Magnets and bearings

[BrokenBiker]

I will be embarking on a new design for the housing and attachment for my crane camera project that hit a bit of a pause recently...

I was planning on attaching to the crane with a threaded bung through a spare rope anchor point, however that would required different bungs for each crane, so magnets are now the desired choice, plus also means I can attach it to the hook block as well if I find that is desirable

I am 3d printing the housing for camera now Instead of making an ally box, 3d printing just seems the more logical choice at this point as it will need to securely house the camera, transmitter, battery, power switch and control board plus have a charging socket for the 4s lipo battery I will be trialling, which also means design changes to accept a different sized battery would be easier with a printed housing as well. There will be a 608 bearing pressed into the printed housing and the plan is to then make an ally housing that takes the magent pressed in 1 side, and a spigot on the other for the bearing to slip over and secure with a likely plastic nut.

Question is, is the bearing going to be affected by the 20x5mm neodymium magnet? The ally housing will be maybe 5mm thick between the magnet and the bearing

Would it be wiser to print a plastic bearing? Total weight is estimated to be around 150 grams hanging off the magnetic mount, rotation speed is low.

Alternatively I could make a brass bush i suppose with a good sliding fit over the ally spigot but I would like to keep the manual machining to a minimum as there is scope for a few more of these to be made once I've got it working well.

 

[fizzy]

You can get ceramic ball races. Stainless steel would be non magnetic depending on grade.
I doubt a normal bearing will be effected much anyway. Try it and see.

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[colnerov]

As said I don't think the bearing will be affected by the magnet directly, but it will attract metallic grit into it which will affect its smooth operation.

 

[BrokenBiker]

As said I don't think the bearing will be affected by the magnet directly, but it will attract metallic grit into it which will affect its smooth operation.

It will be relatively well protected from ingress, they are sealed bearing and will be pressed into an enclosed location and then when in use tight (ISH) against the back of the magnet housing...plus it will be up in the air almost all it's life so not much in the way of debris there.

I have 6x 608 bearings to hand hence wanting to use them but if it is an issue I will just machine a brass bush to get my with

 

[zzr1200]

And being as your now thinking of using magnets to attach, you'll also have to fit a safety lanyard in case the camera gets knocked off....

 

[voipio]

On a 20 x 5mm neodymium magnet, the magnetic field strength will reduce quite quickly with increasing separation distance. Especially so if the magnet is only, say, 1-2mm thick.

As an example, for a 20 x 5mm magnet that is 2mm thick, made from N42 material, the field strength will be ~0.24 Tesla at the magnet pole surface, falling to 0.045 Tesla 5mm away, and 0.015 Tesla 10mm away. .

 

[fizzy]

On a 20 x 5mm neodymium magnet, the magnetic field strength will reduce quite quickly with increasing separation distance. Especially so if the magnet is only, say, 1-2mm thick.

As an example, for a 20 x 5mm magnet that is 2mm thick, made from N42 material, the field strength will be ~0.24 Tesla at the magnet pole surface, falling to 0.045 Tesla 5mm away, and 0.015 Tesla 10mm away. .

Inverse square law!

 

[voipio]

Inverse square law!

Not exactly. Inverse square law applies to situations where the measured parameter radiates equally in all directions, or at least where the flux density is constant across the area of interest at a given distance from the source.

 

[BrokenBiker]

And being as your now thinking of using magnets to attach, you'll also have to fit a safety lanyard in case the camera gets knocked off....

If something manages to knock it off the end of the jib we have bigger problems than it falling off, but yes, I have considered a short length of paracord with carabiners at each end and have designed a little hole into the housing that will accept a little pressed in stainless tube I already have for the carabiner to attach

 

[bricol]

You must have very relaxed employers. Anyone trying the same on our cranes would be shown the door pretty quick! Problems with customers and insurance being two things mentioned about such things here. Anyone caught with a even mobile phone out, never mind a camera would on a disciplinary straight away.

 

[bricol]

But no, magnets won't do much to your bearings.

 

[BrokenBiker]

You must have very relaxed employers. Anyone trying the same on our cranes would be shown the door pretty quick! Problems with customers and insurance being two things mentioned about such things here. Anyone caught with a even mobile phone out, never mind a camera would on a disciplinary straight away.

Why would your employer sack a crane operator for wanting a camera that would improve visibility on blind lifts? Especially given these cameras can be bought as an optional extra at the point of ordering a new crane...I have had cranes with similar cameras, they make a huge difference when working with CPA hire customers that aren't quite as experienced as you would like.

Or have you just assumed I want to mount a camera to be able to record things without first speaking to my employer, our customer at the time and any site management that would likely need to be informed?

 

[Tinbasherdan]

Why would your employer sack a crane operator for wanting a camera that would improve visibility on blind lifts? Especially given these cameras can be bought as an optional extra at the point of ordering a new crane...I have had cranes with similar cameras, they make a huge difference when working with CPA hire customers that aren't quite as experienced as you would like.

Or have you just assumed I want to mount a camera to be able to record things without first speaking to my employer, our customer at the time and any site management that would likely need to be informed?

Playing devils advocate here- Ive worked a few places where sticking any sort of home made contraption to lifting gear, be it a camera or anything else, would be grounds for being shown the door immediately, so his question wasn’t that out there.
There’s a vast difference between home brewed kit and factory fitted, even if they do the same end job, something that would be a point of focus if anything went wrong.