Homopolar motor rotation in Vacuum

[Stoyan]

Hi,
I've found interesting video.
Roller homopolar motor :
Roller Motor
Do you think the motor from 1:08 min Will self rotate in Vacuum/Space
(No other forces : Gravitational or Other type.)
Thank you in advance. 

 

[Snark]

8 hours ago, Stoyan said:

Do you think the motor from 1:08 min Will self rotate in Vacuum/Space

Sure, it should work just fine in a vacuum, same as any other kind of motor.

That said, though:  this is not some sort of magical angular momentum machine.  Conservation of angular momentum still applies.  Like any other motor or rotary device that's free-floating in a vacuum, it will simply rotate the armature in one direction, while the rest of the device rotates in the opposite direction.  Action/reaction.  Net angular momentum remains zero.

Therefore, in this particular example:  what I would expect to happen is that the little wire would spin around rapidly in one direction, whereas the rest of the device (battery plus magnets) will rotate slowly in the opposite direction.  (The battery etc. will rotate a lot slower than the wire will, because it is much more massive and therefore has a much higher moment of inertia.)

[insert_name]

depends on whether it would cold weld shut or not

[Stoyan]

1 hour ago, Snark said:

Sure, it should work just fine in a vacuum, same as any other kind of motor.

That said, though:  this is not some sort of magical angular momentum machine.  Conservation of angular momentum still applies.  Like any other motor or rotary device that's free-floating in a vacuum, it will simply rotate the armature in one direction, while the rest of the device rotates in the opposite direction.  Action/reaction.  Net angular momentum remains zero.

Therefore, in this particular example:  what I would expect to happen is that the little wire would spin around rapidly in one direction, whereas the rest of the device (battery plus magnets) will rotate slowly in the opposite direction.  (The battery etc. will rotate a lot slower than the wire will, because it is much more massive and therefore has a much higher moment of inertia.)

Thank you for the answer.

The motor from 1:08 Rolls (Battery and Magnets and Wire-connecting them) in one direction.

It rolls (All Parts are Rolling in one direction).

Rolling motion = Rotation+Translation.

Is it going to rotate the same way (In one direction)

in Vacuum/Space.

Thank you.

[Shpaget]

Vacuum would have no effect on motion, other than no drag so higher speeds would be possible, but if you are thinking about free fall (floating in zero gravity), then there would be no translation.

In the video, the motor is placed on the surface of a table and the wire is pushing against it. Since there is some torque between the wire and the battery, and the rotation of the wire is constrained, only the battery rotates which leads to rolling. In free fall there would be no such constraint and the wire would rotate freely in the opposite direction of the battery, and since there would be nothing to roll against there would be no translation.

[Snark]

1 hour ago, Stoyan said:

The motor from 1:08 Rolls (Battery and Magnets and Wire-connecting them) in one direction.

It rolls (All Parts are Rolling in one direction).

Rolling motion = Rotation+Translation.

Is it going to rotate the same way (In one direction)

in Vacuum/Space.

Thank you.

Clearly there's some other interaction going on in the video. Either all parts are not actually moving together, or else there's some sort of interaction with the table or something going on. (For all I know, the person who made the video is trolling with that one, and is tilting the table or something. Who knows?)

This is because it's not physically possible to build a device that can simply start spinning with net angular momentum without any external interaction. It would violate conservation of angular momentum, which doesn't happen.

So, no, you haven't discovered a new form of space drive.

 

[magnemoe]

2 hours ago, Snark said:

Sure, it should work just fine in a vacuum, same as any other kind of motor.

That said, though:  this is not some sort of magical angular momentum machine.  Conservation of angular momentum still applies.  Like any other motor or rotary device that's free-floating in a vacuum, it will simply rotate the armature in one direction, while the rest of the device rotates in the opposite direction.  Action/reaction.  Net angular momentum remains zero.

Therefore, in this particular example:  what I would expect to happen is that the little wire would spin around rapidly in one direction, whereas the rest of the device (battery plus magnets) will rotate slowly in the opposite direction.  (The battery etc. will rotate a lot slower than the wire will, because it is much more massive and therefore has a much higher moment of inertia.)

This its just an reaction wheel. you can use it to induce an rotation on main body by spinning up or slowing down an already spinning wheel. In theory it works like KSP reaction wheels. In practice you to have external forces like solar pressure, drag and magnetic fields. 

[Stoyan]

Thank you all for the opinions.

The motor from 1:08

(of which all parts are rolling in one direction-

Rolling=Translation+Spinning).

If this motor is in Vacuum , will it start rotate by self?

Only if you are Sure.

Thank you.

[Snark]

3 minutes ago, Stoyan said:

The motor from 1:08

(of which all parts are rolling in one direction-

Rolling=Translation+Spinning).

If this motor is in Vacuum , will it start rotate by self?

If the "motor" is all one solid piece with nothing moving relative to anything else, and it all just rotates together... then no, this would not work in a vacuum. Because it wouldn't work at all, anywhere.

(And wouldn't work in this video, either, which means that the video creator "cheated" by tipping the table or blowing on it or something like that.)

So, no, you haven't discovered a new kind of space drive.

[farmerben]