Engine S/N 755 still sounds great after 90 years of preservation and overhaul
By ANN Contributor John Schmidt

What would you do with an aircraft engine, stored in pristine condition? Fire it up for public display, of course, even if it is a very rare rotary engine.

Denny Eggers, president of the Minnesota Air & Space Museum, intends to do just that with a 1909 Gnome rotary engine at Anoka County Airport (ANE) in Blaine (MN) on Saturday, June 26th and Sunday, June 27th (weather permitting). Engine runs are scheduled for 11 AM, 1 PM and 3PM.

Though it is a round engine, the 1909 vintage Gnome Omega is a rotary, not a radial. The entire engine spins, as was the design philosophy of the time. The crank is bolted directly to the firewall, and the entire engine, prop, case, jugs... everything acts a bit like a gyroscope, spinning around at engine rpm for cooling of the cylinders.

The nickel-steel alloy engine features seven cylinders, no intake or exhaust manifold, no oil, fuel pressure or CHT gauges, and no gear reduction system. Induction system utilizes the two-cycle principle, but in operation it is a four-stroke engine. The original French Chevalier propeller will not be used, so the Museum is using a Sensenich.

"The engine was carefully packed in grease and lubricated with castor oil. It was overhauled in 2002. The engine was rebuilt by Fred Murrin, of Greenville, Penn. He's done some of the engine rebuilds at Old Rhinebeck, in New York," says Eggers. "It's the most pristine Gnome engine in the United States."

ANN was granted an exclusive interview with the restorer of the engine, Fred Murrin, of Greenville (PA).

Fred's phone answering machine identifies him as Red Baron's Flying Circus, but when you talk with Fred, he claims that it's just a bit of aviation humor. He is a mechanical engineer who started to collect rotary engines out of simple curiosity. He now owns eight of them, including the LeRhone that powers his Fokker tri-plane. His is one of only three Fokkers in the world that has a rotary engine. He's flown behind a rotary in that aircraft for more than 130 hours. Fred's operations are based at Greenville (PA) airport, 4G1. He hosts his own WWI fly-in every other September at Wright-Patterson in Ohio.

His interest in rotaries and his mechanical background led to his rebuilding expertise. This is only the second Gnome rotary engine Fred has restored. The first belongs to a private aviation museum collection in California. Fred restores the rotary engines for the Old Rhinebeck Aerodrome, in New York. He figures he's restored 20 different types of rotary engines. He is  currently working on an 80 hp LeRhone engine for Peter Jackson, director of the Lord of the Rings movie trilogy, who, according to Fred, is quite a WWI aviation buff.

"This one was amazingly complete," Fred claims, referring to the Minnesota Air and Space Gnome. "It didn't need anything. It's the most pristine example I've seen. There was a bit of minor corrosion in the crankcase, but other than that, it was perfectly preserved. These engines used to be lubricated with castor oil. When the engine cooled off to room temperature, the castor oil would harden and preserve the engine."

Fred went on to note, "These engines used to come with a tool kit specific to Gnome engines. In most rotary engines, parts of the engine are missing, and the tools are long since lost. This engine came with spare parts. And, this one not only had the original tools kit, but also came to me in the original crate with French markings on it! I wonder how much that crate is worth."

Fred estimates, by examining the amount of carbon in the engine, that, "this one couldn't have had two hours of running time on it. If it came from the original 1911 Steco airplane, I wonder if it ever flew at all. There is no such thing as a 'yellow tag' to this engine, or any part of it. This was way before there was certification to engines. I just rebuilt it, and it runs great."

Some numbers on the Gnome... according to Fred, the compression ratio of the Gnome rotary was 4:1. It is "about a seven or eight litre" displacement, and was built to run on 73 octane fuel. "It should put out about 50 HP at top engine speed of 1200 RPM."

"One interesting thing about this engine is the intake system," explained Fred. The air/fuel mixture enters the crankcase, where it goes up through a valve in the center of the piston. There is no intake push rod. The valve, in the center of the piston, is only held shut by a spring. As the piston moves, the pressure of the crankcase forces the valve open, and the fuel/air mixture enters through the piston into the combustion chamber." The exhaust is operated by a single valve in the center of the head.

The exhaust valve is the last step between the hot gas and the sky. There is no exhaust stack, manifold, or stub. The valve opens, and the gases are expelled.

Another feature of the Gnome is the fact that the engine operator must decide on and regulate the fuel/air mixture manually. Most people are amazed when, before start-up, an operator will take his finger and manually push open the exhaust valve to put some fuel in the cylinder to prime the engine.

"Everyone thinks of these engines with modern technology and practices in mind," says Fred. "Modern day engines have springs holding the valves shut so firmly that you can't push them open. The exhaust springs on the Gnome are very light, so light I can hold it open with my thumb, and people don't know how they stay closed during a run. Actually, the springs are only there to hold the exhaust valves shut for starting. Once the engine is running, centrifugal force takes over, keeping the exhaust valves tightly closed."

When asked about the oil system, Fred states that it is neither a dry nor wet sump system. "The oil is pushed in through the crank, through the ball bearings -- all bearings in this engine are ball bearings -- through passageways, caught by the connecting rods, past the piston skirts, and out the engine. It's a 'total loss' system. You land, fill up with gas and oil, and go flying again. The engine on my Fokker was built to lose one and a third gallons per hour. These are very messy engines."

Where does one go to school to learn how to work on these engines? Last ANN checked, "Gnome and LeRhone 101" were absent from the course catalogue at Embry-Riddle.

"I don't know," said Fred. "Actually, much of what I know I learned from common sense, my mechanical training, and actually working on the engines. These are fairly simple internal combustion engines. Much of what I read is not correct about these engines. For example, people who don't know always say that these engines need overhaul every 20 hours or so. Actually, the castor oil hardening after disuse is what they're seeing, not overhaul. When the passages get full of hardened oil, the mechanic simply had to take the engine apart to clean it and put it back together. I expect that you could go 200 hours between overhauls on a properly-cared for engine."

"I've discovered that most of the damage to these engines occurs when people try to take them apart without the proper tools, and wreck things using screwdrivers, pry bars, etc.," said Fred. "I usually use some solvent to break up the congealed castor oil. That, and a bit of heat from the benzematic torch, and they come right apart. You have to make your own tools to work on these engines."

The Smithsonian has a project to record rare sounds, sounds that one cannot hear anymore, such as the sound of animals on the verge of extinction, or voices of famous people. Fred thinks he will encourage them to record the sound of a rotary Gnome to add to the collection.

"They really sound nice when you hear them run," he adds. "They aren't loud or obnoxious at all, they make kind of a smooth hissing sound."

As to the price of the engine, Fred commented that "after WWI, you could buy one of these for about $30 or $40. They were so cheap that people bought one just to take it apart and see how it worked."  So, how much can one expect to spend in 2004, restoring a one-of-a-kind antique aircraft engine?

Dennis Eggers just says, "You won't believe how much the rebuild cost." This reporter didn't ask if that was unbelievably cheap or unbelievably expensive, but the engine is significant in aviation.

Fred put the engine's place in aviation history this way: "The Wrights made the first aircraft engine, for sure, but the Gnome, designed and created by the Seguin Brothers in France, was more powerful, and was widely used in Europe for a number of different aircraft designs from aviation's birth in 1903 into the teens. It's really the engine that got aviation 'off the ground' in the early days. It was so popular at one time that it was made by a number of licensees, including General Vehicle Company of Long Island, NY. The Minnesota Air and Space Gnome is an original engine from France, though."

Hear and see a rare piece of history at Anoka County Airport (ANE) in Minneapolis (MN) on June 26th or 27th. Suggested donations are $5, and will go to the Minnesota Air and Space Museum for funding of their next project, an extremely rare 1911 Steco aircraft.

FMI:  http://www1.minn.net/~farls/steco.html, mailto:Steco1911@aol.com