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Old Jun 27, 2006, 03:54 PM
planaholic
bob the builder's Avatar
Zig Zag, OR
Joined Mar 2003
175 Posts
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Motor question.

What is a good brushed motor for a 120 sq. in. biplane with rigging? I've got a LV N20 w/4.2 to 1 gearbox but I'm not sure it will have the gumption.

thanks! Bob
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Old Jun 29, 2006, 04:57 PM
is it flying time?
Jerry Combs's Avatar
Wyandotte Oklahoma
Joined Oct 2004
2,777 Posts
Bob,

Do you happen to know the weight of your model? If it built light your N20 will power it ok. If it is much over an ounce you might want to look at one of the GWS LPS systems.

Jerry
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Old Jun 29, 2006, 10:44 PM
planaholic
bob the builder's Avatar
Zig Zag, OR
Joined Mar 2003
175 Posts
Thanks Jerry! I haven't built the model yet and I haven't built an RC model this small. I'm guessing it will come in between 1 to 1.5 ounces.

Best Regards, Bob
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Old Jun 29, 2006, 10:58 PM
Team 30 Micro EDF
Mike Taylor's Avatar
Camarillo, California
Joined Apr 2002
4,516 Posts
The N-20 with that gearing will power a one ounce model with authority. It will also power a one and a half ounce model, but it would fly more like the original rubber powered plane. Add a second cell, and an N-20 with pull 40 grams. I have a 2-cell N-20 in a model that weighs almost 50 grams with 2 x 145 LiPolys, and it loops from level flight.

Here is a link to Gordon's N-20 test data. Find the motor you have, pick a voltage, and read the results... You will note there is a HUGE difference in output (as well as current draws) with different gears, propss and voltage.
http://home.comcast.net/~gordon-johnson/n20.htm
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Old Jun 29, 2006, 11:17 PM
planaholic
bob the builder's Avatar
Zig Zag, OR
Joined Mar 2003
175 Posts
Thanks Mike! I think you guys have given me some perspective on the matter. I'm still stuck in the days of .020, .049... or 1/8, 3/16, 1/4 rubber... electric ain't natural to me (but I do like it ).

Bob
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Old Jun 30, 2006, 09:40 AM
Team 30 Micro EDF
Mike Taylor's Avatar
Camarillo, California
Joined Apr 2002
4,516 Posts
It is tough to pick the best option out of so many possibilities and variables. Gordon has done a huge amount of work to collect the data he presents and it is most useful when planning a system. He also had a great article in John's online publication pointing out that you can acheive results similar to brushless motors at 1/10 the cost (or less) with the N-20... Good info to have since I have 90 or so of them left!
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Old Jun 30, 2006, 11:21 AM
Registered Hack
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Joined Aug 2005
232 Posts
Geared N20

Bob,

I just built a small biplane at 36g and the N20 pulls it great! The model is little too heavy (and sloppy) but it really does fly. I'm using the 3-bladed prop from MicroInvent. I'm not sure if that's the best option, but it's working. Here's a small video of it flying in my shop yesterday. There's a little more info at smallrc.com's LRF cookup forum.

HACK
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