servo/motor stress

i am building a claw (gripper) for my robot
i was wondering if it is bad for the servo when you grip something and the motor starts humming
if you know post your thoughts thanks

Well when I hum it means I am in a good mood. I do not think the same goes for sevos/motors.:slight_smile:

Is it humming or vibrating, basically try and figure out if the gears inside the motor are stripping. If they are stripping that’s really bad. If it’s just humming then I’m guessing thats not good but not horrible.

i have done the same thing, yes it is bad, try to gear-reduct 2 of the motors, so that the claw may stop working when you let off the joystick. when the servo hums, it means that it is rying to center itself, with a gear-reducted motor, you get a powerful claw, and when the joystick is let off, the claw stops working. i would reccommend a 12 (smallest gear) on the motor and a 48 tooth (two sizes bigger) on the claw.

i am using only one motor and it is a servo and i am using the middle siz with no gear reduction

if it is a hum, it may be a bad servo if it is clicking, the clutch is stripped. It may also be the gears, or the fact that your claw is too heavy for it. If you have a spare motor, not servo, it is probably best to use that instead.

i dont think it is a bad servo i just think it is when the gripper grips somthin and it hums i dont think it is bad any more but if you could test this let me know your results

I agree with Bobby C. I think what you are hearing is from the servo trying to center itself and you are holding it open or closed. This is a good place for a motor module. A servo is better suited for short bursts that dont require much travel like a rack and pinion steering system. Use a motor sensors are meant to be centered most of their time.

I had the same problem with my wheel motors.
The gearing I used did something to the engine which started to hum after a couple of minutes. Not thinking it was anything bad I kept going until I stripped something on the inside of the engine. After re building the inside of the motor, I changed the gearing around a little, so now my robot is slower, but dosn’t go through engines anymore.

can u post pics so we can see wat u see?

you cant see it dude it is all int eh hummin

no but the set up.

it is in the gallery it is the gripper bot posted my me and the gears are the meadum ones and i am using a servo but you guys arere telling me other wise

which motor/servo is stressing the one lifting the arm or the one closing the claws. if its the 1 closing the claw i can’t see the gears/motor/servo, can u take pictures of the motor/servo/gears that are on the actual claw?

to keep the motor from stressing the internal gears i think you should have the claw so that the center position closes the claw and the remote opens it which would keep the motor from humming and stripping the gears

When you grip down on something, the servo is applying some force to “grip” the object. This “grip” is what causes the servo to hum. The servo is in a stall condition.

This is not good for the motor. How bad is it? Hard to say.

Instead of relying on the force of the motor to “grip” your object, you could try using a passive grip. Try using rubber-bands, or other elastic bands to hold the gripper closed. These bands will provide the “gripping force” on the object. Alternately you can try using some sort of foam/rubber pads on the gripper to accomplish the same thing.

Remember: the less load a motor/servo is under, the happier it is.

Regards,
John

While battery life is not quite the factor in Vex that it is in FRC, a motor at stall is also drawing maximum current. This will reduce the amount of power available to other devices in the robot, and will drain the battery much faster than normal. “Otis”, our larger, more complex Hangin’ Around robot pretty much goes through a battery every two matches. Stalling motors would make that worse.

I’m not sure that’s true, I’ve noticed significant changes in autonomous when not using sensors when the battery charge goes down. Such as an arm not going up as high.

Noted. I was just trying to comment that, in my experience, FVC doesn’t eat batteries as fast as FRC does. In FRC it’s pretty common to replace the battery for every 2-minute match. In Vex, we’ve gone as many as three rounds before replacing the battery. I’m sure your mileage may vary, but Otis weighs a ton, and has (at the last count) eight motors and servos. Surprisingly, Otis works pretty well…

EDITED: Our team policy is, “New round, new battery” but the discharge runs faster than the charging, and we only have three robot batteries.

EDITED AGAIN: When you are testing, it’s really easy to run your battery down without noticing it. Make sure you change batteries in testing, too, so that you know your mechanisms are working properly. This is especially true if you are having turning problems. Robots that don’t turn with a discharged battery will work great with a fresh charge. Sometimes, anyway…

Without sensors and using dead reckoning autonomous programming will give you varied results as well.