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small strong magnets put to shop use.

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  • Guest's Avatar
    Guest replied
    This is a black sand magnet used in gold mining, I use it to pick up swarf, it works like a syringe, put your fingers on each side and push with your thumb, when your ready to dump its spring loaded, so just release thumb pressure, originally it had one of these Alnico washer magnets in it, I pried it apart and added another. Haven't done it yet but I was thinking of using the same basic idea with more powerful magnets using pvc pipe or whatever works, it wouldn't need a spring in it if you put a couple of rings on each side for your fingers and one for your thumb, or just use both hands.

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  • Fasttrack
    replied




    ... I'm going to go do something in the shop now... really i am.

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  • darryl
    replied
    I had a van der wall force experience once. I accidently hit the wall of my garage with the van. I don't know if the metal curled away from the wall, but I got unglued easily. A bit of molecular displacement was evident in the side of the van. It was not a particularly magnetic moment for me.

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  • Evan
    replied
    I see you didn't catch my goof in that statement. I should have excepted gravity too.

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  • Fasttrack
    replied
    Originally posted by Evan
    Yes, you are right. However, they don't operate in the same way as gross domain electromagnetism, especially with respect to distance as a power law force. All interactions between gross quantities of matter at the macroscopic level are strictly electromagnetic with the exception of particle mediated events in radionuclides. Good thing too or everything would be stuck to everything. The gecko isn't in any danger of falling off a wall. The Van der Waals forces in his foot pads are strong enough to support many times his body weight. The real question is how it manages to peel it's feet loose.

    Yep - its just that modern, entry level textbooks often equate "Van Der Waals" forces with London Dispersion forces and then seperately identify hydrogen bonding, dipole-dipole and etc. And since London dispersion forces exist because of magnetic moments your statement just struck me as sort of silly if you think about it too much.

    Of course its perfectly valid, as you point out, on the macroscopic level where it "matters" and since Van Der Waals forces are generally considered to be the entire range of intermolecular forces, it makes perfect sense.

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  • BigBoy1
    replied
    I bought a bunch of the flat disc neodynuim magnets from www.magnet4less.com and used them to hold the tarp on my truck. I made small colth bags for each magnet and left a small cloth strip to get a hold of the magnet. The cloth prevents the magnet from scratching the paint surface and the strrip makes removal easy. They really hold the tarp as the strongest winds have not removed the tarp from the truck. The trick is to make sure the tarp is tight to the truck's surface so the wind cannot get under the tarp.

    Bill

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  • Peter N
    replied
    I have one of the small (6mm dia) magnets epoxied onto the the end of a 6" long, 6mm dia piece of mild steel rod.
    It's invaluable for pulling small spacer blocks, bearing balls, springs, and similar items from the bottom of deep holes, particularly where they have been retained by a grub screw (set screw to you lot ).

    Very useful if you have ever stripped a Bridgeport head down for repair.

    Peter

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  • Your Old Dog
    replied
    Originally posted by darryl
    I went into a restaurant one day and took the clock off the wall (where it couldn't be seen very well) and hung it on one of the metal pillars using a pair of small nib magnets. The clock was fairly heavy, but it never slipped down.
    Remind me never to go to lunch with you

    Now that we got all this Geico stuff figured out maybe we can save a few bucks on our car insurance.

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  • Doc Nickel
    replied
    The little article I saw on that (the gecko pulling his foot loose) showed that they curl (or roll) their toes up- like the end of a classic elf shoe.

    With the majority of the effective surface in the toes, once they're "unhooked" due to the rolling, it's easy for the gecko to shift that foot, and once shifted it "unrolls" the toes again, helping assure complete contact.

    At least, that's what the video showed- they shot some high speed as a gecko walked across some glass. Fascinating stuff.

    And as for the magnets corroding, I was told it had to do mainly with moisture- like clean steel, it'll be fine for years in a dry environment, but it'll corrode overnight when it's humid. Also, if the "roughened" side is subsequently sealed with the epoxy used to adhere it, it shouldn't corrode. Your mill magnets should be fine, unless you add flood coolant.

    Doc.

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  • Evan
    replied
    Yes, you are right. However, they don't operate in the same way as gross domain electromagnetism, especially with respect to distance as a power law force. All interactions between gross quantities of matter at the macroscopic level are strictly electromagnetic with the exception of particle mediated events in radionuclides. Good thing too or everything would be stuck to everything. The gecko isn't in any danger of falling off a wall. The Van der Waals forces in his foot pads are strong enough to support many times his body weight. The real question is how it manages to peel it's feet loose.

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  • Fasttrack
    replied
    Originally posted by Evan
    Paul has it right. Here is a pretty good explanation.

    http://www.chemguide.co.uk/atoms/bonding/vdw.html

    I should point out this is not what holds matter together but it is in large part what make things tend to stick together. That includes in large part the wringing effect of Johansson blocks and is how a gecko lizard is able to walk on a wall or even a window.

    I know what Van Der Waals forces are, i was referring to the fact that they are intimately related to magnetism on the relativistic and quantum levels.

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  • darryl
    replied
    One day I'm actually going to build a direct-drive motor for the lathe using super magnets. I'll probably attach the magnetic component directly to the pulley and if I can I'll make the coil component without iron at all. I'll have to make dam sure that swarf can't get into it. It will be three phase at least, though it could be five phase.

    I could use the actual circuitry from a vcr capstan motor to control commutation and speed- mostly what else is required is to interface the vcr motor drive signals to higher power electronics. Essentially, I'd just be expanding the size and power of a capstan motor, but using the same 'brains'.

    I played with some small disc magnets one day, sticking them to a metal strip then heating them with a torch. Predictably, at a certain fairly low temperature, the magnetism disappeared and the magnets dropped off the metal strip. I managed to re-magnetize them, but didn't have the proper set up to do it fully.

    I went into a restaurant one day and took the clock off the wall (where it couldn't be seen very well) and hung it on one of the metal pillars using a pair of small nib magnets. The clock was fairly heavy, but it never slipped down.

    It's interesting to see how you can destroy a ferrite magnet with one of these.

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  • PaulF
    replied
    Hi,
    I bought some real killer ones for a magnetic coupler on an under water motor.

    Be careful they will erase your credit card stripes and magnatize your tools so they pick up swarf!!!
    PaulF

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  • dang
    replied
    On of my local surplus stores carries Neodymium Magnets. I use them for everything. Got 'em on every machine tool, and on the walls to hold up charts, lists and prints. I glue them to metal surfaces using two part epoxy. As stipulated above, this requires the surface be roughed up. But you wanna talk about permanent magnets!
    I also use Magnets harvested from the insides of my old hard drives. They're REALLY cheap! When I'm forced to buy them, I drive home with the paper bag stuck to the top of my car's roof.

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  • Evan
    replied
    I've never had either result happen. If you want to glue them you need to rough up the surface. There are about six of the 1/2" supermagnets glued to the back frame of my mill. They hold the 50 lb counterweight in it's track so it doesn't rattle or vibrate. They don't quite touch the steel can that holds the lead so they are frictionless. They are still there and haven't corroded or crumbled.

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