Oscillating Steam Engine Model
While looking around the internet for a new project to keep me busy for the weekend, I came across the plans to make this little model engine. I found the plan on Prof. McCabe's Engineering Students site.
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These are small parts!
The upright beams are 1/2 " square stock. The flywheel the print called for is 1" diameter and 1/2" thick. It proved to be too light to carry the engine through it's cycle, so I ended up making a heavier one. Same 1" diameter, but 1-1/2" long.
Another issue was too much friction between the crankshaft and the frame bore. To fix that, I bored the frame out to .250" and made a tiny brass bushing with .002" clearance on the crankshaft. The crankshaft was made from sections of .165" pins fit into a link, made of .083" thick flat steel.
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Making the parts was easy. Making it run was another thing. After making a heavier flywheel, bushing the frame, grinding clearance on the cylinder for the crankshaft link and enlarging the air holes in the frame and cylinder, I did get it running.
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OK, let's see if I can explain how it works. It's pretty simple actually.
The cylinder on the left has a hole that intersects the cylinder bore. The cylinder pivots on the main frame at the hole labeled 1. Air enters the frame through intersecting holes on the right 2. As the cylinder pivots over that hole, air enters the cylinder forcing the piston down, and the cylinder pivots to the right. Flywheel inertia continues the cylinder movement. As the cylinder lines up with hole 3 in the frame, which is a through hole, the air pressure escapes, allowing the the piston to pass top dead center, and line up with the air inlet hole again. OK, that's kind of a sloppy definition.
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This is the end result.
And the video of it running for the first time.
