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


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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.

The cylindrical piece under the head (where the spark plug is located) was a piece of 1/2-inch wall steel tubing, which Bob thinks may be a cylinder from some kind of aircraft (Bob was a crew chief for 30 years in the fuel division of what was TWA prior to his retirement). According to Bob, this piece took a considerable amount of machining to make it work. He also cut a small access hole in the side of it so he can keep an eye on the exhaust valve and make any necessary adjustments.

Fuel is introduced through a mixer built by Bob. It is similar in design to the mixer seen on his blue Au-To engine in the February 2004 GEM. It is made of simple brass fittings, with a brass venturi inside, soldered in place.

The muffler was cast by one of Bob's fellow Mo-Kan Antique Power Assn. (Kansas City, Mo.) club members, Leonard Arbor. Bob claims Leonard does a lot of casting for the club members and his work is always top-notch. The heavy, sphere-shaped gas tank was originally used as a watering bottle (for watering flowers, plants) from India, bought for $10 at a swap meet. Bob machines his own grease cups because he claims he can make them faster than they can be shipped to him if he bought them.

Bob prepped the engine's surface, then custom-mixed his own shade of Rust-Oleum paint and sprayed it on the engine. He then took his trusty polisher to all the brass, as well as the steel crank, shining everything up to a high luster. After that, he went around and pinstriped the engine in a nicely contrasting gold. Finally, he built a "scrap wood" base that's been planed, sanded, routed, stained and top coated with polyurethane. The wheels on the base are your everyday, run-of-the-mill cast iron wheels found at most any hardware store or Harbor-Freight-type outfit.

Anyone who has taken on a sizeable project such as this will know just how many trips it takes to various scrap yards and hardware stores to get everything needed to complete such an undertaking. Bob says he, too, had to make countless trips to get all the right materials. But noticing how resourceful he was, I asked, "You're quite the recycler, aren't you Bob?" to which he replied, "I just prefer to use what I've got before I buy something I don't really need."

As for the inverted compressor engines, Bob claims this is the last one he will build, as this is the third one. All we can do now is hope he changes his mind.

Contact engine enthusiast Bob Best at: 3521 N.W. 60th Terrace, Kansas City, MO 64151;