Author Topic: A Tandem Compound Mill Engine  (Read 3517 times)

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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Online 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 donít 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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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