Harvard/Stickney Jr Model

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JPar

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You have to be careful about putting the setscrew over top of the key.
Make sure that the hub is thick enough, where both the key and setscrew will be.
That's a good point. I took a closer look at the hub, and after subtracting half the thickness of the key, I'm not sure there's enough "meat" left for the screw. The drawing actually shows the key and set screw placed 180 degrees apart, but I don't like that because the burr left by the set screw can make if difficult to remove the gear.
For this application (camshaft), I wonder if it would be sufficient to omit the key, and just mill a flat on the shaft for the screw to bear on. I wouldn't think a camshaft gear would be subject to the same loads as a flywheel on a crankshaft. Thoughts?
John
 

JPar

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I got distracted by other things, but finally got back to the cam gear. I broached the gear and cut a keyway in the shaft, 180 degrees opposite the set screw as suggested. I also milled a flat for the set screw to bear on. It was my first attempt at cutting a keyway in a shaft. I'm happy with the way it all came out!
John

Keyway1.jpg
 

JPar

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I'm finally getting back to the little Stickney after a hiatus of 9 months or so. It's starting to come back together now. Last week I assembled the crankshaft, base, eccentric shaft, and flywheel. Yesterday I assembled the piston, sleeve, cylinder casting, and top casting.

CylAssembled.jpg
 

gbritnell

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It's coming along great!
 

LorenOtto

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I'm finally getting back to the little Stickney after a hiatus of 9 months or so. It's starting to come back together now. Last week I assembled the crankshaft, base, eccentric shaft, and flywheel. Yesterday I assembled the piston, sleeve, cylinder casting, and top casting.

View attachment 128882
Very glad to see you are back at it - keep the posting coming.
 

JPar

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The little Stickney is back together and essentially complete, except for some work on the ignitor. I've set it up for spark plug ignition, so the ignitor work can wait. I tried to run it and got a few putts. But then I discovered a serious issue. The crank throw, which is supposed to be a tight press fit, is slipping on the shaft. :( It's really frustrating and depressing to discover this at this stage of the game.
I disassembled the engine. Here's a photo of the crankshaft, showing the throw and crank pin. There are probably a couple of ways to fix this. I'm thinking of drilling and tapping for an axial set screw, which will be half in the shaft and half in the throw. There's probably a name for a screw like this, but I don't know what it is. The second photo is a crude drawing, trying to illustrate what I mean. The drawing also shows a set screw to ensure the crankpin is secure. I'm thinking that might not be a bad idea, and it's relatively easy to do while everything is apart. There's very little twisting torque on the pin, but it would be a disaster if it were to work its way out of the hole.

Crank.jpg

CrankFix.jpg

I'm thinking of using #8 screws. The crankshaft diameter is 0.500. The pin is a little smaller.

What do ya'll think of this approach?

Thanks,
John
 

JPar

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I decided just to go for it, and made the fixes as described in my previous post. I used 2 #8 screws to secure the throw to the shaft, and 1 #8 to secure the pin to the throw. It looks pretty good to me.

CrankFixed.jpg
 

JPar

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Here are a couple of photos of the little Stickney, reassembled with the repaired crankshaft. The engine is more or less complete, with the exception of the ignitor which is non-functional at this point. I've rigged the engine for spark plug ignition, with an electronic buzz coil and hall sensor for timing.
I've run the engine a few times, but never for more than about 30 seconds or so. It ran fairly well for short periods, but then stopped for reasons that I'm not yet sure of.
During the last run, the head gasket blew out. Fixing that will not be easy, as the head is actually inside of the cylinder casting. It will require a complete disassembly of the engine. I think I'm just going to put it aside for awhile and work on other things.
John

Stickney1.jpg

Stickney2.jpg

Here's a short video of it running.
 

JPar

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I just realized I should have put something in the pictures for scale. The engine is about 25 inches tall, including the wood base and the brass fuel tank on top.

John
 

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