On my robot there are are two motors that make a loud rattling sound, and have no strength. What is going on with them? I’ve only been practing for three days with them
It’s possible that either one of the gears is broken/stripped (take off the tiny screws and check if that is the case), or the actual dc motor popped out of its spot in the back of the motor and is rubbing against the gears.
Make sure what you are hearing is coming from the motors and not from any external gears to which they are attached. For example, sometimes if a motor is connected to a long shaft, the long shaft might flex under load and allow gears (especially smaller gears like pinions) on the long shaft to slip off the gears they are meshed with.
You can buy motor refurb kits for $5 that include replacement internal gears if they have stripped or broken: https://www.vexrobotics.com/vexedr/products/accessories/motion/motors.html
If you can’t wait for the refurb kit to be delivered you can take apart dead motors and use the gears from there.