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Inny or outy

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Old 01-27-2013, 05:16 AM
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Adub
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Default Inny or outy

Hi guys, new to this, and would like to hear your views.

Which is preferred out-runner or in-runner brush-less motors? (thinking of a hexapod)

Iimagine that in-runners run cooler (coils exposed to the outer body)? While out-runners have a moving case and the mass further out. Would in-runners have more armature space?
Isee that some peeps have built their own motors, is that a worthwhile proposition?

What's the thinking? Are there cost/power/noise/mounting trade-offs to consider? Are there any good web pages that you would recommend?

Thanks
A
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Old 01-27-2013, 07:37 PM
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Default RE: Inny or outy

Most people use outrunners on quad or hexa-copters because outrunners typically have lower Kv and can spin large props in direct drive. Most inrunners are high Kv and need a gearbox to spin such large props. Quadcopter motors are typically low Kv/large diameter/short stator (exactly the opposite of an inrunner).

Here is just one example: http://www.hobbyking.com/hobbyking/s...copter%20motor
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Old 01-28-2013, 12:34 AM
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Default RE: Inny or outy

Thanks very much for your answer Doc.

So basically outrunners tend to have higher torque/lower speed & short bodies : inrunners lower torque / higher speed long bodies?


Ihave read about horror stories regarding bearings not acting as bearings, breaking up, sizing etc, and having to be replaced after one or two flights.
Iuse (much larger) bearings in a very hostile (sand &salt) environment, and with careful maintenance they last a very long time. Are these stories about maintenance/model design/prop balance or is it more to do with poor manufacture/motor design? Obviously individual cases will vary, but what is the conciseness?

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Old 01-28-2013, 06:05 PM
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Default RE: Inny or outy

Yep it can be hit or miss with bearings, I have "cheap" motors that I've run for years and not one problem. Big name ones that went south after a few runs.
And just the opposite. "Cheap" with bad out of the box, name brand that just keep going and going.

If it's something that may be questionable then it's worth the time/money/effort to replace the bearings.

When you are talking multi motor operation the big thing is matching them. It's a PITA when you have one that runs differently from the rest, and it's not always the motor, could be a faulty esc. And on something like a 6/8 motored beast it could be a real bear getting em all perfect when you use the lowest cost items trying to save a buck.
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Old 01-29-2013, 06:37 AM
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Default RE: Inny or outy

Some good insights there GG
Thanks for your input.
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