Air Trajectory B/C

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Re: Air Trajectory B/C

Post by chalker » October 4th, 2014, 7:08 am

You should also keep in mind rule 3.c. This was one we wordsmithed very carefully as we want to minimize the danger due to pressure vessels. For example, a design where the competitor pulls a string to drop a weight, building up pressure in a chamber, then pulls another string to open a valve to release the pressure, would likely be prohibited because that doesn't allow everything to AUTOMATICALLY return to ambient pressure.

Of course, as always, this isn't the place for official statements or comments. VIsit soinc.org for that.

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Re: Air Trajectory B/C

Post by 1nxtmonster » October 7th, 2014, 9:57 am

So the 5 KG weight limit...

if your design was one where there was a drop tube with a piston located at the bottom and a weight that falls and hits the piston after building momentum, would the 5kg weight be for the weight or the piston and weight?
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Re: Air Trajectory B/C

Post by bernard » October 7th, 2014, 10:01 am

1nxtmonster wrote:So the 5 KG weight limit...

if your design was one where there was a drop tube with a piston located at the bottom and a weight that falls and hits the piston after building momentum, would the 5kg weight be for the weight or the piston and weight?
If the piston decreases in potential energy, then it is counted as part of the falling mass.
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Re: Air Trajectory B/C

Post by cifutielu » October 7th, 2014, 6:37 pm

Hey guys,

So i'm doing this event this year and I have NO IDEA where to start. I've looked at the forum and wiki, but nothing's helped. I just can't visualize how everything works together to launch the ball. Are there any tutorials or models online that I can build to help me?

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Re: Air Trajectory B/C

Post by chinesesushi » October 7th, 2014, 7:39 pm

You could try using the falling mass and using pulleys to pull a piston that compresses air and then have another string to turn a valve or something to release the air.
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Re: Air Trajectory B/C

Post by JonB » October 8th, 2014, 4:54 am

chinesesushi wrote:You could try using the falling mass and using pulleys to pull a piston that compresses air and then have another string to turn a valve or something to release the air.

See the comment above from Chalker. Not an official clarification, but a good point that might prohibit this.

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Re: Air Trajectory B/C

Post by iwonder » October 8th, 2014, 8:11 am

I think the easiest way to handle that is to use a system like the spring launchers for scrambler, so the mass falls and hits the second valve, I would think that's an automatic return to normal pressure.
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Re: Air Trajectory B/C

Post by chinesesushi » October 8th, 2014, 11:58 am

JonB wrote:
chinesesushi wrote:You could try using the falling mass and using pulleys to pull a piston that compresses air and then have another string to turn a valve or something to release the air.

See the comment above from Chalker. Not an official clarification, but a good point that might prohibit this.
Or skip the second valve as use the falling mass to push the air using something like Bernoulli's principle to push the ball.
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Re: Air Trajectory B/C

Post by chalker » October 8th, 2014, 4:08 pm

cifutielu wrote:Hey guys,

So i'm doing this event this year and I have NO IDEA where to start. I've looked at the forum and wiki, but nothing's helped. I just can't visualize how everything works together to launch the ball. Are there any tutorials or models online that I can build to help me?
First, please be sure to read the rules. Than read them again. There are many details you need to know before you get too far into designing / building a device. It's better to catch a detail early, than to catch it late in the game after you've completely built something.

At some point I"m sure someone will update the Wiki. In the interim, you could consider getting the Air Trajectory DVD at the soinc.org store, which has some good videos from previous National competitions. You also could do some Google searches for things like 'tennis ball cannon'

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Re: Air Trajectory B/C

Post by joeyjoejoe » October 9th, 2014, 2:55 pm

bernard wrote:
1nxtmonster wrote:So the 5 KG weight limit...

if your design was one where there was a drop tube with a piston located at the bottom and a weight that falls and hits the piston after building momentum, would the 5kg weight be for the weight or the piston and weight?
If the piston decreases in potential energy, then it is counted as part of the falling mass.
Since the piston has to have mass, If the following statement above is correct, then this implies that every pump that is not mounted horizontally will have this problem.

Uh-Oh! The pressure chamber which houses our piston has been sealed with PVC glue to prevent it from blowing off due to the pressure. Guess we will have to rethink our design.
Last edited by joeyjoejoe on October 9th, 2014, 6:40 pm, edited 1 time in total.

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