Author Topic: Stew Hart's Popcorn Engine  (Read 1632 times)

Online ImIndoors

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Stew Hart's Popcorn Engine
« on: January 12, 2018, 10:40:20 PM »
At last I have the Popcorn engine finished (sort of!).
After reassembling it following stripping and painting I discovered that I had somwhow managed to bend the piston rod and it no longer moved freely or lined up with the crosshead.  My first attempt at a replacement failed when I cut an M4 thread on it and found that the brand new thread die I used chewed a thread which was horribly undersize and barely even made contact in the crosshead.  The second new rod worked.  Also the whistle valve, which held air when I made it, now doesn't for reasons unknown so I hope that will be fixed when I replace the bronze ball in it with a nitrile one.   
 
Anyway,a video:


I think I also need to slow down the governor flyballs a bit which I can do by reducing the diameter of the drive pulley.

Jim
The person who never made a mistake never made anything.

Offline Kim

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Re: Stew Hart's Popcorn Engine
« Reply #1 on: January 12, 2018, 11:01:39 PM »
That is a very nice looking engine, Jim.
Love the whistle!
Kim

Offline zeeprogrammer

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Re: Stew Hart's Popcorn Engine
« Reply #2 on: January 12, 2018, 11:11:22 PM »
Beautifully done and I love the whistle.  :ThumbsUp:

This has been at the top of my project list for some time.

Did you scale the plans?
Are the plans the same as the ones Julius posted some time ago?
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Offline Gas_mantle

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Re: Stew Hart's Popcorn Engine
« Reply #3 on: January 12, 2018, 11:46:09 PM »
What a great little engine Jim, looks to be a very smooth runner.

I like your attention to detail with added embellishments such as the attractive whistles and the valve knob.

One to be proud of  :)

Online b.lindsey

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Re: Stew Hart's Popcorn Engine
« Reply #4 on: January 13, 2018, 12:09:58 AM »
Beautiful Jim. And the finish is wonderful. I do agree the flyballs should be slowed some...they are really dancing, but that's a minor issue. Well done.

Bill

Offline Brian Rupnow

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Re: Stew Hart's Popcorn Engine
« Reply #5 on: January 13, 2018, 01:16:45 AM »
Very nice. I built one of those just after Stu posted the plans a few years ago. A great little engine. I like the governor.---Brian

Offline sbwhart

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Re: Stew Hart's Popcorn Engine
« Reply #6 on: January 13, 2018, 06:08:39 AM »
Excellent job Jim:- you've got a lovely finish, and it run and sounds really well to, the whistle has a good tune.

If any one wants a copy of my plans all they have to do is drop me a PM.

Cheers
Stew

A little bit of clearance never got in the way

Online ImIndoors

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Re: Stew Hart's Popcorn Engine
« Reply #7 on: January 13, 2018, 12:53:27 PM »
Aw, shucks.:embarassed:  Thanks for the kind comments everybody and special thanks to Stew for providing the drawings.

Zee.  I built it from Stew's drawings which he kindly sent me.  I can thoroughly recommend his designs (this is the second of his I've built) which he generously offers to all, just send him a PM.

Now it's on with Ray Hasbrouck's number 3 engine, which has a rocking valve system, then a Hit'n'hope miss.

Jim
The person who never made a mistake never made anything.

Offline tinkerer

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Re: Stew Hart's Popcorn Engine
« Reply #8 on: January 18, 2018, 07:05:56 AM »
Very nice piece. I'd love to make a full sized one. The cross head guide is a rather unusual piece. I've been looking at a lot of pictures of the original ones. Did you make it from plans or casting set?
You never know what you can do, till you try. Don't be afraid to try & fail. We learn more from our failures than our successes.

Online b.lindsey

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Re: Stew Hart's Popcorn Engine
« Reply #9 on: January 18, 2018, 01:30:40 PM »
Tinkerer, If you are interested in a full size casting set you might consider this one:

http://www.myersengines.com/engines/popcorn_engine.htm

Apparently they are now offering the governor castings and gears but in addition to the price shown.

I have the half scale version currently aging under the workbench and the castings seem well done though I haven't done any machining on the yet.

Bill

Online ImIndoors

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Re: Stew Hart's Popcorn Engine
« Reply #10 on: January 18, 2018, 03:24:30 PM »
Tinkerer
I built my engine from drawings given to me by Stew Hart.  No castings were harmed in the making of this engine.
Bill's link is to a scale Cretor's engine at full size; my non scale model is, I believe, based on a Dunbar engine.  For scale my flywheel is 3 inch diameter.
Jim
The person who never made a mistake never made anything.

Offline tinkerer

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Re: Stew Hart's Popcorn Engine
« Reply #11 on: February 03, 2018, 05:21:38 AM »
I've been studying popcorn machines lately. It looks like Dunbar & Kingery pretty much copied the Cretors design. Very slight variations l noticed on a friend of mine's Kingery engine. On the cross head. Where it reduces in size is more angular than Cretors (it's more rounded). But almost identical.
You never know what you can do, till you try. Don't be afraid to try & fail. We learn more from our failures than our successes.

Offline tinkerer

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Re: Stew Hart's Popcorn Engine
« Reply #12 on: February 03, 2018, 05:39:58 AM »
Here's the Kingery engine I was talking about. A friend of mine has this wagon.
You never know what you can do, till you try. Don't be afraid to try & fail. We learn more from our failures than our successes.

Offline bent

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Re: Stew Hart's Popcorn Engine
« Reply #13 on: February 05, 2018, 11:24:29 PM »
Love that slide whistle!  Nice job, Jim.

Offline tinkerer

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Re: Stew Hart's Popcorn Engine
« Reply #14 on: February 06, 2018, 03:30:16 AM »
I plan on building one of these. Only full size once I get more comfortable with my new lathe. Really a great looking & sounding little engine there!
You never know what you can do, till you try. Don't be afraid to try & fail. We learn more from our failures than our successes.