Page 2 of 2 FirstFirst 12
Results 11 to 15 of 15

Thread: overhead hoists

  1. #11
    Join Date
    Jul 2012
    Posts
    364

    Default

    Quote Originally Posted by T. Cotten View Post
    When a connecting rod is degaussed, the ends are no longer north and south poles. The ends have the same polarity, and the other pole is moved to the middle.
    In the interests of accuracy, the situation you describe has a magnetic monopole in the middle which, if you discovered one, would undoubtedly get you the Nobel Prize in Physics. The situation is a bit different than this. When more of the microscope "magnetic domains" in the steel are aligned pointing one direction than another the metal is magnetized. The more that are aligned in a given direction, the more "magnetized" the steel is. However, this is an energetically unfavorable condition so it doesn't take much energy to cause domains to flip. If some of them flip direction the steel becomes "partially demagnetized," and if nearly all flip it is essentially "fully demagnetized."

    Demagnetizing coils have enough turns of the right diameter wire to provide enough electrical resistance that when plugged into the wall the current is limited so they don't burn out. While plugged in the current that is oscillating at 60 Hz in the coils creates an oscillating 60 Hz magnetic field. If designed properly for the application at hand the field strength is high enough to impart sufficient energy to the magnetic domains to allow them to flip.

    The first of the of the coils shown in your post looks to have been made to demagnetize components inside a television. I doubt if it generates a sufficiently large oscillating magnetic field to demagnetize a part like a connecting rod.

  2. #12
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    3,680

    Default

    BoschZEV!

    As far as the "monopole" phenomenon, it is is readily observable with a compass (footnoted in the last attachment to my last post. Do you want it to run 'like a Swiss watch" or not?)
    What little I know beyond that, I now thank you for googling for me.

    Rods are best demag'd on something more like the Magnaflux and growler coils. Mine's a cheapo, works great if you don't leave it on for long.

    One buddy told me to hold the object aligned N-S and rap it with a brass rod.

    ....Cotten
    Attached Images Attached Images
    Last edited by T. Cotten; 05-29-2015 at 03:09 PM.
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

  3. #13
    Join Date
    Jul 2012
    Posts
    364

    Default

    Quote Originally Posted by T. Cotten View Post
    One buddy told me to hold the object aligned N-S and rap it with a brass rod.
    Because of the "shape anisotropy" N and S will be aligned along the long direction of the part and, since the design of many demagnetizers has you pass the object through their coils, by default you normally would do that by passing the long direction through (unless you have your dog do your demagnetizations for you, in which case he might try to do it like when he tries to carry a stick through a gate).

    Hitting it with a brass hammer will make you feel like you're actively participating in the process but it's unnecessary. This practice dates back to the early days of steel magnets. The hysterisis loops of those metals were so narrow that acoustic energy could help a bit with the demagnetization. With most steels you might encounter it's unlikely to do any good (but, it won't do any harm).
    Last edited by BoschZEV; 05-29-2015 at 04:22 PM.

  4. #14
    Join Date
    Aug 2009
    Location
    rural eastern South Dakota
    Posts
    934

    Default

    qu: " acoustic energy could help a bit with the demagnetization."

    My, My! The "Aha!" moment! The kids with those boom boxes in their trunks, ... that's why they're seemingly so aimless, right? no compass?

    and gee, now I can lose sleep over all those itty-bitty steel particles and ring wash sticking to my rollers. Got a magnetic drain plug in the case, and it collects that break-in ring wash pretty well. Fingers crossed.

  5. #15
    Join Date
    Jun 2001
    Location
    Central Illinois, USA
    Posts
    3,680

    Default

    I forgot the acoustic aspect, Folks...

    You are supposed to chant "Bad motorcycle,... BAD MOTORCYCLE!" while you rap it with a rod.

    ....Cotten
    AMCA #776
    Dumpster Diver's Motto: Seek,... and Ye Shall Find!

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •