ayadabd000 wrote:How can I know that a motor will have a good thrust to lift the quad?
There is a long and convoluted formula to work out thrust, the most difficult is to do with prop ratios. There are so many variables ( like the Manning formula for hydraulic flows) that it could be easier to trial some physical tests.
Construct a motor test bed with prop and place on a set of electronic scales ( 0-2kg would be best) run the setup in reverse and measure the down thrust according to the scale. try a variation of props and motor speeds, have a watt meter in the loop to calculate power consumption.
Try something like http://www.hobbyking.com/hobbyking/stor ... hless.html
As Bill said you may have to gear down the motor for improved torque, or experiment with small diameter props that can handle the high KV to produce thrust required.
A minimum thrust to weight ratio of 2:1 is considered best for a quad.
I'm just working on a theory to get it off the ground as no flight plan is indicated 
