Air Trajectory B/C

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Re: Air Trajectory B/C

Post by chalker » February 16th, 2015, 4:55 pm

bernard wrote:
I think most teams have the ball inside the PVC pipe because the friction from the contact between the ball and the PVC requires your device to reach a minimum pressure before the ball launches. If the friction is less, the ball will launch at a lower minimum pressure, so your ball will probably travel less far. Hopefully this makes sense, if not let me know and I'll try and re-explain.
It actually has to do with a physics principle called impulse (https://en.wikipedia.org/wiki/Impulse_%28physics%29). Essentially, in order to significantly change the momentum of the ball, you need to have the force from the air acting on it of a long period of time.

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Re: Air Trajectory B/C

Post by Type » February 17th, 2015, 12:16 pm

I was going to post a picture of what I made just in case other people needed ideas but it says my picture is too large. Oh well. I did find out that if you cut a small hole in a kickball you can just fit a garden hose in the end and not have any leakage. I over-complicated my original idea. Since there is not that much pressure, it doesnt need to be perfect. Also, I was looking at safety glasses and such, it says that you need #5 protection which can be translated, i guess that would be the term, to ANSI Z87+ rated. I have a couple pairs of safety glasses that are ANSI Z87.1 that I believe I am going to use. Would that be fine or do you have to have actual goggles or full seal?

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Re: Air Trajectory B/C

Post by flash2705 » February 18th, 2015, 9:41 am

Question... what exactly do the charts have to be calibrated to? Is it for the 2 4 6 and 8 meter shots? And do you need to bring data tables?
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Re: Air Trajectory B/C

Post by TheGatesofLogic » February 18th, 2015, 10:59 am

I think it's kinda funny how people are stressing about getting a ball to fit precisely in the tube when there's an EXTREMELY simple solution to the problem. My device uses HDPU golf balls without the slightest issue, and I could use standard golf balls if I wanted to and still get maximum distance. I'll drop some hints here and there for the solution if you're REALLY desperate over the imprecision of ping-pong balls.

On a side note, I wouldn't recommend kickballs of any size for your transfer volume without an extremely consistent method for keeping the kickball both precisely in place and precisely expanded, as well as a very fine guide for the falling mass to fall through so it hits precisely the same spot on the ball every time. What I'm getting at here with my redundant use of "precisely" is that they're nice at a glance, but in testing they're wildly inconsistent.

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Re: Air Trajectory B/C

Post by chinesesushi » February 18th, 2015, 11:34 am

TheGatesofLogic wrote:I think it's kinda funny how people are stressing about getting a ball to fit precisely in the tube when there's an EXTREMELY simple solution to the problem. My device uses HDPU golf balls without the slightest issue, and I could use standard golf balls if I wanted to and still get maximum distance. I'll drop some hints here and there for the solution if you're REALLY desperate over the imprecision of ping-pong balls.

On a side note, I wouldn't recommend kickballs of any size for your transfer volume without an extremely consistent method for keeping the kickball both precisely in place and precisely expanded, as well as a very fine guide for the falling mass to fall through so it hits precisely the same spot on the ball every time. What I'm getting at here with my redundant use of "precisely" is that they're nice at a glance, but in testing they're wildly inconsistent.
Please drop some hints :D
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Re: Air Trajectory B/C

Post by bernard » February 18th, 2015, 11:56 am

flash2705 wrote:Question... what exactly do the charts have to be calibrated to? Is it for the 2 4 6 and 8 meter shots? And do you need to bring data tables?
The rules are rather vague on graphs, but "collect data regarding device parameters and performance" in the event description makes me thing we are adjusting a single variable for each of the graphs and measuring its effect (most likely how far your ball launches). If launch distance (my term for how far the ball lands on first impact with the ground) is your dependent variable, your data for launch distance measurements wouldn't have to be 2, 4, 6, and 8 meters but instead whatever data you get for your independent variable manipulations. Rule 6. c. ii. indicates that graphs and corresponding data tables must be on the same page, so you will need to include data tables if you want full points.

I posted a template for the graphs a while back, feel free to use it! Your trendline might not be linear, so adjust that as needed.
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Re: Air Trajectory B/C

Post by asthedeer » February 18th, 2015, 12:07 pm

Type wrote:I was going to post a picture of what I made just in case other people needed ideas but it says my picture is too large. Oh well. I did find out that if you cut a small hole in a kickball you can just fit a garden hose in the end and not have any leakage. I over-complicated my original idea. Since there is not that much pressure, it doesnt need to be perfect. Also, I was looking at safety glasses and such, it says that you need #5 protection which can be translated, i guess that would be the term, to ANSI Z87+ rated. I have a couple pairs of safety glasses that are ANSI Z87.1 that I believe I am going to use. Would that be fine or do you have to have actual goggles or full seal?
ANSI Z87 will not work. You'll need to have Z87+, which counts as #5 protection.
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Re: Air Trajectory B/C

Post by bernard » February 18th, 2015, 12:37 pm

asthedeer wrote:
Type wrote:I was going to post a picture of what I made just in case other people needed ideas but it says my picture is too large. Oh well. I did find out that if you cut a small hole in a kickball you can just fit a garden hose in the end and not have any leakage. I over-complicated my original idea. Since there is not that much pressure, it doesnt need to be perfect. Also, I was looking at safety glasses and such, it says that you need #5 protection which can be translated, i guess that would be the term, to ANSI Z87+ rated. I have a couple pairs of safety glasses that are ANSI Z87.1 that I believe I am going to use. Would that be fine or do you have to have actual goggles or full seal?
ANSI Z87 will not work. You'll need to have Z87+, which counts as #5 protection.
The eye protection doesn't necessarily have to be full seal, which is typical for chemical splash goggles. Our goggles look like clear sunglasses. Look for the words "high impact" on the container for the goggles, too.
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Re: Air Trajectory B/C

Post by chalker » February 18th, 2015, 4:19 pm

TheGatesofLogic wrote:....My device uses HDPU golf balls without the slightest issue.....
You might want to take note of 2 related FAQs:

http://soinc.org/node/1459

"The most common type of plastic golf balls are plastic dimpled and plastic with holes and HDPE foam types are legal. As long as they are commercially marketed as "plastic practice golf balls", they may be used. It is recommended that students bring the packaging if there is a question. "

http://soinc.org/node/1513

"All the words "plastic", "practice", "golf", and "ball" must appear somewhere on the packaging or advertising description of the product, but not necessarily all in the same spot. "

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Re: Air Trajectory B/C

Post by HPerez10 » February 18th, 2015, 4:57 pm

My event is in three days and I'm worried because I have tried multiple angles for the pipe and the ball still doesnt go far enough to reach 8 meters. My falling mass is about 7.5lbs and i dont know if that has anything to do with it? Thanks

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