freddo4 (Mar 8, 2021), Jon (Mar 6, 2021), nova_robotics (Mar 8, 2021), that_other_guy (Mar 18, 2021)
baja (Mar 9, 2021), kboy0076 (Mar 9, 2021), machining 4 all (Mar 8, 2021), nova_robotics (Mar 8, 2021), that_other_guy (Mar 18, 2021), Toolmaker51 (Mar 8, 2021)
A single .75 x .125 neodymium is 8 lbs of pull....2 or 3 oriented poles must have 12 minimum pounds at that distance. maybe a thick soft iron puck in slick plastic sled, is enough. It doesn't have to pull wire, just the nylon leader.
Another way they send leader through conduit is compressed air, connected to a feathered dart like a blow gun.
Sincerely,
Toolmaker51
...we'll learn more by wandering than searching...
No way. Magnetic attraction falls off rapidly with distance. 1/distance^2 in fact. I don't believe that tool will have 12 lbs of force at that distance. If it did, it would be a legitimate health hazard when they snap together.
If they're overmolded with 1mm of x plastic, and they have 12 lbs of force through 1/2" of plywood, then they'll be held together with over 2200 lbs of force when they snap together. 1. You're not getting that tool apart with your hands. 2. That's a trip to the hospital the first time you use it. Completely impossible.
Also they just slide them apart with almost no effort at the 27 second mark. Zero chance there's 12 lbs at 1/2".
Magnetic field strength falls off as distance cubed (R^-3), not distance squared. But things aren't that simplistic...
https://van.physics.illinois.edu/QA/...-at-a-distance
Last edited by mklotz; Mar 9, 2021 at 12:18 PM.
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Regards, Marv
Experience is always far worse than pessimism
Toolmaker51 (Mar 9, 2021)
1] I guess-t-rated three 8 pounders conservatively at 12 pounds, wouldn't be surprised if higher.
2] Only the tool [puller] portion is a magnet - acting on whatever suitable material they chose for the chaser.
As well, packaging on neodymium magnets any bigger than 4-5mm diameter affirm definite risk around mishandling them.
Compared with two flat surfaces adhering [and pinching] so well, a chord-like form of minimal contact is less challenging.
Don't all of us picture a common magnet holding an inverted straight pin, even a nail, with hardly any surface area at all?
The page offered by our friend Mr. K points out mere strength isn't only consideration in attraction of magnetic materials.
Just conducted highly scientific test with a common refrigerator magnet and a washer; there was noticeable magnetic activity through what I surmise a 3/8" plywood cabinet door.....holding the washer in place.
Last edited by Toolmaker51; Mar 9, 2021 at 03:56 PM. Reason: after trip to laboratory mentioned above
Sincerely,
Toolmaker51
...we'll learn more by wandering than searching...
What a revelation! Math works the same in two places, despite fixation on arbitrary 12, something I literally pulled out of the air.
Proper magnets will add, compound, or subtract, depending on variables.
https://en.wikipedia.org/wiki/Magnet
In other news; different project wants attention now.
Sincerely,
Toolmaker51
...we'll learn more by wandering than searching...
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