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Old Feb 27, 2004, 03:47 PM
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Jody Bradshaw
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Question

What is the difference in the GW/EPS-300C (2/1/A/B/C/D)?


GWS lists GW/EPS-300C (2/1/A/B/C/D). All these different models. What's the difference?2/1/A/B/C/D
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Old Feb 27, 2004, 04:30 PM
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These are the different gear ratios. Why they use both letters and numbers to designate the gear ratios is beyond me. Note that the ratios for the EPS-400 are different from the EPS-300, as are the IPS (DX). With enough time you may end up memorizing the more common ones (C=5.33, D=6.6, B=4.4 or so, A=3.75). The higher the gear ratio the larger the prop it can spin, which tends to be more efficient than spinning a smaller prop faster.
Old Feb 27, 2004, 06:06 PM
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Jody Bradshaw
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Prop size.


When figuring prop size is the 1st # the length and the 2nd # the aggresivness of the pitch on the blade? Give me an example, Of say a 12x4.
Last edited by JMBRAD; Feb 27, 2004 at 06:08 PM.
Old Feb 27, 2004, 07:32 PM
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The best analogy for 'pitch' is to imagine your 12x4 prop is (a bit like a corkscrew) rotating in a mass of Jello. For each complete revolution of the prop it will move forward 4". A 6" prop would move 6" and so on. "Pitch speed" is important in flying planes at a suitable airspeed and can be calculated from an equation, simplified as: pitch speed (mph) = rpm x pitch (inches)/1052.

Cheers, Phil
Old Feb 27, 2004, 07:43 PM
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Thanks Phil.

Are there any free programs similar to Motocalc that calculate flight times given a particular motor, prop, and battery?
Old Feb 28, 2004, 09:39 AM
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http://brantuas.com/ezcalc/dma.asp


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