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Project, parts id and physics explain

  1. Apr 28, 2013 #1
    im going to need help filling holes and someone to explain to me what im trying to say/do
    ill start with what i want to do, and hopfully someone will be able to tell me what i need
    part-wise (i have some idea but not much)

    1) im looking at needing some sort of spring assembly in order to have stored force
    release in a slow and semi-constant fashion maybe over 5-10 seconds

    the idea being to make 2 "wheels" spin and not abruptly stop if disturbed within that time

    2) how to transfer force from spring to the "wheels"

    im thinking maybe i can drive a chain/belt to a relatively large gear, then to drive the wheels
    have one interact directly with big gear then 2 on the other side one driving the other which
    drive the wheel so they spin opposite of eachother

    my thought is to use easily found/made materials so maybe a chain/belt isnt the best idea

    2,a) what connects to the "spring"? (to transfer force)
    b) in cant have the wheels driven directly, or theyd stop abruptly,
    so i need to have them on some sort of free/flywheel?

    3) what forces am i dealing with
    on the spring, i think its measured in weight units, ie foot-pounds
    at the wheels its velocity

    weight and size is a concern, end product hopfully would be near or less than a wood 4x4
    (yes i do realize that weight differ by wood species)

    in a 2 wheel pitching machine
    obviously the wheel rotation affects how fast and/or hard the ball travels
    but is it the wheels speed or the torsional force privided by the motor used to measure the force imparted onto the ball?

    whats the math part behind it... in moron please, because im bad with this stuff and
    especially numbers (dyscalcula)
  2. jcsd
  3. Apr 29, 2013 #2
    ok as for part one all i come up with is a mainspring or "going barrel" (clock parts)
    but can i make one that will deliver enough power?

    2) i could use 2 springs coiled in opposite directions
    then since the housing of a going barrel is a gear, i could directly power both wheels

    please reference barrel (horology) at wikipedia for description of what im talking about

    still trying to find out if the force on the springs directly corralates with force imparted by the wheels

    i wasnt going to post in my own thread, but i couldnt find an edit button to add this to the main post
  4. Apr 30, 2013 #3
    force stored = force exerted? clarification

    ive asked this in my other posts and elsewhere but no answers
    but here i think its cause the question is "burried" among other stuff

    ...the base model i guess youd call it, that im going to use this time is
    a "plunger" as found on a pinball machine

    i think the formula would be (correct me if im wrong)

    force (base) is spring under "full load" = #
    force exerted is # - ball weight - gravity

    therefore if the ball weight is neglegible and the table was flat or gone then
    the ball would travel with the force of # untill gravity, friction etc, slows it to zero

    am i on the right track,
    or am i just clueless?
  5. Apr 30, 2013 #4


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    Staff Emeritus
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    Homework Helper

    Your post is unclear. Additional information is required to make sense of what you are trying to do.
  6. Apr 30, 2013 #5


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    Staff: Mentor

    Your reference to horology is a bit confusing, since in the other parts of your posts you are referring to delivering energy over a 5-10 second interval (rather than just keeping time).

    You should do some reading on wikipedia about momentum and inertia (both linear and rotational). You don't store "force", you store energy. A compressed spring stores energy, and you can use wikipedia to learn how much energy is stored. That energy can do work over some distance, Work = Force * Distance. The force available in a compressed spring has to do with its spring constant and how far it is compressed.

    If you store rotational energy in a spinning disk, the time it takes to slow down and stop depends on its Moment of Inertia, and how fast it is spinning, and the retarding torque that is trying to slow it down.
  7. Apr 30, 2013 #6
    all i could find web searing for something that would release mechanical energy over time
    was the clock part,
    if i didnt need to worry about the wheels stopping the moment someone breathes too hard
    i could do a "pull cord" type deal like a mousetrap car

    so making something similar but stronger was the idea i came to

    my project is to make a "post-apocalypse" themed tech piece
    (using readily available salvagable or makeable parts)

    so trying to think of what kinds of "bits & bobs" i need, with my limited knowlege of tech,
    i come up with springs gears pins and other simple things,

    i maybe my problems is that i am trying to explain things, and just "making mountains" as they say

    in simple terms ...relativley (just look who your dealing with here)

    i want to use a ratcheting lever to build up energy
    [part name] to store energy
    apply that energy to make 2 wheels spin opposite of eachother
    and use the spinning of the wheels to impart/exert [term] upon and object
  8. Apr 30, 2013 #7


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    Staff: Mentor

    You could use a come-along to ratchet/lift a heavy weight up a few feet, and then release the weight to pull down on a cable that spins your wheels. That might do what you want...

    http://www.erasmatazz.com/Personal/WeirdProjects/Gateway/files/comealong.jpg [Broken]
    Last edited by a moderator: May 6, 2017
  9. May 1, 2013 #8
    a come-along might work...

    pull on a spring, disengage ratchet stopper... i think its called a catch?

    can use sprockets on wheels instead, put them close enough together
    so a bike chain can be pulled between them

    would function similar enough to what i was thinking

    would be "instantaineous" or "burst" release of energy though

    if i could just figure out how to get a prolonged reaction
    in berkeman's example, thats solved by travel time of the weight, if im thinking right

    but for my use, i want to keep small scale, as to make a hand-held device

    i had an idea, but ruled it out once i realized how it worked... (garage door spring)

    new thought,
    maybe i can negate the need for a prolonged reaction
    if said object is already in contact with the wheels,

    which raises the question again, (admitedly i worded it bad)

    in a senario of a pitching machine, is it the velocity (speed) of the tire rotation
    or the amount of force used make the tires spin,
    that is the power behind the pitch?

    in otherwords, do i have to get the wheels spinning "at speed" first
    or does the "instant" release of energy of a spring take care of that
    Last edited: May 1, 2013
  10. May 1, 2013 #9


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    Staff: Mentor

    You didn't do the reading assignment that I gave you. Bad on you.

    Please do the reading on energy and moment of inertia. That will answer your questions. If you have specific questions about those readings, post them here with links to the articles.
  11. May 1, 2013 #10
    ow, my brain hurts,

    i had an easier time reading "the republic" by plato (gave up on that rather quick)

    all i see is math written in symbols (the equasions) and the little bit trying to explain what it means
    by using the equasion, most of it is going over my head (i did legitimatly try)
    so far all i really understand among all that is

    the potential of a spring is proprtional to how much its stretch/compressed
    and if force is applied to something, it moves (with equivalent force)

    lets see if i can guess at it,

    in my situation, the force applied is equal the tension on the spring

    wheel spin is, propotional? to the force,
    velocity imparted would be proportionate to how fast the wheels spin
    ie put a speedometer on the wheel and that would tell me how fast the object would travel if the objects mass?
    was the same

    so force for calculating spin
    but for the work potential of the object wheel spin = velocity
    its weight and velocity to calculate impact strength

    so, all my confussion was cause i had it backwards in tring to figure force to impact
    instead of force to spin, spin to object, velocity x? weight = impact force

    and as far as object simply causing the wheels to stop
    is a matter of having just enough contact pressure for the wheels to "grab"

    would i be better off with something where i squeeze/pump a trigger causing the wheels to spin
    Last edited: May 1, 2013
  12. May 1, 2013 #11


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    Staff: Mentor

    I would probably just use a hand crank through a gear box to spin up the wheels...
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