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Old 07-15-2006 | 11:51 PM
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micro_builder
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From: Fort Worth, TX
Default RE: Propellers

thats good info, thanks for posting it for us.

in the AA thread, we mentioned making a prop that matches your needs perfectly. well, say you're using a 6mm motor and you make a prop for it. you measure how much thrust you're getting and the amount of power its drawing. if you dont think its producing enough thrust, or if its drawing too much power, you make a differant prop and test it. as you mentioned, it can be a time consuming project, but eventually you would have a prop that gives you the most amount of thrust, for the best amp draw.

all motors have a max power RPM and a max efficiency RPM. if you had a tachometer, you could check the props RPM along with the thrust and amp draw to get an even closer match.

on top of all that, you could try motors of the same size, but with differant resistances.

this link has some incredibly usefull info for this sort of thing. Gordon Johnson did all the tests, and he knows his stuff. check out the rest of his site while you're there, he's got a lot of lipo and actuator torque tests, lots of other info, and some nice models too: http://home.comcast.net/~gordon-johnson/home.htm with all the info on that site, you could figure out the perfect electronic setup for whatever plane you're doing.

thrust stands arent too difficult, and there's lots of differant kinds. i havent gotten a chance to build mine yet, but i'll need to soon. the easiest is an L shaped design. i attatched a pic. best way to figure out if yours is accurate, is to test the same prop and motor that has been tested before and see if they're close. doing this sort of thing could basically be a 2nd hobby, but getting the right prop for the motor you're using will help figure out how big of a battery you need, and give you an estimate if she'll fly. static thrust tests dont always match in-flight thrust numbers though. when the prop is going through the air when the plane is flying, it unloads a little and usually produces better numbers.

nick
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