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Determining Vibration Frequency

  1. Apr 4, 2014 #1
    Good Afternoon, all...

    I design professional pitching horseshoes. I am trying to determine if the method used to mount the stake in the horseshoe pit affects the recoil of the stake when a horseshoe hits it. A stake that loosens over time will reject a horseshoe more readily than a solidly mounted stake. However, the method used to mount the stake in the first place may also affect the recoil. Is there a simple method available that will generate a vibration that could be read. I would like to be able to test the results if the stake is hit at the top (15" above the pit surface), middle (7.5" above the pit surface), and base of the stake. Thanks for any suggestions.
     
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  3. Apr 4, 2014 #2

    sophiecentaur

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    You are certainly right that the mounting of the stake will affect the way the shoe interacts with it.
    You could use a strain gauge to measure the deflection of the stake in the hole and you could mount an accelerometer inside the top of the stake to plot its motion. Or, perhaps, some high speed photography would be a better approach. Then you could see the angles and distortion of the stake during the whole process. You could 'calibrate' the stake by putting static loads on it and noting the displacement. Putting the static and dynamic measurements together could yield some useful insight.
    One thing you need to avoid with a system like this, I think, is resonance, which could end up with rejection of the shoe. Have you considered some lossy medium, say a loaded rubber sleeve, to hold the stake. This could slow the shoe down and absorb the energy, rather than return it (elastically ) to the shoe and throw it off.
     
  4. Apr 4, 2014 #3
    Thank You, sophiecentaur...
    It is very common to add a piece of rubber hose to the stake as it's mounted into a bucket of cement. Unfortunately, there are a number of other methods used to mount the stake. Typically, the stake is welded onto a metal plate. This is generally true of temporary pits that are only 4" thick. In other cases the 1" stake is driven into a couple of 4"x4" timbers and driven through a 15/16" hole. What I was hoping to find was a simple device that a pitcher could use to determine his/her best hope of non-rejection. I have filmed a number of horseshoes hitting the stake in slow motion, usually 420 fps and shown on Youtube. I was perhaps thinking of something like a tuning fork that might provide some idea level of information. Thank you for your information. If there's something that is simple that would give some level of feedback I'd appreciate it. Regards
     
  5. Apr 5, 2014 #4

    sophiecentaur

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    I have never pitched a horseshoe so it's only a thought experiment for me. I have just watched some YouTube videos of pitching and the technique seems to rely on some rotation of the shoe so that it 'captures' the stake, once it's hooked on.
    The relevant oscillation mode seems to be due to the mass of the stake plus shoe and the stiffness of the stake and or its mounting. If the rubber sleeve can dissipate enough energy in the half cycle after the shoe strikes then the shoe will not be ' rejected' back the way it came - a 'critical damping' situation as in car dampers. Is it ever as well behaved as that? What do your slo mo movies show?
    If the shoe can fall to the ground in time, then the rejection will be killed by friction with the ground. The actual angle of the stake to the vertical will make a difference here - if the stake slopes backwards towards the pitcher, the shoe could hit the ground sooner - and vice versa.
    I'm not sure where you plan to go with this. Are you trying to design the 'ideal' stake + mounting or do you want to assess a new stake that you are presented with (with a view to choosing the best shoe to use)?
     
  6. Apr 5, 2014 #5
    Thank You sophiecentaur...you can see a variety of horseshoes hitting the stake on Youtube if you search for "Photon713". There are 7 videos from me several of which show the impact of a horseshoe against the stake at 420 fps. I am trying to determine if there is a way to tell the horseshoe pitcher what to expect when his horseshoe hits the stake at various venues. There are a number of generally accepted way to pitch a horseshoe. Most world champions pitch a "turn" shoe. That would be considered frisbee style. Seniors, juniors and women typically throw a flip shoe, i.e., shoe turns end over end usually a single flip. It's the flipping shoe that is frequently rejected even if it's pitched as a perfect shoe. Horseshoe stakes slant back toward the pitcher by 12 degrees and are between 12"-15" above the pit surface. You can see shoe rejection on my Youtube video for the Viking horseshoe. There are also videos for the Trident and GrabIt. The inner perimeter of the GrabIt is based on the parabolic curve and is hardly ever rejected, but, is more difficult to master. Turn pitchers don't need any help, it's the flip pitcher that is at a disadvantage. Unfortunately, elders, juniors and women pitch from 30 feet and don't usually turn the shoe. No, I'm not interested in the ideal stake, just, how to read the stake that's at any venue. It's important to know where to concentrate on hitting the stake if you know whether the stake is mounted without dampening. Hope that helps. I was hoping that there was a way to easily determine by the "ring" sound of the stake whether dampened or not. Thank you for your interest.
     
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