View Full Version : [Question(s)] Would the AX-12W be better then AX-18A for the PhanomX Hexapod MarkII

05-27-2013, 10:40 PM
I'm looking into getting a hexapod and I came across the AX-12W. Before I was thinking of getting the full kit that comes with the AX-18A, but the AX-12W seems worth looking in to. Seeing as the 18's have 18.3 kg·cm stall torque and the 12W's only have 2.0 kg-cm, would 2 kg-cm be enough to allow the robot to function or would it just stall and overheat? If this has already been asked and answered or anyone has any useful advice that would be great.


05-27-2013, 10:47 PM
It would be too weak, for sure. You're talking a factor of 9 weaker than AX-18As, 7.5 weaker than an AX-12. If I'm wrong, you'd still have no payload capacity whatsoever :)

The W servos are for wheeled applications that don't require lots of torque. They aren't for joints in robot arms/limbs.

05-27-2013, 11:06 PM
Haha I love your picture. That's what I was think but two heads are better then one.

Thanks for the advice, take care.

05-27-2013, 11:57 PM
The math is very simple. Distance of lever, times force on lever, equals torque. The robot weighs perhaps 1-2 kg depending on payload, which means the distance of your leg span can be a whopping 1-2 centimeters before stalling out. That's smaller than the size of the servo itself! And, ideally, you should design for a normal load of 1/4 to 1/5 of the stall torque.
The AX-12W are intended only for rolling applications, where the torque needed is much smaller, but speed (in RPM) can be useful.