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I'm looking for a motor/ESC combo recommendation for a 1/4 Cub

Old 02-09-2020, 06:34 AM
  #1  
SWMO wingnut
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Default I'm looking for a motor/ESC combo recommendation for a 1/4 Cub

Call it 17 pounds with all equipment. I'd like to find an ESC/motor combo that will allow me to use 2 6s batteries in series for a total 12s input. Or a 6s motor/ESC solution. Thank you
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Old 02-09-2020, 06:06 PM
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ron_van_sommeren
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You could search for similar Cubs and just copy a good power system.

Do all your 6s packs have same capacity? A 12s pack of same capacity as a 6s pack has twice the energy and twice the mass, and it will let you fly twice as long.

Below an excellent quote about motor selection.
From
brushless motors Kv? - RCG.
Originally Posted by scirocco View Post
While an absolutely critical part of the system ...
... Kv is actually the item one should choose last.
  1. Decide your peak power requirement based on the weight of the model and how you want to fly it.
  2. Pick a preferred cell count (voltage) and pack capacity for how to deliver the power.
  3. Pick a prop that will a) fit on the model and b) fly the model how you want - often as big as will fit is a good choice, but if high speed is the goal, a smaller diameter higher pitch prop will be more appropriate.
  4. Look for a size class of motors that will handle the peak power - a very conservative guide is to allow 1 gram motor weight for every 3 watts peak power.
  5. Then, look for a motor in that weight range that has the Kv to achieve the power desired with the props you can use - a calculator such as eCalc allows very quick trial and error zooming in on a decent choice. For a desired power and prop, you'd need higher Kv if using a 3 cell pack compared to a 4 cell pack. Or for a desired power and cell count, you'd need higher Kv if driving a smaller diameter high speed prop compared to a larger prop for a slow model.

The reason I suggest picking Kv last, is that prop choices have bounds - the diameter that will physically fit and the minimum size that can absorb the power you want. On the other hand, combinations of voltage and Kv are much less constrained - at least before you purchase the components.

So Kv is not a figure of merit, in that higher or lower is better, it is simply a motor characteristic that you exploit to make your power system do what you want, within the constraints you have, e.g. limited prop diameter, if it's a pusher configuration, or if you already have a bunch of 3S packs and don't want to buy more, and so on.

Minor lay-out changes by RvS
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Old 02-09-2020, 08:08 PM
  #3  
solentlife
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Originally Posted by SWMO wingnut View Post
Call it 17 pounds with all equipment. I'd like to find an ESC/motor combo that will allow me to use 2 6s batteries in series for a total 12s input. Or a 6s motor/ESC solution. Thank you
eCalc ... register for a few cents ... input basic info ... out pops the answer ...

Try different motor / prop / battery combinations - its often surprising what can be done ...
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