Specific motor for arm

Hey,
Our team is building the robot using the 118’s Everybot model. We find an issue during choosing the arm motor because we don’t have the NEO Brushless Motor.
We thought of using the Snow Blower Motor (we have it), but we don’t know if the arm will lift up the intake (we tested with the CIM motor and it didn’t work) because we aren’t using the same material proposed in the build manual of Everybot.
So, my question is: Is it better to buy another motor or use the Snow Blower? If buying another is better, which motor to choose?

Image of intake

A snow blower motor almost certainly will not be a suitable motor for this application.

A CIM motor should be, though. Would you mind elaborating why the CIM motor did not work? Was it properly geared down?

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We don’t know exactly the answer, but we believe the different materials (for example, compliant wheels and a hex shaft on the intake) resulted in the insufficient motor’s torque because the mechanism became heavier.

And yes, we have this warning in Everybot manual:

I think it’s time for you guys to pull out one of the calculators that are out there and see what kind of torque/gearing you actually need. (Or even just a motor data sheet, like this one.)

If you assume that the NEO is “adequate” for the original arm, then make some adjustments for the upgrades you guys did, you should be able to see what motors and gearing will work. You need >= torque, and enough speed to move quickly, but other than that…

As a first pass, I’d probably say to pull 2x MiniCIMs with a slight extra reduction. You’ll need 2 speed controllers and some way to combine the MiniCIM outputs (whether that’s putting them on opposite ends of the shaft or using a combining gearbox or doing something completely different is a design decision you get to figure out the answer to).


As for why your CIM option didn’t work: If you used the same gearing, a CIM has 2/3 of the torque of a NEO, so you only got 2/3 of the required torque. If you then added extra weight, then you needed more torque. It might not have worked even at original design weight.

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If you are building the everybot to the instructions you physically wouldn’t have space on the robot to fit the cim motor, since it is physically longer than a neo.

Though it looks like you have made some other changes so it could be you could use a cim if it fits. If not the suggestion above of using the mini cim and changing the gear ratio would work, unless you bought the Andymark gear box and only have the one gear ratio.

A neo might be your easiest solution, but be mindful of the design choices on the everybot, a lot of them are either cost limited, space on robot, game challenge, or machining capability. The whole thing is a good lesson in design decisions for all.

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