When I first started building VP props I used to do test runs with a torque meter and 1/4 motor (F1D) on a jig I cobbled together. It was useful to see when the spring would start closing the prop and how long until the prop was in full low pitch. I found that the motor runs would be about 10 to 15% longer than actual flights with the same sized motors and the RPM was also slower than in flight do to larger loading in the still air. I found that the information was next to useless, other than seeing the VP mechanism function, flying was the best way for me to get useful information and a proper prop setting, plus a lot more enjoyable that sitting and recording RPM and torque while a prop spins on a stand.
I think that Bernie Hunt got some useful data from his spinning arm jig as he simulated flying speed with a drag plate to control the rotation speed. He could then compare speeds, and RPM generated with different props and rubber motors, and he could if I remember correctly record the torque though I don't know if he stopped the jig to record the torque or he could read it as it rotated.
I still think flying is more fun.
Fred Tellier
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Received on Mon Apr 30 2007 - 15:18:39 CEST
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