Author Topic: A Tandem Compound Mill Engine  (Read 32528 times)

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #210 on: April 26, 2024, 07:37:45 AM »
Thanks Per! It's good you are still following along.

David
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Offline cnr6400

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Re: A Tandem Compound Mill Engine
« Reply #211 on: April 26, 2024, 12:31:51 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

Online Kim

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Re: A Tandem Compound Mill Engine
« Reply #212 on: April 26, 2024, 06:01:46 PM »
Your build is coming along nicely, and the governor looks great!  :ThumbsUp: :popcorn: :popcorn:

Congrats on having your build published in ME! That's a great :D

Kim

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #213 on: April 27, 2024, 02:05:14 AM »
Thanks Kim!

"All" I have to do now is write, make the drawings, prepare the pictures and write the captions for a bunch more parts of the article.

David
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Online Kim

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Re: A Tandem Compound Mill Engine
« Reply #214 on: April 27, 2024, 04:46:04 AM »
Thanks Kim!

"All" I have to do now is write, make the drawings, prepare the pictures and write the captions for a bunch more parts of the article.

David
You're almost done!   :ROFL:

Kim

Offline MJM460

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Re: A Tandem Compound Mill Engine
« Reply #215 on: April 27, 2024, 01:00:19 PM »
Hi David, good to see the latest progress.  And congratulations on having the build in print.

I seem to remember the involute form on a gear tooth is supposed to provide rolling contact, rather than sliding contact of other forms.  Lower friction s always good in a governor mechanism, but it would need to be accurately profiled and set up to give much advantage.  It would be impressive to achieve that by hand filing.

Those bevel gears look impressive, and the governor looks great sitting up in position.

MJM460
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Offline steam guy willy

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Re: A Tandem Compound Mill Engine
« Reply #216 on: April 28, 2024, 04:08:14 PM »
Hi David , good to see the work continuing and also I have been in touch with Martin from the Model Engineer Magazine and he is quite keen to have moire stationary engine articles  and so I have started on a Beeleigh Mill series that I constructed
 a few years ago ... Also the Engineering in Miniature mag has now stopped being produced for some reason ,

Willy

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #217 on: April 28, 2024, 11:49:23 PM »
Hi MJM and Willy, Thanks for still following along!

I don't know if it was Arnold Throp or Peer Southworth who wrote "file to involute" on the drawing for a part about 3 mm high but I'd love to know if they were serious, or just having a laugh.

I'll look out for the Beeleigh Mill series with pleasure but I'm unlikely to start another stationary engine build any time soon (the choice of the next projecti s down to one of two with one a strong favourite). My tasks now are to finish the engine which involves cladding the pipework, making the handrails and finishing the painting. The beast runs but final adjustment of the trip gear is proving tricky. Writing a load more articles also has to happen!

Blackgates have told me a year ago that they have the castings available for the big mill engine, but they aren't replying to my emails. Maybe a 'phone call is called for?

I'm sorry to see EiM go out of business - I was a subscriber and the explanation seems to be simple economics. I'll particularly miss Harry Bilmore's articles on the Fairbourne Railway, maybe another magazine could pick up his work (hint, hint Martin E).

David
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Offline jadge

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Re: A Tandem Compound Mill Engine
« Reply #218 on: April 29, 2024, 09:19:02 PM »

I seem to remember the involute form on a gear tooth is supposed to provide rolling contact, rather than sliding contact of other forms.


The involute tooth form has both rolling and sliding contact. The key characteristic is that it gives constant angular velocity, and that is not affected, to a first degree, by centre to centre errors.

I would agree though that the bevel gears look great.  :ThumbsUp:

Andrew

Offline Roger B

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Re: A Tandem Compound Mill Engine
« Reply #219 on: May 03, 2024, 07:45:23 AM »
Excellent work on the gears  :praise2: and congratulations on the publication  :wine1:  :wine1:
Best regards

Roger

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #220 on: May 14, 2024, 12:00:55 PM »
The LP cylinder came as a GM casting with no obvious reference surface. After a lot of tentative filing and "fondling" I chose the cored bore as the starting point as this was clean, circular and more or less in the right place. As with most of the other castings there was precious little machining allowance anywhere. An expanding mandrel was used to hold the casting between centres on the mill with an angle plate clamped to what will become the valve port face:



The as-made centre height of the bore was measured:



and the underside of the base milled off to give the first datum:



The x- and y- datums were located from the bore (y) and a guesstimate of the longitudinal centre of the body (x):



Then the casting was turned through 90░ to clean up the port face at the correct distance from the bore centre:



After moving the part to the lathe, the ends were machined:



The height of the lathe centre line above the boring table was measured:



and a steel block ("fixture"? "nest"?) made to set the bore height:



The final use for the mandrel was to locate the casting into the fixture (actually, move the fixture onto the part-machined casting):



and machine the bore:



Marking out for the ports showed up a problem:



Which I really, really hope was fixed with some JB Weld (time will tell):



Finally - for this post - the steam passages were drilled in the long-established way:



David
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Offline Admiral_dk

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Re: A Tandem Compound Mill Engine
« Reply #221 on: May 14, 2024, 06:44:39 PM »
Nice progress and desciption of setups  :ThumbsUp:

Congratulations on publishing  :cheers:

Per

Offline Chipswitheverything

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Re: A Tandem Compound Mill Engine
« Reply #222 on: May 15, 2024, 08:50:30 AM »
 Just been looking back through this very interesting build log of the fine engine.  Liked the recent pictures of the cylinder set up on the mill, with the dividing heads : a neat machining set up is a sort of small work of art in itself! Good that the digital camera can keep a record of the work that goes into these temporary but time consuming manipulations. Back in the past , pre digital, most of what model engineers did in this practical and often ingenious way was just lost as soon as the work was broken down!  Dave

Offline deltatango

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Re: A Tandem Compound Mill Engine
« Reply #223 on: May 15, 2024, 12:35:05 PM »
Thanks, Per and Dave, it's good to know you are following along.

As Dave said machining set-ups, particularly for difficult parts, are one of the arts of the machine shop. It's very satisfying when everything stays in place and doesn't vibrate - essential for that other good feeling that comes from getting a good finish:



 I hadn't really thought about how I'd record the build without a digital camera, but I used to process my own films, so I guess that would be the way to go. Whether or not I'd take the trouble I really don't know.

The steam chest casting wasn't hard to hold, just very short on machining allowance and ended up a bit undersize even with some rough bits remaining:



The glad boss and hole for the spindle were standard 4-jaw work:




If you look at the pattern of stud holes you can see that it is not symmetrical which opens up the possibility of having to plug some holes up and re-drill the pattern:




There were a lot of studs to make, and the short ones are just lengths of thread:



Most of the other bits were straight forward turning tasks apart from the valve which I'll describe next time.

David
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Offline cnr6400

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Re: A Tandem Compound Mill Engine
« Reply #224 on: May 15, 2024, 02:59:19 PM »
 :ThumbsUp: :ThumbsUp: :ThumbsUp: :popcorn: :popcorn: :popcorn:
"I've cut that stock three times, and it's still too short!"

 

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