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Mcgyver
07-06-2008, 01:41 PM
Haven't been posting much, but i'm alive and kickin' here some pics of whats currently been occupying me. This engine is something i've on for years, sort of pick up and put it down from time to time. I put these up on Home Engine Machinisht and thought you guys would get a kick as well

Here's an interesting little thread, its a 2 start 3/16 20 for the reversing mechanism. One of the guys on HEM single point cut the 3/16 20 double start internal thread - I wouldn't have believed it possible but he did so i tried to do the same. I actually almost got it cut in the lathe and then through a moment of mental fraility broke the itty bitty tool (not by cutting, just a very dumb movement). This stuff is small Ė boring bar only .100 in dia! I made a tap to chase it to finish it off.

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/assemblyoftwostartthread.jpg

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/multistart9-readyforengine.jpg

I'm further along than the following pic shows but had the engine apart to clean and fit some recently manufactured parts.

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/Stuarttriplebottom.jpg

Mcgyver
07-06-2008, 01:42 PM
pt II

In the previous post, the pics show the oil cups I made for the main bearings, but I felt eccentric straps and big ends should also have some way of delivering oil.

Here are the little cups I made for the eccentrics, the small OD is 1/16, the six are sitting on a dime.

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/oilcupsforeccentricstraps.jpg

Here’s a shot of them installed - its triple so there's 3 or 6 of everything!

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/eccentricassembly.jpg

The big ends required a bit more thought as the counter weights narrow in on the connecting rod once the bearing is cleared – you can see that in the pic of the crankshaft above

So I decided to have a base, pipe and cup at the top and to twist it around to the side so it would clear the counter weight.

Here are the parts are being assembled. The brass tube is only .047 OD and that’s #67 reamer to clean out the brass tube ID after cutting. You can see the visor magnifier in the background that gives me a fighting chance on these parts

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/connectingrodoiler.jpg

And here they are installed Incidentally, the geometry formed by the tapered connecting rod where it meets the U shape at the top was one very challenging aspect of this engine – the parts have to blend together with a radius to look right. Maybe a five axis cnc? Still would require hand work to blend it me thinks. This was a close to sculpting as my machining as ever come, tedious needle file and emery work!

The cup had to be where it is to clear the counter weights and looks somewhat like prototypical practice

http://i20.photobucket.com/albums/b201/michael0100/Stuart%20Triple%20Expansion/connectingrod.jpg

spkrman15
07-06-2008, 01:57 PM
Ok that is some amazing work. Wow

Rob :)

John R
07-06-2008, 03:49 PM
That's beautiful.
When I was a kid I would run the tripple expansion engine in my daddy's ship before they got underway. They were really neat engines. Look forward to more porgress from your project.
John R

japcas
07-06-2008, 05:31 PM
Mcgyver, that's some real nice looking work. Please keep sharing as you progress. I look forward to seeing the finished product.

Quetico Bob
07-06-2008, 05:51 PM
That is just outstanding Mcgyver, donít think I want to post pictures of my scrap built engine anymore.

Can you describe a double start thread for those of use who donít know.

Cheers, Bob

Al Messer
07-06-2008, 05:55 PM
EXCELLENT work!!

Mcgyver
07-06-2008, 10:25 PM
thanks guys, pics are with a Nikon D80 on a tripod, no flash, high iso long exposures

Bob, a double start thread is, well, picture a regular thread as V profile wrapped around a cylinder. A double thread is the same thing but there two of them 180 degrees apart- a nut on the thread will move twice as far per revolution than a single start.. So to cut a 3/16 20 double thread, you set the gear box to 10 tpi instead of 20 and cut two threads - indexing the spindle 180 degrees between cutting each threads (i make it sound way more complicated than it is)

Mark Hockett
07-07-2008, 12:56 AM
Mcgyver,
Is this the engine your building,
http://i24.photobucket.com/albums/c10/mahockett/stuart1.jpg

I got some old Stuart catalogs (73, 80) in an auction lot a couple of weeks ago, the 73 catalog even had a price sheet. I'm thinking about ebaying them but haven't decided yet.

Fasttrack
07-07-2008, 01:04 AM
"Holy Sh*t" was the first thing that came to mind - which is impressive because I actually swear very rarely. That is really exceptional work. I was very impressed!

Thanks for sharing. Model making is truly an art.