Has anyone ever checked the rotor speed of their machine? I just got back from the field made two nice flights on my Kellet The AK-2 There was a helicopter pilot there and he had a optical tach and he used it to check my in flight rotor speed This is a rotor with 36 inch Aerobalsa blades that I cut down to 2 1/2 inches wide I cut the undercamber off of the 2 3/4 inch blades Well on a slow pass the blades were turning 670 RPM on a high speed pass 820 RPM I would be interested to know if anyone has any comparable numbers There was a wind around 12 mph and passes were into the wind

900 rpm on the sparky (650g, SG6062, 1deg incidence), pretty stable. approx 600-700 rpm on the Pitcairn PA22 from A Co Az (1750g, clark Y, 1.5 deg incidence). And around 500 RPM on the Kirara (1850g, airfoil ?), which is too slow except if you increase tip weight.

For comparaison, a full size Magni M16 fully loaded has its rotor turning at approx 380 rpm (420 kg).

The rotor of the 1/10e C30 runs at 600 rpm (Weight 550g) with scaled blades (Rotor diameter 113 cm, clark Y, 1.5 deg incidence).

I recorded my BEGI between 1000 to 1100 rpm (Aerobalsa blades).

The problem is that rotor speed is highly dependent on airfoil, blade incidence, giro weight and blade shape. 1 degree less in incidence can cause the speed up by 100 to 200 rpm. Same if airborn weight increase or lift coefficient of airfoil is lower.

My G3PO, etc. are around 1500 from a skytach.

Hi Al...
The article that Les Garber and I published in RC Modeller, August 2001 has some data we recorded in our wind tunnel tests at the U of Minnesota tunnel. If you don't have a copy, I can send you one. (let me have your surface mail address.)

Bill