Magnet Sweeper

Ever drop a bunch of nails or screws? Tired of picking them up with your hands? Use some magnets!

• Lumber
• Plastic wheels
• Bolts (axles)
• Washers
• Broom handle
• Aluminum/plastic sheet
• Neodymium Magnets

Optional: We also added a steel backer to the bottom of the sweeper. This helped us configure the magnets!

First, cut your lumber to size. We used a 2 x 6 stud, cut down to 14". We choose this size so we could get two long rows of magnets.

Next, center drill two blind holes on either end of the wood for your axles. Pick a drill bit just under the size of your bolt, so you can make threads into the wood.

Once the holes are drilled, use the bolts and a socket wrench or impact driver to screw the bolt into the hole, creating threads.

We knew we needed a removable/hinged cover for the magnets. A cover protects the magnets from damage, but more importantly it creates a way to remove the attracted materials easily. Without a cover, we'd have to remove each nail or screw one by one. That's not something we want to do with rusty junk picked up with a magnetic sweeper!

We used a scrap piece of aluminum sheet metal, bent to fit our sweeper. We screwed the aluminum cover on each end to create a movable hinge.

Lastly, we drilled a 2 x 4 on an angle, for the broom handle to screw into. Drilling it on an angle gave it an ergonomic feel.

Finally, assemble all of the parts.

We attached a thin steel sheet to the bottom of the wood, allowing us to just stick magnets right to it. This made it easier to test out various magnets. Countersunk magnets can be a better, permanent option.

We used some strong, 2" x 1" x 1/4" block magnets.

You could use smaller magnets, but they won’t reach across the same distance with as much force as larger magnets do. If you decrease the magnet size, you’d also want to decrease the gap between the magnets and the ground. The magnets in our sweeper are about 2” off of the ground. That may not seem like much distance, but our sweeper has trouble picking up tiny steel balls from 2" away!

The strength also depends on the size of the object and the amount of ferrous material in that object. You’ll see more pull force to a large, thick steel washer than to a small staple!

In the video linked here, we show different magnets and how much weight they can hold.

Here is a chart of various magnets we tested. You could also use a mounting magnet screwed to a handle, like in the picture!

Besides distance, are there other factors that can help maximize the force from the sweeper? We tested a few different configurations of the magnets to see what worked best.

1. Configuration One: Alternating poles

   1. Alternating the poles like this can increase the force to a steel plate but it doesn't do well reaching across a gap. Why is this? If we consider the field lines of a magnet a “magnetic circuit”, this can help us see why configuration one doesn’t perform well at all. The magnet circuit “shorts” itself. The fields flow from one magnet to the next and don’t extend very far at all. An alternating setup can provide more pull force close to the magnets, but at the cost of weaker attraction at larger gaps.

2. Configuration Two: One row NORTH, one row SOUTH

   1. The second configuration placed one row of magnets with their north poles facing the ground and the second row with their south poles facing the ground. This created a strong field in the middle of the rows as the field flows from one row field to the next.

      This still is a "short circuit," but it reaches out a lot farther. While the following, "Configuration 3," was better for picking up some objects, this setup worked quite well on our sweeper.

3. Configuration Three: All NORTH

   1. Finally, the last configuration had each magnet with the same pole
      facing the ground, shown with all north facing down here. This worked very well, and had good reach.

      One challenge with this setup can be assembly. The magnets, side-by-side to one another, repel each other in this configuration.