magnetic coupling torque calculations 7

[dnleng]

Although this is my first post here, I have spend many hours during the last years following the forum and getting information from others, but this time it seems that I am in a dead end.

As far as magnetism goes I am a complete newbie ... So take it easy with the answers !

I am looking to construct a magnetic coupling with N52 magnets. Imagine a disc with a circular array of 9 magnets 10mm in diameter, 5mm thick. North pole facing out. Another disc (the driven one) with the same array but this time South pole facing out. I did some preliminary testing and it works, but I need to get the calculations done so instead of manufacturing every time new things we simulate and then we validate what suits us best. At work, we have ANSYS but it seems that only electromagnets are there so I did not have any luck with that...

The other thing is the polarity of the magnets. Is it better to have each array with a North-South-North configuration or the North only South only will work ?

The problem is that we are working in a very small space so we have to keep everything as small as possible and the air gap should be as large as possible. Therefore I think a simulation, or a method of calculating the max torque would be really helpful.

Many thanks in advance !
D.

 

[RyreInc]

I don't understand why having them in contact would prevent removal... With appropriately smaller magnets the coupling and removal forces could be kept consistent while using much less material--this is simply the extreme case of reducing the air gap. This would also solve the problem of axial forces while in operation.

 

[IRstuff]

There's always a spline drive, which would allow a decent gap between the rotors

TTFN
faq731-376

 

[dnleng]

It is a little bit more complicated than this. Because the right side is removable, I have to allow for tolerance (manufacturing) errors and minimize the removal force required due to the geometry of the rest of the assembly. It is not easy to grab and pull up due to geometry constraints so the tangential force required should be kept at its minimum. The most important part though is the one I explain in the last paragraph.
The spline drive if understand the suggestion would work, but only if one side slides into the other. In this case the removable parts go up (y-axis) so the spline would not work. But was that the suggestion?
The other thing is that ultimately I want to enclose the left side inside a box, so I protect it from the elements. So the airgap will help me in this situation even if it not as important now it will be in a later stage so I want to find the max air-gap - max-torque for a given geometry now and I bother later about the box !