Motor Mayhem Magnet Rotor Speed Test at 12 Volts (6 Magnets)

Hook

I pulled six magnets off the rotor and the thing immediately went faster than the full 12-magnet setup. This motor mayhem magnet rotor speed test at 12 volts gave me some surprising numbers and a few new questions.

Watch this experiment

I fired it up with the 20-gauge drive and 30-gauge trigger coils on 12 volts. The rotor took off and the tach jumped straight to around 734 RPM. After swapping the battery in the meter it settled right at 736-750 RPM steady.

What you'll learn

You’ll see real rotor speed numbers for both 12-magnet and 6-magnet configurations, how amp draw changed, and why magnetic levitation might have affected the results. All measurements come straight from the bench.

From the bench

The 6-magnet rotor hit a steady 730-750 RPM range. That’s a small improvement over the 680-720 RPM I measured with all 12 magnets. I had to stop and restart a couple times because the first reading looked too low. After changing the tach battery it read consistently around 734-736. The circuit board fell off the table once so I killed the power quick to avoid any shorts on the clips.

How it works / what we changed

We’re using the same bifilar coils (20 gauge drive, 30 gauge trigger) and monopolar MPN transistors. The only change is removing six magnets from the 12-slot rotor. I also noted that with fewer magnets the rotor is now magnetically levitated about half a centimeter higher because the stacked flanges lift when weight is reduced.

Mayhem magnet rotor speed

The mayhem magnet rotor speed jumped from the previous 680-720 RPM range up to 730-750 RPM steady at 12 volts. It wasn’t a huge gain but it was consistent across multiple restarts and the motor drew about one amp less.

Magnet rotor speed test

During the magnet rotor speed test I ran the motor at a measured 12.2 volts. After the initial spin and a tach battery swap the readings settled between 730 and 750 RPM. The 6-magnet setup felt smoother and used less current than the 12-magnet version even though top speed was only modestly higher.

Rotor speed test volts

In the rotor speed test volts stayed fixed at 12 volts (measured 12.2). The tach gave clean readings once the meter battery was swapped, showing 734 RPM on the first good run and then holding 736-750 RPM. Amp draw dropped noticeably compared with the 12-magnet test at the same voltage.

Mayhem magnet

The mayhem magnet configuration with only six magnets on the rotor produced slightly higher RPM and better efficiency. The reduced weight also let the magnetic levitation mechanism raise the rotor about half a centimeter, which might have changed the coil gap just a little.

Rotor speed

Rotor speed settled in the 730-750 RPM range with six magnets versus 680-720 RPM with twelve. Even though the difference isn’t huge, the lower amp draw makes the six-magnet rotor speed look more efficient on the bench.

Rotor speed test 12

The rotor speed test 12 volt run showed the 6-magnet rotor clearly outperforming the 12-magnet version in efficiency. RPM range improved from 680-720 up to 720-750 while current dropped by roughly one amp at 12.2 volts.

Builder checklist

• 12-slot rotor with exactly 6 magnets installed
• 20 AWG drive wire paired with 30 AWG trigger wire in bifilar coils
• Monopolar MPN transistors on the circuit
• Tachometer with fresh battery for accurate RPM
• Stacked flange magnetic levitation setup
• 12-volt power supply or battery
• Safe distance from spinning rotor

Troubleshooting

If your first tach reading looks too low, check the meter battery. My initial 700 RPM reading was wrong until I swapped it and got 734-736. If the circuit board falls, kill power immediately so clips don’t short. Make sure the rotor spins the same direction each restart.

Safety

Keep fingers clear of the spinning rotor. Cut power instantly if the circuit falls or any wires look like they might touch. These neodymium magnets are strong; keep metal tools away from the spinning disk.

FAQ

Did the 6-magnet rotor really spin faster? Yes, 730-750 RPM versus 680-720 RPM with 12 magnets, though the gain is modest.

Why did amp draw drop? Fewer magnets reduced the magnetic drag so the motor drew about one amp less at the same 12 volts.

What is the magnetic levitation doing? With less weight the rotor lifts about 5 mm on the stacked flanges, changing the height slightly.

Will 4 magnets go even faster? That’s what the next test is for. So far fewer magnets improve efficiency more than raw speed.

Related on this site

• How to Build a Pulse Motor: Parts, Coil Gap, First Spin
• Pulse Motor Rotor Design: Magnets, Materials and Balance
• Best Neodymium Magnets for Pulse Motor Rotors
• How to Maximize RPM on Your Pulse Motor
• Pulse Motor vs Bedini Motor: What's the Difference?

Watch this experiment on YouTube

• ▶ Watch full on YouTube