Ok, I’m taking a little break from the steam engine project. After getting the piston and valve made, it became apparent the precision I’m capable of with my Dremel and drill press are not sufficient for the rigors of rapid cyclic motion (as suspected from the start).

While I think more about that, I am working on a wooden arcade game that challenges the player to drop or launch .50 ball bearings down a slope to hit targets. The game will be fully enclosed (to prevent removal of the ball bearings) and will feature a pistol-grip ball launcher/gun as the input mechanism.

Below is a video demonstration of the prototype launcher. The brass receiver tube (the internal magazine) is so closely matched to the .50 balls they occasionally jam in there, so I’m looking into remedies for that. But you can see how the device drops out one ball while retaining the others until the player releases and pulls the trigger again. Ultimately, a supply of balls from within the game itself will replenish that brass tube as the player launches balls, since the tube only holds four.

I’ll post more details about how this works if the project looks ultimately feasible.

Piston/crank test

I have redone the pistons and rods quite a bit since the last post. The rods now connect to a pin I installed through the middle of the piston head and rotate in a slot I cut in same. This is more like how real pistons work and limits (or ideally eliminates) the ability of the rod to impart a torque on the piston head, which would cause it to bind.

Additionally, I used a longer rod and removed the lever between the rod and the crank. This lessens the angle of the rod to the side of the cylinder, reducing the risk of the rod contacting the cylinder, and also reduces piston head torque/binding.

Below are two close-up pictures of the piston/rod connection, and there is also a video showing the motion of the piston when connected to the crank.

Steam engine taking shape

I worked more on the rods and cranks tonight, and I now have a picture to show of the parts laid out.

The steel-colored parts from left to right are the piston cylinder, the piston itself with rod and crank lever, and the valve with its two heads, rod, and crank lever. I also put the crank itself along the top the way it will be arranged in the final product.

To do yet:

  • Cut out a cylinder for the valve
  • Cut out new thicker risers for the crank
  • Glue the crank parts and remove the sections of the 4mm rod that shouldn’t be there
  • Drill steam ports in the cylinders and run some kind of pipes or hoses between them

Rods and cranks

I continued working on my steam engine tonight. I fashioned a rod or lever to connect the piston rod to the crank in a pivoting fashion (first two pictures). These are made from 1/8″ steel rod I ground and drilled to accept a 2mm pin (jumping back and forth between measurement systems, sorry about that).

The crank (third picture) is a 4mm rod (so chosen because my old Erector set pieces have 4mm holes in them) with little plywood risers that also accept 2mm rods. The latter 2mm rods will be what the piston rods ultimately connect to. Once I get things more permanent, I’ll cut out the pieces of the 4mm rod that would interfere with the motion of the piston rods.

I’ve had a good amount of success drilling through these thin steel rods by first grinding a flat spot with my Dremel, centerpunching a guide divot in the desired spot, then carefully applying the drill press until the bit finds the guide divot.