Originally Posted by
DaveL322
Hi Jim,
I think from a narrative perspective, "we" have come to use phrases like "more torque" in imprecise ways
My intent was to convey that a geared system generally has peak torque available over a broader RPM range (when compared to direct drive) and a geared contra system has a broader torque range than a geared single prop system. So, the contra has "more torque" when considering the full range of throttle. In practice, when transitioning from horizontal flight to a climb, the airspeed lost (given constant throttle position) is the least with a contra, and the most with direct drive. And with the larger surface area in the prop disk of the contra (and the taller gearing), the braking effects are also greater, so the end result is less throttle work is required to fly constant speed.
It would be interesting to see a speed/torque curve for our "power units". I assumed that both direct drive and geared have the same linear curve from max torque at zero rpm to no torque at max rpm. I was trying to make a case in my mind that the geared motor would spool up faster as the load at the motor output (gear box input) is much lower than the direct drive. I don't know how to quantify that but it probably is not significant. The contra is another case. It is geared for lower rpm and more torque and thus can swing larger props that are no doubt more efficient. Another advantage is the torque on the airframe is reduced by the gear ratio, by about a factor of ten.
Have you seen the videos of the guy with what looks like a helicopter head for variable pitch and vector control? That could really be interesting.
Best Regards, Jim