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Electromagnetic Toy (part 2)

  1. Dec 6, 2013 #1
    So the other day I posted about designing an electromagnetic toy for my physics class project (https://www.physicsforums.com/showthread.php?t=726492). Unfortunately, where I live, finding disc magnets with conductive plating, is like really finding that needle in a very very big hay stack.

    With that being said, I decided to brain storm and see if I can improvise, for the lack of having said disc magnets.

    I was thinking of getting regular ceramic disc magnets, that have no conductive plating on it. Then using some magnetic material, that's disc shaped from a hardware store, and attach it to said magnet and using that as the wheels for my toy car. I am thinking, the only reason the design concept asked for a conductive magnet, was to save the hassle and just attaching the magnet to the metal axle and hitting two birds with one stone, instead of trying to adhere the metallic wheels to the axle, through other means (if I have explained myself correctly).

    Would this be feasible to move along aluminum foil, that's been magnetized by a 9 volt battery?

    I really need feedback on this. Going tomorrow to pick up the magnets, and all the stuff I need for my toy.
  2. jcsd
  3. Dec 6, 2013 #2

    Simon Bridge

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    You can buy disk magnets though?

    Can you ask a machine works to electroplate them for you?
    Maybe it is good enough to glue tin foil over them?

    If the only reason for metal on the magnet is for the magnet to double as the axle of the car as well ... why not just have a ceramic axle? (looks - oh I see, it's a railgun!)

    Your best bet is actually to build the metal wheels and glue the magnets on them.
    Say - glue a washer on each side of the disk magnet or put a circle of small magnets around the axle.
  4. Dec 6, 2013 #3
    The design I am following, is to use a linear homopolar motor, to move the toy car along aluminum foil that's connected to a 9 volt battery. They say I need to use disc magnets which are plated in gold or any other conductive material.

    I have been trying to find alternatives because I wouldn't have the time to order any plated magnets. So, saw online while I was looking up other means of using the magnet as wheels but without having them plated, is to use foil as you recommended....

    Would this help to make the magnet conductive? I am thinking yes, but can't find a definitive answer online.

    Here's the concept I am following, if it would help: http://sci-toys.com/scitoys/scitoys/electro/railgun/railgun.html

    Thanks for responding, by the way.
  5. Dec 6, 2013 #4

    Simon Bridge

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    I don't think you need the magnet itself to be conductive - you do need a conductive path between the wheels.

    I like the homopolar tractor design shown later (where the battery is the wheel) ... reminds me of the rubber-band + bobbin tractors I used to make as a kid. It has the advantage that you don't need rails for a start.

    You know you can buy model train wheels and track?
    You could make the car go in a circle ...

    The key to this is to make sure you understand how it works.

    Do you need the magnets to be attached to the axles?
    Will it work if you have conducting wheels and you mount the magnets on the car chassis so they hang over the outside of the wheels? Do they have to hang outside the wheels?
  6. Dec 6, 2013 #5
    No, I don't need the magnets to be attached to the axles, I was just going for the easiest method because this is the first physics course I have EVER taken. So, I am now getting into the whole thing. I was thinking of utilizing conducting wheels, as you mentioned but I am not sure if those would work with the linear homopolar motor? I mean, if they would, then awesome. I will just get some disc conductive material that I can buy at a hardware store and figure out a way to attach it to an axle and follow the same concept in the link.

    My issue is just finding wheels that will move along the aluminum foil track and be the toy car set, that I present to my class and it actually working :P
  7. Dec 6, 2013 #6

    Simon Bridge

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    Well you have run into an issue with making the wheels using ceramic magnets ... you could just use iron or steele wheels and stick the magnets to those - but there is still the issue of centering the magnets - making sure the wheels are balanced etc.

    But with very strong magnets, and a light chassis, you may not have the option ... you should try out different configurations.

    When you are refining a design it is important to work out the lynchpin of the process.
    In order for the device to work - something is special about the relationship between the current and the magnetic field? It is important that you use this relationship in your design. Identify it and you'll have a much better idea of your options - things are more flexible than you seem to think.
  8. Dec 6, 2013 #7
    Could you provide a suggestion then? I only have until Monday to get this thing designed and working.
  9. Dec 6, 2013 #8

    Simon Bridge

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    If you only have over the weekend and you already have a magnet - you should do something simpler.
    That's another reason I like the tractor over the rail-gun design ... you can whomp one together in a few minutes, and you'll have the whole weekend to try stuff out. This lets you focus on the fun stuff - re: exploring Nature.

    No reason not to do the cool thing in your own time though.
    If this is part of a physics course though - you should see if you can understand the actual physics ... no amount of coolness will help if the science isn't understood.

    This sort of project, the marker is usually looking for:
    1. you have shown what you are starting with (web site)

    2. you have identified the physical principle(s) important to it's operation (yet to do)

    3. identified what is needed to turn it into the desired object
    (child's toy - should it be brightly colored and hard-wearing?)
    (i.e. don't just duplicate the design on the website)

    4. displayed a design approach - identifying obstacles and strategies for overcoming them.
    (i.e. limited time is a design parameter)

    Actually having a working prototype at the end is a bonus - it's the process that is important.
    #3&4 are where you display your understanding.

    OTOH: it is extremely important that you enjoy yourself.
    If it was fun, you'll probably do a reasonable job at this level.

    Start by listing what you have and/or can get in the next 24 hours.
    Then pick the project. If you have enough parts right now for the railgun - cool! Go for it!
    Put a simple one together and play with it - what does it need? Don't second guess Nature.
  10. Dec 6, 2013 #9
    I like your train of thought. I was just sitting down and going through the mechanism in my head and trying to understand it, so I can work with what I have.

    I think I will go ahead and get those magnets, and the other supplies and see what happens. Thanks again!
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