Small engine

[Brad]

I decided to challenge myself and work on making a small model engine.
Got the plans online and the majority of the material are on now on hand. Still need to get some taps and dies but that isn’t a big deal, just an expense.

I went with steel for the flywheel as brass is really expensive when it needs to be 2.75” in diameter.

First part worked on is the flywheel. Never needed a bolt hole circle so that was a learning experience. I also made a mandrel to turn the outside to final diameter after the majority of the turning was done.

 

[KeithB]

Good start.

 

[Brad]

I spent almost as much time thinking about how to make the part as I did making it. Getting the hub and outer rim diameters right took some thought and a search for a cutting tool with the right angles on it,
Bolt hole circle was easy once I got it in the DRO. Looking at it the math wouldn’t be too hard to calculate it by hand, just a simple trig problem really.

Need to get the bearing before I can bore the hub to final size.

Next up will likely be the cylinder. Need a smooth, straight, parallel sided bore for proper running.

 

[KeithB]

What material do you plan to use for the cylinder and piston? Is the piston a standard size that you could use a piece of hydraulic cylinder rod or even a piece of turned ground and polished tool steel? Nice and round and smooth to start with...

 

[Brad]

Plans call for stainless for the cylinder and graphite for the piston and valve. He used graphite for the piston and valve as it is self lubricating and doesn’t corrode. The stainless for the cylinder to eliminate corrosion issues.

He used a 22 mm bore for the cylinder and said the piston needs to be within .01 mm for proper running.

He used an adjustable reamer run by hand to get the cylinder bore right. Small adjustments, lots of oil, and patience.

I was leaning towards using the largest boring bar I can in the lathe. A 22 mm reamer would be 50 bucks or so and wouldn’t be something I would likely use again.

 

[popper]

Air or steam operated?

 

[Brad]

Neither. Strictly a vacuum engine.