### Working out lifting capacity.

Is there a simple formula for working out the lifting capacity of a quad based on engine and prop sizes?

#### Replies

• For designing for your lift capacity you'll start by a prop. (Given that you do not have any HW purchased yet).  In quads its all about static thrust, so you want to go large diameter and small pitch.  Then you add rpm until you are somewhere in 2x desired all-up-weight.  ( In quad that is 50% of the AUW per prop).

Having a selected prop with a certain RPM can be used to derive the prop axle power.  Divide that number with 60 - 80% to allow for the motor efficiency. That number is the power consumption of your motor.

With the rpm and power requirements know these you can get to a ball park kV value for the motor for candidate battery voltage (11.1V for 3S LiPo; 14.8V for a 4S).

Calculating the prop power consumption and thrust is not difficult, but requires some rather specific measured values for the very prop type.  Better than calculating those yourself would be to use some of the calculators and tools available for free - or for money.  Some links for those tools below.

DriveCalc - works on Win and MAC.  Pretty good actually.

http://www.drivecalc.de/

http://www.motocalc.com/

Web tool - no personal experience - prop selection looks .. emphh .. limited..

http://brantuas.com/ezcalc/dma1.asp

Web tool - looks more comprehensive for its prop selection

Good old Slogh RC calculator:

In quads I have understood the challenge may be in finding left handed props for your selected size.  You may want to check for the prop supply for those before locking down your power train sizing.

cheers

-mikko

Drive Calculator