AEAJR

While I enjoy researching and writing the articles in this book I also like to share other resources I find that may be helpful in your understanding of electric powered flight.

Here is a good article from Model Airplane News, October 2014

Tips for Getting Started with Electric Airplanes
by Gerry Yarrish
http://www.modelairplanenews.com/blo...s%20and%20more

Glacier Girl

Ed, something maybe to include is a warning that you need to have your brain fully engaged before doing anything related to flying or working on your plane.

I got my reminder today launching a pusher set up. Had a nice headwind so I didn't throw it as hard. Yep, 4 cuts to the bone, 3 not quite so deep, and one partially removed fingernail on my right hand.

Broke both blades on the prop, pulled the motor off the stick mount, and broke one motor lead. Not a scratch on the plane.

Been launching fast pushers for years and years, and all it took was this one time of not thinking it through.
I won't post the photos as they sure aren't pretty.

xmech2k

Ouch! Sorry to hear about the accident. I hope the injuries aren't something that will cause long term distress. I only have a umx F-27 Stryker 180, and I launch it with the motor off, only hitting the throttle after it left my hand even though it's a little one. Too many horror stories, and now another one. Hope you get healed up soon.

kyleservicetech

Yikes!

We've had two guys in our club during the past year with very serious injuries to their hand when getting mixed up with big glow and gasser engines. One of the guys permanently lost half an inch off of two different fingers.

This is a good reminder that even the "Smaller" electric models can also do substantial damage to one's person.

Got to be careful out there.

AEAJR

Always good advice: Put brain in gear before putting body in motion.

Hope your injuries heal fully.

AEAJR

I just updated the chapter on BECs to bring it up to date.

Benstarr

Thank you for sharing, the detailed introduction. I have learnt something.

drummaker

Engaging the brain fully is not only a safety thing in this hobby, It can save thousands of dollars.

AEAJR

Anyone have a good reference resource for flight stabilization systems? I don't use them but they are becoming so common I would like to have something in the discussion on the topic.

Turner

The EagleTree GUARDIAN seems to be one of the more popular stand-alone systems.

Cezzna

Had an UBEC freeze the servos on my hotliner once.
It crashed uncontrollably

AEAJR

you may have overloaded it. When that happens they overheat and will shut down. Like ESC they ahve amperage ratings. In some cases as the voltage of the battery goes up the amperage rating of the BEC/UBEC goes down.

What BEC were you running? What voltage battery pack.

How many servos were you running? What type?

What kind of flying?

F22trainer

This site is a wealth of info!

So - check my numbers here. I started from the prop. (See my post here on MEN Trainer). I know the plane flew well with a 9x6 prop and that's about as big as I dare swing as she sits kind of low. All up weight should be around 25 oz. that said I figured 75 watts per pound for a little more spirit than a docile training and the ability to fly around on 50% thottle. (Gee, this is fun.)
Now, since I am breaking new mental ground and have gotten familiar with eflite power systems. I'm favoring the Park 370 and based on what I've digested from their specs, go with 7.4 V 3S.
Here's where the water gets murky...specs say 10 amp continuous, ok... works out to a 1500 mAh battery, right?
I have tons of room in this old bird, and I am sure I can lighten up the landing gear and wheels. It has 60 inches of wing and about 7in chord.
How am I doing so far? Like I said I kinda worked backwards but I live in that world.

AEAJR

You are working with all the right elements.

Note that your 3S pack would be 11.1V not 7.4V.

You mention specs say 10 am continuous? Not sure what you are referring to.

Battery and ESC

If you are going to have 150 watts of power and you are going to use an 11.1V battery then the motor will have to draw about 150/11.1 = 13.5 Amps, so lets shoot for 15 to be safe.

So you need an ESC that will handle at least 15 amps, I would go for a 20 to 25 amp rated ESC so the ESC is not being over taxed.


You need a battery that can put out 15 amps on a continuous basis.

1500 mah pack rated 10C can produce 15 amps - This battery meets the need but is working hard at 15 amps

1500 20C can produce 30 amps - this battery is loafing. I like this better.


Need to go lighter?

750 mah pack rated at 20C can produce 15 amps - Again, working hard

750 mah pack rated at 30 C can produce 22.5 amps, I like this better.


Need more fight duration, anything above 1500 20C rated will work and will extend your flight time. Look at size and weight and see what fits.


Naturally you can use higher C rated packs but you don't need them and they cost more. So 30C, 40C, 50C all work too but are unnecessary, but they won't hurt anything either.



Here is how I would approach it.


25 ounces, about 2 pounds. So I want a motor that will produce between 150 and 200 watts for trainer to sport plane performance. Power to weight ratio target of 75 to 100 watts/pound.

I have a 9" prop limit based on ground clearance. So I want a motor that will produce 150 to 200 watts spinning a 9" or smaller prop.


My preferred tool for modeling this would be the eCalc prop calculator
https://www.ecalc.ch/motorcalc.php?ecalc&lang=en


However the free Electrifly power calculators is simpler and works well for their motors
http://www.electrifly.com/powersyste...tem-index.html


Let's use the Electrifly for this example - Brushless and let's use an outrunner
http://www.electrifly.com/config/

Brushless
Rimfire Outrunner
Enter weight= 2 pounds
maximum prop diameter - 9 inches
type of performance - trainer
System recommends 11.1V/3S lipo


We are given three set-ups

Motor Recommendations

Best Speed Setup, Motor 28-26-1600 / GPMG4535
Best Thrust Setup, 28-30-1450 / GPMG4570
Best Combination 28-30-1450 / GPMG4570

Each is about 94 watts/pound

It gives approximate flight speed, approximate flight time and more. Run the model and see. You can go back and change the flight character and can adjust battery size to get longer estimated flight times.



As I said I prefer the eCalc because it lets me work across multiple brands and more combinations. It also gives me more information but that also makes it more complicated to use. This Electrifly calculator is very easy to use and yields good results for Electrifly motors.

Does that help?

F22trainer

Big thanks!
Have enjoyed reading your material - nice style. I write training material on a regular basis for full size pilots at all skill levels. You have a smooth delivery that is logical, easy to follow and fun. Keep up the good work.
MH

AEAJR

Thanks for your kind words. Glad I could help.

Best of luck with your project.

AEAJR

I am going to be making some updates to the articles.

Does anyone have any suggestions as to what might be needed or things you think I should add? I am always open to your suggestions.