Timeline for reducing rotational speed from gearmotor to below 1rpm

Current License: CC BY-SA 3.0

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Feb 28, 2018 at 17:01	comment	added	Donald Gibson		The slower gearmotor with the higher ratio gearbox will produce the smoothest motion. Consider that the controller will be able to adjust the motor speed reliably between 35% and 100%. Below about 35% throttle, there may not be enough power (in smaller motors) to overcome cogging, friction and inertia which might result in uneven rotational speeds. The most important aspect of the machine will be rigidity within the drive system if precision speeds are required.
Feb 27, 2018 at 22:52	comment	added	RCH		Donald -- I agree that in many applications, a belt & pulley (or chain & cog) would be a good solution to lower the drive ratio, but the reasons I chose to not go with either were these: > the plane of motion is horizontal, which means that chain or belt sag would be an issue > I need precise indexing between the various driven components (of which the disk is just one) > wear would eventually be a concern > Unless a chain is kept under tension (which isn't practical in this application), there tends to be a "snatch" at the start. I need it to be smooth and jerk-free.
Feb 27, 2018 at 22:45	comment	added	RCH		Thank you for the advice, Donald Gibson! The DC gearmotor I already got from Servo City is 165rpm (selected due to a mistake in my calculations). I might try to exchange it for their lowest-speed unit (12rpm), but I first wanted to ask if there's a "sweet spot" for speed-reduction using a PWM chopper. IOW, would the speed, being reduced through a 165rpm gearmotor down to 5rpm, be smoother or stronger than the chopper being used with a 12rpm motor? (I'm thinking of internal-combustion engines as an analogy; some are smoother or stronger at different rpms than others.)
Feb 27, 2018 at 22:03	history	answered	Donald Gibson	CC BY-SA 3.0