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Old 01-11-2006, 07:55 PM
fly boy is offline
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brushless

hey guys
i need to under stand somthing foamys usaly require
2 to 3 times the thrust to wight rasio am i right
ok im working on a few foamys now. i found that i
can get a Himaxx 2015 4100 for $49 now drop it in
a 6.6 to 1 gear box and a 12 6 prop you have 26 oz
thrust or thers the axi 2212/34 $89 a 11 4.7
at 22 oz thrust so how can these combos hover a 10 to 16 oz foamy at 1/3 throttal.
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Old 01-11-2006, 11:10 PM
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It will fly!!!
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Washington, Indiana
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Re: brushless

Your best bet is to go with an outrunner type motor. They have more torque and fewer things to go wrong. If you use a gear box you always have the chance of stripping gears. I have been using a Hacker A20-22L for my foamies all year. I found that if you mount them as an axial mount they are tough. I hate to think of how many times the entire motor has been ripped from the front of the plane without damage to the motor.

As for thrust to weight. most say 1.5 to 2 times thrust to weight. Most of the faomies that I have flown have an all up weight of about 16 - 17 oz. they say that the Hacker is about 35 oz of thrust. I can hover at about 1/2 throtle. unlimited vertical
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Old 01-12-2006, 12:46 AM
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Re: brushless

Props are more efficient at lower RPM's, that's why you can hover at 1/3 throttle, yet not take off like a rocket when you hit full throttle. As prop rpm's increase, more and more air gets slung outward and less and less air is diverted back, so to speak, in the form of thrust.
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Old 01-12-2006, 12:50 AM
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Lodi CA
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Re: brushless

If you really want a good flying foamie its gotta be under 7oz Get the little axi or a little screamer and a 350 milliamp pack and cirrus servos and a phoenix 10.......then slap it all on an Animal or Shocky then go to your nearest gymnasium and proceed to Huck it up.
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Old 01-12-2006, 08:06 AM
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Re: brushless

Just a little gee-wiz info, but thrust is not the result of air being thrown rearward to make the plane move forward. It is the result of the low pressure in front of the spinning prop that draws it forward.
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Old 01-12-2006, 08:38 AM
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Temecula, Mexifornia
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Re: brushless

Fly Boy,

Foamies are not any different from nitro or gassers. A 1.5:1 Thrust to Weight ratio is good enough for decent 3D. I like outrunners too, but I stick with AXI for the quality. Himaxx is not bad, and they are cheap, but you can't push them like you can the high-dollar motors.

The deal is, to keep it light, you are forced to push the motors over spec considerably. Most everyone does it. The good quality (costly name brands) better tolerate overloading (125-150% of rated wattage). I have found that this is definitly a "get what you pay for" item. Take a $39 motor and run it over spec, they tend to be far less efficient (shorter battery life), run pretty hot (shorter motor life) and produce less thrust for the power consumed.

So, it is most common to prop them for WOT to be close to the motor's Burst Current Rating. Then, be sure your Continuous Current rating of the Battery and ESC will support full-time Burst to be safe.

For most foamies running strong 3D setups, you will need 12-15 watts per ounce (at the battery) to be happy. Over 15 W/oz is ideal, but that usually pushes you into heavier setups, good in wind but you start losing the light-on-the-wing feel and CG sometimes becomes a problem.

The AXI 2208/34 is an awesome motor. Rated at 8 amps, we ran it at 13.5 amps all day without overheating. Makes about 145 watts on a 3S TP1320 and APC 10x3.8. That produced 17-18 oz's thrust, and is good for planes up to 12 oz's for good 3D. We had this setup on a 15 oz plane, a little weak but hover just over 1/2 T. We upgraded recently to the AXI 2212/20 and went ballistic, but had to bump up battery to make 18 amps, 195 watts also on a 10x3.8.

Hope that helps...
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Old 01-13-2006, 10:25 AM
fly boy is offline
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Re: brushless

ok im building a full fuce bie plane katana and a F15 3d foamys bie plane is my own desing so
im thinking the bie plane willl have an axi 2212/34 and katana 2015 4100 gws gear box and
the himaxx for the f15 4.43 to 1 with 9x6 or 9x7
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Old 01-13-2006, 05:53 PM
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Re: brushless

Quote:
Originally Posted by fly boy
ok im building a full fuce bie plane katana and a F15 3d foamys bie plane is my own desing so
im thinking the bie plane willl have an axi 2212/34 and katana 2015 4100 gws gear box and
the himaxx for the f15 4.43 to 1 with 9x6 or 9x7
Flyboy,

You won't like the 2212/34. Kv (rpm/volt) is way low, You'll have to swing a pretty big prop to get it to work and make thrust, probably 11-12 inch diameter. You got room for that (ground clearance)? I would go with the 2212/20 or 2212/26 swinging 9-10" props if you are tight.
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