1916 electric motor build

[odysseus2000]

Lovely short video showing a 1916 text book that describes how to build an electric motor which is then made very similarly to the original design:

https://youtu.be/-nadoDBenms?si=menqmTRfGG8n1AT3

It is interesting to me how this simple motor demonstrates the science in such a clear practical putting the builder in a position to understand both the science & the technology to make a practical machine.

Regards,

[mc2fool]

Maybe not such a practical motor, but (IMHO) more lovely to watch and just as educational ... https://www.youtube.com/watch?v=LoSGSawJCO0

[odysseus2000]

Maybe not such a practical motor, but (IMHO) more lovely to watch and just as educational ... https://www.youtube.com/watch?v=LoSGSawJCO0

Nice!

So incredibly simple demonstrating the basic concepts. Compare this to an heat engine, external or internal combustion, and the reason why I believe electric cars will replace internal combustion due to their much lower cost construction & maintenance become obvious.

Regards,

[jfgw]

Maybe not such a practical motor, but (IMHO) more lovely to watch and just as educational ... https://www.youtube.com/watch?v=LoSGSawJCO0

I was trying to fathom out how that could work so I checked the comments. One commenter makes the point that the enamelled wire needs to be sanded on one side only, making a crude commutator.

If the motor would work with the wire sanded all the way around, it would be possible to replace the coil with a permanent magnet and build a perpetual motion machine.


Julian F. G. W.

[odysseus2000]

Interesting historical table, made known to me by the creator of the first video, that shows the time development of electric motors, beginning in the 18 th century:

https://en.m.wikipedia.org/wiki/Timelin ... tric_motor

Regards,

[odysseus2000]

Maybe not such a practical motor, but (IMHO) more lovely to watch and just as educational ... https://www.youtube.com/watch?v=LoSGSawJCO0

I was trying to fathom out how that could work so I checked the comments. One commenter makes the point that the enamelled wire needs to be sanded on one side only, making a crude commutator.

If the motor would work with the wire sanded all the way around, it would be possible to replace the coil with a permanent magnet and build a perpetual motion machine.


Julian F. G. W.

It would be interesting to try & see if a fully stripped wire would work.

My guess is that it would as the motor is not self starting, but needs an impulse to get it going.

If a permanent magnet replaced the coil it would likely spin for a while but friction on the “bearings” would eventually cause it to slow & as its momentum falls it would soon become stuck with North or South Pole of the rotated magnet becoming locked to the South or North Pole of the fixed magnet.

As presented the battery produced current will counter friction losses keeping the coil spinning.

The.mechanism is similar to the electric pendulum clocks were an electronic circuit detects when the pendulum is at the bottom & gives it a repulsive kick that keeps it going.

A short 6 minute video shows how they work:

https://youtu.be/psHVTiIoAWA?si=uULNk-syxxFfK_ZZ

Regards,

[jfgw]

As presented the battery produced current will counter friction losses keeping the coil spinning.

I don't see how it could do that as the nett effect of the coil would be zero.

The.mechanism is similar to the electric pendulum clocks were an electronic circuit detects when the pendulum is at the bottom & gives it a repulsive kick that keeps it going.

A short 6 minute video shows how they work:

https://youtu.be/psHVTiIoAWA?si=uULNk-syxxFfK_ZZ

That is an interesting video which explains simply how such a circuit works. The important thing is that the circuit detects the movement of a magnet on the pendulum and uses a transistor to switch power to the coil at the right time to keep it going. This is similar to the commutator on an electric motor except that a commutator/brush combination repeatedly reconnects the armature windings in order to keep the armature magnetised at (usually) about 90 (electrical) degrees to the external magnetic field.

A heteropolar motor needs some means of changing the direction of the magnetic field on either the stator or the rotor. (If the rotor is wound, it is usually called an armature.) A DC motor uses a commutator. An AC induction motor uses the alternating current to produce an alternating field.

The first electric motor, made by Michael Faraday, was homopolar and ran on DC without a commutator. He used mercury as the lower contact but it is safer to use brine. https://www.youtube.com/watch?v=r967ko07qg8.


Julian F. G. W.

[odysseus2000]

As presented the battery produced current will counter friction losses keeping the coil spinning.

I don't see how it could do that as the nett effect of the coil would be zero.

The.mechanism is similar to the electric pendulum clocks were an electronic circuit detects when the pendulum is at the bottom & gives it a repulsive kick that keeps it going.

A short 6 minute video shows how they work:

https://youtu.be/psHVTiIoAWA?si=uULNk-syxxFfK_ZZ

That is an interesting video which explains simply how such a circuit works. The important thing is that the circuit detects the movement of a magnet on the pendulum and uses a transistor to switch power to the coil at the right time to keep it going. This is similar to the commutator on an electric motor except that a commutator/brush combination repeatedly reconnects the armature windings in order to keep the armature magnetised at (usually) about 90 (electrical) degrees to the external magnetic field.

A heteropolar motor needs some means of changing the direction of the magnetic field on either the stator or the rotor. (If the rotor is wound, it is usually called an armature.) A DC motor uses a commutator. An AC induction motor uses the alternating current to produce an alternating field.

The first electric motor, made by Michael Faraday, was homopolar and ran on DC without a commutator. He used mercury as the lower contact but it is safer to use brine. https://www.youtube.com/watch?v=r967ko07qg8.


Julian F. G. W.

To be sure we would have to make both a half stripped enamel wire version & a fully stripped.

This is how I think it would work as a fully stripped version.

The battery produces a field in the rotating solenoid with a North & South Pole. At rest the solenoid North Pole would align it with the South Pole of the permanent magnet, or vice versa depending upon the orientation of the permanent magnet.

For simplicity let’s assume the permanent magnet is positioned South Pole up.

When the solenoid is perturbed from this configuration with sufficient angular speed, the permanent magnet can’t keep attracting the solenoid North Pole & it now finds the solenoid South Pole coming towards it which it repels, but with sufficient angular velocity it can’t stop the solenoid reaching the distance of closest approach & at that point the two magnets are forced apart by the mutual repulsion. This cycle repeats with the battery providing energy to maintain the solenoid field & resisting the tendency for friction to slow the rotating solenoid to the point where it would become stuck in the original configuration.

If half of the enamel wire was stripped in half of the cycle there would be no magnetic field in the solenoid, so that there would either be no attraction or no repulsion in half of the cycle.

A more sophisticated motor would have a commutator that provides current to the coil that is in anti phase to the permanent magnet so as to create acceleration on the approach to minimum separation & repulsion beyond that point.

It is possible that the thing was built & spun & worked the first time as shown, or there were several adjustments made till they got a configuration of permanent magnet, coil & separation that worked. My guess would be the latter as these kinds of things can be awkward.

More sophisticated would be multiple coils all synced to provide attraction & repulsion as needed.

Yes more sophisticated would be a brushless motor that uses electronics to provide the appropriate field timing to keep a permanent magnet rotating:

https://en.m.wikipedia.org/wiki/Brushle ... tric_motor

Regards,

[jfgw]

I have been pondering over Hannah Fry...

...'s video. There are a lot of YouTube videos which show the construction of this type of motor in more detail, mostly accompanied by annoying background music. They show that the wire one end should be sanded on one side only, for example, starting at 1:23 in this video: https://www.youtube.com/watch?v=WI0pGk0MMhg.

Some video titles describe this as a homopolar motor. It is not; it is heteropolar.


Julian F. G. W.

[kempiejon]

So I learnt from this thread that the wire, battery, magnet motor I found the other year and made to some delight for work colleagues is homopolar. Like this un
https://www.sciencebuddies.org/stem-act ... olar-motor