Originally Posted by WyrTwister
At first thought , I find it puzzling , for the roller bearings would have had to be split too ? Did they also have split inner and outer races ? Again , it seems like they would have had to ?
The rods do have "rotations" separate from each other. Not a full rotation but as the crank spins the rods would turn slightly different; if you pick one rod as a reference point, at times the other would be rotating clockwise, then counterclockwise. Thus the roller for each rod surface would have to be separate, to allow for the rotation necessary.
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Makes me wonder , what the average engine life , in hours , was ? Were conventional insert bearings wearing out in that time period ? If not , what was the point in using roller bearings ?
I don't think it was very high at all. At least for us, we used high amounts of lead, and these were carb engines on what we'd think of as lousy motor oil.
The recent B-17 crash had me look it up; the one that crashed was painted to look like a real B-17 from the war. From the "real" Nine-o-Nine:
https://en.wikipedia.org/wiki/Nine-O-Nine
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Her first bombing raid was on Augsburg, Germany, on February 25, 1944. She made 18 bombing raids on Berlin. In all she flew 1,129 hours and dropped 562,000lb (225 tonnes) of bombs. She had 21 engine changes, four wing panel changes, 15 main gas tank changes, and 18 changes of Tokyo tanks (long-range fuel tanks).
I'm not sure if that 1,129 hours is flight time to/from Germany, or total. But if total... she needed a new engine every 54 hours. 4 engines so that's what, 220 hours MTBF? Cruising speed of 250 mph, so engine lifespan of 55,000 miles? time for the aero guys to chime in, they know more than I do.