Step 3: Attaching the weight better.
First, make sure that the clip can rotate around the motor shaft without catching on to any parts of the motor.
Once you are sure of this, turn on your soldering iron and wait for it to get very hot. Once hot, hold it to the alligator clip for about 20-30 seconds. This should be more than enough heat to melt the clip's teeth into the plastic.
After heating up the clip, carefully without touching the alligator clip and burning yourself, solder the top and bottom half of the clip together at the side hinge. This will prevent the clip from being able to open up.
It now should be melted and permanently clamped into place.