Motors Choosing the "correct" motor and prop

[someguyinsandy]

I recently completed a scratch build which (of course) involved picking out a motor, prop, and ESC. In my case I simply picked out the motor, and made sure to pick an ESC with pleanty of overhead (thanks to Tony's motor and ESC YouTube video)! The prop choice was a "guestimate" at best. After the build I found that the setup had a 1.6:1 power to weight ratio. That tells me that I bought too much motor for the plane. At this point I do not have a lot of motors and props lying around to experiment with, and I don't want to waste money if I can avoid it.

I would like to know what process people use to determine the correct motor for a project. Or, is there a resourse available that I can use to input some basic parameters that will then output reasonable accurate notor and prop combinations? Searching the Internet provides a lot of information, but I haven't found anything I can actually use.

Thanks for your advice.

Steve in Sandy

 

[Tony]

The way I have always done it is trial and error. On the first RCH trainer, I had an Alpha 370 motor on it spinning a 10x4.7 prop. That motor only lasted about 7 flights then it burnt up during the very first night flight it did. It sat for a long time then I got a deal on two 450 size motors so I put those on there. Now with bigger props, I don't have enough prop for the bigger motors. As stated, trial and error.

I think the 1.6:1 you have going now is great for that plane. On my mcpx, I purchased the HP05 brushless motor and I did it for a reason. I would rather have the power and not need it rather than need the power and not have it.

If you don't need that much power, go into your throttle curve and turn the max down to 75% keeping the linear curve in it. Or something like 0 20 40 60 80. That will cut your power by 20%. But in regards to your question, I just try it adn if I like it I stick with it.

 

[Lee]

There's a power calculator app. I have it on my laptop but it's in the apple store being fixed. I'll let you know what it is when I pick it up

 

[someguyinsandy]

Tony, Lee,

I did some more searching based on "power calculator" and came up with this:

Sizing Brushles Motors

It references a program called "ADAMONE" does that sound familiar? Anyway it is an online calculator found here:

http://adamone.rchomepage.com/calc_motor.htm

I have played around with it using the componants in my Foamie build, but the static thrust is shows is low by at least 30% compared to my actuall results...

I look forward to learning about the calculator you use Lee, if it works out it should save me some cash!

Thanks for the replies!

 

[Lee]

Found it. Drive Calculator

 

[someguyinsandy]

Thanks Lee, I apprieciate it.

 

[regme40]

Hi

I'm going to post my question here, since its along the same lines as the first post and when I get home I'll sus the program out.

So I have installed the Turnigy D3548/4 1100kV brushless outrunner with a Hobby King 60A ESC 4A UBEC. All it does is three beeps and nothing after that (the battery is a Zippy Flightmas 2200mAh 3S 1P 30C). When I hook up the H-King 50A Fixed Wing ESC it works fine. My soldering is not up to scratch so that might be the problem.

Anyway my question is can I use the 50A ESC on the D3548/4?

Cheers

 

[Tony]

I don't see why not. Do this. Turn your Tx on and raise the throttle all the way up. Plug in your ESC to the battery and wait for two beeps (I think). When you hear the two beeps lower the throttle stick all the way down. This should recalibrate the ESC to your throttle end points. Also make sure the polarity of the battery is correct going to the ESC. then make sure the plug going into the Rx is plugged in correctly.

 

[someguyinsandy]

Tony,

Does this recalibration method work pretty much with all ESC's?

 

[Tony]

It sure does.

 

[regme40]

Great Success with that Hobby King 60A ESC 4A UBEC after listening to all the sounds to figure out which is the factory defaults (what a pain in the a##e) I reset the ESC to the factory setting and now it works.

 

[Tony]

Good deal. Hope to see it in the air here real soon.

 

[FPV_Pilot15]

I was wondering if 4S 14.8v 5000mah Lipo, 10x7 3-bladed prop, 60-70A ESC and a Turnigy D3548/4 setup is okay or a bit too much for the motor and ESC? Please help

 

[Jerryz]

Hi...I have several electric airplanes. I would like to add a gasser to the fleet. I was looking at an Ultra Stick 40. What would be a good engine to put in it? Hanger 9 says either a 2 or four stroke. Any thoughts?