Originally Posted by
Chris Scott
Well EDML, I'm not going to take the bait! But I'm not sure that a change of only 20 (prop) RPM would look totally different. That would be only one blade per second on a 3-blader, and my pocket camera records at 25 frames per second.
BTW, I gather the RPM on a R2800 at take-off is 2800 RPM at sea-level, but may be 2700 RPM at about 5000 ft. According to Janes, reduction gearing is 0.375 : 1 (3 : 8) - giving prop speeds of 1050 RPM or 1012 RPM respectively (roughly 52 or 50 blades per second).
Hi Chris,
from what I could find out the reduction gear for the R-2800 is 16:9. With a framerate of the camera of 25fps that would be 2666 engine RPM for the prop to look stopped: (25 RPs * 60 * 16) / 9.
That is pretty much in line with the 2700 RPM for the R-2800 at T/O power.
Hard to tell what that means for the perceived rotation of the prop.
Marcus