# My First Steam Engine: The Minikin from Steam and Stirling



## seal killer (Jul 8, 2009)

All--

I have owned a mill for a couple of years and gone from ZERO knowledge to pretty well tooled up plus SOME knowledge. I have built a few things, mostly for the mill(!), and am looking forward to expanding my horizons.

My Dad built a steam engine when he was 14. It was an oscillator. I can remember it whizzing the flywheel as young as four. I imagine that steam engine is what determined my career in technology.

I bought a copy of _Steam and Stirling _ and determined that the "Minikin" was the easiest engine in the book to build and the most like the one my Dad built. The editor, whom I think built the Minikin, as well, wrote the piece about it from the point of view of someone having a lathe and a mill. The lathe being somewhat predominant in the construction of the engine.

I don't have a lathe.

What I do have is a nice knee mill which I am very familiar using. I plan to emulate the lathe requirement in the construction article of the Minikin by using a left handed boring bar to turn a boss. (I will drill or bore the raw material prior to turning the boss. It seems better that way to this inexperienced non-machinist.)

There are many things I do not understand. For one, the editor says to "turn up a bushing to fit on the pivot." Other than a drawing, there is no other explanation. I THINK I can do this via reverse boring, especially since the bushing is so short. I am somewhat worried about using a carbide end mill in an interrupted cut in both brass and bronze (bronze: 932, brass: 360 and 464). My thinking is to take 0.001" off the square work piece and see how if feels and proceed from there. (?) I will mill the work piece down so there is a square "boss" protruding for reverse boring (turning).

My other departure from the article concerns the stainless steel piston. Since I have a large set of stainless steel dowel pins, I plan to use one of them cut to the proper length.

I certainly would appreciate any comments you care to make. I have no ego and criticism is a great learning tool.

Thanks!

--Bill


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## Tin Falcon (Jul 8, 2009)

Bill:
 Minikin was the second engine i started I think it was the third or forth I finished. It is a tweaky little engine to get running. My suggestion is start with something a little bigger

Like this one
 http://npmccabe.tripod.com/mccaberunner.htm

or this one
http://littlemachineshop.com/Projects/OscillatingEngine.php

@ 10psi there will be about .49 lbs of force on the little piston of minikin' a 1/4 inch piston.
the Mcabe runner will have more than twice the force on the piston due to larger area of the piston .
 The LMS Ocsilator will have almost two pounds of force on the piston or 4 times that of the minikin piston. 
Bottom line is the fit and finish has to be excellent on the minikin due to small piston size and fly wheel diameter. 
The LMS oscilator would be a lot more forgiving if there is a little friction or air loss there will still be power to keep things moving. 
If you look around here you will find examples of the above engines made by members of the board.
Good luck with your first engine looking forward to seeing it completed.
Tin


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## seal killer (Jul 8, 2009)

Tin--

Wow! I REALLY like the second one. It looks _very _ much like a scaled up Minikin. (I am not in love with the Minikin. It just looked like the easiest thing for me to build.) Plus, the instructions are written for a mill-based project, which I believe the Minikin could be, as well.

Thank you very much.

--Bill


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## Tin Falcon (Jul 8, 2009)

Bill:
You can always do a minikin as a third project or even a second. I think building a couple of easier ones first will build your confidence and your skills.
Tin


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## seal killer (Jul 8, 2009)

Tin--

I _totally _ agree with you. It is not the Minikin that I want to build, it is the easiest engine that will go back and forth and round and round that I want to build.

--Bill


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## shred (Jul 9, 2009)

Dave Goodfellow's Brassy Babe is a good easy one and doesn't have much lathe work.

http://www.homemodelenginemachinist.com/index.php?topic=4043.msg41967#msg41967

http://www.davegoodfellow.com/plans.pdf


The crank might be a little tricky as-drawn, but a press-fit or built up one could be done. You could also do some lathe work by chucking the stock in the mill and a lathe bit out the side of the mill vise, like in this video but manual:

[ame]http://www.youtube.com/watch?v=wbfXXeiSHsw[/ame]


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## seal killer (Jul 9, 2009)

shred--

Ha! Now I have returned to my normal state of indecision! 

Thanks for the link!

--Bill


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## deverett (Jul 16, 2009)

seal killer  said:
			
		

> Ha! Now I have returned to my normal state of indecision!
> --Bill



I used to be indecisive, but now I'm not so sure.

Dave
The Emerald Isle


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## shred (Jul 16, 2009)

Ah, just pick one and go for it. You can have it made in a week or two and be on to the next one... At the end of the month you can pick the ones you liked best.
 ;D


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## JMI (Jul 16, 2009)

seal killer  said:
			
		

> shred--
> Ha! Now I have returned to my normal state of indecision!



Indecision is the key to flexibility. 

Jim


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