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Old Feb 27, 2004, 03:47 PM
Jody Bradshaw
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Salisbury, North Carolina, United States
Joined Feb 2004
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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
Motor Maniac
Orange County, CA
Joined Feb 2002
2,875 Posts
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.
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Old Feb 27, 2004, 06:06 PM
Jody Bradshaw
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Salisbury, North Carolina, United States
Joined Feb 2004
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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.
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Old Feb 27, 2004, 07:32 PM
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Chattanooga, Tennessee, United States
Joined May 2003
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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
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Old Feb 27, 2004, 07:43 PM
Jody Bradshaw
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Salisbury, North Carolina, United States
Joined Feb 2004
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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?
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Old Feb 28, 2004, 09:39 AM
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http://brantuas.com/ezcalc/dma.asp
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