I'm currently stuck in a college project: a floating turtle that swims powered by 2 SM-S4303R continuous rotation servos and a simple row mechanism. Thing is, we can't calibrate both to rotate at the same speed, as you can see in the video below:
Any ideas on how to calibrate them? We've tried some delays values or different rpm but we can't manage to do it properly. Also consider that 1 servo is rotating backwards.
Looking at the video, it almost seems as the rotating plates were cog wheels rotating against each other. If that were the case, your problem would be solved.
Although the encoder plates would be the geek way to do it. Just mechanically connecting them would lead to two motors doing the same job. One would force the other if you don't know exactly how much power you need to put to each of them. With the encoder plates you could have them in perfect sync. But you could also have them run in different speed, making the turtle turn.