This isn’t an E-Board build, but it is an interesting challenge and this forum seems to have the most knowledgeable peeps when it comes to high powered brushless drive design. If this topic has no place here, let me know and I’ll delete it!
Anyways, I’m trying to build a winch that fits on a co2 propellant grappling gun that can pull me up 7-10 meters at least .33 m/s. So far I’ve settled on using an SK3 6374 149 Kv motor on 12S, driving a 12mm diameter reel through a 12:50 timing pulley transmission. The rope is a 3mm Nylon cord used for spearfishing, breaking strength 1050 lbs.
149 Kv gives a Kt of 0.064, which at the max current rating of the motor (70 A) gives a max torque of 4.48 Nm. The theoretical load being pulled up is 100 kg, or 981 N. On a 12mm diameter reel, that requires a torque of 981*0.006= 5.886Nm. So through the 1:4.167 reduction, the motor has to supply 1.41 Nm torque. Assuming a max theoretical angular velocity of 687.5 rad/s at 44V and a max theoretical torque of 4.48 Nm and assuming a linear torque-speed curve, when the motor is providing 1.41 Nm torque it is spinning at 473.33 rad/s, which means a reel speed of 113.59 rad/s, which means on a 12mm reel an ascending velocity of 0.68 m/s. So I figure even after tossing out losses and efficiency and such that should still give me at least 0.33 m/s, while consuming at least 22 A, which doesn’t seem that bad!
I’ve got a BS in electrical engineering but I’m a total noob when it comes to these high powered outrunners, so I was hoping I could get some opinions on this set up. Does the math above make sense? There’s a ton of assumptions being tossed around there. And what’s your gut feeling about this kind of performance? I’ve never even held a 63mm brushless outrunner before, so I have no feel for what they realistically can or can’t do.
Also, I’m trying to finish this build ahead of Batman V. Superman, so I don’t know if I can wait the 3-4 weeks for the legendary VESC. I’ve also got concerns about the VESC max 50 A spec, since once the 3mm Nylon rope gets reeled up the effective diameter doubles, which means the motor will likely be drawing over 50 A. Do you guys think the Torqueboards 12S ESC would do? Or should I chance using the VESC?
Thanks for reading! This board really looked like it had some of the smartest dudes around, and if this is too off topic I sincerely apologize!