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


| February 2005

  • 02-05-017-RWpic-01-piston-rod-bearing.jpg
    Assembled piston, connecting rod and bearing.
  • 02-05-017-RedWingX.jpg

  • 02-05-017-RWpic-05-cam-2.jpg
    Assembled timing gear components.
  • 02-05-017-RWpic-02-piston.jpg
    Holes drilled in the piston allow the wrist pin to be attached.
  • 02-05-017-RWpic-03-rod.jpg
    The wrist pin end of the connecting rod is made from a piece of 1/2-inch round tubing, turned sideways and brazed to the rod itself.
  • 02-05-017-RWpic-07-cam-4.jpg
    Here you can see the cam mounted on the gear itself.
  • 02-05-017-RWpic-06-cam-5.jpg
    A standard bolt was modified for use as a shaft in the assembly.
  • 02-05-017-RWpic-08-cam-3.jpg
    Arrow points to the sleeve, slid over the shaft, that protrudes past the gear and comes to rest against the engine frame to allow the timing gear to turn freely.
  • 02-05-017-RWpic-09-3-timing.jpg
    Timing gear assembly installed on the engine.
  • 02-05-017-RWpic-10-timing-w-gov.jpg
    Arrows point to the latch-out bar, which is controlled by the governor and shift collar
  • 02-05-017-RWpic-11-valves.jpg
    Valves fabricated, machined, lapped and installed in the head.
  • 02-05-017-RWpic-12-head-1.jpg
    The head mounted to the engine, including valves, rocker arm and pushrod.

  • 02-05-017-RWpic-01-piston-rod-bearing.jpg
  • 02-05-017-RedWingX.jpg
  • 02-05-017-RWpic-05-cam-2.jpg
  • 02-05-017-RWpic-02-piston.jpg
  • 02-05-017-RWpic-03-rod.jpg
  • 02-05-017-RWpic-07-cam-4.jpg
  • 02-05-017-RWpic-06-cam-5.jpg
  • 02-05-017-RWpic-08-cam-3.jpg
  • 02-05-017-RWpic-09-3-timing.jpg
  • 02-05-017-RWpic-10-timing-w-gov.jpg
  • 02-05-017-RWpic-11-valves.jpg
  • 02-05-017-RWpic-12-head-1.jpg

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.