Rotary Internal Combustion Engine

I do tours at Air and Space by Dulles and one of the things I talk about is engines. Remember the time frame. It is 11 years since the Wright brothers first flew with a 250 pound engine that produced 12 hp and 5 years since the Wright brothers commercial engine of 1909 that was 200 pounds and about 30 hp. Both water cooled. The Seguin brothers, Gnome et Rhône Model J rotary was about 325 pounds and 110 hp. Since it spun, there was no way to do a carburetor, so it always ran full power. Gasoline and oil were mixed in the crankcase. The pilot could throttle it with a switch on his stick that grounded the magnetos, When he did that he got a face full of unburned gasoline and engine oil. One of the reasons for the silk scarf. The engine oil was caster oil (that at the time had another use). Since it ran at full speed all the time, cooling was less of a problem. The cylinders were steel with the cooling fins cut on a lathe. This was the most popular engine in the first half of WWI with about 100,000 made. 9-cylinder, with spares, that meant that about 1 million cylinders were hand turned on a lathe. The engines were good for about 15 hours between overhauls, but that was not much of a problem since the aircraft rarely lasted 10 missions (roughly 1.5 hours at most for a mission). The first models had the intake valve in the piston. Without any springs or pushrods, the valve would pop open on the downstroke when the exhaust valve opened, allowing fuel to be drawn into the cylinder from the crankcase area. Unfortunately it was also very difficult to service. It works great until a valve sticks and when the spark plug fires the crankcase comes apart. The second model had to run both valves from one rocker, so no valve overlap and a loss of power. The third model used the Monosoupape (single-valve) system instead, using a single exhaust valve at the top of the cylinder and using a series of ports to allow the fuel mixture into the top of the cylinder when the piston had moved down in the cylinder past the ports. Very similar to all high performance two stroke engines today.
 
Illinoyance, your description is correct for some WW1 rotaries, but not all. The Gnome Monosoupape works as you describe. As you can see above, the Le Rhone has both intake and exhaust valves.
 
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