Air Trajectory B/C

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SOCoach
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Re: Air Trajectory B/C

Post by SOCoach » March 4th, 2015, 4:39 pm

I apologize if this has been posted earlier, but I am assuming per rule 3h. "Electrical components are not allowed as part of the device or triggering device" that using a laser pointer as a sighting device is not allowed?

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Re: Air Trajectory B/C

Post by bernard » March 4th, 2015, 5:24 pm

SOCoach wrote:I apologize if this has been posted earlier, but I am assuming per rule 3h. "Electrical components are not allowed as part of the device or triggering device" that using a laser pointer as a sighting device is not allowed?
A laser pointer can be used as a sighting device as long as it is removed before launch. An FAQ was posted about this:
Science Olympiad wrote:Is a laser permitted for use as solely as an aiming device? (section: 3 / paragraph: h / line: 1)
Yes, as long as it is a removable tool that is not part of the device and removed prior to launch. The official SO laser policy must also be followed: http://soinc.org/lasers
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Re: Air Trajectory B/C

Post by Type » March 5th, 2015, 2:55 pm

chalker wrote:
bernard wrote:
sjwon3789 wrote:

It has to reinflate it by itself. So you cannot use any mechanism to re-inflate it, I believe. When I attempted to use the kickball, we just switched to using a soda bottle because it was really irritating to work with.
Could you direct me to the rule that suggests that or explicitly says it? All I see is the rule about ambient air pressure, which could be met even if it is re-inflated with a bike pump.
Correct, there is no requirement in the rules to 'reinflate by itself'. Only to remain at ambient air pressure, which is a completely separate thing. General rule #1 applies: http://soinc.org/ethics_rules However note that you can't expect there to be a power socket available to plug your air pump into, so I wouldn't count on using that.

As always, this is not the place for official comments of clarifications though.
I picked up a portable air mattress pump that is powered by a battery. So if I understand what you are saying, it would be fine to use even though it is electrical?

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Re: Air Trajectory B/C

Post by bernard » March 5th, 2015, 3:09 pm

Type wrote:I picked up a portable air mattress pump that is powered by a battery. So if I understand what you are saying, it would be fine to use even though it is electrical?
I would use the same reasoning used for the laser FAQ in this situation. As long as the electrical component is not part of the device during launch, it should be allowed. See rule 3.h..
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Re: Air Trajectory B/C

Post by joeyjoejoe » March 5th, 2015, 3:21 pm

What is your take on the part of rule 4f which states that you have 8 minutes ...to launch a maximum of two shots at two targets.

I mean lets say that a team forgot to load a ball in the launch tube prior to launch (hypothetically) or the ball failed to launch for some reason.
Would that count as a launch or not?

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Re: Air Trajectory B/C

Post by chalker » March 5th, 2015, 4:00 pm

joeyjoejoe wrote:What is your take on the part of rule 4f which states that you have 8 minutes ...to launch a maximum of two shots at two targets.

I mean lets say that a team forgot to load a ball in the launch tube prior to launch (hypothetically) or the ball failed to launch for some reason.
Would that count as a launch or not?

Rule 6.b.iii. addresses that. A failed launch is 0 points.

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Re: Air Trajectory B/C

Post by ImNotSmart » March 6th, 2015, 8:42 pm

Hello! I'm currently using a stomp rocket as the base for my design. The tube connected to the stomp rocket is a fraction of an inch in diameter. I've tested the design with the actual rocket, and it can fire the correct distance. However, I have been unsuccessful in connecting the tube to the PVC pipe fit for my ping pong ball. When I drop the weight to launch the ping pong ball, it barely shoots out of the barrel, unlike the actual rocket which can fire up to 8 meters. Do you have any suggestions as to how to fix my barrel so that a table tennis ball may be launched? Thanks!

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Re: Air Trajectory B/C

Post by hogger » March 7th, 2015, 1:31 am

ImNotSmart wrote:Hello! I'm currently using a stomp rocket as the base for my design. The tube connected to the stomp rocket is a fraction of an inch in diameter. I've tested the design with the actual rocket, and it can fire the correct distance. However, I have been unsuccessful in connecting the tube to the PVC pipe fit for my ping pong ball. When I drop the weight to launch the ping pong ball, it barely shoots out of the barrel, unlike the actual rocket which can fire up to 8 meters. Do you have any suggestions as to how to fix my barrel so that a table tennis ball may be launched? Thanks!
Try getting wide foam insulation strip at Home Depot and line the inside of the barrel with it so that the ping pong ball snuggly fit inside it to create a pop gun effect.

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Re: Air Trajectory B/C

Post by ImNotSmart » March 7th, 2015, 4:16 am

hogger wrote:
ImNotSmart wrote:Hello! I'm currently using a stomp rocket as the base for my design. The tube connected to the stomp rocket is a fraction of an inch in diameter. I've tested the design with the actual rocket, and it can fire the correct distance. However, I have been unsuccessful in connecting the tube to the PVC pipe fit for my ping pong ball. When I drop the weight to launch the ping pong ball, it barely shoots out of the barrel, unlike the actual rocket which can fire up to 8 meters. Do you have any suggestions as to how to fix my barrel so that a table tennis ball may be launched? Thanks!
Try getting wide foam insulation strip at Home Depot and line the inside of the barrel with it so that the ping pong ball snuggly fit inside it to create a pop gun effect.
Thanks for the response! My ping pong ball is actually already pretty snug in the barrel, but I was thinking the same thing. Could I get the same effect by lining the inside of the barrel with plastic from a binder sleeve?

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Re: Air Trajectory B/C

Post by joeyjoejoe » March 7th, 2015, 12:44 pm

ImNotSmart wrote:Hello! I'm currently using a stomp rocket as the base for my design. The tube connected to the stomp rocket is a fraction of an inch in diameter. I've tested the design with the actual rocket, and it can fire the correct distance. However, I have been unsuccessful in connecting the tube to the PVC pipe fit for my ping pong ball. When I drop the weight to launch the ping pong ball, it barely shoots out of the barrel, unlike the actual rocket which can fire up to 8 meters. Do you have any suggestions as to how to fix my barrel so that a table tennis ball may be launched? Thanks!
Ping pong balls and solid plastic golf balls are typically less than 3g each so all you need is a moderately tight fit and they should soar. With the average ping pong ball, you should have a tight enough fit with any schedule 40 (thick walled) 1.5" PVC. To demonstrate what I mean, I performed an experiment: I took an 8" piece of 1.5 PVC and pressed it against my thigh so that it was air-tight at the bottom. Then I dropped a ping pong ball in the top. It took a little under three seconds for the ball to reach my leg due to the difficulty in pushing the existing air in the tube out of the way. If you look at many of the videos on YouTube, you will see that most of the teams that launch ping pong balls or plastic golf balls do not have anything lining their launch tubes.
I'll bet your problem is that not enough air volume is being forced down the tube quickly enough- possibly due to an air feed tube that is too narrow. We started off hooking our air reservoir to a dishwasher drain tube (i.d. about half an inch) and found that by simply going to a flexible hose with an i.d. of1.5 inches, we increased our launch distance drastically. If you think about it, the typical launcher utilizing a 2L bottle is putting a softball sized dent in the bottle at each launch- that's over 300cubic cm of air being forced out in a fraction of a second. If the ball fits fairly snuggly and is very light, it will go very far.

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