Compressed air, stored at 3500 psi in three scuba tanks, enters the McLeish engine's cylinder through what was the spark-plug hole at the top of the remaining cylinder. Coming up with a throttle took a lot of experimentation, but the solution was a simple ball check valve, McLeish simply added a return spring and linked it to the accelerator pedal.
Two conventional high-pressure regulators were used to meter the air leaving the tanks.
Getting the timing right was the greatest hurdle. "I looked at using solenoids," McLeish says, "but we couldn't find ones that would close fast enough. Eventually what we came up with is what I call a 'tubular rotary valve.'"
McLeish's tubular rotary valve is basically a piece of pipe with a hole in it mounted to the end of engine crankshaft. As the pipe spins in its housing, it allows the air through from the input hose to the hose that runs to the top of the cylinder.
McLeish's exquisitely small, steel tube-framed "Silver Rod" can be configured as either a streamlined motorcycle or as an open-wheel "lakester," depending on which axle assemblies and wheels are bolted in.
Despite the fact that there's nothing on board that is likely to ignite, McLeish wore the required fireproof suit. Seems ridiculous in the usual high temps of summer in Utah.
Except for its low speed, McLeish's run in the compressed-air powered Silver Rod was uneventful—and he topped out at a scorching 54.058 mph. Based on his two-way average speed of 46.723 mph, he set a record.