Hi,
I have some quick questions I was hoping someone might be able to help me out with. Overall, my project is pretty straight forward but I could use some help on specs.
I need to build a bot that can carry a 50-60lb load (either horizontally along a straight plane or up/down a 13% grade (roughly 7.5 degree angle)) and maintain at least a speed of a walking person. Optimally I’d like to see a brisk walk - ie 4mph If that’s possible without getting the robot too heavy in size on it’s own.
I don’t really know how to spec out motors of if I should be looking for a single motor with a daul shaft or two motors, etc… Any thoughts on what is out there that would work?
Thanks in Advance.
We have the perfect tool for you:
robotshop.com/blog/en/drive- … -tool-9698
You can try with two or four drive motors and see the difference in torque required (per motor).
Once you know continuous torque and RPM, you can search for a suitable DC gear motor:
robotshop.com/en/gear-motors.html
robotshop.com/en/compare-dc- … l?__pc=103
Coleman.
Thanks for the great jumpstart. I’ve plugged in the numbers I think are accurate but still a bit overwhelmed by all the options.
#1 You list links for both Geared and DC motors. Any specific advice on geared vs brushed vs brushless etc…?
#2 After using the tool, what do I base my search on?
info: ( 60lbs / 2 motors / 3" wheels / Vel 5.86 / incl 7.5 deg / 12V / 0.5 Accel guess / 4hr batt / 65% eff guess )
The results were (each motor with) 23.4 vel / 324 torque / 53.6 Watts / 4.46A / 35.7 Ah battery
Obv I think I’m going to need to tweak my numbers, perhaps go with a 24 or 36 v system etc… but am I looking for motors based on Stall Torque? ie 324? or some other combination of factors?
My guess is that motors like the RB-Ban-71 or RB-Pol-185 would qualify (Pol only being in the 250 rang though).
]60lbs total weight/:m]
]2 drive motors/:m]
]3" radius wheels/:m]
]5.86 feet per second/:m]
]7.5 degree incline/:m]
]0.5 feet per second squared/:m]
]4 hour operating time/:m]
]65% total efficiency/:m]
Results:
]223 RPM/:m]
]323.65 oz-in (minimum torque)/:m]
]35Ah battery/:m]
You’ll definitely need gearing to get that kind of torque and RPM. Consider spur gear and (likelier) planetary gear motors.
We offer mostly brushed DC gear motors, with very few brushless. We suggest you stick to brushed just for the ease of use and available options.
323.65oz-in would be the maximum continuous torque under those conditions, and the motor’s stall would be closer to 4-5 times this number.
RB-Pol-185 has a stall torque of 250oz-in, so the maximum continuous torque is closer to 1/4 to 1/5 this number (50oz-in) which is far less than the 323oz-in you need.
Consider a P60 gearing system with RS555 motor (an example: robotshop.com/en/banebots-rs-540-motor.html)
It’s always better to select a motor which can provide more rather than less torque than you calculate. Speed can always be reduced using a motor controller.
