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New and need resources to learn with

Old 01-11-2021, 12:32 AM
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Default New and need resources to learn with

Hi all,

I am new to electric flight. I am wanting to convert a Great Planes PT-Electric from a brushed motor (No ESC on it right now. Uses servo to turn on and off, no speed control) to a brushless. I also have a DynaFlight glow powered I would like to convert to brushless. I am looking for reading material I can study to figure out what I need for these conversions. I would also like to know the best place to get the motors and ESC. Seems like all the hobby sites I look at have slim variety to pick from.

I have read the sticky in this forum, and will read it over and over I am sure. But the more information I can get the better for me.



PT-Electric specs

Butterfly specs
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Old 01-11-2021, 04:37 PM
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Our stickies here and (cough, cough) RC Groups are both good resources. Castle creations has a nice calculator for comparing motors. props and esc's. it is fun to play around with it looking for good combos.

You won't need too much. Especially for the Butterfly. It says a .15 size equivalent but I have a 12ft Foxbat from PeterGoldsmith designs. All up weight is 54 ounces and i fly it on an E'Flite power 10, 40 amp ESC and a 3s 2200. Plenty of power to get her aloft.

Good luck and welcome to WattFlyer!
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Old 01-12-2021, 10:51 AM
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Below an excellent quote about motor selection.
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:
    Magic numbers for modellers.
  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 01-12-2021, 10:56 AM
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Originally Posted by billkater View Post
... need resources to learn with...
Some well-structured reading for rainy/windy days, so you know what we are talking about.
Including e-flight_101 & 102, and some handy e-tools. Will save you, and us a lot of questions. Notably the 'what went wrong?' kind of questions Will also prevent you from burning up several controllers and/or motors and/or battery:
E-flight primer and tools

And pleasepleaseplease, do your RC equipment, wallet, ego, battery, controller, motor, house/garage/car a big favour ... get a watt-meter. It will more than pay for itself, will save you at least one fried motor and one fried controller. Will also help you finding the best setup.
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