Author Topic: Arnold's take on the MEM Corliss  (Read 134605 times)

Offline ProdEng

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Re: Arnold's take on the MEM Corliss
« Reply #315 on: July 28, 2013, 02:19:35 AM »
The valve arms look great Arnold.  M1.4 is a very small screw, more like clock making  ;)
Jan in Perth

Online steamer

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Re: Arnold's take on the MEM Corliss
« Reply #316 on: July 28, 2013, 12:48:10 PM »
That's really coming along beautifully Arnold!.....I like it! :ThumbsUp:

Dave
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Damned ijjit!

Offline Tennessee Whiskey

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Re: Arnold's take on the MEM Corliss
« Reply #317 on: July 28, 2013, 01:26:34 PM »
Arnold, nice job. I kinda like the screw ends as they are. In the photo I see nice straight lines around the outside and roundness in the center part. They just look like they fit the design. Just my 2 cents, hadn't checked the exchange rate let me know if I owe you any extra :cheers:

Eric

Offline Bearcar1

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Re: Arnold's take on the MEM Corliss
« Reply #318 on: July 28, 2013, 06:48:28 PM »
Looking good Arnold. I like seeing skillfull model engineers making small parts.


I'll second those sentiments ......  :ThumbsUp:


BC1
Jim

Offline arnoldb

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Re: Arnold's take on the MEM Corliss
« Reply #319 on: July 29, 2013, 12:28:09 AM »
Thanks very much for looking in All  :praise2:

Vince, the small bits aren't all that bad; it just takes a bit more planning to do the machining - especially for work-holding.  Oh, and not dropping them; that's instant shop-monster food.  Actually I'm enjoying making the small bits; except for the smaller threads, these are of a similar size to quite a few parts I've made for the various versions of Elmer's engines I've built - though Elmer had a knack for simplifying the small parts a bit.

Don, yes; they do take time - as today's progress might show!

Marinus & Jim, thank you; that's high praise, but I don't consider myself a skillful model engineer.  I'm still learning every step of the way, and in this build there are a lot of "firsts" for me.

Jan, yes, the screws are small - and some horological tools would be a boon.  In fact, my list of "tools-to-make" still keeps on growing, and a lot of it especially for smaller parts.  After this engine is completed, I'll spend quite a bit of time doing some tool-making jobs.

Eric, your 2 cents run through the exchange rate is worth a whopping 19 Namibian cents today, so I'll gladly take it  ;)

On to some more small bits.  The disk arms are the smallest parts on the engine, and I'd been puzzling over how to make them.  If I made them from three separate pieces each like on the plans, I'd have to single-point thread the spindles either M1.4 or M1.6 as I don't have dies for those sizes.  That would have been a nice challenge; I'm one of the few people around who actually likes screw-cutting on the lathe, and even though these are very fine threads, I'm pretty certain I can do them with a razor-sharp honed toolbit.  What I couldn't figure out was how to make the eight arm ends with the tooling I have...

"Arnold" is derived from "Eagle" - so it's with great trepidation that I sully my majestic avian namesake with what's to follow...

I turned "lazy" mode on, and decided to make the disk arms as single pieces.  There were still some machining issues to overcome, but a plan was hatched and off I went.

Things started off with short sections of 5mm hex brass rod - much longer than needed, as I needed a way to hold things later on:


I turned a 2mm pip about 4mm long at one end of each of the pieces.  My Myford's 3-jaw chuck is pretty badly off center at this size, so I marked the flat that lied between the #1 and #2 jaws so that I could later on chuck up the workpieces again and keep the best possible centering on the pip I turned.  Then it was off to the milling machine with the tooling plate mounted in the vise, and I set things up so I could repeatably drill the workpieces with the 14.7mm distance between the holes.  A bit of scrap aluminium plate served to both lift the workpieces a bit so the clamps didn't foul on the cap screws at the back and prevent proper clamping, as well as prevent drilling into the tooling plate:


After drilling the holes, I switched to an 8mm cutter and set it to height to mill off 1.25mm.  Things were a bit tight between the clamping spaces on the tooling plate, but it worked:

As always, between milling each side of the workpieces, I followed that golden rule that Mr Philip Duclos mentions so often in his writings.  Clean away the chips and de-burr the workpiece.

With the milling done, I ended up with this lot:

As you can see, there's the 2mm spigots I turned on each workpiece, and on the left, on the faces facing the camera, the permanent marker markings I mentioned earlier that corresponds to the opening between the #1 and #2 jaws of the Myford's three jaw chuck.  Also, the metal-munching rat left it's hallmarks in the middle of the cut-outs; I didn't worry about that.  Boring really, but there's a little method to this madness...

Back to the lathe with the workpieces, and a type of set-up I'd never used before.  All the boo-hah about the 2mm pip at the end of the stock and marking the place to re-mount in the chuck now came into play.  I wanted to turn down a section between the holes drilled into the workpieces to 1.5mm.  I could have used my small revolving center for support at the tailstock side, but that puts an axial load on the end of the workpiece, and when things get this small, it could just buckle it up.  So a bit of 2mm inner diameter tube chucked up in the the small drill chuck in the end of the big tailstock drill chuck, with a drop of oil added would provide a running center without adding axial tension to the workpieces.  After digging around all my HSS cutting tools, I selected a suitable toolbit; this one was originally shaped to cut the worm gear from back when I made my rotary table:


With a drop of oil on the spigot at the end I shoved it into the bit of tube in the tailstock chuck.  Some turning followed.  Very carefully.  The joys of turning brass with a nice sharp toolbit with zero rake manifested itself; with 10 thou initial and later 5 thou in-feeds as things got smaller, everything turned out well.  The shaft of the workpiece is 1.5mm, and the steps up from that is 2mm:

 :-[ I have to say, most of the turning was just eyeballed - I just used the same settings on the cross-slide for in-feed for all the bits, but no measurement for the shoulders or the distances to the holes.

The bits were just hacked off the parent stock with a junior hacksaw, and then I started cleaning them up on the mill and with files.  All too soon, shop time ran out, but I managed to mostly finish off one bit after a lot of loving care with a needle file after rounding it over on the mill.  One done, one partly done, and the rest to go...  Well, that's some progress of sorts anyway:


The small bits can be a bit tricky, but it's a lot of fun.  I'm really enjoying this  :whoohoo:

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Offline vcutajar

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Re: Arnold's take on the MEM Corliss
« Reply #320 on: July 29, 2013, 07:15:01 AM »
Nice one Arnold.  You are making my life easy. :ThumbsUp:

Vince

Offline ProdEng

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Re: Arnold's take on the MEM Corliss
« Reply #321 on: July 29, 2013, 11:51:52 AM »
The arms came out very well and I love the methods.  Using hex stock with the flats for reference surfaces is a gem along with the bush in the tailstock for workpiece support.
Jan in Perth

Online Jo

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Re: Arnold's take on the MEM Corliss
« Reply #322 on: July 29, 2013, 12:05:53 PM »
The small bits can be a bit tricky, but it's a lot of fun.  I'm really enjoying this  :whoohoo:

 8)

I agree, I always find that it is the tricky bits that (can) give so much satisfaction and pleasure .

Jo
Usus est optimum magister

Online b.lindsey

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Re: Arnold's take on the MEM Corliss
« Reply #323 on: July 29, 2013, 12:33:16 PM »

The small bits can be a bit tricky, but it's a lot of fun.  I'm really enjoying this  :whoohoo:



And we are enjoying watching Arnold !!!  Lovely work as usual.

Bill

Offline spuddevans

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Re: Arnold's take on the MEM Corliss
« Reply #324 on: August 05, 2013, 03:48:23 PM »
This is coming on really well, looking really good Arnold. Keep up the good work.


Tim
Measure with a Micrometer, mark with chalk, cut with an axe. MI0TME

Offline arnoldb

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Re: Arnold's take on the MEM Corliss
« Reply #325 on: August 11, 2013, 04:05:07 PM »
Vince, Jo, Bill & Tim, thanks for checking in!

Things were very quiet in the shop of late; there was this little matter of a week-long business trip I had to take to South Africa and all the preparations that went with it...

Yesterday I finally made it back into the shop for the first time in two weeks, and finished off the spindle arms:


All the threads I used for mounting the spindle arms to the valve disk and valve arms are 10BA (which is as close as can be to 1.6mm), but the holes in the spindle arms I made 2mm, as I prefer to use shoulder bolts in this type of application.  This is not on the plans; it is merely my own personal preference.  As these bolts are fairly small, I didn't want to make the bolts from brass, and rummaging through my stock I found I had silver steel and stainless steel of a suitable size.  I went for the stainless purely because it won't rust.
After grinding up and finely honing a new toolbit from a HSS blank, I started turning up the bolts - jotting down the cross-slide readings once the first one was on size to make it easier to make the rest.  Lazy as always, I used the grooves in the collet closer nut to index by eyeball where I needed to file the flats to make the hex head, and just counted file strokes to get the flats all to the same size.  Here's the first one basically finished:


I just used a junior hacksaw to separate the bolts from the parent stock, and afterwards chucked them up in the small ER11 collet chuck to face the heads to equal thicknesses.  After a while, I had the 8 bolts needed; I actually made ten, but the shop monster was really hungry and ate two of them...:


Then I assembled things on the engine:


While assembling things, it occurred to me that the engine was now at a point where it might just run, even though it's not mounted and still missing some bits like the valve covers and so on.  Quick as a flash I turned up an impromptu air connector (already visible in the photo above, and set all the valves to "just closed" by turning the engine to top dead center and adjusting the valves so their slots showed the were in a definite "just closed" position (that's why they're slightly angled):


Well ? - does it work ?




YES!  :whoohoo:
Even though the piston still needs a ring, and nothing is bolted to the base (the screws you see are just dropped in to locate things but not bolted up), and there's not a gasket in sight, it runs, and surprisingly well at that:
<a href="http://www.youtube.com/watch?v=7Xlw7IaVVsY" target="_blank">http://www.youtube.com/watch?v=7Xlw7IaVVsY</a>

The valve covers still needs to be made, as well as the proper steam valve, and then it needs lots of studs and painting, so it's about 50% done.

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

Online Jo

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Re: Arnold's take on the MEM Corliss
« Reply #326 on: August 11, 2013, 04:28:40 PM »
Well done Arnold  :praise2: now why can't I get mine to do that  :lolb:

Enjoy the studs.  ;D

Jo
Usus est optimum magister

Online Jasonb

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Re: Arnold's take on the MEM Corliss
« Reply #327 on: August 11, 2013, 04:34:59 PM »
Well done on a nice engine, just the beutyfiying to do now.

J

PS keep it on the slow speed :)

Offline Don1966

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Re: Arnold's take on the MEM Corliss
« Reply #328 on: August 11, 2013, 04:46:35 PM »
Awesome Arnold, that is one beautiful running engine, it sure runs good at slow speed. I like..........  :praise2:

Don

Offline vcutajar

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Re: Arnold's take on the MEM Corliss
« Reply #329 on: August 11, 2013, 04:58:25 PM »
Yippee it works.  Nice one Arnold.   :praise2: :praise2: :praise2:

Well it gave me a deserved kick in the backside to get on with mine.

Just a silly comment if you don't mind.  Why don't you put the linkages on the front side of the wrist plate.  They might look nicer.

Vince