Air Trajectory B/C

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Re: Air Trajectory B/C

Post by Type » March 12th, 2015, 2:51 pm

Sidaddybombdaddy7 wrote:I am having a different problem. The rules say, "All air device chambers must start launch at ambient air pressure and must automatically return to ambient pressure." We are using a red rubber "dodge ball" that begins at ambient pressure, gets deflated during launch, thus returning to ambient pressure - but not the original shape of the ball - meaning it does not "re-inflate." Is it expected to "re-inflate" to the original shape or if deflated ambient pressure ok and then we just blow into the tube to return into the original shape?
What it means by ambient pressure is that it isnt pressurized, so all long as you dont have a valve and are not forcing air in, you should be fine.

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Re: Air Trajectory B/C

Post by chalker » March 12th, 2015, 5:50 pm

Type wrote:
Sidaddybombdaddy7 wrote:I am having a different problem. The rules say, "All air device chambers must start launch at ambient air pressure and must automatically return to ambient pressure." We are using a red rubber "dodge ball" that begins at ambient pressure, gets deflated during launch, thus returning to ambient pressure - but not the original shape of the ball - meaning it does not "re-inflate." Is it expected to "re-inflate" to the original shape or if deflated ambient pressure ok and then we just blow into the tube to return into the original shape?
What it means by ambient pressure is that it isnt pressurized, so all long as you dont have a valve and are not forcing air in, you should be fine.
We issued an FAQ last week about this: http://soinc.org/node/478

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Re: Air Trajectory B/C

Post by goodcheer » March 13th, 2015, 7:41 am

Type wrote:
bernard wrote:
Type wrote:So they picked easy distances, 3 and 6 meters. I got between 100 and 200 MM for all four shots but only got second. Probably would have done better if my partner agreed to do a bucket shot. The judge gave me a problem with the air pump but he caved and gave it to me, thanks everyone for the help and good luck to you guys.
What was the issue with the air pump?
The air pump I was using was electrical. I used it to fill air into a kickball and a mass fell on that.

Maybe he thought the pump was adding pressurized air into the ball greater than the ambient air pressure. If the pump was being used just to re-inflate the ball and the final pressure inside the ball equalized with the outside pressure, should be ok. I can imagine pressure building up inside the ball momentarily while pumping, but once you stop pumping, the pressure should equalize.

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Re: Air Trajectory B/C

Post by jimbo1qaz » March 15th, 2015, 12:04 am

Is it OK to have a "pneumatic" system where there's a single piston in a sealed tube, where force is transmitted linearly through air pressure? Does that qualify as pneumatic?

Second, is it OK to have a two-stage trigger where the first stage creates a pressure difference, and the second actually shoots the object?

Third, is the weight of a small piston pulling on the air chamber, acceptable for "atmospheric pressure"?

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Re: Air Trajectory B/C

Post by chalker » March 15th, 2015, 7:35 am

jimbo1qaz wrote:Is it OK to have a "pneumatic" system where there's a single piston in a sealed tube, where force is transmitted linearly through air pressure? Does that qualify as pneumatic?

Second, is it OK to have a two-stage trigger where the first stage creates a pressure difference, and the second actually shoots the object?

Third, is the weight of a small piston pulling on the air chamber, acceptable for "atmospheric pressure"?

There are some official FAQs you should look at which address each of these issues:
http://soinc.org/node/286

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Re: Air Trajectory B/C

Post by UTF-8 U+6211 U+662F » March 21st, 2015, 12:44 pm

Do y'all think a whoopee cushion would be effective, like a REALLY big whoopee cushion?

EDIT: in place of the soda bottle, I mean.

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Re: Air Trajectory B/C

Post by goodcheer » March 21st, 2015, 8:33 pm

UTF-8 U+6211 U+662F wrote:Do y'all think a whoopee cushion would be effective, like a REALLY big whoopee cushion?

EDIT: in place of the soda bottle, I mean.
Might work if it is tough enough. We saw a lot of teams in competition using a ball instead of a bottle. Seemed to work very well.

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Re: Air Trajectory B/C

Post by theoriginalweevil » March 21st, 2015, 9:56 pm

UTF-8 U+6211 U+662F wrote:Do y'all think a whoopee cushion would be effective, like a REALLY big whoopee cushion?

EDIT: in place of the soda bottle, I mean.
My experience with whoopee cushions is that they are frankly quite poor quality. Seals are bad, the bindings might open, and there may be variations between each cushion. Also consider the possible wear and tear of it?

My school had one "swinging arm" device and the accuracy was great; the other "falling weight-soda bottle" machines deviated. We attributed this to the wear of the soda bottle and the "shaking" of the device.

Not sure how much time you have left before your next competition?
:D

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Re: Air Trajectory B/C

Post by UTF-8 U+6211 U+662F » March 22nd, 2015, 7:11 am

theoriginalweevil wrote:
UTF-8 U+6211 U+662F wrote:Do y'all think a whoopee cushion would be effective, like a REALLY big whoopee cushion?

EDIT: in place of the soda bottle, I mean.
My experience with whoopee cushions is that they are frankly quite poor quality. Seals are bad, the bindings might open, and there may be variations between each cushion. Also consider the possible wear and tear of it?

My school had one "swinging arm" device and the accuracy was great; the other "falling weight-soda bottle" machines deviated. We attributed this to the wear of the soda bottle and the "shaking" of the device.

Not sure how much time you have left before your next competition?
My team has a lot of time, so it's just trying out all possibilities. Do you guys think a ball bladder would work better?

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Re: Air Trajectory B/C

Post by theoriginalweevil » March 24th, 2015, 9:53 am

UTF-8 U+6211 U+662F wrote:
theoriginalweevil wrote:
UTF-8 U+6211 U+662F wrote:Do y'all think a whoopee cushion would be effective, like a REALLY big whoopee cushion?

EDIT: in place of the soda bottle, I mean.
My experience with whoopee cushions is that they are frankly quite poor quality. Seals are bad, the bindings might open, and there may be variations between each cushion. Also consider the possible wear and tear of it?

My school had one "swinging arm" device and the accuracy was great; the other "falling weight-soda bottle" machines deviated. We attributed this to the wear of the soda bottle and the "shaking" of the device.

Not sure how much time you have left before your next competition?
My team has a lot of time, so it's just trying out all possibilities. Do you guys think a ball bladder would work better?
We had about a month left before the competition (which has passed since) and we used soda bottles to build. I'm curious to why you won't use the soda bottles. They don't need to be huge, they're inexpensive, common and easy to find.

Those 24-pack of 1L water bottles that are relatively "squishable" was easiest for us, and the air from the bottles was constant. They did wear easily though, so we went through about a dozen.

Later we were experimenting and then we used a gatorade sipper. It reinflates after the weight hits the bottle and launches.

Image

I'm here to advocate for the bottles. Drill a hole into the cap, stick in connecting tube, seal the joints. Worked for us :)
:D

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