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  • June Project of the Month (Click "x" at right to dismiss)
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A Tiny Hit And Miss Engine

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gbritnell

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Joined
Mar 22, 2013
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#1
A couple of years ago a fellow named Arv, alias Put Put Man, designed and built a Tiny hit and miss style engine, although the hit and miss part wasn't functional.
He then shared his drawings with the modeling community and quite a few others built the engine, along with myself.
Another fellow, Gail, created a true hit and miss into his build. His design intrigued me but after seeing it I wanted to try and make a more conventional hit and miss style. Not wanting to just replicate the first engine I then changed the design and made and air cooled cylinder.
To accommodate the governor mechanism a number of modifications had to be made to the existing components, along with some new pieces.
The result is what you see here.
gbritnell
 

davidh

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Jan 23, 2012
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#2
very nice. a couple questions: what are you lubricating the connecting rod and the main bearings with ? what are you using to create spark ?
it appears to be quite well balanced and not jumping all over the table. . . . nice. what rpm is it running at ?
 

gbritnell

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Mar 22, 2013
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#3
Hi David,
The original design of the engine used a bronze or brass connecting rod so a couple of drops of oil sufficed. I wanted to lighten up the rod so I made mine from aluminum. Knowing that the high surface speed of the steel crankpin against the aluminum wouldn't last long I made split bronze inserts for the big end. The crank is made from one piece of 1144 stressproof steel.
The main bearings are ball bearings, .187 I.D. x .312 O.D.
For spark I have a Hall transistor on the side opposite the gear side. It triggers my electronic ignition box.
When I built the first engine I had increased the drawing size of 1.75 to 2.00 for the flywheels. Knowing that these things need a little more flywheel weight. When I redesigned this one somehow I didn't increase the size so even with it hitting and missing the rpm is probably about 2500. In the future I'll probably make a set of larger wheels to see if I can slow it down some. With the small size I doubt I can get the RPM below 1500.
gbritnell IMG_6326.JPG
 

Fabrickator

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Jan 22, 2014
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#4
Great Job! I've been wanting to make a H&M for a long time now. I was going to make an engine using a BBQ lighter (re-circuited) for the ignition, but I couldn't get it to work consistently and set aside the project.
 
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