Motor to drive closed loop drawstring for blinds

[hyperutila]

Hi Everyone,

I'm a definite beginner when it comes to this sort of thing. As such, I have two very beginnerish questions:

1. How are you supposed to use little hobby motors when they don't have any gears or anything? Are you supposed to attach some sort of gear to the end? It seems like if you squeezed a plastic gear onto the end and had any sort of load on the motor, it would just slip. Am I wrong? (I warned you I was a beginner, didn't I?)

2. How do you determine if a motor will be powerful enough for your application? I am trying to attach a motor to a closed-loop drawstring for some blinds. If I attach an 8 lb weight to the drawstring, that's usually enough to move the drawstring. How do I convert that into torque and such? Also, any ideas on how to connect the motor to the drawstring such that the drawstring won't slip or get ripped up as it goes through the motor?

Thanks a bunch! Sorry I'm such a noob.

 

[BobK]

You can buy gear motors.

Torque is the product of a radius and a weight. If you need 8 pounds of force on a pulley 1/2 inch radius pulley, that would be a torque of 4 inch pounds.

Bob

 

[hyperutila]

Thanks for the response! That is very helpful. Just out of curiosity, how do people use the motors that are just straight, smooth shafts?