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Curtiss Wright T-32 Condor

Old 05-01-2020, 07:23 PM
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skyhawk940
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Default Curtiss Wright T-32 Condor

Building from plans. 82 inch wingspan, electric twin.
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Old 05-02-2020, 02:02 AM
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ron_van_sommeren
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Originally Posted by skyhawk940 View Post
Curtiss Wright T-32 Condor
That's a cutie.
Originally Posted by skyhawk940 View Post
... electric twin.
Keep battery wires short, extend motor wires.
However, if that is not possible/incovenient:
too long wires batteryside will kill ESC over time: precautions, solutions & workarounds - RCG
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Old 05-02-2020, 02:50 PM
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skyhawk940
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Thanks for the info. I'm newer to electric power systems and I love twins. I am an Electronics Eng. I'm figuring 70 to 90 amps to each motor depending on the weight of the plane. There is no weight info on the plans. I've ran 12 gage copper wire through the wing to feed the EMC's. I've built an OV-10 Bronco that has about 440 watts max and it works great.
I'll take some measurements and post.
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Old 05-02-2020, 03:01 PM
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So far...
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Old 05-02-2020, 07:38 PM
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Your work looks great !
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Old 05-02-2020, 11:26 PM
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ron_van_sommeren
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Originally Posted by skyhawk940 View Post
... I love twins ...
Will you be using righthanded and lefthanded props, counterrotating?

Originally Posted by skyhawk940 View Post
... I'm figuring 70 to 90 amps to each motor ...
Current drawn is proportional to pitch, #blades, voltage≤, Kv≥, gearing≥ and prop-diameter⁴.
Power drawn differs only for voltage, proportional to voltage≥.
extra current with one or two cells added, simple table - RCG

Originally Posted by skyhawk940 View Post
... depending on the weight of the plane. ...
Plane type and mass are leading when choosing power (in watt). The first link is a good start, otherwise it would be a bit too much.
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Old 05-02-2020, 11:28 PM
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Note that Kv (in rpm/volt) says absolutely nothing about motor max.power, max.current, max.torque, efficiency.
Kv only depends on desired rpm and battery voltage: Kv = RPM_noload / voltage.
It does effect current and power drawn greatly though, both are proportional to Kv cubed.


And below an excellent quote about motor selection.
From
brushless motors Kv?.
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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