SCIENCE DIY

SCIENCE

EXPLOSION ENGINE

DIY internal combustion using Home Depot parts. By David Simpson

A few months ago, some of the cadets in my Civil Air Patrol squadron were stumped by the chapter we were reading on internal combustion engines. The pictures failed to convey what really happens, and even the word “combustion” sounds like what a candle does. Engines are all about explosions, front and center! So we needed to make some explosions and show the students how these blasts get turned into the power that runs cars, airplanes, and weed whackers.

I thought it would be fun to make my Internal Explosion Engine entirely out of parts available at Home Depot, and I did it (almost), basing my design on the classic PVC spud gun. The result has all the parts of an engine and shows how they work together. After building this project, you’ll feel a lot more knowledgeable talking to your mechanic.

160 Make: Volume 13

Overview

Our combustion cylinder is 2" PVC pipe, and the fuel is butane, which you squirt in manually. The ignition spark comes from a piezoelectric grill starter wired to 2 pairs of screws inside the cylinder. A 12V electric air pump blends fresh air with the butane and flushes out the exhaust.

The explosion forces down a PVC piston and its dowel connecting rod, turning the galvanized pipe-and-flange crankshaft, which rotates 4 or 5 times until balance weights on the flywheel pull it back for the next firing. I made the frame from a PVC composite board that tools like wood, but looks spiffier. A complete list of materials and tools is on page 164.

Construction

Keep everything as square as possible, so linkages

Photography by David Simpson