Author Topic: A Tandem Compound Mill Engine  (Read 14168 times)

Offline kvom

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Re: A Tandem Compound Mill Engine
« Reply #90 on: October 21, 2020, 12:52:15 AM »
If I understand the cutoff/trip action, the normal motion of the steam lever causes the lower arms of the admission valve to oscillate but pushing open, and the dashpots pushes the upper arms to close on the reverse stroke.

For cutoff, the governor links cause the triangular bar to raise the lower admission arm so that at some point it slides over the top of the lever allowing the dashpot to close the valve.

That motion in the running engine will be fascinating to watch.  :o

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #91 on: October 21, 2020, 01:02:01 AM »
Thank you, Gary and Tug!

Gary, I hope the French workshop roof is in place - how is it going?

The Aciera was a once-in-a-lifetime opportunity that I only spotted on ebay because I happened to look at the right time. I now look out for them for sale here in Oz but I haven't seen another as yet. Even W20 collets and tooling are very unusual Down Under.
F3s and other Aciera universal mills are easy to find in Europe (and a few in the US) but the asking prices, when visible, are outrageous. It would be very interesting to know what the real price would be if one was to start bargaining as I would have thought that the market was pretty small.

The basic mill is quite worn in places (e.g. the x-axis feed nut but not the screw) but most of the attachments haven't had a lot of use. In fact the slotter looked to be seized when I got it home but turned out to be gummed up with old grease and I don't think it had ever been used. Not often needed but extremely useful when teh need comes along!

David
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Offline gary.a.ayres

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Re: A Tandem Compound Mill Engine
« Reply #92 on: October 21, 2020, 08:54:37 AM »
That was a great score, David!

You are right about the prices. Several thousand is the norm I think.

I saw an F1 on a sales website in France a few years back, and e-mailed the owner to discuss. He didn't get back to me (probably had sold the machine already), which was just as well really as it would have entailed a drive from North-Western France down to the Swiss border and thousands of euros to procure a machine that would probably have got soaked in the rain a couple of weeks ago due to the missing roof section...

My neighbour has now sprayed the machines with WD-40 and wrapped them in the kind of black plastic used for silage, and my builder friend and his helper will be arriving there this coming weekend to get started on the new roof. So, we're getting there. Not looking forward to seeing the state that my workshop and machines are in when I finally get over there, but at least it's going in the right direction now. Kind of you to ask - thanks.

Following your build, here. Immaculate work!   :popcorn:

Offline gary.a.ayres

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Re: A Tandem Compound Mill Engine
« Reply #93 on: October 21, 2020, 11:20:11 PM »
which was just as well really as it would have entailed a drive from North-Western France down to the Swiss border and thousands of euros to procure a machine that would probably have got soaked in the rain a couple of weeks ago due to the missing roof section...

And just to be clear - thousands of euros that I couldn't afford...!

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #94 on: October 23, 2020, 10:21:24 AM »
Yes Gary, if I'd had to pay the European dealer's prices the Aciera would not have happened! Just very lucky and prepared to pay just that little bit more than the next bloke. To be fair on the dealers the machine is a very early one.

As to the rust, Evapo-rust is a great product, hope it's available over there.

David
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Offline gary.a.ayres

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Re: A Tandem Compound Mill Engine
« Reply #95 on: October 23, 2020, 01:28:43 PM »
Amazing that you could get it cheaper in Australia than is available in Europe!
Still, these things are the luck of the draw sometimes, and you won that one.   :)

I haven't tried Evapo-Rust but I believe it is available here. Will check it out.

 :ThumbsUp:

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #96 on: November 02, 2020, 05:33:06 AM »
The connecting rod with its bearings should end up looking like:



There was this piece of unknown but steel-like material just the right size for the connecting rod that had been sitting in the heap for a long time. It hadn't rusted but it was attracted by a magnet so maybe a ferritic stainless? Nevertheless it wasn't too hard to file and had been cut with a bandsaw so it was worth a try. Roughing out the outline with a 12 mm solid carbide endmill didn't go too badly:



and produced a lot of pretty blue chips:



The machining sequence for the two ends needed a bit of thought and the first surfaces to be machined were the curved ends. Holes were drilled for a centre pin to align the part on the RT and the cutting of the radius went well:



although my miss-timed drilling of centres for machining the shaft can be seen and those had to be re-done which was one of those tasks where a universal mill comes to the rescue:



Mounted between those centres the shaft was first turned parallel, the internal ends roughed out and the outsides of both little and big ends turned to diameter:




With the long slender shaft looking like it needed gentle treatment I, at first, took things slowly which gave the "unknownium" a chance to bite back. As soon as I slacked off the rate of metal removal the damn stuff work hardened and lumps formed where the tool didn't penetrate. (The second picture shows finish turning later on, I'd used a tough grade of carbide for the roughing). At first it looked like I'd have to start again with some FCMS but, with nothing to lose, I got brutal and a big cut went into the softer stuff underneath. There aren't any pictures of this part of the process, there was too much swearing going on. With the trauma over the part was re-mounted with a set over tail stock centre (sorry, no picture) and the taper turned, no messing about this time!

That's enough for today!

David

« Last Edit: May 03, 2022, 12:49:33 PM by deltatango »
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Offline Ramon Wilson

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Re: A Tandem Compound Mill Engine
« Reply #97 on: November 02, 2020, 09:27:06 AM »
Hello David,

Nice to see more progress  :ThumbsUp: but have to say looking at those burrs thrown up don't envy you the task of machining and finishing the two pockets. Certainly sounds (and, by the look of that spragly swarf)appears to have a stainless connection there somewhere  :) Lovely stuff  ::)

Just coming to the end of all the ferrous parts - lots of litle brass bits now.

Good luck with the remaining ops on the rod

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 #98 on: November 07, 2020, 11:14:19 AM »
As Tug said, the next task is to dig out the pockets for the bearings and wedges in each end of the rod. Like Tug I was expecting problems and thought I'd try these two ways - it certainly looked like it was going to be a learning experience. The first one was started by chain drilling with a 3 mm stub drill and using the DRO to get the holes very close together. There was a lot of clamp juggling going on for this:



then the scrap was knocked out and the rough bits cleaned off with a 3 mm endmill:



Either the drill had wandered or the part hadn't been clamped accurately because, with the top of the opening to drawing, the lower end still had slight scallops from the drill holes which are just visible in the picture above. On the second end I used a new centre-cutting endmill directly. This didn't do much better, no scallops this time but the finish wasn't that good:



However, what those pictures do show is the result of successive grades of wet-or-dry followed by Garyflex on this otherwise rather horrible material - it takes a lovely satin finish without excessive work.

The little blocks of steel and bronze for the wedges and bearings weren't exciting enough for much photography but the sine vice came into its own for cutting reproducible 16* faces for the wedges:



Close to the last operation was to drill and tap for the wedge tightening screws with the bearing bits wedged in their final places:



Sorry about the colour shift, lighting is dim and mostly halogen globes in the far recesses of the cave.

Now there are just the bearing holes to drill and ream and a couple of special screws to make for next time.

David
« Last Edit: May 03, 2022, 12:42:12 PM by deltatango »
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Offline kvom

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Re: A Tandem Compound Mill Engine
« Reply #99 on: November 07, 2020, 11:24:02 AM »
Surface finish on an inside pocket doesn't seem too dire.

Stressproof is an excellent material for parts like that, assuming you can find it where you are.

Offline Ramon Wilson

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Re: A Tandem Compound Mill Engine
« Reply #100 on: November 07, 2020, 03:37:59 PM »
All that effort with wet and dry paid off David  :ThumbsUp: - those radii came up a treat and good to see those pockets didn't cause too much stress (on you ;)) either

Very nice bit of kit you have there in that vice, that's one milling accessory I could do with at times - usually cobble a toolmakers vice in the six inch ::) Works but not repeatable with any degree of accuracy - whats the make of yours?

Not long for mine now - just final brass bits and the pipework to lag left to do.

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 #101 on: January 04, 2021, 05:08:16 AM »
Thanks kvom, unfortunately 1144 stressproof is unobtainable - at least the couple of mentions I can find in stock lists are for odd sizes. All sorts of supplies are much easier to find in the northern hemisphere.

Tug, sorry not to answer the sine vice question earlier but there aren't any markings on it, generic Chinese product I think. Despite that it works very well and makes accurate, and reproducible, angles a doddle. Now your engine is finished I really have to crack on  :)

The connecting rod looked like it was nearly finished two months ago but house maintenance and a nasty bout of gastro took a month or more out of that. The final little bits of work on the rod seemed to drag on and on but we're there now. One of the adjusting wedges moved in the vice and had some shallow gouges so I remade that; this time on the end of a larger bit of steel:



You can just see the dud first attempt on the other end of the stock, 90* - 84* = 6* NOT 16*  :-[

After that was in place I polished the rod ends and tidied up bits of scuffing it had acquired on the bench, then made the adjusting screws to end with the whole looking like:



The other bits waiting for finishing were the eccentrics. I gave these a fake split line with a sideways mounted tool in the lathe, polished them and glued in some fake studs and nuts. The fits on the crankshaft were almost good enough to prevent sideways movement but I added M4 SH grub screws to make sure.:



I'm not entirely convinced by the appearance on the bench but when installed not much shows unless you really go looking for the detail. All the bits now fit together:



The crank is still un-glued as I want to check the alignment with the slide before committing that final fixing. Now I have to take the base plates apart to drill holes for the slide and valve rockers, at least those bits are simple shapes after the con-rod.

David
« Last Edit: April 27, 2022, 11:22:35 PM by deltatango »
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Offline Ramon Wilson

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Re: A Tandem Compound Mill Engine
« Reply #102 on: January 04, 2021, 09:31:34 AM »
Ah, looking at that it's a real case of 'deja vu'  :D

Good to see you back home with some time to spend on it David - your con rod looks great and those eccentrics look fine to me  :ThumbsUp: (BTW Incase you missed it - I marked my shaft as per Peters annotation on the drawing and set the eccentric (CL marked) to them. Have not had to move either eccentric)

Thanks for the info on the vise - a forthcoming birthday treat to myself I think ;)

All the best for the New Year David, may it prove an ever improving one on the last and that you get as much time on your engine as you can :ThumbsUp:

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 MJM460

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Re: A Tandem Compound Mill Engine
« Reply #103 on: January 04, 2021, 10:42:33 AM »
Hi David, sorry to hear that you have been unwell.  Glad you got over it ok

Good to see you back on the job and making progress again.  Itís looking very good.

MJM460

The more I learn, the more I find that I still have to learn!

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #104 on: January 25, 2021, 01:20:16 AM »
It's good to be back again but there is always something to distract me from the workshop so progress is still slow.
The bits for the slide started out as the usual (for me) bits of scrap bronze and steel from the hoard along with the governor body casting:



After using the bandsaw and squaring up on the mill the three parts of the slide start to look like the final product:



The main body was simple milling, as close to drawing size as possible, no pictures for that. The bronze slipper I increased in thickness from the drawing so that any contact with the keeper bars would be steel-to-bronze, not steel on steel. Accurate size is also needed as the four screw holes need to be accurately located in both parts, CS head screws don't give you any room for error. The marking out was as a sanity check as the DRO did the hard work:



The crosshead itself I made twice (measure once, cut twice wasn't it?) and has a lot of details to get right. The pin hole is reamed 1/4" one side, 5/16" the other so that side had to be done with a D-bit (I don't have any Imperial machine reamers):



then the slot for the connecting rod little end milled out in one plane:



and then the other to square off the end. This is all quite tight around the little end, can't leave the slot with rounded corners:



The slide body has a slight taper on the ends, I left that until last and used the sine vice with black marker to indicate when the cut had gone far enough:



Having the four CS screws and both bits line up gave a good feeling:



and having the four 8BA studs fit spot-on improved the feeling again:



The corners of the slipper were rounded off to make sure it could travel the length of its slot.

Interruptions and errors aside, this all seemed to take longer than it should have but the result is satisfying!

David
« Last Edit: April 27, 2022, 12:22:36 PM by deltatango »
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