LeRhone Gnome

Very cool video, thanks for posting.

 

As I mentioned on Adrome, that is one fine running engine.

 

Is this engine going into an aircraft, or ground run only?

 

While looking up into the sky at WOW in 2008 I could hear the chop as the mags were switched off - the aircraft was overhead at the time and could just make out the announcer describing how the pilots slowed everything up a bit during WW1

 

Planes using that engine could turn one way on a dime, but the other... forever. (or Just due to the force of the rotating mass of all the cylinders.

Crankshaft was fixed, bolted to the firewall and the prop was bolted to the cylinders.

 

I was just looking through a book written about the operation and maintenance of rotary engines published in 1918. Written by Paige. I was amazed at the machining tolerances then but if one thinks about the rotating mass of a Clerget it better be in balance without any slop. Wonderful video !
Switches

 

Tcar- Aircraft with rotary engines turn fine in either direction, a common misconception about rotaries. The gyroscopic forces tend to make them climb in one direction and descend in the other unless control forces are used to counter the precession. I have good friends who fly aircraft with rotary engines, and there are many old wive's tales out there we work to dispel. Fred Murrin, who has a LeRhône 9Jb Fokker F.I Triplane and a Gnôme 9N Camel, and I published an article on the Gnôme 9N engine in the WW- I historians' magazine Over the Front. This is the same engine shown in Tom's video, I believe.

As Tom knows, LeRhône and Gnôme were two separate engine manufacturers whose engine designs were quite different. The 9N actually used intake ports instead of pushrod driven intake valves, which the LeRhônes had. The 9N used relatively conventional (by rotary standards) pushrod driven exhaust valves.

Tom also simplified the details of the ignition system because it is quite difficult to explain. In actual fact, to control the rpm/power on a Gnôme 9N, used in both the Camel and Nieuport 28, the firing order is actually changed. Every cylinder still fires before the order is repeated to prevent spark plug fouling, but the time interval between firing pulses is increased so that you get an equivalent of a 50% or 25% throttle, although throttling is not involved. Unlike the LeRhônes, the Gnôme engines did not use a carburetor, but a simple, unthrottleable injector. A coupe or blip switch, which grounded the ignition, was still used when the 25% position did not slow the engine sufficiently, but its use at the 100% position was not recommended and could cause engine failure from the abrupt torque stop and start.

Fascinating engines and I have a dozen or so books on them, most from the WW-I period. Let me know if anybody has questions on the 9N ignition system, and I can explain more fully. Most people's eyes just roll back at retro-tech stuff.

Taz
Terry Phillips