I was playing around with fridge magnets last night.
These have magnetic parallel strips of N and S polarity.
It occurred to me that if you wrapped a fridge-type magnet around a cylinder it would act as a gear wheel. As one span it would cause an adjacent one to spin.

Have you heard of magnetic gear wheels like these?

At first I thought there wouyld be no applications, because above maximum torque it slips.
So definitley not useful in systems that require either very high torque or zero backlash.
Then I thought that mag-lev trains use a linear type of magnetic gears
Ditto rail guns.
I also have a toy on my mantlepiece, where a spinning disk of permanent magnets arranged radially makes a dancer with a permanent magnet base twirl and move unpredictably.

The gears could be bevelled or have spiral “teeth” with no problem at all.

And the torque limited slippage could be useful. A normal gear with teeth is damaged if the maximum torque is exceeeded but magnetic gears would slip harmlessly. Which would be useful in applications with torque limiters. No need for accurate machining of gear teeth. Also you could overcome the tyrrany of diameter. By placing magnetic stripes closer or further apart a driven wheel could spin faster or slower than a driving wheel of the same diameter.

So, cheap lightweight gears made mostly of plastic, magnetised as a replacement for teeth, could be used in torque limited devices such as dremels, drills, mowers and angle grinders, where adding a clutch would add to the cost, and where the speed doesn’t have to overly precise. They could be used in clocks, too, but I wouldn’t.

Opening up the wheel into a belt with magnetic stripes would be useful for such an application as a toothless fanbelt, as it slips completely harmlessly if overloaded.

Or another application would be magnetic strips on a conveyor belt for recycled rebbish. The converyor belt then holds onto steel items for longer to make separation of steel from plastic much easier. A tentative posibility would also be in separation of magnetite iron ore from unwanted stones.

Do you know of any applications where permanent magnet gear wheels are actually in use? Or belt drives or conveyor belts?

mollwollfumble said:

I was playing around with fridge magnets last night.
These have magnetic parallel strips of N and S polarity.
It occurred to me that if you wrapped a fridge-type magnet around a cylinder it would act as a gear wheel. As one span it would cause an adjacent one to spin.

Have you heard of magnetic gear wheels like these?

At first I thought there wouyld be no applications, because above maximum torque it slips.
So definitley not useful in systems that require either very high torque or zero backlash.
Then I thought that mag-lev trains use a linear type of magnetic gears
Ditto rail guns.
I also have a toy on my mantlepiece, where a spinning disk of permanent magnets arranged radially makes a dancer with a permanent magnet base twirl and move unpredictably.

The gears could be bevelled or have spiral “teeth” with no problem at all.

And the torque limited slippage could be useful. A normal gear with teeth is damaged if the maximum torque is exceeeded but magnetic gears would slip harmlessly. Which would be useful in applications with torque limiters. No need for accurate machining of gear teeth. Also you could overcome the tyrrany of diameter. By placing magnetic stripes closer or further apart a driven wheel could spin faster or slower than a driving wheel of the same diameter.

So, cheap lightweight gears made mostly of plastic, magnetised as a replacement for teeth, could be used in torque limited devices such as dremels, drills, mowers and angle grinders, where adding a clutch would add to the cost, and where the speed doesn’t have to overly precise. They could be used in clocks, too, but I wouldn’t.

Opening up the wheel into a belt with magnetic stripes would be useful for such an application as a toothless fanbelt, as it slips completely harmlessly if overloaded.

Or another application would be magnetic strips on a conveyor belt for recycled rebbish. The converyor belt then holds onto steel items for longer to make separation of steel from plastic much easier. A tentative posibility would also be in separation of magnetite iron ore from unwanted stones.

Do you know of any applications where permanent magnet gear wheels are actually in use? Or belt drives or conveyor belts?

Why do the words ‘induction motor’ spring to my mind?

captain_spalding said:

mollwollfumble said:

I was playing around with fridge magnets last night.
These have magnetic parallel strips of N and S polarity.
It occurred to me that if you wrapped a fridge-type magnet around a cylinder it would act as a gear wheel. As one span it would cause an adjacent one to spin.

Have you heard of magnetic gear wheels like these?

At first I thought there wouyld be no applications, because above maximum torque it slips.
So definitley not useful in systems that require either very high torque or zero backlash.
Then I thought that mag-lev trains use a linear type of magnetic gears
Ditto rail guns.
I also have a toy on my mantlepiece, where a spinning disk of permanent magnets arranged radially makes a dancer with a permanent magnet base twirl and move unpredictably.

The gears could be bevelled or have spiral “teeth” with no problem at all.

And the torque limited slippage could be useful. A normal gear with teeth is damaged if the maximum torque is exceeeded but magnetic gears would slip harmlessly. Which would be useful in applications with torque limiters. No need for accurate machining of gear teeth. Also you could overcome the tyrrany of diameter. By placing magnetic stripes closer or further apart a driven wheel could spin faster or slower than a driving wheel of the same diameter.

So, cheap lightweight gears made mostly of plastic, magnetised as a replacement for teeth, could be used in torque limited devices such as dremels, drills, mowers and angle grinders, where adding a clutch would add to the cost, and where the speed doesn’t have to overly precise. They could be used in clocks, too, but I wouldn’t.

Opening up the wheel into a belt with magnetic stripes would be useful for such an application as a toothless fanbelt, as it slips completely harmlessly if overloaded.

Or another application would be magnetic strips on a conveyor belt for recycled rebbish. The converyor belt then holds onto steel items for longer to make separation of steel from plastic much easier. A tentative posibility would also be in separation of magnetite iron ore from unwanted stones.

Do you know of any applications where permanent magnet gear wheels are actually in use? Or belt drives or conveyor belts?

Why do the words ‘induction motor’ spring to my mind?

and linear motors.

JudgeMental said:

captain_spalding said:

Why do the words ‘induction motor’ spring to my mind?

and linear motors.

Those words do indeed spring to mind. That’s why I was specific about saying “permanent” magnet.

Yes, there are permanent magnet motors, used for example in driving the wheels of electric cars, but I’m thinking here of gears that don’t require electricity, such as those in clockwork.

Perhaps like this?
Magnetically Assisted Gears

Spiny Norman said:

Perhaps like this?
Magnetically Assisted Gears

That’s fascinating. Not at all what I was expecting – essintially zero wear.
This would be ideal in space, where contact can lead to “contact welding” that stuffs up mechanical movement in Skylab, Galileo, Beagle etc.