it the oh beep test. If a chip lands on the back of the hand and you don't think, or say, oh beep then it's not hot enough.  :)

The close up of the finish on the crankshaft looks a bit odd. The pattern is quite uniform but there is evidence of tearing of the material. You could try upping the rpm and hence surface speed. The 'ridges' due to the feedrate look rather pronounced; what was the nose radius on the tool?

Andrew

Offline jadge

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Re: A Tandem Compound Mill Engine
« Reply #29 on: February 02, 2020, 11:09:57 AM »
The flywheel looks like it machined nicely. There's an art to producing nice to machine cast iron. The castings for my traction engines look a bit rough, but they machine beautifully.

When bolting a flywheel to a faceplate it can be helpful to align the flywheel by looking at a tool tip against the inside edge of the rim. That way the rim should run reasonably true after machining. If the boss runs eccentric so be it, and it's much less obvious. I had similar reach problems with my flywheel. But I bought a cheap left hand boring bar so I could run the lathe in the normal direction. Gneerally it's a bad idea to clamp on spokes as there's a risk of breaking them. Here's how I mounted my flywheel:



The two steel bosses bolted 1 and 7 o'clock locate the flywheel and also provide the drive. The clamps on the spokes are simply to stop the flywheel from falling off the faceplate. The clamps are nipped up, but by no means tight.

Andrew

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #30 on: February 02, 2020, 11:46:01 AM »
You blokes are getting ahead of me here, slow down please ;D

Andrew, You're right about the finish. This was from a TCMT tip with 0.4 mm tip radius, the finishing cut (hard to get a meaningful picture of this, I'll have to play with the lighting and find something to show the scale) was from a DCGT also 0.4 tip. The DCGT was run fast with a shallow cut and fine feed and, what's more, it survived pretty well. I don't mind writing off a tip or two for jobs like this crankshaft. Gary Neasby suggests that his Eccentric tools can be turned through 90* and used for a shaving cut to give a very fine finish, haven't tried this yet. Following Eccentric Engineering on Facebook is very entertaining - worth a look. The tip re mounting a flywheel on the faceplate is timely, it is going to have to go back to cut the rope grooves - see later.

Jason, you must be psychic, the barring teeth were anything but concentric and the next set of words and pictures will deal with that. Also, I just came in from the workshop where I had the flywheel on the crankshaft between centres and the chatter drove me to pack up for the night, clearly it has to go back on the faceplate before the neighbours start throwing things! Before I started the grooves I made a boring bar to take a 4 mm square HSS bit and run at the front, didn't know that you could buy LH boring bars but the HSS form tool was easy enough to grind up using the Worden.

Thanks for all the advice!

David
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #31 on: February 02, 2020, 12:33:55 PM »
Now to deal with the current crop of stuff-ups. The intention was to fit the flywheel to the crankshaft with a few microns of interference to get it to stay where it was put. The old engine erectors used wedges for this but I didn't feel like trying to emulate them, they were in a totally different class. Before Christmas I just failed to achieve this and overshot boring the flywheel and got a nice sliding fit. Christmas intervened and when I got back to it three weeks later the fit was rattling, not sure if this could really be shrinkage, maybe just a poor memory of what was?? Anyway it had to be fixed and, as described in an earlier post, I turned down the crankshaft and Loctited on a sleeve. This was turned down with a flywheel half being used as a gauge for the final fit:



which has worked well with the flywheel gripping nicely:



Following on from Jason's earlier query, the barring teeth definitely didn't come out concentric and in addition almost all of them were partially filled in where sand had fallen off in the mold. I'd concentrated on getting the bolting flanges lined up and to drawing size which also had the two halves of the outer surface nicely aligned as well.  If I had another set of castings to work on I might be tempted to go back and have another go at getting the barring teeth concentric - but I think I'd be able to resist the temptation! As it was the casting machined very well but the teeth were a couple of mm eccentric. I came up with two plans to fix this:

1) The elegant but very time consuming one - machine the tooth ring off, cut a new ring of teeth on a piece of plate and attach

or 2) turn the tops down to be concentric then approximate the tooth shape by milling on the rotary table.

No. 2 won, at least I can go back to 1 if the result isn't good enough.

Of course things are never that simple and I had to make an auxiliary table for the 6" RT to take the flywheel:



The flame-cut disc of 5/8" plate was another find from the hoard and drilling and tapping didn't take very long. It will surely come in handy again?

The starting point was having the centre of the flywheel under the axis of the spindle. The wheel was moved in X to bring a 3 mm cutter outside and then offset in Y by about 40 mm which brought the cutter to the position where it could generate one side of a set of straight-sided teeth. The stepper motor drive was set to give 96 divisions and one side of all the teeth cut. With a ~40 mm offset in the other Y direction the other flanks of the teeth were cut:



The teeth definitely aren't the specified "10 DP" shape but at least they are near to uniform and they look a lot better. If I ever get really inspired a new ring can be made to drawing and fitted, right now I can't see this happening!

Now I have to cut the rope grooves without driving everyone nuts with the chatter.

David
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Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #32 on: February 02, 2020, 01:19:38 PM »
Hi David,

When I did my flywheel you may recall that originally it was for the Twin Tandem. The OD and grooves were the only machining I coudn't do at home so were done at work on a Colchester student on a mandrel. I gashed the grooves first before going in with a form tool for the final profile - that may help some. I spaced the grooves using a 'slip' and moving the dead stop up to the carriage after each groove.
Don't know if that will help curb the chatter for you a bit - it does make a bit of noise doesn't it - just think about the guys doing the fullsize - Throp in his book describes this process as going on for two weeks or so  :o - imagine the noise that had to be tolerated by all those around - no noise regulations in those days for sure!

Comiserations on the barring teeth - I did have better success in getting them to be uniform but as with yours some of the tooth form leaves a mite to be desired.

Good to see your progress and the excellent coverage of your pics

Regards - Tug
« Last Edit: February 02, 2020, 01:23:35 PM by Ramon »
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Offline MJM460

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Re: A Tandem Compound Mill Engine
« Reply #33 on: February 03, 2020, 09:39:54 AM »
Hi David, you are off and running on those new castings.  The flywheel is looking good.  It will be an impressive looking engine.  Following along, even if I don’t have a copy of the drawings.

So long as the appearance is good those gear teeth should be fine.  The speed barring gear works at and the usual duration should mean the tooth form is not very critical.  Better to have them running true. 

I have been a bit slow to jump in, but my lathe has 12 inch swing and D-4 chuck attachment.  If you need access to the larger lathe to complete the flywheel, please give me a call.  I believe you have my number.

MJM460





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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #34 on: February 03, 2020, 11:36:09 AM »
Thanks Tug and MJM!

Tug - after your message I ground up a 1 mm wide grooving tool in HSS and used it to gash the rope grooves. This is a great improvement with almost no chatter and that only at full depth when the form tool is cutting all round:



Only another 11 grooves to go, maybe an hour's work, not another week or two. In the picture you can also just see the scrap of 1/8" gauge plate, used as a spacer, sitting on top of the carriage stop. The flywheel was centered on a piece of rod in the tail stock chuck and I left that there for location to reduce the need to over tighten the clamps. Interestingly, one half of the flywheel cuts very nicely whilst the other is harder and is where the chatter happens ( we are well under any skin here I would hope!).

MJM - many thanks for the generous offer! I may be out of the woods now with this one but there could be others! I'll call anyway.

I'm not actually sure why Arnold T specified "10 DP" for the teeth when he then drew the engine to use a manual barring lever. It isn't supposed to need a barring engine but AT may have had it in mind to design one as an alternative. Apparently the lack of a barring engine "encouraged" the driver to be careful where he stopped the engine, if this wasn't right and the engine wouldn't start under steam then he had to get out the lever and turn it by hand. AT shows several pictures of machining Corliss engine castings in his little book "Vertical Milling in the Home Workshop"(MAP, 1977) and Figs 38 & 39 show him making the ring of teeth to go on the pattern. "This is a gunmetal gear needed as part of a metal pattern {my emphasis} from which the flywheel of Fig. 18 was made" - p54.

As to the noise of machining, Tug, this should be compared with the noise level of a weaving shed where even a shouted conversation was impossible. My Mother had a story from pre-war Burnley where she'd seen weavers holding a conversation by lip reading - one on a passing tram and one on the footpath. Apparently this was the only way to communicate in the shed.

Thanks again guys!

David
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Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #35 on: February 03, 2020, 01:00:10 PM »
Hello David, glad to hear that was of help, looks like you are well on the way now :ThumbsUp:

I just had another read of Throp's book 'The Last Days of Mill Engine Building' where he decribes this process in full size...

The wheel was buit up on a short shaft spanning a deep pit set on plummer blocks. This could take up to a 32 foot diameter flywheel  :o With it's centre line two feet above the pit the pit itself must have been very deep indeed (he doesn't say exactly) but he does say it had to be deep enough to contain the many tons (sic) of swarf generated as once turning began it had to be finished. A cross slide was set across the face that had two saddles on that were driven by a pinion meshing in the barring teeth. This was driven by line shafting through a worm gear. He makes the comment that the teeth had to be there for this turning operation whether for a barring engine or not in final application - interesting, hadn't realised that before.

He goes on to say that it took two turners, day and night, on twelve hour shifts with a large wheel taking over three minutes for one revolution - the teeth being preformed with a 'stepped tool' followed by a form tool manually operated - no carbides in those days, possibly not even HSS so lots of work for the tool makers I guess!.

It also took two men several days to dig out the swarf ready for the next wheel - that must have been a very unpleasant task, probably just a bit of rag over their mouths for protection.


The stories of the noise that factories produced and long term deafness of workers as a consequence has been well documented and recognised here.
When I began work at a company called Utilux in 1984 (an Aussie company actually) here in the UK they had three twenty ton presses without any form of sound protection and one fourteen ton press with a 'home made' booth running multi stage progression tools. The noise when all were working at the same time was unimaginable and extremely invasive - at it's worst it would run right through your body - despite ear defenders you simply couldn't get away from it. Fortunately Health and Safety finally ensured sound booths being installed and life was much better after that. Well I stayed there for fourteen years till made redundant!

Good luck with the rest of those grooves.

Tug
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(a very apt phrase - thanks to a well meaning MEM friend)

Offline pgp001

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Re: A Tandem Compound Mill Engine
« Reply #36 on: February 03, 2020, 10:35:54 PM »
I used a similar setup for grooving the 12" diameter flywheel on Agnes, I found that a couple of chunks of lead sat on the boring bar reduced the harmonic vibration and noise quite a bit.



I was running at approx 9 rpm for this and using a home made tool with the correct scale rope groove profile, that is not a plain vee groove but one with a radiused root and parallel sides for the outer half.



After a bit of a clean up it looked OK. I was glad to get that bit over with though.



Phil

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #37 on: February 05, 2020, 10:17:35 AM »
My "shop elf" (4 y o grandson) was here last night for his first sleep-over with Grandma and Grandpa so I was late getting into the workshop. If a machine doesn't start I now know not to panic, just check the e-stop, he loves pressing them but never gives them a flick to release. One of these years I hope I can start teaching him, then he'll learn what those buttons do when a machine is running...

Tug, I didn't know of Throp's book 'The Last Days of Mill Engine Building' and there's a copy on order now - thanks! With the barring teeth being needed for driving the pulley for final machining then the 10 DP form make sense for a model. I've used a lot of Utilux connectors, 1/4" push-ons in particular over the years, didn't know they had a UK factory.

Phil, that flywheel for "Agnes" is a magnificent piece of work I really hope to see that model finished sometime, please! I didn't have lead hammer heads on the boring bar but if you look closely you can see the sheet of roofing lead wrapped around the bar with Blutak under it. With this precaution and the wheel on the faceplate the chatter went away.

After gashing the grooves on the Corliss flywheel took just over 4 minutes each to turn with the form tool, I almost managed a shadow picture of the tools:



The bump on the left side of the gashing tool is shadow, the tool was ~ 1 mm  wide and parallel sided. The drawings show a groove with a 40* included angle which seems to be a later "Improved English" form shown in figures from Fletcher "Rope Driving: a Treatise on the transmission of power by means of fibrous ropes", Wiley, NY 1900:



although the included angle there is 45* rather then 40. I guess that the section Phil is using is something like Fig 67?

After a lot of work and a major sigh of relief the flywheel looks like:



so I can move on knowing that all the other bits are well within the capacity of my machines.

David

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Offline cnr6400

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Re: A Tandem Compound Mill Engine
« Reply #38 on: February 05, 2020, 12:19:29 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:

Offline scc

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Re: A Tandem Compound Mill Engine
« Reply #39 on: February 05, 2020, 10:49:17 PM »
David,  You are making excellent progress.  I have a soft spot for mill engines, especially the big ones like this.  They were not well received at first..........our house, built in 1842 is situated opposite a row of handloom weavers houses, builtin 1802.  Soon after many big mills were built nearby, putting the hand men out of work.  Riots followed with many engines being damaged. In 1842 Chartists gangs dropped the boiler plugs at Farington Mill, about 2 miles up the road and all work stopped. As this was the biggest mill in the area there was much disruption. I often wonder if folk involved in the construction of my house were involved.  Anyway there are now several preserved engines in Lancashire to enjoy.
Apologies for the digression.....your build is great :ThumbsUp:            Terry

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #40 on: February 07, 2020, 12:32:27 AM »
Terry, I think digressions a great! When we are building models of older engines there is always an historical context that I think is worth knowing. Part of the motivation for modelling old things is to preserve them and keep their history a little bit alive. From where you live it's a bit easier to tour the preserved engines, they are a bit further away from here  :(

David
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Offline john mills

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Re: A Tandem Compound Mill Engine
« Reply #41 on: February 07, 2020, 11:25:09 AM »
Hi David
you have done a great job on your fly wheel using your machines the hercus lathe looks like it must be one of the latter models mine is the 9".
I to are not keen on lead on skinny litte boring bars  i have usually used a much bigger bit of steel mild steel is as good as any thing .have used bars with a piece welded on the side that will fit in the tool holder 1 1/2 or 2" dia
will do wonders .
it is interesting to know what happened running the full size engines we don't know what regular jobs needed doing to keep them running or if they run with little problems.

  john

Offline Mcgyver

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Re: A Tandem Compound Mill Engine
« Reply #42 on: February 07, 2020, 08:07:31 PM »
thats a great looking engine - thanks for posting the build..will be watching!

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #43 on: February 08, 2020, 02:59:14 AM »
Thanks Mcgyver - I hope I can keep going and any encouragement is welcome and helpful!

John M, The lathe is a Hercus 260 from 1983. The bed and saddle are the same as the 9" machines but the headstock is new and has roller bearings. The tailstock and top slide look like Hercus just stuck blocks onto the old patterns to raise the centre height.

The books by George Watkins give a bit of information about the running of the engines and the very rare occasions when something broke. All the main bearings have adjustments for wear but with  speeds in the range 60 to 90 RPM wear was small. Some of these engines ran for many decades without failure. The mills ran 50 weeks in the year so any maintenance had to be well planned.

David
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Offline john mills

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Re: A Tandem Compound Mill Engine
« Reply #44 on: February 08, 2020, 06:43:45 AM »
HI David
my lathe was from the early 70's 72 and i did get tapered roller head stock bearings.

          John

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #45 on: February 11, 2020, 01:02:28 AM »
The crankshaft needs keyways for the flywheel, governor pulley and the eccentrics although I'm still doubtful about the eccentrics. Those could be made in two pieces as drawn and located with a key or made in one piece and secured with hidden grub screws. Right now the 3D printer is making the two part versions in PLA so I have something to handle and work out how to get the studs and nuts in (or that it isn't possible). Tug has discussed this in his build and went for the solid version. The other reason for using grub screws is valve timing, if the keyway angles aren't right then your stuck, I may well start with solid, get the timing right, then cut the keyways but all that is in the future.

The crankshaft was set up in v-blocks and brought true to the x-axis of the mill:



Then the flywheel keyway cut:



followed by that for the governor pulley ( angular position doesn't matter here so it might as well be done with this set up):



When I bought the Aciera mill it came with a lot of attachments and among these was a slotting head. At first I thought this was seized but on stripping it down it was just clogged solid with ancient grease. The complete lack of wear makes me think it has never been used and I have been waiting for a good reason to use it - the keyway in the flywheel was perfect for this:



The angle plate not only prevented lateral movement it was also a reference for a square that I used to align the flywheel split line with the machine axis. The simple, square-ended form tool cut well:



although I was probably over cautious with the feed. A little bit of fitting with a needle file was needed to get the key to go in but it all seems nice and firm now.

The family now looks like:



In a couple of hours I should be able to play with the plastic eccentrics...

David
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Offline Johnmcc69

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Re: A Tandem Compound Mill Engine
« Reply #46 on: February 11, 2020, 02:04:18 AM »
 :ThumbsUp:
 :popcorn:
Excellent work!
...wishing I had a Aciera...

 John

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #47 on: February 11, 2020, 03:09:20 AM »
Thanks John,
What I bid for the F3 felt like a lot of money at the time but it doesn't seem that way now! A Schaublin lathe that takes W20 collets would be great but they are very very rare here Downunder.

David
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Offline crueby

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Re: A Tandem Compound Mill Engine
« Reply #48 on: February 11, 2020, 05:04:38 AM »
That flywheel assembly is a beauty!

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #49 on: February 11, 2020, 05:20:39 AM »
Thanks Chris, just wish I could get somewhere near your levels of productivity!

As yet (tempting fate here) I don't have too many problems with shop elves, apart from the e-stop pusher, and I'm glad of that - just imagine your lot turning it into an elf unicycle and riding around the shop at 3am...
David
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Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #50 on: February 11, 2020, 10:40:05 AM »
Hi David,

Lovely result on the flywheel and shaft  :ThumbsUp: - you do have me inspired BTW got all the drawings out yesterday  ;)

I know it's looking ahead a bit for you but on my drawings there was a small annotation by Peter Southworth defining the angular positioning of the eccentrics. Do you have that on yours?

I decided I would stick with this and have marked the shaft accordingly (and the C/L of the eccentrics) to ensure this is as close to his recommendation as possible. My thinking was that even if this is out slightly there is enough variation in the linkage make up to make allowance for any discrepancy. Though mine aren't keyed I have the grub screws biting into deep centres for positive location. Unless Peter's anotation is out I'm fairly confident I won't have to remove the straps to adjust the eccentrics.

Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #51 on: February 11, 2020, 12:15:27 PM »
Hi Tug,
Thanks! Well, it would be great to see your build make progress again. Maybe we can restart, or even start, one or two others?

I know there's no need to look at fixing the eccentrics anytime soon but I do like to get each part finished in its turn, OK I try to ignore the OCD but that isn't always possible  :)

The drawings that Bob P sent me also have the extra sketches that help with the angular positions of the eccentrics but I still had a hell of a time interpreting them. Please take a look at the attached drawing and let me know if you think the keyway positions are correct. Just looked again myself and see I need to add an arrow for direction of rotation and a note to confirm that the crankshaft sections are viewed from the crank end. If Arnold T drew all this up and got it right then he was something special!

I've just been cleaning up the 3D prints of the two-part eccentrics, I'll play with these soon to work out if I want to make the real ones that way or follow you with solid and accept the possibility that the crank might have to come off sometime in the future.

Regards, David
Don't die wondering!

Offline Jasonb

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Re: A Tandem Compound Mill Engine
« Reply #52 on: February 11, 2020, 04:59:57 PM »
I wonder whether those angles are optimised for running on steam, if you are going to be running on air it may be worth going for something with a bit more adjustment.

Don't let Tug get distracted I'm waiting for him to get on with his "Twin Shaft"  ;)

Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #53 on: February 11, 2020, 05:45:38 PM »
Hello again David,

I gave quite a bit of thought as to whether to make the eccentrics more scale like and from two parts as they ideally should be. Came down in favour of impression rather than realism mainly due to the time I wanted to give to them. Also, in the way mine were made (from the drawing) there was little space to get a functioning nut in without a lot of secondary machining of the cut out and subsequent thinning (and likely potential for distortion) of the outer wall thickness.

I still feel comfortable with that decision but would encourage you to go the two part route if desired as it will certainly look much better.

Your angles match mine for the Corliss and exhaust but I do not have any indication for the slide valve ? Wonder why?

Ne'er fear Jason - Twin Shaft and Corliss intentions are 'on the bench' together - hopefully get a start on them by the end of the month :) possibly sooner  :) :)

Regards - Tug
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(a very apt phrase - thanks to a well meaning MEM friend)

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #54 on: February 11, 2020, 09:38:11 PM »
Jason's point about running on air vs steam hadn't occurred to me - I doubt I'll be building a boiler big enough to run this engine on steam.

With that point, and Tug's experience, in mind the solid eccentrics with grub screws look like the way to go. Maybe a two stage process, solid first, then when the timing is optimised re-make with keys? I'll have to think about how best to secure the crank, maybe a taper pin left over long until the final fix?

David
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Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #55 on: February 12, 2020, 09:37:07 AM »
Apart from the engine in the Wide a Wake and my first, a Stuart Twin Victoria, I've made the slide valves in other engines (destined to run on air only) with no lap, the length equalling the port spacing. Whether this gives any great advantage I'm not sure but the engines do run better - that is smoother - at slow speeds.  How this will translate to Corliss valves I'm not sure - it's been a bit too far ahead to really contemplate.

I've taken the angular location of the eccentrics as drawn at face value and fixed them as such. Thoughts so far are that any adjustment can be made either in the linkage or on the valve lever itself. My plan is to replace the square drive to the valve with a tapered seating so allowing variation - certainly on set up - possibly fixing with a drop of Loctite if required once settings are established. Thinking of course is only part of the equation  ::)

You have the nub David - once that crank is fixed those eccentrics are there to stay - well mine are for sure ;)

Best - Tug
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(a very apt phrase - thanks to a well meaning MEM friend)

Offline gbritnell

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Re: A Tandem Compound Mill Engine
« Reply #56 on: February 12, 2020, 03:01:07 PM »
What a gorgeous flywheel!
gbritnell
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #57 on: February 18, 2020, 06:07:52 AM »
Thanks George - I'm pleased with it as well!

Still working on bits associated with the crankshaft, and before thinking any more about how to make the eccentrics, I made the governor pulley. This is a straight forward piece that started as a rather rough gunmetal casting. This had a cast-in line marking the diameter and I cut along this with a slitting saw:



Note the very carefully judged sliver of metal being left behind by the saw, this kept the top piece in place so it didn't fly off when the cut finished. Next time I do a job like this I'll know to set it up like this deliberately  :D .

The two halves were soft soldered back together. In this picture you can just see that I should have marked this out for myself and no relied on the cast in line:



Set up in the 4-jaw the bore was finished to size and one face cleaned up:



This was then superglued to a mandrel turned in place on the 4-jaw SC chuck and the outside and other face finished:



The mandrel moved to the rotary table and a drawing made with the set of angles and offsets needed for machining the four cutouts (the drawing is attached as a .pdf file):



After heating the mandrel to both break the superglue bond and de-solder the joint two 7BA studs were made up using 2.4 mm stainless TIG welding rod and the whole lot fitted together:



The slightly rough patches are the consequence of not quite getting the original split line across a diameter as there is very little metal to spare on this casting. As the part will eventually be painted the rough bits can be cleaned up later.

Now I have no more excuses for not getting on and working out how I'm going to make the eccentrics.

David
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Offline Flyboy Jim

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Re: A Tandem Compound Mill Engine
« Reply #58 on: February 18, 2020, 01:56:59 PM »
Nice writeup on the machining process for this part.

I like those clamps on your rotary table.

Jim
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"You can do small things on big machines, but you can do small things on small machines".

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #59 on: February 19, 2020, 03:35:24 AM »
Thanks Jim, I made five of the clamps to a design in either Model Engineer or Model Engineers Workshop, I've tried to track down the reference but so far it's eluded me. Hopefully someone else on the forum will recognise them.

A few days ago I 3D printed samples of the eccentrics for the tandem compound so I had some bits to handle whilst I made a decision about making them split (as drawn) or solid. In the picture the slide valve eccentric is on the right, Corliss valve eccentric (there will be two of these) on the left:



The studs are 7BA and on the slide valve eccentric it is possible to fit standard 7BA nuts using tweezers and needle-nose pliers but it's awkward and getting a spanner on the nuts to tighten them properly just about impossible. The one nut I got on for the Corliss eccentric is an 8BA thin nut tapped out to 7. Getting it in there was tedious and tightening it impossible. I'd really like to hear from anyone whose has made the parts to the original drawings but, for me solid eccentrics will be the way to go. Tug has pointed out that even with everything fixed it will be possible to adjust the valve events so I'll get on and cut the keyways in the crankshaft and make the crank. Making the eccentrics will keep until I've made the straps, it will be easier to turn the eccentrics using the straps as gauges; the other way around isn't really possible.

David
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Offline Ramon

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Re: A Tandem Compound Mill Engine
« Reply #60 on: February 21, 2020, 04:56:59 PM »
Nice work on that governor pulley David :ThumbsUp:

It was the likely hood of not being able to tighten the nuts inside the eccentric cut-out that was the real deciding factor for making them one piece. As someone pointed out on mine after fitting dummy bolts, once in situ they can hardly be seen anyway  ::)

Plus one on doing the straps first too :)

Regards - Tug


"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)