Beam Engine
I decided to try to make my first spoke flywheel for this model. It was a learning process to say the least. The first attempt was a disaster. The second attempt went well until I drilled 6 holes 30 degrees out of location. The third attempt produced a usable flywheel. The print looks simple enough.
Now making it wasn't so simple. To start the print calls for it to be 2-1/2" O.D. All I had was 3" aluminum bar. So to start I cut a 1/2" thick disk from the stock.
Next I faced one side and turned the O.D. to size. I could only chuck on 1/16" and you have to spin aluminum pretty fast to get it to cut cleanly, so it was interesting. Having done that, I tuned the undercuts and drilled the bore for a press fit on the eccentric hub that I'd already made.
This flywheel is to have 6 spokes. To do that you first have to lay out the holes. I used this formula to determine the distance between the holes.
B = D x sin( 360 / (2 x N))
where
B = distance between
bolt holes
D = diameter of bolt circle
N = number of holes in circle
OK so I ended up with something that looked like this.
Next I set a piece of 1/4" round stock in the mill vise that was a snug fit to the bore. Doing that I can just rotate the flywheel around the pin to drill the holes. It should keep them all on the same radius. First all the holes were center drilled. After they were all drilled I used a 1/8" end mill to cut the outer radius of the pockets. I dropped the end mill into one of the drilled 1/8" holes and rotated the flywheel on the pin to cut the radius.
Next the spokes were laid out and cut with a scroll saw. A little cleaning up with a file, and it looks OK. Not perfect, but not too bad for a first time attempt.
By this time I had already made the cylinder. It was made from a solid 5/8" round bar. Air will flow to the top and bottom of the cylinder through .040" ports that were drilled from the outside. After drilling the hole that pass through the valve bore into the cylinder, the outside holes were soldered closed. A 3/16" air inlet tube was then soldered onto the side.
The valve and piston were were made from brass stock. The valve is 1/8" O.D. with 1/16" undercuts. I used a part off tool to cut it. The piston was made from 1/4" brass. The rod area is 1/6" dia. I was able to set it up between centers in the lathe to turn it. The picture shows the valve and piston assembled to the cylinder head. All the parts including the piston rod guide hade to be in place before soldering the rod ends on.
The crankshaft and it's linkage were next. A couple of rod ends were made from 1/4" square brass. The rod is 1/8" brass threaded 4-40 on one end to match the 4-40 thread tapped in the beam rod end. The picture also shows the valve eccentric. That was actually the first part I made for this engine. I wasn't sure I'd be able to make it at all with my awkward 4-jaw chuck. Once it was done I decided to carry on with the project.
I'd been a little concerned about making the valve linkage. A lot of tiny parts that have to line up perfectly. I tackled it tonight, and it was about as difficult as I had anticipated, but it did come together.
The two side beams are 1/32" thick and 1/8" wide. The pin through the top is 1/16" with a press fit to the beams and clearance fit to the valve. The lower levers are pressed onto a .093" shaft that runs through the base. Each one has a .060" X .125 pin pressed into it. They protrudes inward that slip into clearance fit holes at the bottom of the beams. Pressing a .060" pin into a 1/32" beam takes some good old fashioned finesse. Thank goodness for magnifier safety glasses!
The last part to make was the valve connecting rod. It runs from the eccentric hub on the crankshaft to the lower valve lever. It wasn't nearly as difficult as I had expected it to be, but it did take a lot of tweaking to get it right.
The connecting rod can be seen in this picture.
And it's FINISHED!
Better yet, IT RUNS!
