Curious device

[8ob]

Can two south pole magnets be attached to the input rotor to help initiate retraction?

Bob

 

[Prajna]

Can two south pole magnets be attached to the input rotor to help initiate retraction?

Bob

If I understand you, @8ob, there's no need since once the finger is moved out of the field the repulsion will be in effect again.

 

[hotponyshoes]

I agree with you completely, @hotponyshoes, but you've missing the point. The input (rotating the disc) is not driving the output, it is merely flux switching. The movement of the magnets is what is doing the pushing and Mr Newton would have no problem with that part. Where we have to go beyond Newton's mechanics is looking at the disc and it's magnets. The input is, as far as I can tell, completely decoupled from the output - we are using one system to cause unbalance in another system. It isn't a simple case of force B = force A - friction.

I'm not missing the point.
I agree that (if it works) the output will be completely decoupled from the input.
I know that magnets will work for this as I have various commercial devices that use a magnetic drive (ie completely isolated)
I also have a couple of home-made versions. (Copy of the commercial design that I have made myself to suit size requirements)

However, the disk will not rotate unless you drive the input. The magnets will not move unless the disc rotates. If the magnets don't move the output won't rotate.

So, you have no way of driving the output without driving the input.
Hence actually, the input is driving the output.
If it works it would be isolated or wireless power transmission but you can use magnets for that anyway in far simpler configuration with fewer losses.

 

[Prajna]

I'm not missing the point.
I agree that (if it works) the output will be completely decoupled from the input.
I know that magnets will work for this as I have various commercial devices that use a magnetic drive (ie completely isolated)
I also have a couple of home-made versions. (Copy of the commercial design that I have made myself to suit size requirements)

However, the disk will not rotate unless you drive the input. The magnets will not move unless the disc rotates. If the magnets don't move the output won't rotate.

So, you have no way of driving the output without driving the input.
Hence actually, the input is driving the output.
If it works it would be isolated or wireless power transmission but you can use magnets for that anyway in far simpler configuration with fewer losses.

Ah good, we're just misunderstanding each other. Yes, the rotor will need to be powered otherwise nothing will happen. I hoped that labelling the rotor "input" that it would indicate that power is input there but it is not as clear as I'd hoped. Sure there are simpler ways to magnetically couple but I'd like to understand this particular device.

 

[8ob]

If I understand you, @8ob, there's no need since once the finger is moved out of the field the repulsion will be in effect again.

I understand that, what I was getting at is there is only a single repulsion stroke , adding some southpole magnets to the input rotor could add a powered retraction stroke into the mix, may be less reliant on the flywheel effect to keep it turning.

Bob

 

[Prajna]

I understand that, what I was getting at is there is only a single repulsion stroke , adding some southpole magnets to the input rotor could add a powered retraction stroke into the mix, may be less reliant on the flywheel effect to keep it turning.

Bob

Sure. I can think of a thousand improvements but I want to keep it as simple as possible at the moment so it is easy for people to understand (it's obviously not that simple because people are finding it very difficult even like this).

 

[8ob]

Sure. I can think of a thousand improvements but I want to keep it as simple as possible at the moment so it is easy for people to understand (it's obviously not that simple because people are finding it very difficult even like this).

You are right, I cant fink but I can lift heavy fings

Bob

 

[qwakers]

 

[Guineafowl]

Yesterday I threaded some opposing neodymium magnets (with a central hole) on a shaft, and moved a spanner in and out of the gap.

The magnet pairs did separate, then close as I did so. However, it took more force to move the spanner if the magnets were free to move, corresponding to the extra energy required to move them, than if I held them with a constant gap.

In your device, the output and input are not decoupled, they’re linked with a magnetic spring. It’s not much different from a mag pump, the sort used on washing machine drains, or my beer brewing machine:

Redirect Notice

Action and reaction are coupled through, just as per Newton’s third law. The switching flux on the rotor end will oppose its motion in proportion to the work being done on the output side, much like a load on the secondary of a transformer (or a motor, which is essentially a transformer with rotating secondary) is transferred over to the primary.

 

[Prajna]

Yesterday I threaded some opposing neodymium magnets (with a central hole) on a shaft, and moved a spanner in and out of the gap.

The magnet pairs did separate, then close as I did so. However, it took more force to move the spanner if the magnets were free to move, corresponding to the extra energy required to move them, than if I held them with a constant gap.

In your device, the output and input are not decoupled, they’re linked with a magnetic spring. It’s not much different from a mag pump, the sort used on washing machine drains, or my beer brewing machine:

Redirect Notice

Action and reaction are coupled through, just as per Newton’s third law. The switching flux on the rotor end will oppose its motion in proportion to the work being done on the output side, much like a load on the secondary of a transformer (or a motor, which is essentially a transformer with rotating secondary) is transferred over to the primary.

This is the kind of feedback I was hoping for, and you experimented before posting I'm off to take a look at your link and then I'll reread your comment. Thanks.

 

[Guineafowl]

This is the kind of feedback I was hoping for, and you experimented before posting I'm off to take a look at your link and then I'll reread your comment. Thanks.

The link was just meant to be a picture of a mag pump, where the rotor is in the fluid and sealed, and the stator is slipped over the plastic housing. Although there’s no direct drive link, the magnetic flux feeds back to the stator according to the load on the rotor.

 

[Prajna]

The link was just meant to be a picture of a mag pump, where the rotor is in the fluid and sealed, and the stator is slipped over the plastic housing. Although there’s no direct drive link, the magnetic flux feeds back to the stator according to the load on the rotor.

Helpful to know and quite expected. Thank you. I will proceed to build this device - there's not much to it - and then I can check that is so for this device.

 

[voipio]

Having just tested a configuration, comprising two magnets with the same poling as the original post i.e. the large flat faces are the north and south poles of each magnet, with like poles facing each other, I can concur that placing a relatively large steel sheet (wall scraper) between the two magnets does indeed largely abolish the repulsion experienced between the two magnets, though it never becomes a perceptible attraction, as such. If the steel sheet is not laterally positioned (vertically in the original diagram) at the mid point between the magnets, it experiences an attraction to the nearest magnetic pole that becomes quite strong with decreasing distance to the magnet, and repulsion between the magnets is again present, albeit less than that which occurs without the steel sheet present. I get the strong sense that some sort of "cogging" is occuring, as described in a previous post, but the system will require a precisely made and rigid fixture, with force measurement capabilities, to actually quantify the forces that occur, as it's quite difficult to do this with the steel sheet being hand held.

The above observations lead to the intriguing possibility that, if the energy required to overcome one cycle of "cogging" (or resistance to movement), experienced by the modulator, is less than the energy capable of being produced by one cycle of repulsion-induced motion of the magnets, then we have the basis for perpetual motion. The logical part of my brain is telling me that it's impossible, considering that the law of conservation of energy will apply to this system as much as any other.

 

[Prajna]

The above observations lead to the intriguing possibility that, if the energy required to overcome one cycle of "cogging" (or resistance to movement), experienced by the modulator, is less than the energy capable of being produced by one cycle of repulsion-induced motion of the magnets, then we have the basis for perpetual motion. The logical part of my brain is telling me that it's impossible, considering that the law of conservation of energy will apply to this system as much as any other.

You can see why I find it interesting, @voipio. It is not easy to see how the load is linked back to the input as @Guineafowl pointed out with the mag motor.

 

[Prajna]

The link was just meant to be a picture of a mag pump, where the rotor is in the fluid and sealed, and the stator is slipped over the plastic housing. Although there’s no direct drive link, the magnetic flux feeds back to the stator according to the load on the rotor.

The linkage is easy to see with the mag motor because it is a direct inline connection, like a magnetic axle, if you like. In this arrangement reciprocation of the magnets by driving the swash cylinder will not drive the rotor. I wonder if this breaks the symmetry of the load feedback so that it is not linked back to the input.

 

[Prajna]

The above observations lead to the intriguing possibility that, if the energy required to overcome one cycle of "cogging" (or resistance to movement), experienced by the modulator, is less than the energy capable of being produced by one cycle of repulsion-induced motion of the magnets, then we have the basis for perpetual motion. The logical part of my brain is telling me that it's impossible, considering that the law of conservation of energy will apply to this system as much as any other.

Another thing, @voipio, this conservation of energy thing, it applies because energy can neither be created or destroyed and therefore in any closed system the total energy is fixed. That only applies in a closed system though. If energy can be brought into a system then energy is not being created but we still need to show where it is entering the system.

 

[Maker]

If energy can be brought into a system then energy is not being created but we still need to show where it is entering the system.

It enters the system as rotation at the input shaft, and leaves the system as heat generated through friction in bearings and slides, and through resistive heating caused by eddy currents in the finger wheel.

 

[hotponyshoes]

Where is this extra energy ment to be coming from? The energy required to overcome the cogging will be the same as the work done by the magnets when they move. Plus a bit for friction etc.

A simple way to test this,
Take the 2 magnets on a folded card version as posted previously.
Weigh it and divide it by 2.
That weight will be the work done by the magnets as they lift the weight of one magnet & half of the card.
Now make up a simple pivoting leaver arrangement that slides the sheet of metal in between the magnets.
Put some weight on the end of the leaver.
If the weight required to slide the sheet in/out is less than the weight of the magnet & half card you are onto a winner.

If you have a 3d printer you could make up all the parts for the machine in the first post over the weekend and let us know if it works on Monday..

 

[Prajna]

Where is this extra energy ment to be coming from? The energy required to overcome the cogging will be the same as the work done by the magnets when they move. Plus a bit for friction etc.

A simple way to test this,
Take the 2 magnets on a folded card version as posted previously.
Weigh it and divide it by 2.
That weight will be the work done by the magnets as they lift the weight of one magnet & half of the card.
Now make up a simple pivoting leaver arrangement that slides the sheet of metal in between the magnets.
Put some weight on the end of the leaver.
If the weight required to slide the sheet in/out is less than the weight of the magnet & half card you are onto a winner.

If you have a 3d printer you could make up all the parts for the machine in the first post over the weekend and let us know if it works on Monday..

Sadly, I have no 3d printer, hence my idea of trotting off to FabLab. But then FabLab is a good half hour's drive from here and I've no transport atm. Besides which, I have not yet engaged with FabLab, so don't know what the process is there, just they have some great kit for prototyping.

 

[Morris]

Oh, and yes also regarding the distance the magnets move but I was quite impressed by how far they do move apart even using the cheap little magnets I used in my investigation.

Here is a pic of my initial test:

View attachment 440904

I attached two small magnets from a fly screen to a folded business card. You can see that the field holds them at a respectable distance.

What happens when you put a sheet of steel between them? If you get no movement you have your answer. If you do get movement you can explore further.