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How fast can you spin your Golf Ball? Answered

I played around with some balls placed into the airstream of a little blower.
Everything light enough just "danced" in the air like being hold on invisible strings.
But not so much the golf ball!

You would expect those dimples are good for reducing air friction but do they also offer stability in some cases by making the ball spin?
Check this video I recorded while playing - to me it looks like with a proper nozzle there is even more speed possible.
https://www.youtube.com/watch?v=014QkXuTL0o

How fast can you make it spin?

Discussions

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Toga_Dan

2 years ago

regulation golf >_ 1.68". And <_1.62 Oz. I've a ball with all dimples filed off. 14 thousandths undersize. It needs polishing. Close enough in size, I suppose. Will it have substantially more drag

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Toga_Dan

2 years ago

a coarse file works better than beltsander to remove dimples. I'm also workin on one by building up paint, then filing. This way, less change in mass and diameter.

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Downunder35mToga_Dan

Reply 2 years ago

Will be intersting to see the results and differences in behaviour.

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Downunder35m

2 years ago

I think I got it even faster this time:

I guess with a properly fitting "cap" under the ball it would be even better.
Still tricky to get it just floating as a bit too much air makes it wobble.
I don't think a smooth ball will act the same way, but if I find one I will try it.

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Toga_Dan

2 years ago

do you have a belt sander? How will the ball behave if the dimples are gone

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Kiteman

2 years ago

In flight, spin only provides stability is the axis of the spin is in line with the direction of flight (American footballs, rifled bullets).

Spin in any other axis causes the object to curve in flight by the "Magnus effect".

The dimples on a golf ball increase drag, which slows down the ball, but it also increases the Magnus effect to a much greater degree - the drag is more than compensated for by lift, which allows the ball to fly further than a smooth ball.

So, in normal use, the back-spin (~300rpm) is caused by the impact of the club, and the spin effects the flow of the air around the ball.

In your example, the flow is causing the spin.

When you put a smooth ball on the nozzle, the nozzle is sealed all around the ball. This makes pressure build up in the nozzle; pressure lifts the ball so that air escapes equally all around the ball. Significant levels of spin are not induced, and the ball is kept in the air-flow by the Bernouilli principle.

When you put the golf ball on the nozzle, the dimples mean that there is no seal around the ball - air will immediately escape around the ball as soon as you start the pump. Because the dimples do not line up exactly with the nozzle, the air will escape unequally (faster on one side than the other), which will naturally drag the ball in that direction, causing spin. That spin will then drag the flow of air in the direction of spin, making more air flow in that direction, increasing the spin in a feed-back loop. Enough air spills out the other sides to lubricate the ball, reducing friction and allowing the spin to increase to very high levels.

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Downunder35mKiteman

Reply 2 years ago

For a little fun you went a long way to disect the case LOL
I know about the dimples and how they work, but what made me wonder was why the ball is getting so fast.
Mind you increased air pressure will make it tumble around, less and it drags on the nozzle too much.
I tried to make it spin in different directions and orientations and in some cases it was even spinning with the spin axle aligned with the airstream.
Not long though as it started to tilt a bit.
Funny thing is that the ball actually rolls as well, so the spin does not stay in the same rotational axis.
Not sure how good it came out in the vid but you can see the text moving all around the ball from one side to the other.

And according to the Mythbusters the drag can't be increased, at least not for their test with a dimpled car:

http://www.discovery.com/tv-shows/mythbusters/vide...

This would explain the insane speeds because if I trust the guys it would mean once the ball spins the air goes around with far less friction losses - maybe that's why I can't get the spinning ball to lift even with max air pressure...!?
Anyway I really like this game of spinning balls!

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Toga_DanKiteman

Reply 2 years ago

according to Sept 19 2005 scientific American, those dimples create a surface layer of turbulence which makes for a smaller wake. Net result: 50% reducion in drag. Although I know the magnus effect, I've not heard of it in regards golf.

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KitemanKiteman

Reply 2 years ago

If somebody could 3d print or mill a ball with a belt of curved grooves around the equator (see bad Paint sketch), I think its spin would be something to behold...

spin ball.jpg
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Toga_DanKiteman

Reply 2 years ago

I have some steel tubing, and a torch. Maybe those grooves could be melted/burned into a ball.

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Downunder35m

2 years ago

Somehow links are not embedded properly anymore :(
Maybe this one works better: