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Extreme golf ball backspin: Theory

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Extreme golf ball backspin: Theory

Unread postAuthor: DR » Sat Dec 06, 2008 8:22 pm

If any of you ever happened to come across the YouTube video, entitled:
<a href="http://www.youtube.com/watch?v=ObjygBGDStI">70,000 rpm golf ball</a>... I wonder then, if you ever thought it would benefit a pneumatic golf ball launcher, in terms of lift.

By drilling and tapping a 1/4"NPT thread, into a 2" Coupling, a smaller port (1/8", perhaps???) could then be drilled into the 2" Spigot x 1"FPT Reducer - after it was solvent-welded into the coupling.

<img src="http://i35.tinypic.com/2lwn72x.jpg">

180* opposite, would be the same diameter hole (1/8"???), for the exhaust port.

With the launcher assembly mounted in a fixed (and slightly elevated) position, direct air could be routed into the barrel, from your compressor.
The flow could be regulated... and by experimenting with the correct flow AND the correct elevation, would a golf ball fly much further?

<img src="http://i34.tinypic.com/faydyu.jpg">

<img src="http://i36.tinypic.com/j7f1gz.jpg">
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Unread postAuthor: mark.f » Sat Dec 06, 2008 8:33 pm

Seems interesting. Sort of a hop up which effects the ball before exiting the barrel. An effective one, at that, if you can get it spinning fast enough.
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Unread postAuthor: Velocity » Sat Dec 06, 2008 10:43 pm

I REALLY like that idea for adding hop-up without having something at the end to cause it. It would undoubtedly create far greater spin if done correctly. I have no idea how well it would work, but I think its an ingenious idea.
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Unread postAuthor: Daltonultra » Sat Dec 06, 2008 11:50 pm

You would have to have an escape for the pressurized air behind the ball. Otherwise, pressure would build behind it and overcome the Venturi effect that is holding it in, pushing the ball down the barrel.

It can still be done though, the hole doesn't have to be huge, and the pressure of firing wouldn't be decreased that much.

I think a more practical way of getting backspin might be a strip of rubber, or something else high-friction, along the length of the barrel.
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Unread postAuthor: xboxteen01 » Sun Dec 07, 2008 12:38 am

Wouldnt the weight of the ball at the contact points prove to be too much to spin it?
This sorta reminds me of the experiment/trick where a ping pong ball is "levitated" above a hair dryer but is kept in place and at a consistent height by the air flow.
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Unread postAuthor: jook13 » Sun Dec 07, 2008 12:44 am

This seems like a good idea for sure. I know in my gb cannon, I just put a screw at the end of my barrel on the top. it sticks down into it about an 1/8 of an inch. It has increased my distances by about double as far as the naked eye is concerned. Probably not double, but it made one hell of a difference. Plus the shots are a lot more predictable.
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Unread postAuthor: Daltonultra » Sun Dec 07, 2008 12:58 am

xboxteen01 wrote:Wouldnt the weight of the ball at the contact points prove to be too much to spin it?
This sorta reminds me of the experiment/trick where a ping pong ball is "levitated" above a hair dryer but is kept in place and at a consistent height by the air flow.

Similar, but with an added complication. You're familiar with the effect of having a shower curtain suck in when you're taking a shower? Or holding your hand next to a fast stream of water from a tap and seeing it bend slightly toward your hand? When air moves across the surface of an object, it tends to generate lift. When it moves between two objects, it pulls them together. This is the Venturi effect. So the air flowing between the funnel and the ball actually pulls the ball towards the wall of the funnel. But their is an equalizing effect, in that as the gap between the objects closes, it blocks the air and pressure forms, pushing the objects away from each other. You quickly either reach an equilibrium, or develop a massive oscillation.

Basically, with the ball and funnel, this has the effect of creating an "air bearing" that keeps the ball from either touching the funnel, or flying out of it.
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Unread postAuthor: D_Hall » Sun Dec 07, 2008 1:31 am

Yes, adding backspin to golf balls results in greater range (and more predictable trajectories).

But you're making it MUCH harder than it has to be. Just put a mild bend in the barrel (Note: The "Tippmann Flatline" system does this for paintball guns.).

Actually, you probably don't even have to do it intentionally. On my golfball gun (RIP), I did this but the bend was something from the factory. That is to say that the piece of pipe I used for a barrel wasn't perfectly straight. Just that mild bend was enough to achieve the effect I needed; I just had to mark the barrel so that I would know which way to mount the barrel so that I was adding backspin rather than top spin (or worse, side spin!).
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Unread postAuthor: Brian the brain » Sun Dec 07, 2008 4:13 am

Come on DR!
You made that tennisball launcher that fired 7 TB's automaticly right?

You should know that the golfball is just going to get sucked up and spat out...I believe it is called the bernoulli effect...not sure though...

You need an axle to hold the golfball in place when you want to make it spin like that in the airflow.

It would be much easier mounting a drill to the side of the cannon, and a ajustable blot on the opposite side.That way you can grip he ball just very gently and spin it using the drill.
Then you trigger the main valve.
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Unread postAuthor: ALIHISGREAT » Sun Dec 07, 2008 5:46 am

you could simply use an airsoft style hop-up (although i doubt it could spin the ball at 70000rpm :lol: )

or you could put a friction inducing thread along the top of the barrel?
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Unread postAuthor: scavies » Sun Dec 07, 2008 6:57 am

I'm actually seeing here a good potential to use a blowback system... or at least the same concept. Maybe when you fire you can rout a small portion of air from the tube to the bottom of the barrel, so a little more air is pushing at the bottom from the top. Cool idea man, I'm wondering what kind of a difference it would make.
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Unread postAuthor: jimmy101 » Sun Dec 07, 2008 6:28 pm

I wonder, what would be the optimal rotation speed? Lets see, figure a decent gun firing a GB at say 600 FPS. GB diameter is 1.7". I believe you would want the ball spinning such that the effective air velocity at the top of the ball is zero, so the ball's edge is moving at 600 FPS. GB diameter is 5.3".
(600FPS)(12in/ft)/(5.3")=1360/sec (revolutions per second)
roughly 81,000 RPM
About the same as the 70,000 in the OP.

Will a GB hold together at 70,000 RPM? I wouldn't think so.

D_Hall wrote:But you're making it MUCH harder than it has to be. Just put a mild bend in the barrel (Note: The "Tippmann Flatline" system does this for paintball guns.).

To get a bent barrel to impart spin doesn't that require some blowby? A tight fitting ammo wouldn't get much spin from the bent barrel. Aren't paintballs a pretty crap fit in their barrels? (Probably to reduce the chances of the paintballs rupturing in the barrel.)
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Unread postAuthor: DR » Sun Dec 07, 2008 7:59 pm

Daltonultra wrote:You would have to have an escape for the pressurized air behind the ball. Otherwise, pressure would build behind it and overcome the Venturi effect that is holding it in, pushing the ball down the barrel.

It can still be done though, the hole doesn't have to be huge, and the pressure of firing wouldn't be decreased that much...


There IS an escape for the pressurized air behind the ball! - I've highlighted the porting in this photo, for you

<img src="http://i35.tinypic.com/14dfuxs.jpg">

D_Hall wrote:Yes, adding backspin to golf balls results in greater range (and more predictable trajectories).

But you're making it MUCH harder than it has to be. Just put a mild bend in the barrel (Note: The "Tippmann Flatline" system does this for paintball guns.).


Not that much harder, at all, actually? A couple of drilled holes and a tapped fitting, is all.

I thought of this to be a half-decent idea, because the screw or o-ring method of imparting backspin, has to impart of a slight amount of drag to the ball, even though it's only for a fraction of a second.

With this method, there's no drag at all... No o-ring to hit, no screw to hit, and no bent-wall to ride, before it exits the barrel. - Just a cushion of air.

Besides- This idea may be lousy, because: If the ball wasn't spinning perfectly backwards(on a perfect axis), it may cause erratic flight?
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Unread postAuthor: mark.f » Sun Dec 07, 2008 10:02 pm

Well I wouldn't think those airsofters and paintballers needed to install bubble sights on their guns?
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Unread postAuthor: TurboSuper » Sun Dec 07, 2008 10:21 pm

I imagine this would cause the range of the ball to increase simply due to it rolling...
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