how to tell if a motor can pull a certain plane - RC Groups
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Oct 17, 2001, 03:12 AM
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how to tell if a motor can pull a certain plane

Without the help of motocalc, how do you tell if a motor (glow or electric) can pull a certain plane? Would you use static thrust measurements, rpm, etc?
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Oct 17, 2001, 03:43 AM
high-speed freak
opualuan's Avatar
imho, spend the money, buy motocalc. for example, the wes-technik dc5-2.4 with 8:1 gearing and 9x3 prop generates something like 60 g of thrust.

so, any plane under 120-150g should work, right? wrong. It's kinda hard to tell unless you have tons of experience estimating it (I DON'T, that's why i use motocalc). But, if your stall speed doesn't match the pitch and stalling characteristics, it doesn't work... so, that 9x3 setup really doesn't seem to work on anything faster than about 10-15mph. so, you better match the stall speed to your setup... I would buy motocalc...

no, I don't have any association with motocalc other than using it
Oct 17, 2001, 03:55 AM
Registered User
I do own motocalc and it has helped me tremendously with electric power. However I am trying out glow power and I am back in the dark. I picked up the pattern in motocalc that bigger props with small pitch create more static thrust generally. As long as diameter to pitch is between 2:1 and 1.5:1 I think the plane should have enough forward speed to beat the stall speed. Glow engine manufacturers only recomend a few props so you are pretty limited and there is no gearing. Basically I need to find out how to measure static thrust and pitch speed like motocalc does. I just want to be in the general ballpark so that I know if my plane will maintain a reasonable speed and have good torque for its weight. Unfortuanately glow engine specs do not reveal any sort of thrust measurments or plane weight guidlines.

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