designing a machine, engineering question. (1 Viewer)

[Justin Ward]

In my university one of the big projects is to design a device that will fire a golf ball onto the green to help study turf damage. So far we have determined the following regarding it:
It will be powered by some form of compressed air.
It will not launch into the air, it will only fire into the ground.
Spin must be simulated.

Now, to get the spin on the ball we decided we could fire the ball through a cylinder, with more air pressure being concentrated on one part of the ball, generating spin. Now we are trying to figure out what kind of air supply would be adequate to launch the golf ball. We determined that the kinetic energy of a paintball at 300fps is essentially the same as a golf ball at 20m/s. So, does this mean we could use a similar pressure to launch the golf ball as a paintball? What we want to do is adapt a compressed air tank designed for paintball to do this but we are unsure if it is capable of meeting our demands.

Would this type of tank be appropiate? And would the ball acquire a spin like we predicted?

 

[Mike SJ]

Well woldnt you need to compensate for the difference in mass from paintball to golfball? OK WAIT, you are studying turf damage? may I ask why? just repair your divots and all is good

the way I see how to add spin is that when the gball is shot thru the muzzle/tube, that there is some sort of friction on one point close to the end of the tube. you dont want the ball spinning like a bullet, I assume you want the ball to mimic a golf shot, so you need back/forward spin. When the gball is shot thru the muzzle/tube, when it hits the friction point, it will slow down one side of the ball creating spin. lemme know if I make sense. How far do you plan to launch th gballs?

 

[Keith Mickunas]

There's nothing specific about the tanks for paintball guns. In the guns there are other factors that determine the final speed, and there's usually some sort of adjustment that can be made to lower the fps if it's too high.

Just to assist in your design you might want to do some searching for paintball mortar launchers and bazookas on the web. These are usually custom made out of PVC and similar materials and launch either large paintballs or groups of regular paintballs and are typically powered with the standard CO2 tanks used by the guns.

 

[Justin Ward]

OK WAIT, you are studying turf damage? may I ask why? just repair your divots and all is good

Not sure, maybe so they can design courses more resistant to damage.

I determined the pball and golf ball had similar KE by using the equation KE = .5mv^2

 

[Mike SJ]

KE = .5mv^2


gball= 45.36 grams Diam.=1.680 in v=2.4827127095378762
gbll KE=139.79639918892847633196883538002
pball= 3.6 grams Diam.=.69 in v=0.17200691017303285
pball KE=0.053255478865092825139069260922421

well this explains why im not an engineer, i know these should be much much closer.

"Not sure, maybe so they can design courses more resistant to damage." lol

"but the calculations were getting pretty difficult" forgot it all has to be documented and precice.

so for your final hypothesis, youll need to know exact spin speed? AND trajectory speed? Will you use different types of grass too? I guess I dont see where this leads to but its a brain teaser and Ill try to help

 

[Justin Ward]

The "v" is velocity, not volume

so for your final hypothesis, youll need to know exact spin speed? AND trajectory speed? Will you use different types of grass too? I guess I dont see where this leads to but its a brain teaser and Ill try to help

We don't need to know the effects or how to study them. We just need to design something that will allow them to accomplish this. So we need to simulate the impact of the golf ball as closely as possible. So, yes, both the trajectory and spin speeds need to be simulated. I have a paper around here that gives the speeds, but I need to find a way to achieve these speeds.
Thanks for the help so far.

 

[Mike SJ]

v=velocity, doh!

"We just need to design something that will allow them to accomplish this."
And THIS would be shooting golf balls at grass...?

Heck, just drop them from a tall height and for spin, have them roll off of something like a board, the longer the board the more spin.

 

[Joseph DeMartino]

I guess hitting golf balls with clubs in the direction of the turf is out of the question?

Geez, give the engineering students class credit for showing up on the driving range and you'll have all the test data anybody needs without having to build the bloody machine. It would be a lot cheaper and probably more fun.

Also I'm not sure how they think they're going to simulate the action of an actual golf shot - which goes through the air - by firing golf balls out of a machine directly at the ground.

Is this a government study by any chance?

Regards,

Joe

 

[Brian W. Ralston]

I would think that using a paintball as a model for comparison in any aspect would not be a good idea. The paint ball has a liquid center....which will greatly affect how a paint ball travels, spins and reacts to being launched through the air in all aspects. A golf ball has a solid center.....so it will behave much differently.

 

[BrianW]

Now, to get the spin on the ball we decided we could fire the ball through a cylinder, with more air pressure being concentrated on one part of the ball, generating spin.

I don't think you'll get good, reproducible results with this method, but not having built one, I must admit to guessing here.

Mike's method of achieving spin seems like a good idea, though I don't know why the calculations would be any more difficult than with a lopsided blast of air.

If I may suggest, how about a curved (as in not straight) cylinder? The curve would impart an acceleration to the golf ball that would keep it against one side of the cylinder, causing the ball to "roll" as it passes through. The tighter the radius of the curve, the more spin you get (to a point), making the calculations fairly easy, once you've accounted for slippage. (Don't forget to account for the fact that the increase in final angular momentum will cause a requisite decrease in linear momentum.)

I know that there's a brand of gray PVC (-like) pipe that can be bent to a radius of six inches, though I don't know if any can be found of such a diameter that it would be a suitable barrel for firing a golf ball.

 

[Tom Meyer]

why not avoid all the compressed air shenannigans and design your own 'Iron Byron' ?

 

[Eric Kahn]

you would be better off using a spinning wheel device, if you put the spining wheel at the bottom, in a notchout in the tube, it would simulate the backspin that a golf ball arrives at the green with

 

[Justin Ward]

Thanks, for the ideas. I'd really like to stick with this idea though.

The paint ball has a liquid center....which will greatly affect how a paint ball travels, spins and reacts to being launched through the air in all aspects. A golf ball has a solid center.....so it will behave much differently.

That't a good point. I was mostly just comparing the pball to the golf ball in terms of energy requred to move them, not their trajectory or spins.

 

[BradleyS.]

I think a paintball air tank would be a good air source, but have you considered using co2 instead of compressed air or nitrogen. Co2 tanks are alot cheaper than nitrogen or compressed air tanks. Co2 tanks are about $10 for a 12 ounce tank, which has enough power to get about 1000 shots out a paintball gun. The cheapest nitrogen or compressed air tanks i have seen retail for around $70 for a 68 ci. 4500psi tank which will also get about the same number of shots. Have you also considered using hair spray like they do in potato cannons? if you get a tight enough seal you can make the potatoes fly a pretty good distance.

 

[Mike Wladyka]

i agree with Eric about using a spinning wheel...like a pitching machine


one more thing to remember that could throw you calculations off a bit, is that different golfballs has different covers that are either softer or harder, which would make them spin more or less

 

[Nathan Patrick]

one more thing to remember that could throw you calculations off a bit, is that different golfballs has different covers that are either softer or harder, which would make them spin more or less

Not to mention that the different covers could influence the transfer of kinetic energy when the ball hits the green, resulting in a larger or smaller ball mark from ball to ball.

 

[Mike Wladyka]

Not to mention that the different covers could influence the transfer of kinetic energy when the ball hits the green, resulting in a larger or smaller ball mark from ball to ball.

like you ever hit the green to notice

 

[Nathan Patrick]

like you ever hit the green to notice

Every once in a while.

 

[Eric Kahn]

I hit the green about 2% of the time
I have an air cannon that I just pump up with an air compressor to about 100 PSI, for it to work properly, the air tank needs to be at least twice the diameter of the barrel and the air valve should be the same diameter as the barrel, mine is shaped like a big U with the valve at the bottom bend
I do not know what kind of muzzle velocity I am getting but I have launched a potato over 200 yards which is pretty good considering that it comes out of the barrel with no spin on it, golf balls actually fly due to the back spin, if they did not have any spin, they would only go half as far as they do

 

[Justin Ward]

Heres an update:
I went with my original compressed air idea and my presetation went well. I had an autocad drawing done to scale that turned out pretty well. I am trying to decide what to do for the barrel though. I am trying to find some friction coefficients for golf balls on different materials. Any idea where I could find something like this?