I Finally Got My Ferrite Donut Magnets Spinning Smooth

Hook

I slid a quarter-inch pole into these ferrite donut magnets and the disc spun like it was greased. The magnetic drag is so faint you can barely feel it.

Watch this experiment

I show two completed 8-inch wooden discs loaded with ferrite donut magnets. Everything faces the same way so north is dominant on both sides. You can see the shaft is three feet long but only a quarter inch thick and it drops right into the quarter inch holes.

What you'll learn

How stacking ferrite donut magnets hides the south pole, why the spin feels almost frictionless at first, and how these big magnet discs might become the top and bottom of a cyclotron-style setup.

From the bench

I started every video saying "okay so" and this one is no different. I'm looking at these discs trying to figure out the right orientation for a cyclotron. North on the bottom, south on the top, and a special spinning disc in the middle that is either half north half south or north and neutral. The goal is push up from the bottom and lift up from the top.

I already have two finished 8-inch discs. Each one has all the ferrite donut magnets facing the same direction. When they're this close the south pole gets hidden and you get almost perfect levitation. You can still feel the magnets pass each other but it's faint. The disc spins like it's been oiled up but it does eventually stop because of that faint presence.

How it works / what we changed

These are not levitating like there's a magnet directly above or below. It's more like the fields cancel enough to let it spin freely for a while. Anyone can overcome the drag with a little push but the point is to need the least amount of energy input. Some people like to keep the foot on the gas the whole time. That's fine too.

The poles are three feet long but only a quarter inch in diameter. Each wooden disc has a quarter inch hole so they fit perfectly and that's what lets them spin so freely. I use graphite powder lubricant and it gets all over everything.

magnet holes

The ferrite donut magnets have magnet holes that are exactly a quarter inch. The wooden discs also have quarter inch holes. That means the quarter-inch poles slide right in with a perfect fit. No slop, just smooth rotation. The poles are steel and the fit is so good the disc can spin for a long time before the faint magnetic drag stops it.

big magnet

These are big magnet discs. Each 8-inch wooden disc is loaded with ferrite donut magnets all facing the same way. That makes one side almost entirely north and the other side also north because the south is hidden when they're packed close. I can flip them to create north-south facing pairs that pull together hard but still come apart. I only have two complete 8-inchers right now so I'm thinking about making an 8-inch top, 8-inch bottom, and a 6-inch middle rotor.

magnet image

If you can magnet image in your head these discs are basically big magnet north and south sides. I picture using the existing discs for the top and bottom of the cyclotron and building a special center disc. The center one might be half and half or north and neutral. The magnet image I'm carrying around is push up from the bottom disc and lift up from the top disc. It should work either with all north or by flipping one disc.

Builder checklist

• Ferrite donut magnets with quarter-inch center holes
• Wooden discs cut to 6 or 8 inch diameter with matching quarter-inch center holes
• Quarter-inch diameter steel poles (up to 3 ft long)
• Graphite powder lubricant
• Vacuum plate and pump if you want to try reduced pressure
• Way to flip and test north-south orientations

Troubleshooting

If the disc stops too quickly the south pole might not be hidden well enough. Try spacing the magnets differently or flipping the entire disc. If it binds, check that the pole is perfectly straight and the holes are exactly quarter inch. Graphite powder helps but it makes a mess.

Safety

These big magnet discs can snap together hard if you let north and south face each other. Keep fingers clear when testing attraction. The three-foot poles can be awkward. Work in a clear space and watch for the graphite powder getting slippery on the floor.

FAQ

Do the magnets actually levitate? Not really. They still touch the shaft but the magnetic field makes the drag very faint so it feels like levitation.

Can I use neodymium instead? The transcript only covers these ferrite donut magnets. I haven't tested stronger magnets in this exact setup yet.

Will a vacuum make them float? I doubt it because the magnets are heavy. It might be zero error but not zero gravity. We'll test it.

How long does it spin? Long enough that you notice how little friction there is, but it always slows and stops because of the faint magnetic presence.

Related on this site

• How to Build a Pulse Motor: Complete Beginner's Guide
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Magnetic Levitation with Six Donut Magnets
• Donut Magnets — Outside Poles & Motion
• I Finally Got My Pulse Motor Running (Reed Switch)

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