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Advanced egg drop

  1. Sep 27, 2012 #1
    Having a little trouble with this latest advanced egg drop assignment. The main assignment has two parts -

    1. Create a rocket that can reach a minimum height of 120 ft
    2. Create a vehicle that can land with an egg for a passenger, and not have it crack.

    We also aren't allowed to use anything that would act as a parachute. The goal is to meet the objectives whilst using as little material as possible.

    To meet the requirements, I added half of a 24oz bottle on top of the 2 liter bottle which the pressurized air & water will be in, to act both as the "nose" of the rocket and make it more aerodynamic, while also acting as a container for the egg. I then filled it with soft clay, with the theory being that upon impact, the clay will compress and let the egg decelerate slowly, keeping it from breaking.

    Is this a good idea? I've done egg drops before but the size of our container is extremely limited (half a 12 oz bottle) and also never dropped an egg from as high as 120+ ft. Would just stuffing it with newspaper suffice?
     
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  3. Sep 27, 2012 #2

    Simon Bridge

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    Or foam ... or make a glider... or reinforce the shell (you only need to keep the shell intact, the insides can still get scrambled ;) )

    You will need to experiment with different materials - see if you can work out how much padding you need from different heights.
     
  4. Sep 27, 2012 #3
    Use the foam that is used for plants... I did an egg drop project and we used two blocks of that material, cut an egg shape into it, and filled the rest with peanut butter(so that the egg was snug against the foam. Lets just say 40ft up and throwing it straight down as hard as I could didn't do squat to the egg.
     
  5. Sep 27, 2012 #4
    How fast will the egg be traveling at impact? How much force will cause it to break? I think answers to these two questions are the most important to success. For instance they will tell you how much your cushioning material must compress in order not to exceed the breaking force.

    That said, I've often wondered if the force required to break the egg would be increased if the egg were submerged in a gelatin solution at the same density as the egg. Would the gelatin, not being compressible, apply an equal pressure on all sides of the egg? One thing that may destroy this idea is the small bubble inside the egg.
     
    Last edited: Sep 28, 2012
  6. Sep 28, 2012 #5

    mfb

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    Air cell (larger end) up is probably a good idea.

    I think it should work, especially with fresh eggs - or try to fill the air bubble with water.
     
  7. Sep 28, 2012 #6

    Simon Bridge

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    Soak the egg in water overnight.
    Incased in gelatin just provides a cushion... it is the Δp you have to spread out in time so the peak force does not exceed the breaking force for the shell. The other way is to reinforce the shell so its breaking force is higher... unless you care if the insides are scrambled.

    Of course the gel also provides impedence matching between the egg and the medium... so better allows the shockwave from the bottom of the vessel hitting the ground to get through the shell...
     
  8. Sep 29, 2012 #7
    If the rules allow soaking, it would be better to soak in vinigar for a few days.
     
  9. Sep 30, 2012 #8

    Simon Bridge

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    For that matter - paint the shell... no, have it encased in a snug outer coating of hardened steel :)

    If you supply your own egg, there is a lot of scope for finessing ("cheating" is such an ugly word) things.

    There are all sorts of things you can do with a rigid frame to channel the shockwave around the egg ... suspending the egg in an cradle inside such a frame may do well.

    The bottom line is still to find out what sort of decelerations the egg can withstand without the shell breaking. Is it just a matter of keeping it from impacting hard surfaces?

    Also - not allowed a parachute, presumably a glider would also be cheating, are you allowed vanes on the capsule so you can be reasonably sure a particular side hits first? Then you can build a shock-absorber into just that side.
     
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