The Best Au-To Yet

Bob Bests Third and Final Au-To Air Compressor Engine is a Hit at the Ottawa, Kansas, Power of the Past Show


| November 2005



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If this inverted engine looks familiar, well, it should. Two very similar engines appeared in Gas Engine Magazine in both the February 2004 and January 2005 issues, both owned and built by engine enthusiast Bob Best of Kansas City, Mo.

I caught up with Bob at the 11th Annual Power of the Past Antique Engine and Tractor Show in Ottawa, Kan., this September. As I was walking the show grounds that morning, just taking everything in, I noticed an engine I knew I had seen before. Upon closer inspection I confirmed that yes, this was the little burnt-orange air compressor engine featured in the January 2005 issue of GEM. It had those unmistakable lion heads and feet on the base, and I knew there could only be one set.

As I approached Bob's engines I saw another larger, brighter engine sitting next to the little burnt-orange one. Just like his other engines, this one is made from an old Au-To air compressor. Or rather, two of them.

Bob bought two decrepit Au-To compressors at a farm auction just outside of Lawrence, Kan., this past spring. He bought the pair because each of them came equipped with a belt pulley on one side, and Bob wanted matching "pulleyless" flywheels. So naturally, that required him to buy both compressors.

The crank, rod, cylinder and piston are all original, yet the engine still produces good compression. Bob machined the inside of the working side flywheel to secure the necessary governing flyweights. The cast iron flywheels were so badly pitted that Bob cleverly TIG welded strips of 0.050-inch-thick brass onto their faces. It turned out so well, even looking at it in person you'll never know what he's done until he points it out to you.

Ignition timing is controlled via a "wipe"-type ignition. The long, black shaft that runs vertically up the engine pushes the exhaust valve down and won't make contact again until the valve is ready to close. Bob says it's essentially a spark saver, which conserves a lot of energy in his total-loss ignition system. The timing gears are store-bought 2-to-1 ratio gears. Rather than use a multitude of pieces, Bob machined a cam onto one of the timing gears to make a one-piece unit. The bracket just under the working side main cap is made from a steel plate designed for securing railroad ties to the ground.