Thank you guys for help.
But one more question for Bajdi's robot.
I'm currently working on a bigger beast with 18 standard sized metal gear servos (MG996R).
MG996R is a power hungry servo motor. 18 servos should be need 18A for motion if all of the motors are moving at the same time. And I just found 1 DC to DC converter to provide power in your video. The standard output current for that converter is 8A . So, I think the hexapod may have some problem when it walking. But I am not sure. Please make a correction if I am wrong.