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A Tandem Compound Mill Engine

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deltatango:
In my former world of w##k the saying was "if it hasn't been written up, it hasn't happened" so I guess it's time that I started a build log for the current engine.

The choice of engine for this project is the result of my interactions with MEM so I hope you all like it, particularly Tug and Bob Potter who have played their parts in getting this one started. Tug has written of the origins of the Arnold Throp/Peter Southworth compound mill engine model in "Tug's Corliss Tandem Compound Project" build log so I won't duplicate too much of that here, just enough to set the scene.

Arnold Throp, who was an apprentice with Cole Marchent & Morley, engine builders in Bradford (Yorkshire, UK) described a model of a typical small-to-medium sized mill engine in "Model Engineer" in 1982 but didn't give any construction details and as far as I know no such details have been published. The design was worked on by Peter Southworth and he evolved five basic versions and made (or modified) patterns and was the original supplier of castings. Since then the availability of castings has been patchy. At the Forncett day out two years ago I saw Tug's progress with his all-Corliss valved tandem compound version and was impressed with it (both the design and the workmanship!). At that time Bob Potter was running "Southworth Engines" and supplying drawings and castings for boiler feed pumps and for the mill engine and he sent me a set of drawings.  The engine was, just, within what my machines could deal with and I was very taken with the idea of building one so parted with the money. Bob had given up on sending castings via the post/couriers but he, very kindly, delivered the 23 kg of metal to friends of ours "to await collection". Customer service indeed! Since then the Southworth range has been taken over by Blackgates Engineering and their 2019 catalogue only lists the feed pumps, I really hope that Arnold and Peter's legacy isn't going to be forgotten!

Of the five versions shown on the drawings my choice was the tandem compound with Corliss valve HP and slide valve LP cylinders and an "air pump" (spray condenser, really). The cross-compound versions were attractive but too bulky for easy storage, transport or display. The tandem is long but will at least fit on a shelf.

As I've done with previous projects I re-drew the design using the "Alibre" CAD package and here are three screen dumps of the results:







Next post I'll put in a drawing and make a start on the big bits i.e. the flywheel and crankshaft.

David

crueby:
Oh, now that is a real beauty of a design!!  How big will the model be?


Hey, shop elves, break out the popcorn!!   :popcorn: :popcorn: :popcorn:

deltatango:
Great to have you watching and commenting Chris!

The baseboard as drawn is just over 1 m long and the flywheel is 250 mm OD. The Hercus "260" lathe swings, not too surprisingly, 260 mm. As you will see soon this is a tight fit.

Hope you have lots of popcorn on hand as this won't be a quick build!!

David

Larry:
Great looking design. Anxious to follow your MEM Corliss build.

cnr6400:
"OK Chris, I'll back the dump truck full of   :popcorn:  into your cellarway now, and then go get another load for  me"    :Lol:

CAD looks great David, look forward to watching the build. Have you checked the workshop door to be sure you can get it out when finished?  :shrug: :Lol:

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