Rotary Engines.

[Crash]

Hope I'm not asking a question thats allready been beaten to death but does anyone know how long a rotary engine would last? Can't think of anything getting more abuse and especially with an aircooled motor the temperature ranges must have been in the redline range during a dogfight. Modern day radials with the best in technology that get handled with kid gloves only last in the range of 1000 hours.

For all intents and purposes an RFC rotary lasted 40 flying hours. After that point it was taken out of its machine and sent to the central workshops for a complete overhaul. (Stationary engines had this done every hundred hours.)

Given the number of diary entries about "dud" engines I've seen, and the frequency with which those duds were replaced, I'd guess that many rotaries didn't make it to the 40-hour mark.

(For comparative purposes, let's assume that 40 flying hours works out to about two and a half weeks of steady routine flying. During more hectic periods you could put in 40 hours of flying in eight to ten days.)

I read McCudden's book a few months ago. He was working on aircraft engines even before the war started.
I can't remember the exact numbers but the period between engine changes early on was very short. McCudden and his mates developed engine modifications that allowed them to extend reliable service cycles. I think they even applied these to new engines and the rebuilds they received from the depot.
He also talked about the required maintainence that was applied during normal service cycles. Some components, like exhaust valves ,had to be relaced at short intervals because the metallugy of the time couldn't produce items that would last.
The use of castor oil as a lubricant suggests that lubrication was a problem on rotories. Bean oil was and still is a very fine lubricant. Mc Cudden and his cronies spent a lot of time cutting groves and channels to increase oil flow to keep cylinders from frying.
One thing I can't figure out is what type of oiling system they used. Was the castor oil premixed with the gas or was it a total loss sytem that pumped the oil from a tank?
Charlie

[R Pope]

Castor oil was used in rotaries because the lubricant sprayed in all directions, soaking man and machine. It is not flammable, which would be a great comfort to the pilot! Even if they had to make a fast trip to the privy after every flight. And yes, it was a "total loss system."

[Crash]

Interesting info. That would explain the oil markings on this photo between the cowl and fuselage, and he's not even airborne yet!

Actually, castor oil was used in rotaries because it was the only lubricant available at the time whose viscosity didn't break down under the stress of use in a rapidly rotating engine.

[Rbailey]

Originally posted by Michael Skeet@Apr 18 2004, 02:30 PM
[b]Actually, castor oil was used in rotaries because it was the only lubricant available at the time whose viscosity didn't break down under the stress of use in a rapidly rotating engine.

I thought castor oil was used because gasoline is not soluble in it, as it is in petroleum based lubricants. Because of the way fuel is fed into a rotary, dissolution in the lubricating oil would interfere.

[R Pope]

There are any number of oils that would work perfectly in a rotary, but the only one available cheaply and in quantity in the time frame that wasn't flammable was castor oil. The non-flammability issue cannot be overstressed--regular oils would mean every flight would end in a fireball.

[R Pope]

"dissolution would interfere"? Millions of chain saws, skidoos and lawn mowers would prove you wrong.

[jumpinjan]

I have ran 2-stroke engines on castor oil mixed with gas from back in the '60s. This was straight from a can of castor oil (not a racing castor oil that was meant to be mixed with gas). It mixes pretty well and it's not what you think; Like oil & vinegar salad dressing. It doesn't really dissolve completely (completely transparent), but I was amazed how well it worked in my Sears Moped.