Author Topic: A Tandem Compound Mill Engine  (Read 2943 times)

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



"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 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
Don't die wondering!

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
Don't die wondering!

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.
Ars longa, vita brevis.

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
Don't die wondering!

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
Don't die wondering!

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
Don't die wondering!

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