kamenges
Member
We have an application where an operator needs to move an idler roll assembly up and down an incline of about 45o. This will be a completely manual motion with the operator providing the energy to move the assembly using something similar to a handwheel. The assembly well be held in place with a ratchet and pawl assembly. The idler roll assembly will act as a lay-on or gap roll for a winding product roll so it needs to be able to move freely if it comes into contact with the building product roll.
Our concern is if the operator releases the pawl without having control of the assembly. At that point it will simply fall, which isn't so good. We looked at hydraulic rotary dampers but they are custom with 12 week delivery and are very expensive. So we thought we would use a PM motor to act as a rotary damper by connecting it to the handwheel shaft and shorting the motor leads. We can tweak the max speed by putting resistance into the armature circuit. We can make the damping action unidirectional by putting a diode into the armature circuit. A roll takes about 45 minutes to build so at worst the motor will see one cycle every 45 minutes. The assembly will contain about 200 lb-ft of potential energy and the majority of this will need to be eaten by the motor as heat as the assembly moves down. Based on the curent mechanical design we believe the motor will see about 75 lb-in of torque.
Now for the question. We are looking to cut costs out of this thing. So we are looking for a low cost permanent magnet motor to use in this application. Since the motor needs to move with the assembly the smaller the motor the better. I plan to size this thing small since the duty cycle and active duration are both so small. Does anyone have a good source for low cost PMDC motors?
Thanks,
Keith
Our concern is if the operator releases the pawl without having control of the assembly. At that point it will simply fall, which isn't so good. We looked at hydraulic rotary dampers but they are custom with 12 week delivery and are very expensive. So we thought we would use a PM motor to act as a rotary damper by connecting it to the handwheel shaft and shorting the motor leads. We can tweak the max speed by putting resistance into the armature circuit. We can make the damping action unidirectional by putting a diode into the armature circuit. A roll takes about 45 minutes to build so at worst the motor will see one cycle every 45 minutes. The assembly will contain about 200 lb-ft of potential energy and the majority of this will need to be eaten by the motor as heat as the assembly moves down. Based on the curent mechanical design we believe the motor will see about 75 lb-in of torque.
Now for the question. We are looking to cut costs out of this thing. So we are looking for a low cost permanent magnet motor to use in this application. Since the motor needs to move with the assembly the smaller the motor the better. I plan to size this thing small since the duty cycle and active duration are both so small. Does anyone have a good source for low cost PMDC motors?
Thanks,
Keith