Author Topic: A Tandem Compound Mill Engine  (Read 24483 times)

Offline Ramon Wilson

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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


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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 #61 on: March 09, 2020, 11:03:50 AM »
Thanks Tug, it's good to have you following along.

This reply has taken longer than I'd expected, a week away in South Australia and a mini CNC machine project have got in the way. I'm back in the workshop now but with two projects on the go together. On the mill engine front the crank and crank pin were the next bits. The crank starting out as the end of a bit of flat steel bar that came in the kit for the Wyvern (think it was intended to become the con rod but I fabricated that instead of carving from the solid):



After the holes were drilled and reamed the blank was roughed out using the bandsaw:




A bit of tool making followed to make a centering pin to locate the part on the rotary table and to drill and thread a hole in the RT adaptor plate for a clamp screw:



the stepper motor drive for the RT handled the rounding of the ends and I'm pleased with the finish from a 10 mm carbide end mill:



The same tool cleaned up the flat sides as well:



The pin was turned on the end of a scrap shaft from a washing machine gearbox, which I hope will be a steel with good wear properties, and then the oil holes drilled:




The two bits won't be fixed together for a long time yet but this is what they'll look like:



The two 8BA threaded holes are for fixing the bit that catches oil from the lubricator.

I feel the need to get the flywheel and crankshaft bits spinning so the main bearings and supporting cast iron will be next.

David
« Last Edit: May 04, 2022, 09:45:41 AM by deltatango »
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Offline J.L.

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Re: A Tandem Compound Mill Engine
« Reply #62 on: March 27, 2020, 08:23:57 PM »
Beautiful photography as well as superb machining.  :ThumbsUp:

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #63 on: March 27, 2020, 11:18:25 PM »
Thanks John, it's good to hear from you again.

Right now I'm trying to finish off another project that has been occupying desk and bench space for too long, I'll get back to the Compound "real soon now". The other project is a miniature CNC mill based on a scrapped microscope; this provided cross-roller linear rails for the XYZ guides and a stiff frame. Adding steppers and lead screws etc didn't look too hard but it would probably have been quicker to start over, ah well...

David
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #64 on: May 02, 2020, 01:25:24 PM »
The project that was holding up work on the tandem compound is showing promise of working and I'm getting back to machining. The pile of bits that might turn into a mini (micro?) CNC machine was clogging the desk and I either had to try to make something of them or chuck them out, which wasn't really an option. It's taken about six weeks to get the three axes working under the control of bCNC on an old laptop and GRBL in an Arduino Mega interpreting the G-Codes. The Dremel I tried out as a spindle proved to be useless and a real 500W spindle is currently tangled somewhere in the bowels of a very disrupted postal system. The little Frankenmachine looks like:



It may turn out to be useful but even if not I now think I understand the basics of CNC.

The flywheel and crankshaft for mill engine are sitting on the bench and I really want to see them spinning so some bearings and bed plates are needed. The bearings started as bits of some bronze flask clamps that came from my late father-in-law's dental practice. Careful marking out will allow the threaded holes to end up being machined away:



which were reduced in stages using the bandsaw and mill:





until there were two little piles of bronze blocks:



that were reduced to finished size in groups:



which hopefully leaves them all the same size. The little excursion over the marked line with the bandsaw will largely get  machined away:



To make these stacks of bits easier to handle for setting up in the 4-jaw they were super-glued together in a lightly greased nest made from a glass plate and angle plate:



Once in the chuck and centered using a dial gauge the holes were piloted with slot drills and then bored out to size:





Its good to have the engine and other workshop distractions with the world going crazy outside and I really feel for anyone who have suffered from the effects, direct or otherwise, of the pandemic. We've been keeping our heads down here along with a lot of the rest of Australia and are just starting to see some hope of positive change, we are thinking of everyone where things may be going less well - hang in there folks!

David
« Last Edit: May 04, 2022, 09:38:27 AM by deltatango »
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Offline Admiral_dk

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Re: A Tandem Compound Mill Engine
« Reply #65 on: May 02, 2020, 09:32:05 PM »
Nice to see progress again David - though the CNC project can turn out to be very useful later  :ThumbsUp:

Best wishes

Per

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #66 on: May 04, 2020, 11:43:25 PM »
Thanks Per it's good to know you're following along.
The new spindle came out of the dungeon dimensions on Sunday morning - full marks to Australia Post for getting things moving - and I've pulled the CNC machine apart again to fit it in so progress on the mill engine is slowed again. When I get the spindle working in the  machine I'll know how useful it is.

David
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #67 on: August 18, 2020, 07:26:10 AM »
It's time to go back to reporting progress with the mill engine.

There have been a number of distractions including the current Stage 4 lock-down in Melbourne. Most businesses are shut down, for most purposes we are confined to staying within a 5 km radius of home and there is a 8pm to 5am curfew. It is now said to be harder to get permission to leave Australia than it is to leave North Korea.

In the previous post there was a picture of starting the boring of a main bearing - in the end this didn't go well as the irregular existing hole deflected the boring bar enough to cause a dig-in that moved the bits in the 4-jaw chuck. You can see the evidence for this on the 2nd block from the right in the vice below. Plan B meant taking the parts back to the mill and using a 12 mm round-nosed cutter to rough out the hole:



as it turned out the result from that wasn't at all rough:



and the bearings went back to the 4-jaw and were bored to size without any more trouble. The upper halves of the bearings have a deep groove in which the oil distribution ring turns. I made a 4 mm square ended tool and mandrel to cut this (the cutting edge was very sharp - the picture didn't capture this) :



and approached the machining rather carefully as this was working something like form tool with all the cutting edge engaged at once. As it turned out I didn't need to stress about this as it went really well and produced a very satisfying finish:



The lower bearing halves are stepped to make a groove for the oil ring and this was straight forward turning in the 4-jaw, no dig ins this time round:



The oil rings themselves were turned and bored on a stub of MS and were about 35 thou thick. This was a lot less difficult to part off than I expected - the learning process keeps on going:



Two little families of bits were the end result:



Making homes for these means a long session of milling cast iron, its a dirty job but I really like the metal.

David
« Last Edit: May 04, 2022, 08:19:31 AM by deltatango »
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Offline john mills

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Re: A Tandem Compound Mill Engine
« Reply #68 on: August 18, 2020, 08:05:06 AM »
Hi David

good to see you making progress  the end result is looking great .
In melbourne we don't have much choice we have to fill in time so a good excuse to be working on these projects

I  feel for people how don't have hobbies living in apartments  it must be a long slow process to fill in the time
with this curfew and restrictions it must be hard to find what to do
               John

Offline Ramon Wilson

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Re: A Tandem Compound Mill Engine
« Reply #69 on: August 19, 2020, 10:08:49 AM »
Hello David - it's been a while since I've looked in on MEM - just had a PM notification to bring me here.

Good to see you back on the Throp andf making some more progress. Strangely enough I picked up on mine again about a month ago.

Now have the valves etc made and the internals all up and running - packing in etc and the cross head built and Con Rod made, all turning over nice and smoothly.

Incidently - don't know what you use to break super glue but after making the big end bearing by the usual soldering together method I broke it apart (intentionally) before all the machining was done :facepalm2: Decided to super glue it together which was successful but messy with dried cyano on the bearing surface itself. Concerned that heating it to to break it apart might bake the glue on I tried dropping it in a small container of acetone and left it for a hour or so for lunch - came back to find it laying in two parts with all traces of cyano completely gone  :)

Working on the exhaust valve linkage at the moment - good luck with further progress on yours. I don't look in here much these days but will keep an eye out for further updates

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 deltatango

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Re: A Tandem Compound Mill Engine
« Reply #70 on: August 19, 2020, 01:22:01 PM »
Hello John and Tug,
Thanks for the interest (and thanks to any and all who may be following along).

As John says we're very lucky to have full time, if unpaid, employment to keep us sane (or at least no less sane than we were pre-Covid-19). It's hard to imagine trying to work from home with a couple of small children when home is a 5th floor flat.

Tug, I'm pleased that you're back at work on the engine and following along here. It sounds like the mechanical bits of yours are just about finished and the timing must have worked out as we discussed earlier. My actual progress is a bit ahead of the description here on MEM and I bit the bullet and cut the timing keyways in the crankshaft last week; I'd simulated the valve motion in Alibre and convinced myself that it was at least close enough to work.

For breaking superglue I use heat, at around 200 C the stuff denatures and the bits fall apart. The residue has no strength or adhesion and usually flakes off, if it doesn't then it will scrape off a metal surface with a hard plastic scraper. There hasn't been any sign of "baking on". The only thing to be careful of is the fumes, I don't know if they are actually dangerous but it is a job that needs a well ventilated area. I've read about using acetone (or an acetone/water mix) but haven't tried it.

Regards, David
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Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #71 on: August 20, 2020, 01:21:01 PM »
The main bearings are mounted in CI housings, one is just a pillar with a slot in the top, the other a substantial baseplate. Whilst fondling these - with a steel rule - it became clear that there wasn't much, if any, machining allowance so there had to be some compromises made as to finished size. The story is that the aluminium  patterns for the current casting sets were cast from the original wooden masters without adding any more material for shrinkage allowance so the results are bound to be a bit on the small side. Fortunately the metal machines beautifully and there are only a few thin hard patches on the surface.

The first bit tackled was the main bedplate which had no smooth, flat or right-angled surfaces anywhere on it but a bit of filing on the top surfaces got some usable references. These allowed the casting to be mounted upside down to flatten the base. Getting at the whole surface required a lot of clamp juggling:



Then the flange where the slide casting attaches was faced:



and one edge cleaned up as the other datum surface:



The final width is under size by the drawing but I'll have to live with that.
The outer end bearing was much simpler and I dealt with this the same way, first filing the top as flat and square as I could then machining the base:



With clean, square bottom surfaces clamping became easier and the two castings were mounted up together to machine out the bearing housings together:



By a fluke the nominal housing width was the same as that of my thick parallels, having one of these in a smooth, sliding and shake-free fit was very satisfying:



Each bearing needs an oil well beneath it where the oil ring picks up lubricant. The slot drill was just long enough to get to the bottom of this even if there wasn't all that much of it in the collet:



Drilling the mounting holes and the holes for the handrail stanchions was easy with clean datum surfaces from which to set things up:



The set of 1/2" thick parallels is a recent purchase and they are so very useful I should have bought them long since.

David
« Last Edit: May 04, 2022, 08:01:18 AM by deltatango »
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Offline kvom

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Re: A Tandem Compound Mill Engine
« Reply #72 on: August 20, 2020, 02:35:47 PM »
For me 1/8 and 1/32 parallels are lifesavers.   :)

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #73 on: August 25, 2020, 12:37:19 PM »
Hi kvom, and anyone else who's reading,
I've had 1/8" parallels for along time and they've done some of what was needed, however they can be a right b@#$%r to keep standing upright in some situations. The 1/2" set don't have that problem. I haven't seen any at 1/32" thick but those would have been very useful on lots of occasions, must look out for some.

The bearing caps for the main bearings are also iron castings and were provided as a single casting for the two parts. Machining these went in stages, first to make a flat reference surface on the top of the stud bosses which is where the low-profile clamps came in again:



Then the parts were turned over and the bosses supported on parallels (much easier on the 1/2" jobs) in order to flatted off the bottom surface:



and clean up the oil pot tops to height:



After hack-sawing the two bits apart and machining them to width I used a small round-nosed end mill to tidy up the sides of the pots:



The stud holes were drilled 4BA tapping size at first and the caps used as drilling jigs for the tops of the bearing housings, afterwards opening out to clearing size:



Looking at that last picture reminds me to round over the ends of the caps some time soon.

Tug's progress on his version of Arnold T's engine reminds me of just how much work there is still to go. Tug's workmanship is also something else I can only aspire to matching!

David
« Last Edit: May 04, 2022, 07:17:29 AM by deltatango »
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Offline Ramon Wilson

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Re: A Tandem Compound Mill Engine
« Reply #74 on: August 30, 2020, 11:28:07 AM »

Quote Tug's progress on his version of Arnold T's engine reminds me of just how much work there is still to go.

I guess you are not far off there David but every step eh? Although I have a lot of small items to get through I've only just realised that I am actually not that far off - surprising how it all comes together.

Not able to send you the details of the valve lever at the moment but will do soon

Keep that progress ticking along

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)

 

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