Building off the medicine ball I made in a previous instructable, I've made a tornado ball for use with sledgehammer style slams.
This tornado ball is designed almost specifically not to rebound, so it isn't good for any sort of fast repetition training, but it's phenomenal for swinging over your head by the rope like a sledgehammer. And this, despite seeming pretty basic, is a great workout.
Step 1: Materials:
One 55 yard roll of "professional duck tape" duct tape, $4 at walmart.
6 feet of thick rope, I used some rope I had laying around, aka free.
Two spalding heavy duty cloth basketball nets, $3 each from walmart.
One thin yoga mat that I had bought online for another project, less than $10, though I don't remember the exact price. Got it off amazon though.
And a warning: This Instructable is going to be pretty picture heavy, because I took pictures at every little step. So pay attention to the pictures to replicate my results!