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Ball drop -design

Ball drop -design

Ball drop -design

(OP)
Someone asked me to design a 6 feet diameter ball to be dropped for new year eve. It will be steel skeleton. What force should I keep in mind to resist?

RE: Ball drop -design

How far is it going to fall? How heavy is it? What is it going to land on? Hard to help without this sort of info.

RE: Ball drop -design

Gravity.

Mike McCann
MMC Engineering

RE: Ball drop -design

(OP)
40 feet drop.
Weight will be depend on size of steel section used to resist design loads.

RE: Ball drop -design

mgh=1/2mv^2
F=ma
Energy has to be dissapated somehow.

RE: Ball drop -design

Every time I watch "Rockin New Year's Eve with Dick Clark", the ball in Times Square drops real slow to add some suspense.  I strongly suspect that's what they're doing, not pushing it off a ledge and having it free fall for 6 feet.  
If that's the case, the dynamic loads should be negligible.  If they're actually dropping the ball, the forces will be large, plus the ball might start rolling somewhere.

RE: Ball drop -design

dgkhan,

   Does the ball have to survive the drop?

   Can you control what the ball lands on?

               JHG

RE: Ball drop -design

Calculate the velocity of the ball when it strikes the ground.  For such a large diameter, you will need to consider drag forces.

Determine the coefficient of restitution between the ball and the object it is striking.  This will be a function of the elastic properties of the two bodies.  Determine the length of time the two objects are in contact before the ball bounces up.  If the ball doesn't bounce up, determine how far its centroid moves after first making contact with the ground.

The following may help:

http://www.jw-stumpel.nl/bounce.html

BA

RE: Ball drop -design

Assuming that the ball is not in free-fall, what is the lowering apparatus?  That will need to be designed structurally for the weight of the ball.

RE: Ball drop -design

You may want to consider wind loading.

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