Quote:
Originally Posted by AustinSchuh
Curious. Experimentally, we found that adding mass to one of our prototype kickers increased it's range from something like 5 feet to 15 feet. Then again, that prototype kicker was an extremely light and small piece of metal.
If you run some numbers with Va = 0 and Vb = 1, and the coefficient of restitution equal to 1 in the equation given at Wikipedia, you will find that equal masses of the two objects will result in perfect momentum transfer. I'm going to go out on a limb and guess that since our kickers are swinging around an axis, what you really want is equal moments of inertia around the axis for perfect energy transfer. |
The CR of a soccer ball is in the region of 0.6-0.7, so try your calculations again.
A large contact area on the ball is also important for good momentum transfer, large deformations of the ball result in lost energy, so a big striking surface is probably better than a small one, in general. I would imagine your small thin piece of metal was not very stiff, again a very inefficient way to transfer momentum because the kicker will deform and absorb energy. Things designed to transfer momentum like pool balls and sledge hammers are all very stiff.
Quote:
Originally Posted by IKE
Mass of a kicker is important to a point. the kicker and the ball need to be in the same order of magnitude otherwise there are different governing equations.
[...]
For something this light, it would have to go really fast and might puncture the ball. Thus more surface area would be required, and it would loose a lot to areo losses before striking the ball.
[...]
Too little and it is difficult to store and transmit enough kinetic energy. Too massive and it is difficult to get the mass up to an effective speed.
|
Your first point is very valid, the mass of the kicker needs to be compromise between efficiently absorbing the energy that's applied to it and transferring that energy to the ball. Though for spring-fired kickers lighter is better because springs can deliver their stored energy at very high power levels.
Any kicker of reasonable design (i.e. not a giant flat board) would have to be traveling incredibly fast to see any sort of significant aerodynamic losses, I would consider them negligible for any design.
Final point is again correct, but I feel that as long as the kicker is stiff enough (ours is 4130 steel tubing) then faster is better. IIRC the PGA has banned the use of certain clubs that are super-light and have extra-hard striking faces because they can drive a golf ball significantly further than a softer, heavier club.