Introduction: Brake Rotor Barbell and Dumbbell Set
At the time of writing, we are in the throes of the Covid epidemic. Weightlifting equipment is nowhere to be had, and weights are being sold at $2/lb. I made this project because it combined my hobbies of woodworking and weightlifting. If you can handle an angle grinder, belt sander, saber saw and drill, you can make this project. The number of barbells and dumbbells are only limited by your local garage. I was lucky enough to be friends with a local garage, but you can easily buy old rotors for $2 to $4 a pair. You can make a complete weight set for about $60, not counting the bar collars.
The hard and dirty part is getting the rotors and removing the rust. It's takes dumpster diving!
Matching disk brake rotors
Power tools: angle grinder, belt sander, saber saw and drill (drill press is even better)
3/4" x 8 foot steel pipe (galvanized or black)
3/4" PVC pipe and a pair of end caps for each barbell 3/4" plywood
Bolts, bolts, washers (two or three per rotor, use up to 5/16" diameter, 1 1/2" long but you can get away with 3/16" in some cases of smaller rotors)
Clear plastic tubing (for spacers around bolts and to make handles for plates)
Old bike tires for wedging imperfectly cut plywood
Old school compass, paper to make disk templates
Navy jelly or muriatic acid to remove rust
Wire brush drill attachment
1 1/8" wood drill bit (I used a variable diameter bit. A 1 1/8" bit should work equally well.)
A couple of feet of 12 gauge wire and electrical caps
Step 1: Dumpster Diving and Rust Removal
Actually the first step is to make friends with a local garage. A local garage makes their money off brake jobs. Bring a kitchen scale and a piece of paper to write down the weights. You want to pick up pairs of rotors which combined have roughly the weight increments you want. The best rotors don't have a high hat. (Think of Abe Lincoln's hat.) You want ones with a shallow dish.
It takes a while of sorting through a dumpster, but my advice is to start by finding the lightest and the heaviest.
(There is method which might cost a little more, but save you hours of work -- sandblasting. Most body shops have sandblasters. What might take them a minute per rotor and costs you a few more dollars, may easily make the difference between being able to handle this project in a weekend or over a week.)
Moving on with the spirit of DYI, knock off the rust, rough and sharp edges first with an angle grinder.
Next, comes the belt sander to get large areas.
The next step is a little dangerous, especially if you are not used to working with acids. Be sure to use rubber gloves, goggles, face mask and long sleeves and pants. Lay out the rotors and cover them with a generous amount of acid. Let an hour pass.
Rinse off the acid, flip over and repeat. The 'solution is dilution' when working with acid. Let the rotors thoroughly dry.
Step 2: Paint Prep and Spray Painting
With a wire brush attachment, remove as much visible rust as possible. When done, you want to wipe down the surface with a clean cloth and alcohol. Isopropyl or methanol work equally well.
Mount the rotor on a wine bottle in preparation for painting.
First spray a base primer designed for metal.
Next, go wild with colors. I found the local dollar star has the most outrageous colors. The best results I had was with textured paint. Some of the thin metallic paint leftover from art projects required recoating with clear satin.
Step 3: Cut the Plywood Insert
The thick 3/4" plywood will make the hole for your barbell or dumbbell uniform and centered. In order to match the diameter of the rotor, use an old school compass.
Spread the compass as wide as possible inside the hat. Transfer that to a piece of paper. With that info, draw your circle and cut it out. The paper should neatly fit into both of your domes.
Use this paper as a template for your saber saw to cut out circles.
If it turns out that there is too much play between the plywood and rotor, use an old bike tire to ensure a snug fit. I tacked down the rubber ends with a carpet tack.
Step 4: Drill Out Holes
After seating the rounded plywood into the rotor, mark the holes with a pencil and drill out the holes.
Two holes are fine if you don't want handles. Drill four if you want handles. Choose the widest spaced holes of the largest holes to bolt the plywood.
The hole diameter should match your bolt. 5/16" x 1 1/2" should be right for the largest rotors. You can get away with smaller diameter bolts on smaller rotors.
In order to center the bolt, use one or two successive layers of plastic tubing. In other words, if one layer of tubing is too narrow, cut another segment to completely, or even partially surround the first. That way, you will have no play.
Find the center of the plywood disk by drawing lines between the rotor holes. You can also use an old geometry trick by bisecting any chord of a circle twice and finding the intersection.
You want to drill this central hole to match the iron bar diameter.
3/4" steel pipe for natural gas is 1.1" in diameter. You will need a special (adjustable) drill bit or a 1 1/8" (1.125") drill bit.
Step 5: Finishing Touches on Plates
In a pair of unused holes, use 12 or 14 gauge electrical wire, wrapped in plastic tubing for a handle. This will allow you to use the plate as a hand weight. Secure this with a standard electrical cap.
You can either grip it normally or slip your hand under the handle and grip the edge of the plate for barbell type exercises. Barring that, it helps muscling the plate onto the bar.
Speaking of the bar, you need to purchase two or three items:
1) The bar flange which keeps the plates from slipping inward. I bought this for less than $10:
1-1/8" Double Split 2-PC Shaft Steel Collar Clamp
2) Bar collar. This brand is slightly loose. The iron bar is 1.1 inches or 28 mm in diameter. Add a couple of layers of duct tape on the inside of the clamp to make it cinch down tight. Get the 30 mm one for about $12.
Weight bar collar:
3) Bar grip tape or your favorite handlebar tape:
Step 6: Making Barbells
I used PVC 3/4" pipe since my barbells aren't heavier than 25 lbs.
You can substitute 10" 3/4" iron threaded pipe for a little more heft and money.
I cut a hole in a scrap piece of the plywood and wrapped tape on the inside to keep the plate from slipping inward. This piece of wood should fit inside the rotor hole.
On the PVC ends, you can simply cap glue it with a piece of standard PVC fitting or use another pair of bar clamps.
Step 7: Bonus Kettleball (also Good for One Arm Rows)
This is an easy and optional step requiring three parts: a 8 or 10 inch length of 3/4" threaded pipe ($3), a T-joint ($2) and an end cap ($1). To this you can get a heavy duty caribiner, I got mine from Harbor Freight for $2 or you can thread a dowel. You may notice a pressure compression fitting (washer) for keeping the plate from banging. Add as many plates as you like.
Step 8: Now the Hard Work Begins!
The plates are all different colors and you can see the list of plate weights on the papers hung on the rack. The final product is great, with the only exception that the final weights are all odd numbers instead of ending in five or zero. I made a table adding the various combinations of plates so I don't have to do mental math when incrementally adding weight.
Still, it was a nifty and useful project which my wife and I can enjoy for years to come.