I disagree with this assessment (although agree that the current calibration
step is wrong)
you do want to stretch the chains. We need to measure the difference between the
chains under tension and the theoretical chain length to know what the chain
slop is.
you also want to be able to see if the frame flexes under load or not.
The chain breaking strength is something line 900 pounds, and it’s normal
operational load rating is something like 200 pounds.
If the power supply and motor shield can’t handle this load, they are
under-sized.
Now, the current calibration is not great. you don’t want to snap from 0 power
to full power (especially if you have slack)
But you should also be pulling with both motors.
so what should be happening is
measure the distance between the motors with a tape measure
apply low power to both motors
repeat
sample motor positions
until motor positions stop changing (this step takes up the slack
ramp up power to both motors to full power
shut off power and measure the distance between the motors with a tape measure
back off one motor to release the tension
David Lang