Building the 1/4-Scale 5 HP Red Wing: Part IV

| February 2005


Assembled piston, connecting rod and bearing.

Editor's note: This is the fourth installment in a planned five-part series on building the scale Red Wing engine.

It's that time again! This month we'll cover the piston, connecting rod and bearing, as well as the timing assembly, pushrod and valves. There is quite a lot of material to cover, so let's get started!

Step 13: Assembling the Connecting Rod, Piston and Bearing

The piston is made of 1-1/4-inch cast iron round stock, 1-3/4-inches in length and uses a 0.312" (5/16-inch) diameter wrist pin (Photo 1). After adding its two piston rings, my wife said, "It's just the cutest little thing!"

I used a parting tool to cut the slots for the piston rings, which worked very well. To hollow out the piston, I drilled a 1/2-inch hole in the bottom while it was still in the lathe. Reaching through the hole, I used a carbide cutter and turned the piston from the inside out until my wall thickness was about 0.100".

To allow room for the connecting rod, I used a 1/2-inch end mill to cut a little deeper into the piston (Photo 2). The arrows point to holes drilled for set screws that are used to hold the wrist pin in place.