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More on the golf ball launcher, and Ozzy make some interesting comment.

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LAN_403

w1vlf

Wed May 21 2008, 11:28PM

Registered Member #1329 Joined: Mon Feb 18 2008, 07:31PM
Location: Harwinton Connecticut
Posts: 53

Fellow Launchers of things mettalic and otherwise.
Since wire for my flat coil has been delayed I thought if you guys didn't mind looking at the some other aspects of this launcher I would be most appreciative.

In any of my posts please chime in if it appears that I have a fact or concept incorrectly or put forward a theory that just seems wrong.

From the earlier golf ball experiments.
Here are some things learned.

The golf ball make a superior projectile from the perspective of cost, aerodynamics, it is infact designed to have the "bleep" knocked out of it and return smilimg.

In the vertal tests it was very obvious that the GB time of flight was much better than the AL disc

Everything happens so quickly during a test that it is very hard to see what happens to the AL disc.
The size if the disc again is 1/4" thick by just a bit over 2" in dia.

The AL disc always langs very close to the launcher, with in a few feet and I would guess never rises about 3' abouve the ground.

With that in mind OZZY put for the proposition that the GB may be compressing violently, from the force of the rapidly acceleration of the AL disc.
According to conservation of momentum the lighter disc at 35 grams should bounce of the heavier ball at 46 grams, duriong the elastic collision.

Perhaps that is why the disc gives up its inertia to the GB but at the same time get bounced back to the launcher.
If this is true should not a disc weight equal to the GB impart more energy to the GB?
This of course assumes that the new heavier disc has the same velocity as the older lighter disc.

A disc heavier than the ball should result in a GB speed of greater than the disc, but it would contiue to hold on to some of its original force.

Please comments anyone I want to learn about this.
Thank you

PC
W1VLF

Dr. Slack

Thu May 22 2008, 01:44PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

If this is true should not a disc weight equal to the GB impart more energy to the GB?

Equal weights, together with no energy loss in the rebound of the GB, will result in all of the energy of the disc being transferred to the ball, and the disc dropping dead.

With finite rebound loss (non-unity coefficient of restitution) and equal weights, their seperation speed will be slightly less than their approach speed, which means the disc will still have some forward speed after the collision. The residual energy in the disc is not much of a problem as a) it depends on speed^2, so is very small and more importantly b) surely the main task is to maximise the speed of the ball, not necessarily minimise the residual energy of the disc. Although efficiency will mean using the least energy to fling the smallest disc practical.

Now whether it's better to use a slightly heavier or lighter disc depends on how the disc speed depends on its mass for any given launcher. For discs of equal speed, a heavier disc will kick the GB to a higher speed (no surprise there), but at the cost of efficiency. I suspect a thicker disc would fly slower for a given launcher energy, but maybe a wider disc would intercept more of the field and so be launched as fast as a narrower one.

If you can come up with some measurements for launcher efficiency versus disc thickness and diameter that you can approximate, and get a figure for the large deflection coefficient of restitution for the golf ball (small deflection obtained by observing bounce height from the ground may be a good first stab, but I reckon that large deflection will be different), then you could derive the optimum disc dimensions - for either max GB energy, or max efficiency, or min disc residual speed, but the different criteria will give different optima.

Quantum Singularity

Sat May 24 2008, 02:11AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

I think most of the above comments are based on a collision between the disk a ball and transfer of energy at the time of collision, much like the graphical thing you previously linked to was about. I donâ€™t know how true to this your ideas will be, as I have said in the past unless you setup a specialized setup so that the disk accelerates to full speed and then strikes the ball... I donâ€™t know if you have done this or not. If the disk and ball start as one, youâ€™ll get much less 'transfer' of energy depending on how much the gb compresses upon initial acceleration. If the acceleration is not severe enough, there could possibly be no transfer of energy to the gb via collision, only a loss of total energy as the weight of the gb+disk reduces as the disk falls away. I do believe however the IL's are fast enough to cause the compression of the gb, at least partly... but only high speed video or a specially setup test where a gb attached to disk and one were it strikes it, would tell for sure. I have my flat wire coil built and my first weekend of testing with smaller diameter rounds launched through a barrel didnâ€™t turn out so good. But were fixing to move beginning of June and after we move we need to fix up our old place to sell... could be months before I have any more time for projects.

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