Thanks for the reaction, the Gyems website isn't that clear (nor consistent) but on their download page:
http://www.gyems.cn/support/downloadthey have some manuals on there that explain that the S series has "no current control loop" and the L series is "with current control loop and low power version".
It seems that the S series can be bought with a 12 bit or 16 bit encoder, and the L series is stated to have a 14 bit encoder. Currently I'm thinking of buying the S version with the 16 bit encoder (the high precision version).
I wasn't planning on using a belt in my design (should have specified that), I will instead use the motors to turn the parts directly (and thus eliminate any play between the actual lidar rotation and the encoder readings).
I could use some help in determining what torque would be suitable, I have never calculated this before so this is my first attempt:
For the top motor, which only turn the lidar module itself (so the top motor in the image I posted):
The lidar module weighs 38 grams, and will be positioned to one side of the horizontal axis around which it will turn. I will balance this on the other side with another 38 grams, add to that the plate and rod to which it will be mounted and I estimate it to be around 100 grams total. Most of that will weight is actually close to the axis, so I modeled it like a rod with a 25mm radius of 100 grams. This gives me a moment of inertia of 312.5 g*cm2. The 4010 Gyems motor that I intend to use for this rotation has a rotor inertia of 81 so that would give me around a 4:1 inertia ratio. That seems reasonable right?
For the bottom motor, which turns the whole top part including the motor that turns the actual lidar module:
The 4010 motor weighs 81 grams and will be balanced by another 81 grams on the other side, the part turned but the top module as calculated above weighs 100 grams and I estimate the bracket to fit this all on to weigh around 250 grams. This means that the total thing that the bottom motor has to turn will be around 500 grams. I was planning on using the 5015 motor for this. Do you think this would be suitable?
All the motor specs for the S series can be found here:
http://dow.gyems.cn/RMD-Sxxb.pdf In terms of torq, I would think that I hardly need anything since I will balance everything and the heavy rotating top part will also ride on a thrust bearing. I won't be accelerating or decelerating much, just a constant slow speed. Furthermore, any slight deviations in speed shouldn't matter either since I will just read the real position from the encoder so those variations won't actually influence the accuracy of the measured points (the points will simply be measured at slightly different locations).