magnetic joint

[SMIRRO]

Good morning.
from the search tools of the forum I did not find any discussion dedicated exclusively to this, so I decided to create one, because for my need I am evaluating this application, and I always found myself well to confront the people of this forum.
I come to this point: I would like to model the transmission by mangnetic joint to understand whether or not it can replace it with an existing belt drive in a machine I designed, and that is in operation.
in the past I have found myself to have to use these products in applications where synchronism between engine and load was not important, in this case instead it would be very important, as well as cycle times: In about 250ms it would be necessary to reach the speed of 300rpm, for the couple I have not yet certain data, also because in case I put the magnetic joint I would succeed in eliminating several components, which at this moment create frictions increasing the load on the transmission. I can say that the engine is able to deliver a pair of about 2nm, reduced 7, so you get to a maximum pair of about 14nm.
I have found some products that promise very high pairs, but they work on the circumference, in the sense that the magnets are arranged radially and there are a hub and a tree.
to me they would need to work frontally, like the first image of this link here, and I would like to model the problem analytically to size it.
one of the 2 magnetic complexes, probably the one at the engine, will also have to be an electromagnet, since the engine is one, while the loads are more than one and from time to time alternate.
other problem are the reduced dimensions, maximum 100mm in diameter, and the distance between the 2 parts of the joint, because precisely because for the problem that the charges alternate with each cycle cannot be in direct contact the faces, but at least a couple of mm.
thanks to anyone who can and wants to contribute to the discussion.

 

[TETRASTORE]

Good morning to you.
If your needs are to have a perfect synchronism between engine and load I fear that the disc magnet joint is not the optimal solution because of the load angle, which is basically the angle shift between the two front discs determined by the applied initial couple.
this means that at each start the shaft will start with a slight delay and this will have a negative influence in the presence of frequent starters, motion inversions or torque variations, moreover to the overcoming of the limit torque, you will have a slide that will no longer guarantee a possible synchronization. there is also to consider the axial load determined by the magnets placed in front position, load not present in the axial magnetic joints.
with regard to the encumbrances of a magnetic disc joint, I fear that it is difficult to fall within the 100 mm of maximum diameter imposed; In this regard I attach an extract from the manufacturer's catalog quoted in the document of your second link, but you can always search other manufacturers.

one of the 2 magnetic complexes, probably the one at the engine, will also have to be an electromagnet, since the engine is one, while the loads are more than one and from time to time alternate.

if I have understood well you refer to the application of an electromagnetic clutch; If so, and if you have a high frequency of start-ups or inversions you can consider it as an optimal solution to keep the engine at speed and start-up the application with this device.

 

[meccanicamg]

I'd go with a tooth graft clutch. a magnetic joint would not use it to guarantee phase.

 

[SMIRRO]

Thank you very much for your interest.

if I have understood well you refer to the application of an electromagnetic clutch; If so, and if you have a high frequency of start-ups or inversions you can consider it as an optimal solution to keep the engine at speed and start-up the application with this device.

Yes, I am referring to this product and I am also encapsulated on the same page of catagol. I agree with all the observations made. I was specified that the scroll in particular would happen only to the exceeding of the maximum torque, and it would happen in step, that is every dipole that is created between semi-joint motor and duct, would jump of a position, going to work on the previous one, creating a motorcycle "to snaps", so to speak.
the bike takes place only in one direction always.
I managed to steal something on the 100mm and I think I can return to the guaranteed couple by decreasing the distance between the 2 semi-joints. I'm worried "only" that frontal attraction you mentioned before, I'm afraid it can cause dissolving, or in any case a load too high to the engine that alternates the elements to be rotated.

I'd go with a tooth graft clutch. a magnetic joint would not use it to guarantee phase.

for now I would avoid the clutch wheel, because it would create even more residues of the old belt transmission, and its insertion would complicate not little my mechanics.

If I could get the magnetic joint, it would be the cleanest solution.

 

[TETRASTORE]

I'm worried "only" that frontal attraction you mentioned before, I'm afraid it can cause dissolving, or still a load too high to the engine

for misalignment I would not worry, fundamentally the only force to consider is that of magnet attraction, variable according to the distance between the disks (and, if present, of the eventual material interposed).
the manufacturer should provide you with the graph of how the axial force varies depending on the distance (see example attached) and, according to this, verify its influence as axial force on the bearing (motor) that must support the load.

 

[SMIRRO]

Good morning, I'm going back to evaluate the option of self-build it. mainly because the costs are high and the object is constituted only by a joint with some magnets from a few euros above, and then because I would have the necessity that one of the semi-joints mounted electromagnets, which I have not met anywhere yet.
So I'm trying to model the problem. Firstly: I have not yet found if there is a relationship that binds the force of attraction to the tangential force that the magnet is able to transmit without direct contact.
Moreover, in case I use 2 identical magnets that you look at, can I consider the strength of one another duplicated?
thanks to anyone who wants to contribute.

 

[TETRASTORE]

I would need one of the semi-joints to mount electromagnets, which I haven't met anywhere yet.

search the internet: clutches, triggers and electromagnetic joints, there are many types, systems, patterns and drawings.

I have not yet found if there is a relationship that binds the force of attraction to the tangential force that the magnet is able to transmit without direct contact.

at the indicative level you can see here: torque performance transmitted by the joint depending on the exhaust angle (p. 34-35).
It is obvious that the transmissible couple also varies according to the distance between the opposing magnets; qui you can see some charts with the variation of the torque depending on the distance.

Moreover, in case I use 2 identical magnets that you look at, can I consider the strength of one another duplicated?

you can verify it using this calculator that calculates the attraction force of the magnets according to the data you enter. .
you might be interested in methodology used to measure the friction forcene.