As a kid, my mom was telling me that vegetables would make me stronger. It was true! Here's how :
123D link : http://www.123dapp.com/AssetManager/Publisher?stgAction=getProduct&intProductId=597956
"Submitted by DIN 2012, Universit de Montr al, industrial design program, for the Instructables Sponsorship Program"
Step 1: 3D print
First step it to print the handles! I used white ABS with an UP! 3DP.
The STL Files are below.
Dumbbell moyen (part 1 and 2) is for 83.75 mm diameter cans.
Dumbbell small is for 73.25 mm diameter cans
*Note that not all printers print equally and that different materials wont shrink the same way. If you use a different printer or a different type of plastic, you might have to adjust some settings to get a perfect fit.
If you are having difficulty getting a good resolution with your UP!, I suggest you also build this box as showen in this instructables :
http://www.instructables.com/id/How-to-get-better-results-from-your-UP-3D-printer/ dumbell moyen part 1 ech1.01.stl
dumbell moyen part 1 ech1.01.stl504 KB dumbell moyen part 2 ech1.01.stl
dumbell moyen part 2 ech1.01.stl490 KB dumbell small part2.stl
dumbell small part2.stl442 KB dumbell small part1.stl
dumbell small part1.stl375 KB
Step 2: Remove support
You will have a layer of plastic at the botom of the part and also a little bit inside the bigger cylinder. Remove it carefully with pliers. Make sure not to damage the bumps used to snap unto the tin can.
Step 3: Snap
Your parts should snap tightly unto the tin cans. If to small, you might have to reprint them with a scale of 1.01-1.02. If to big, do the opposite or use glue.
You can use full food cans (peas, corn, soup) or use an empty one that you can fil with sand, concrete or whatever you want.
Liquids might not be a good idea.
Step 4: Assembly
The dumbbell handle is already pressfit, but you might want to merge the two parts using a little bit of acetone. Acetone cal also remove the texture left by the 3D printing, but I personally prefer sandpaper for that task.
Step 5: Color
If you haven't used colored ABS for your 3D print, have fun with a little bit of spray paint. Don't forget to put on a mask.
Step 6: Vegetables do make you stronger
This set of dumbbells won't turn you into an Arnold, but it will sure be enough for some basic exercises or to make your kids feel stronger.