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Wow.. I am lost !?

Old 08-04-2005, 09:28 AM
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lownslo
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Default Wow.. I am lost !?

I have gassers, glow, and one electric that was a "package", so to speak. I did not have to figure out what I needed to power this electric. I just don't get it, that is, figuring what combination I need to power an aircraft with electric. I don't want to make an expensive mistake experimenting OR spending time and money on intruments etc.
Here is what I am asking you all that "understand" electric power!! I want to power a 2 meter sailplane. Sailplane would weigh about 28 to 32 ounces...... with servos, and receiver...NO electric gear yet. I once had a 2 meter sailplane with a can 600 motor. This power is OK for me, more is better but again, cost is a factor.[] I DO want good duration though.
I need to keep the cost down so I may install a can motor OR a low-end brushless.
I also want to keep the weight down....... can a LI-PO pack be used with a DIRECT DRIVE, CAN motor??
What would you electric gurus use? ... for a "can motor" set up.. motor, controller, and battery pack. (LI-PO if possible, NiMH second choice).
How about the "low-end" brushless motor set-up??
Thanks in advance.... lownslo
Old 08-05-2005, 07:34 AM
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Matt Kirsch
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Default RE: Wow.. I am lost !?

Sure, a LiPoly pack can be used with a direct drive can motor. Electricity is electricity. As long as you size the pack for the Amps being drawn out of it, the LiPoly doesn't care what it's powering. For can motors, I'd suggest that you limit the pack to a 2S LiPoly, that is, two cells in series, or a "7.4V" pack, depending on who you ask. Those "in the know" refer to it as simply, 2S. Cheap can motors don't like to be spun too fast, and a 3S LiPoly spins most can motors faster than they can handle.

Remember that last 600-powered sailplane you had/have? Direct drive, I assume. Performance was.... so-so? Duration was.... a little shy of what you'd like to see? In a word, gearbox. Going from a direct drive 7x4 prop to a ~3:1 ratio with a 12x8 folding prop on that 600 motor... you'd think it was jet powered compared to stock.

A typical 2-meter sailplane will do well with a 7-cell NiMH or 2S LiPoly, and a 600 can motor, geared roughly 3:1, with a 12x8 prop. If the nose of the sailplane will allow, a Great Planes offset gearbox is around $15, otherwise, a planetary gearbox is in order, like the 3.33:1 MPJet planetary from Hobby Lobby.

Problem is, add up that expensive planetary gearbox, a couple of motor replacements, and the ESC... The cost is not really that much less than an inexpensive brushless system. Take a look at an AXi 2820/10 with the same 12x8 prop on the same 2S LiPoly, or even a 3S LiPoly for a REAL rocket ship.
Old 08-05-2005, 09:14 AM
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lownslo
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Default RE: Wow.. I am lost !?

Matt. Thanks a bunch. I am headiing out of town so I am hurrying here. I just had to say THANK YOU. It is just
what I needed. (also the comparison to the added costs vs. the low-end brushless!!.... lownslo
Old 08-05-2005, 12:36 PM
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cwrr5
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Default RE: Wow.. I am lost !?

Another good(and easy) method is to simply check what other people are using successfully on a similar size/weight plane.

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