The basic machine is built as a stand and height-adjustable ramp that are combined together with a wood starting gate. This section of the basic machine does not cover the different “samples” used in the demo nor the other modifications I’ve made for the machine.
Design for start gate and final assembly
Pro tip on the design: I’ve given specific numbers for the dimensions of the different pieces of wood used to build this machine. However, you should definitely just buy materials that are close to these sizes at your local hardware store; if you’re numbers don’t exactly match, you’ll be fine.
Ramp Assembly:
1) The disassembled machine: The starting gate, ramp, and height board are all detached.
2) The height board is attached to the support block on the stand using 2 3″ long, 1/4″ bolts. 
3) The ramp is laid diagonally on the stand. The top of the ramp makes contact with the height board, while the bottom of the board rests against one of 4 purple stopping blocks.
The 4 purple stopping blocks are shown in the machine stand design. The position of the blocks are calculated so that the ramp will be either 5″, 8″, 11″, or 14″ high (approximate stand-to-ramp angle 12°, 19°, 27°, or 35°, respectively).
4) Assembled machine. Balls are placed up-ramp above the starting gate. To start balls rolling down the hill (to separate the balls), the wood gate is removed by hand.
All images/designs: Copyright Rachel M. Eaton, 2019. Access to these designs is for non-commercial purposes only.
Rae Eaton 