eCalc Motor and Prop Efficiency Guide

A really nice guide from user Dave Smith on how to use eCalc to help you get the best motor, prop and battery combination for your use.

Go to the eCalc site here: PropCalc

Disclaimer: I have been in the drone business about two months (since Christmas). I have noticed that there is a lack of How-To’s, unlike other RC forums. How-To guides are nice when you want to do a simple search and get results without having to weed through pages and pages of discussions. I hope to keep blogging my progress to help other noobs.

Setting up my first drone, I did a search for “motor and prop efficiency” and came up with a couple of references to eCalc. It is an online calculator that calculates flight times for all sorts of flying drones. I will use the example of my latest build, a Bixler 1.1. eCalc can be pretty overwhelming at first, but it becomes a breeze with some practice.

Weight, Field Elevation and ESC Information

First, you need to plug in your motor cooling, field elevation, and ambient temperature. Notice that when you put in the ESC, you need to put in the surge or burst rating:

http://api.ning.com/files/gWhc*8EYmk*056RibQYQMXEviNvqyB5ZGnpR0Z1zmqYcI0BmrTMtZCi527vap*sDBt6sPcmcGH2DTQk5k2eHLOfSgKr4T16A/eCalc1.png

Battery Information

Now, put in your battery information. If you cannot find your particular battery, find a close match in C-rating and capacity and allow the program to populate the rest of the fields for you. Then, go back to the drop down and select CUSTOM. In my example, I chose a 2100 mAh battery, but went back and changed it to 2200 for more precise flight times:

http://api.ning.com/files/gWhc*8EYmk9l4FEglvwSGqJnQ3PmWGs-3ADj1NEchm15QfjSC1DspdFrq2mMskkwhYkjg13BnXVUBJyxjHi6BlHp5b3EXDaA/eCalc2.png

Motor Information

Next, choose your motor, or one from the drop-down that matches pole count and can size (diameter and can length.) Allow the program to populate the rest of the fields for you and then go back and change the fields with information from the manufacturer’s website. In my example, I had to change power (watts) and weight:

http://api.ning.com/files/gWhc*8EYmk9bKR4yB0KEmw38gVMoVavotgxs2b8CTcYGnWlJg1jvfFjf7v5S3KWLQ0WQG9H2l2Din5-9yzDGvWEffFskMtV-/eCalc3.png

Propeller Information

Next, select a prop and press CALCULATE. You want to experiment with motor and prop combinations that do not give you the red warning letters:

http://api.ning.com/files/gWhc*8EYmk9JGfv7XlQv1U3ancO1aonJ1lZWrz05orWsx21YWX9sIsg10tEl*vn7SUJSHZdOwDUSZ4LD0Xda7HFJ0lk8wL*q/eCalc4.png

Try Various Propellers

After making some changes, the most efficient prop for this motor is a 6 x 3E from APC. Notice the flight times offer you a range, depending on your flying style:

http://api.ning.com/files/gWhc*8EYmk-wH9lw2GStAGUnSZTSyXPeR9a4h5etzgdg5dzjvAsGwmR4cCmXV3hgbpwHtEuEVGKWlx6nn17EZTwEW7kFWWIZ/eCalc5.png

Tune For Actual Requirements

I just flew this particular combination yesterday, and the “most efficient” isn’t always the best. In my case, the plane flew on the cusp of stalling with very little reserve thrust. It would literally stand still in ~20 MPH winds! I changed out for a 6 x 4E prop which gives much more power while sacrificing very little in flight times:

http://api.ning.com/files/gWhc*8EYmk8J8reiqy97JBKUTTQ60akJKaxYiEB2TqaqvAj4aBPUcD*5g8-eLldhuUCx-RbIfnz4I1ozydzbANfZQHXis78s/eCalc6.png

I can attest that the accuracy is dead-on with eCalc. At 10-11 minutes of flight time, my battery is at 50%. I hope this helps someone out on their journey!