Got the new propeller from Prince some time ago (in Mars). It took some time, but it is nice indeed.
Showing posts with label propeller. Show all posts
Showing posts with label propeller. Show all posts
Wednesday, October 14, 2020
Sunday, February 15, 2015
Propeller moment of inertia
In my quest for investigating the press fit hub, the propeller moment of inertia was a needed parameter. The only practical way of finding the inertia is by doing an experiment with the propeller as torsional pendulum. This is explained by EAA here, and by Hepperle here.
I don't have a Rotax diagram, so I did it as described by Hepperle. My dimensions were:
m = 2.5 kg (measured with a bathroom scale, not very accurate), 2e = 6 inch, a = 126 cm. I measured 5 full periods, and they were 38 s on average (did it 4 times). The period time, T, became 7.6 s. The propeller moment of inertia is:
Ip = m*g*T²*e²/(4*pi*a) = 0.165 kgm²
The bathroom scale could be rather inaccurate for this low weight, but good enough for the purpose.
I don't have a Rotax diagram, so I did it as described by Hepperle. My dimensions were:
m = 2.5 kg (measured with a bathroom scale, not very accurate), 2e = 6 inch, a = 126 cm. I measured 5 full periods, and they were 38 s on average (did it 4 times). The period time, T, became 7.6 s. The propeller moment of inertia is:
Ip = m*g*T²*e²/(4*pi*a) = 0.165 kgm²
The bathroom scale could be rather inaccurate for this low weight, but good enough for the purpose.
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