However, in my searches for a DIY solution, everyone used basketballs. I kindof get that - they would be pretty sturdy since they're made of thick rubber and they have the rubber bumps all over the surface for a good grip, but in sealing these up the only solutions I could find (or think of) is to use a **** ton of duct/gorilla tape, or to use a car tire repair kit, with the rubber worm and rubber cement. Either patch solution seemed like it had drawbacks, since the tire repair kit means you have to fill through a hole no wider than 2 or 3 mm, and the tape peels and tears over time, which has obvious drawbacks.
I decided to see what I could do with a soccer ball. I think my solution is durable, elegant, and versatile, hope you enjoy!
Step 1: Gather Materials
-Cheap soccer ball (but with sewn sections) (I got mine for $8 at target)
-50# bag of sand or quickrete would work if you want a denser, harder ball ($3.50 for play sand at home depot)
-needle for inflating soccer balls (optional) ($1)
-super glue or bike tube repair kit or rubber cement (on hand)
-duct tape or gorilla tape (on hand)
-sharp knife (on hand)
-metal pick, seamripper, or other tool that can be used for pulling stitches apart (on hand)
-strong thread (I think mine was made for sewing upholstery) (on hand)
-heavy gauge (maybe hooked) sewing needle (on hand)
All in all, I spent less than $13 to make my 8-pound medicine ball
Step 2: Open Up Your Soccer Ball
Once you have made your flap, while the ball is inflated, cut about a 1" slit into the inner bladder of the soccer ball. Make it big enough that you can insert your funnel, but not too big (we have to close it back up in the end)! Try not to put your fingers in the hole to pick up the ball for any reason - I did this and it made the cut propagate another couple inches, making my repair job more of a hassle.
Step 3: Fill Your Ball
Step 4: Close Up the Bladder
Next, tape up over the sealed cut with your duct/gorilla tape to provide some structural strength to your seal. I used one strip along the cut, then a few long strips going the opposite direction, going under the edge of the outer ball.
Step 5: Seal the Deal!
I weighed my ball on a kitchen scale when I was done, and with a size 3 soccer ball (for kids' leagues, about 7.5" diameter) my medicine ball weight about 8 pounds 2 oz. Size 4 and 5 balls are larger (8 1/4" and 8 1/2" respectively) and would weigh more, maybe up to 10 lbs for a size 5 filled with sand. Another way to increase your medicine ball weight is to fill with rocks first, and then filling the cracks with sand, or to use quickrete mix, which can be up to 80 pounds for a bag the same size as the 50 pound bag of sand. I would guess with that you could get a size ball up to around 16 pounds pretty easily.
Also, this is my first instructable, so please let me know how it was, and if you have any tips for the future! Thanks for reading!