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Magnets Discussion and Help thread

Scrombo

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Sep 14, 2019
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27
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Earth
Out of morbid curiosity, I have a few older 3x3s lying around I'm thinking of magnetizing: an Aolong V2, Shengshou Wind, and Shengshou Legend. I have a few questions:

1. If I go through with this, how do I approach magnetizing the Legend? Both the edges and corners are capped.

2. To anyone that has a magnetized version of any of these cubes, did you feel a significant improvement after any of them? Do they feel heavy after magnetization?

I know we have better and cheaper puzzles available now, many of which I have, but I thought it would be fun to attempt a PB AO12 on one of these older puzzles. Thanks in advance.
 

EngiNerdBrian

Premium Member
Joined
Jun 21, 2018
Messages
385
Location
Denver
Has anyone magnetized the MFJS MF3RS? It is one of my only modern cubes without magnets and i feel it might actually have a purpose if it had magnets. I have a set of cubicle strong and lite magnets available to use. For reference i main an Angstrom YLM from the cubicle.
 

I'm A Cuber

Member
Joined
Jan 28, 2020
Messages
424
Figured as much, i kinda see forums as archives for future reference though too haha. So what did you do and how did they perform?
I did strong in the corners and weak in the edges. It is a too fast for me, although I am currently trying to get Sub-20 with roux, and I really like it for that
 

RFMX

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Joined
Aug 10, 2020
Messages
11
Location
Hong Kong
Are 4x2 magnets actually much stronger than 5x1 magnets? I am using this magnetic gap calculator and found that N35 4x2 has a higher magnetic field strength than N52 5x1, which feels like nonsense to me.

FYI I use 2.09 mm (GAN 356 R) as the gap for both inputs, and got 3460 (N52 5x1) and 4454 (N35 4x2) gauss as the result.
 

xyzzy

Member
Joined
Dec 24, 2015
Messages
1,964
Are 4x2 magnets actually much stronger than 5x1 magnets? I am using this magnetic gap calculator and found that N35 4x2 has a higher magnetic field strength than N52 5x1, which feels like nonsense to me.

FYI I use 2.09 mm (GAN 356 R) as the gap for both inputs, and got 3460 (N52 5x1) and 4454 (N35 4x2) gauss as the result.
Disclaimer: not a physics expert, or even a cube hardware expert.
tl;dr: last sentence of this post

The magnetic field strength when the magnets are already perfectly aligned means basically nothing. The things you should care about (wrt magnets in cubes) are:

- Attractive force when layers are aligned. This influences friction (*); more force means more friction, which in turn means that initiating a turn will be harder. This may be desirable to avoid unintentional misalignments (e.g. not getting a +2 when dropping the cube, or keeping the layers together on megaminx or big cubes). This is what the K&J Magnetics pull force calculator calculates.
- How the force parallel to the turning axis changes with misalignment angle. This is how much the amount of friction changes as you complete a turn. Sharper changes in force means more slowing down at the end of a turn. For the same amount of pull force, a larger magnet diameter usually corresponds to a more gradual change in force.
- Did I say frictional force above? Scratch that; you really care about the torque instead. You're almost always applying force to a layer from a consistent distance from the turning axis, so that's essentially constant. What you can change is magnet placement: magnets closer to the core will have the magnetic effects at a smaller radius, and hence the above two factors will lead to less torque. Conversely, magnets closer to the exterior will lead to more torque.
- The torque induced by magnets pulling each other together. (This concerns force perpendicular to the turning axis.) Again, further from the core means more torque. This controls how "snappy" the magnets are—more torque here means that layers will be pulled towards alignment harder.

(*) Friction is crucial here. If you make the spherical-cow-in-a-vacuum assumption that everything is frictionless, your turns would never come to stop on their own: flick a layer once and it'll keep moving forever, speeding up when it comes near alignment and slowing down when it goes out of alignment, which is the opposite of what we want!

There is no "ready-made" online calculator to determine all of the above factors, and ab initio calculations are very difficult. You'd do well to go by gut feel instead of blindly trusting hard-to-interpret numerical values.
 
Last edited:

RFMX

Member
Joined
Aug 10, 2020
Messages
11
Location
Hong Kong
Thanks for the explanation. I'm actually considering to buy and magnetise a GAN 356 RS using N42 4x2, but I found Yoshi magnetising the R using N48 5x1. I'm not sure how to choose the magnetic strength for a cube. Is there any guidelines for choosing the type of magnets, or is it usually a blind pick?
 

Tabe

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Feb 6, 2017
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Spokane, WA (USA)
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It's kind of a blind pick. Another thing to consider is that the magnetic force of a 5x1 magnet is spread over a wider area than a 4x2 magnet. The 4x2 will have a stronger click to it than the 5x1 because its magnetic force is concentrated into a smaller area in terms of width.
 

I'm A Cuber

Member
Joined
Jan 28, 2020
Messages
424
Thanks for the explanation. I'm actually considering to buy and magnetise a GAN 356 RS using N42 4x2, but I found Yoshi magnetising the R using N48 5x1. I'm not sure how to choose the magnetic strength for a cube. Is there any guidelines for choosing the type of magnets, or is it usually a blind pick?
I magnetized my rs with the 5x1 n48s, and it is a pretty good strength
 

EngiNerdBrian

Premium Member
Joined
Jun 21, 2018
Messages
385
Location
Denver
Disclaimer: not a physics expert, or even a cube hardware expert.
tl;dr: last sentence of this post

The magnetic field strength when the magnets are already perfectly aligned means basically nothing. The things you should care about (wrt magnets in cubes) are:

- Attractive force when layers are aligned. This influences friction (*); more force means more friction, which in turn means that initiating a turn will be harder. This may be desirable to avoid unintentional misalignments (e.g. not getting a +2 when dropping the cube, or keeping the layers together on megaminx or big cubes). This is what the K&J Magnetics pull force calculator calculates.
- How the force parallel to the turning axis changes with misalignment angle. This is how much the amount of friction changes as you complete a turn. Sharper changes in force means more slowing down at the end of a turn. For the same amount of pull force, a larger magnet diameter usually corresponds to a more gradual change in force.
- Did I say frictional force above? Scratch that; you really care about the torque instead. You're almost always applying force to a layer from a consistent distance from the turning axis, so that's essentially constant. What you can change is magnet placement: magnets closer to the core will have the magnetic effects at a smaller radius, and hence the above two factors will lead to less torque. Conversely, magnets closer to the exterior will lead to more torque.
- The torque induced by magnets pulling each other together. (This concerns force perpendicular to the turning axis.) Again, further from the core means more torque. This controls how "snappy" the magnets are—more torque here means that layers will be pulled towards alignment harder.

(*) Friction is crucial here. If you make the spherical-cow-in-a-vacuum assumption that everything is frictionless, your turns would never come to stop on their own: flick a layer once and it'll keep moving forever, speeding up when it comes near alignment and slowing down when it goes out of alignment, which is the opposite of what we want!

There is no "ready-made" online calculator to determine all of the above factors, and ab initio calculations are very difficult. You'd do well to go by gut feel instead of blindly trusting hard-to-interpret numerical values.
Ahh this would be a fantastic real life physics problem for an AP physics or first year university student. Find the magnetic attraction between the magnets based on size and gap between them and then calculate the shear force required to separate them assuming a coefficient of friction of the plastic faces. It’s very possible to do by hand since we know the axis of rotation when we turn and the shear and friction forces will act tangent to the circle of a radius equal to the distance from the core the centroid of the magnets...the torque mentioned in the post above.
 

EngiNerdBrian

Premium Member
Joined
Jun 21, 2018
Messages
385
Location
Denver
Double posting becuase this post is regarding a totally different topic...

Has anyone magnetized a MOFANG JIAOSHI MINI 3X3 (4.5CM) cube for OH? What magnets would you recommend?
 

xyzzy

Member
Joined
Dec 24, 2015
Messages
1,964
Double posting becuase this post is regarding a totally different topic...

Has anyone magnetized a MOFANG JIAOSHI MINI 3X3 (4.5CM) cube for OH? What magnets would you recommend?
I tried 3×2 N38 in mine and it was rather disappointing, so don't do that. I think I've seen some recommendations for 4×1.5 or 4×2 N35 on r/cubers, but I can't remember which. (Maybe @topppits might know…?)

Also, my actual recommendation is that, unless you really have very small hands, a 50 or 54 mm cube will probably work better for you, regardless of magnets.
 

topppits

Member
Joined
Mar 20, 2017
Messages
16
Thx for the tag. Yes, I used 4x2 N38 on my 45mm one.

Can't comment on how those would do for OH, since I don't do OH at all and use this cube for underway if I don't have a bag with me.

Those magnets are certainly on the strong side for this cube, I very much like it for 2H since I can leave the puzzle on very loose tensions and it's still super controllable.
 

EngiNerdBrian

Premium Member
Joined
Jun 21, 2018
Messages
385
Location
Denver
I tried 3×2 N38 in mine and it was rather disappointing, so don't do that. I think I've seen some recommendations for 4×1.5 or 4×2 N35 on r/cubers, but I can't remember which. (Maybe @topppits might know…?)

Also, my actual recommendation is that, unless you really have very small hands, a 50 or 54 mm cube will probably work better for you, regardless of magnets.
Thx for the tag. Yes, I used 4x2 N38 on my 45mm one.

Can't comment on how those would do for OH, since I don't do OH at all and use this cube for underway if I don't have a bag with me.

Those magnets are certainly on the strong side for this cube, I very much like it for 2H since I can leave the puzzle on very loose tensions and it's still super controllable.
Thanks for the responses. I've never tried any mini cubes so the 45mm was a gamble. I do have exceptionally small hands but will also try a slightly larger cube too.
 
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