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What do you guys think is the best?

  1. Feb 5, 2008 #1
    i'm doing a science experiment where i am trying to direct electric current very precisely. in the experiment there is going to be one piece spinning very fast. now if the electricity wasn't an issue i would use copper for the frame and have it spin on that. but copper conducts electricity so i was thinking that i would use pvc pipe instead because it doesnt conduct electricity and will have less friction then wood.

    so i'm wondering if you guys think that is a good idea or if you have any better suggestions for what kind of material i should use for building the frame of the project. (i'm aware of some of the materials i can use like diamond but i'm trying to keep it low budget meaning i dont really want to spend more then about 200 on the whole thing and i need to get magnet wire and steel rods and stuff to go with it so please keep in mind that i'm not going to get something like diamond or any other precious stone to build it because i simply cant afford it)

    thanks
     
  2. jcsd
  3. Feb 5, 2008 #2

    FredGarvin

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    Well, PVC is cheap, easy to work with and easy to get. However, it is impossible to answer you since we have no idea what it is supporting or the loads that it is required to handle. If you can provide some more information on your set up, that would be a big help.
     
  4. Feb 5, 2008 #3

    RonL

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    You mention pvc pipe, so i'm guessing just a few inches in dia? if the project is not too large, you can look around your kitchen, or a recycle store for glass or ceramic cylinders, such as coffee cups or glasses. Using diamond tip dremel type tools you can trim off handles or bore holes ( i bore holes in wine bottles, 12-15mm, in order to insert christmas lights).
    If the ceramic is the part spinning, then great care should be used to stay within a safe rpm range. (more details if you think this might be an option).
     
  5. Feb 5, 2008 #4
    A good choice for an insulator that has a fair amount of strength, machines easily, and has moderate cost is Garolite (trade name), a paper or cloth based phenolic laminate. You can find this at
    www.McMaster.com
    Even though McMaster is an industrial supply house, they will sell to individuals.
     
  6. Feb 5, 2008 #5
    To keep a non-conductive surface, but high strength, you could try this:

    Build the frame with wood, then line it with a thin sheet of plastic. Glue or screw the plastic to the wood. That way you keep the low friction surface, but maintain some rigidity.

    Also, if you could get someone to anodize aluminum and keep it in the anodize "bath", for longer than it should, I think that will make the surface non-conductive, but I am not 100% sure on that one.

    I think that another easily machineable plastic would be UHMW (Ultra High Molecular Weight Plastic) which you can also get from McMaster Carr, but i am not sure about the other mechanical properties, nor if the cost is comparable to Garolite.

    Lignum vitae is a self lubricating wood.........$$

    hope this helps somewhat......
     
  7. Feb 5, 2008 #6
    Good call on the UHMW. I didn't think of that. Cheaper and easier to work with. And prettier colors. Not as strong but the OP might not need that.
     
  8. Feb 5, 2008 #7

    RonL

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    A little more detail from the OP is needed.
    I had considered lignum vitae(vera wood) in a project and found it has a low speed and temperature rating, and a quick search produced a temperature high of 275 F degrees for the UHMW.
    stnbtch15, mentions friction as a factor to be considered, so untill more information is out(as FredGarvin suggested) were just spinning our wheels:uhh:
     
    Last edited: Feb 5, 2008
  9. Feb 5, 2008 #8

    Danger

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    True. My thought, given the limited information, would be to build the thing out of whatever one wants to, and line the pivot points with some sort non-conductive bushings such as ceramics.
     
  10. Feb 5, 2008 #9
    i'm not sure if this is going to work but i'm trying to attach a crude picture i made of what it will look similar to.

    the picture is basically a base (which i'm thinking about using pvc pipe or wood for) two holes on either side to hold the rod in the middle that will be spinning and the support poles to hold those up. to explain what it means.... the rod going between the two circles is going to be spinning (i'm not exactly sure how fast but it will be spinning alot) and it will be made out of the same material as the rest of it. the base is just there to hold it off the ground to give it room to spin. i'm trying to figure out what material will be a low cost and easy to work with material suitable to withstand alot of friction (and heat from it) without melting or breaking, that also will not conduct electricity.

    i'm hoping this will give all you who wanted more info enough to work with.

    and thank you all for your responses they are really helping me.
     

    Attached Files:

  11. Feb 5, 2008 #10

    Danger

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    This is a crude solution... but then again, I'm a crude person. I'd just knock the tops off of a couple of beer bottles and use them as bearing surfaces. If you need tight tolerances, invest in a piece of suitably sized glass tubing.
     
  12. Feb 5, 2008 #11
    Beer....is there anything that it can't be used for?


    Obviously you are going to want to have the center rod as balanced as possible, otherwise once the spinning starts, you are going to have some issues. For the ends, would it be possible to get some wheels off of a set or roller blades from a second hand shop, and then built a bracket which you can mount them on. If you place them at 12 o'clock, 3, 6, and 9 (or N,E,S,W), and leave a slot for small adjustments, you could have the rod spin on the rollers. That should be relatively low in friction....and cheap.

    Just remember...Quality, Price, or Time (Pick Two)
     
  13. Feb 5, 2008 #12

    RonL

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    Your picture is indeed crude, and unless you are trying to conseal the real plan, i would guess the drawing is in some way close to proportion of what you are thinking.
    The rod or pipe that is spinning, can use regular bearings set in pvc fittings, and will be free of electrical conduction, but from what to where?:confused:
    As Danger said, the beer bottle can be used, but thermal shock will render the glass to a marginal use.
    Without more specific detail, it might as well be a segmented, rolled aluminium capacitor, sending spikes of electrical impluses to a DC motor comutator.( just one of many thoughts):uhh:
     
  14. Feb 5, 2008 #13
    first off yes i am trying to conceal my real plan because i believe if i give out to much information someone will beat me to getting it built and i don't want that.

    second the roller blade wheels is a very good idea that i never even came close to thinking about. thank you very much for that. but i am a little confused about the whole 12 3 6 9 thing. i'm not exactly sure what i need 4 points for. it is going to be one rod secured between two points and attached to motor to spin it. so if you could explain what the other two points are for that would make me a lot less confused dingpud.
     
  15. Feb 6, 2008 #14

    FredGarvin

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    How fast are you thinking about spinning the disc/rod? How long do you think the rod will be? How heavy is the disc?
     
  16. Feb 6, 2008 #15

    RonL

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    Maybe i've never had a good one, but you would surprised at how hard it is to get someone to beat you to a plan:surprised
     
  17. Feb 6, 2008 #16
    Kind of like a dead center on a lathe (I think that is what it is called). It helps minimize vibrations at the end of the spinning rod. two wheels would be sufficient as a roller rest. Additional rollers would be used if you wanted to put a small amount of force downward.

    maybe that helps a little.....

    i'll try and make a sketch and post it......
     
  18. Feb 6, 2008 #17
    attached is the 5 minute sketch. the slots in the mounting plate will allow you to adjust the amount of force each wheel is applying on the spinning rod.
     

    Attached Files:

  19. Feb 7, 2008 #18
    well.....what's new with the project? Any successes or failures?
     
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