How to make concrete dumbbells
DA Dumbbell Mold Instructions
Step 1: Gather materials you need to make your dumbbells (DBs)
- DA Dumbbell Mold
OTHER THINGS YOU NEED:
- Pipe for handle – recommend ¾ inch ID (inside diameter) pipe cut to length*
- Concrete – recommend Quikcrete High Strength or Commercial Grade +5000 PSI Concrete
- Silicone spray or paste wax
- Bucket to mix in
- Food or bodyweight scale
- Tie wire or rebar
- Screws (4”)
- Gloves and other personal protective equipment (PPE) as needed
- Isopropyl alcohol
- Plastic trash bag
- Optional: Wood scraps, sandpaper & materials to personalize (paint, plasti-dip, truck bed liner, etc.)
Step 2: Prep the mold
Use your isopropyl alcohol and towel to clean and dry the mold. Lube the mold with paste wax or silicone spray and place on a level surface for an evenly balanced weight.
Step 3: Prep your handle pipe
Cut your handle pipe to the length necessary for a comfortable fit (average handle length for production dumbbells is about 5.5-6 inches) pending on the weight of the dumbbell (DB). (*See chart on back.) Drill through the ends of the pipe – once or twice per DB head – with a bit big enough to allow your screw or wire to fit through and anchor the pipe into the concrete head.
Step 4: Measure the concrete
To figure out how much concrete you will need per dumbbell head, you will need to some math. (See chart on back.) Start by weighing your pipe and anchor materials for both sides of the DB. Take the weight of your DB, subtract the weight of the handle and anchor materials, then divide by two. This will give you the amount of dry concrete to mix for each side of the dumbbell, which will result in the final weight for each DB head.
(Total DB weight - handle & anchor weight) / 2 = Dry Mix weight per DB head
Ex: 50lbs DB = (50-2)/2= 24lbs of concrete for each head
Step 5: Mixing the concrete
Wearing gloves and other PPE as needed, mix your concrete following the directions on the bag. You can make a portion of the concrete slightly wetter for detailing the face of the mold and minimizing bubbles to make a smoother surface.
Step 6: Pour & set the pipe
Take the small portion of wetter mix and rub it into the details of the DB face, then add the drier mix into the mold, a few handfuls at a time, layering until you reach your desired weight. Insert the wire and pipe with screws mid-way through into the mix as you layer to make for a good bond. With each layer, vibrate the mold to release the air bubbles from the face and sides of the mold to give a smoother surface. Make sure the pipe is set straight on the center index, so it will be an evenly balanced dumbbell head. Once complete, tape the handle to the top ridge of the mold to keep it centered and vertical. Cover with plastic trash bag.
Step 7: Patience
Wait 2-3 days to demold. Remember the concrete is at its weakest right now, so treat it with care. You can pull the concrete out by the handle or turn it over and let gravity and some shaking do the work. If you lubed the mold well, it will release fairly easily.
Step 8: Now for the other DB head
Using the same concrete mix weight you previously calculated in Step 4, repeat Steps 2, 5 and 6 – with one slight change to Step 6. Place the other side of the pipe handle with screw(s) into the mold and onto the center index last – after you’ve layered and vibrated your mixed concrete and rebar into the mold for the other dumbbell head. Be sure the top DB head aligns with the bottom and use some wood scraps and/or tape to align and hold the top head straight in place while the bottom DB head sets and cures. Cover with plastic trash bag.
Step 9: MORE Patience…
Wait for the second head to set, release from the mold and let cure for as long as you are able to wait. Concrete gets to 50-70% strength after about a week and full strength after about 28 days. (Keep this in mind if you choose to use the DB before it is fully cured.)
Step 10: Finishing, Painting & Labeling
Once the dumbbell heads are cured and dry, you can sand the edges to take off any sharp corners so that it will be more comfortable to lift. You can now spray them with truck bed liner, plasti-dip or spray paint to make them whatever color you desire. Be creative! You can also label the weight of each dumbbells on the inset space provided. This rectangle is inset so that whatever you use to label the weight will not rub against you and fade over time.
*Dumbbell Calculation Chart*
This chart is a general guideline for average lengths and weights to make your dumbbells. Make sure to weigh your own pipe and handle material to make the best judgement on how much dry mix to use for each dumbbell. Variables like handle thickness, type of concrete, amount of water and amount of anchoring will change the dimensions as well as the outcome of actual dumbbell weights and sizes.
DUMBBELL TOTAL WEIGHT
PIPE HANDLE LENGTH
DRY MIX WEIGHT IN EACH MOLD
Dumbbell chart is based on Quikcrete 5000 PSI, 6-inch handles (between DB heads) and ¾ inch ID schedule 40 galvanized pipe
**To make 5lbs dumbbells, use a lighter concrete like Maximizer to keep the heads thick enough to safely use.