Adjustable Weight Hack
Power Block 50 Problem
The Power Block 50's are convenient because they let you adjust the dumbbells from 10 to 50 pounds in 5 pound increments. That makes for a lot of weight in a small footprint as long as you need a 10, 15, 20, 25, 30, 35, 40, 45 or 50 pound weight. The problem is that sometimes a 5 pound jump in weight is just too much in a dumbbell. For example, going from 25 to 30 pounds is a 20% increase in weight. What do you do when that is too much? With the right tools, some steel and some magnets you make a way to adjust them by 2 1/2 pounds instead.
The Solution - Attach Steel with Magnets
Items Needed
- Magnets
- #8-32 - 1 inch long Machine Screws and Nuts
- Spray Paint
Don't forget to grind the sharp bits off of the cuts or you'll regret it later when you are using them and accidentally cut your finger.
I didn't realize just how abrasive all of those bits of hot metal were that got thrown around by the grinder. If I'd had a lot more to make I probably would have started to notice eventually. lol
Tools Needed
- Angle Grinder
- Drill
- Screw Driver
- Pliers
- Square
- Bench Vice
Step 1 - Math
The steel bar weighed in at 86 ounces which conveniently is 5.375 pounds. 86 ounces divided by 36 inches = 2.3888889 ounces per inch.
I want to have 4 weights that with magnets added are 20 ounces each. This way, I can attach 2 per dumbbell so that everything is balanced.
The magnets and screws/nuts totalled ~1 ounce each. I'd use 2 magnets per weight, so I needed to have 18 ounces of steel.
18 ounces divided by 2.3888889 ounces per inch = 7.534 inches. The Power Block ends are 5.5 inches wide. Easy peasy, we'll just double up the steel bar stock
Step 2 - Cut Steel Into 3.75 Inch Segments
Step 3 - Weigh Segments
There is going to be some variation between steel segments, especially since this is all being done freehand. I picked pairs at random and couldn't believe it when the first pair were 0.07 ounce under the desired weight and the next pair was 0.07 ounce over the desired weight. I swapped some segments around and then both pair were exactly 20 ounces!
Step 5 - Attach 2 Plates and a Magnet with Screw/Nut
Step 6 - Weight Check
The plan is to have 2 pieces per barbell that add up to 2.5 pounds so we can cut the normal 5 pound increment in half. I came up a little short, off by 0.14 ounces. The reason for this is that I forgot to account for the loss of weight when the holes were drilled in the steel. Fortunately I didn't account for weight gain from the paint so maybe we'll get a little better when this is finished.
Step 7 - Paint and Recheck Weight
Paint the segments to match the Power Blocks, the "Forged Hammered" Rust-Oleum was a pretty good match and it got me 0.03 ounces closer to the goal weight ;-)
Step 8 - Done!
Lessons Learned
Use heavier gloves
I didn't realize just how abrasive all of those bits of hot metal were that got thrown around by the grinder. If I'd had a lot more to make I probably would have started to notice eventually. lolAccount for holes
