Air Trajectory B/C

Locked
phoebecaulfield
Member
Member
Posts: 3
Joined: November 12th, 2014, 9:02 pm
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by phoebecaulfield » November 12th, 2014, 9:08 pm

Hi guys, could I please get some advice on our design?
We made a simple quasi-piston design where a mass falls through a vertical pvc pipe so it pushes air through a smaller horizontal pvc which launches the ping pong ball. Our mass (3.5 kg) is pretty much air tight and there seems to be no air leaks between pipe connections, but it's not launching the ball. Either the air just goes out around the ball or the ball is so tight in the pipe that the mass falls slowly.
Does the placement of the ball in the pipe matter? Right now, it's at the very end.
Thanks for your help!

chalker
Member
Member
Posts: 2106
Joined: January 9th, 2009, 7:30 pm
Division: Grad
State: OH
Has thanked: 1 time
Been thanked: 52 times

Re: Air Trajectory B/C

Post by chalker » November 13th, 2014, 5:12 am

phoebecaulfield wrote:Hi guys, could I please get some advice on our design?
We made a simple quasi-piston design where a mass falls through a vertical pvc pipe so it pushes air through a smaller horizontal pvc which launches the ping pong ball. Our mass (3.5 kg) is pretty much air tight and there seems to be no air leaks between pipe connections, but it's not launching the ball. Either the air just goes out around the ball or the ball is so tight in the pipe that the mass falls slowly.
Does the placement of the ball in the pipe matter? Right now, it's at the very end.
Thanks for your help!
You need some adjustable resistance to hold the ping pong ball back a bit. Something like an o-ring or small piece of tape. You want the ball to be able to slide smoothly past it once it overcomes the resistance.

Student Alumni
National Event Supervisor
National Physical Sciences Rules Committee Chair

retired1
Member
Member
Posts: 676
Joined: July 25th, 2012, 5:04 pm
Division: Grad
State: FL
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by retired1 » November 13th, 2014, 7:17 am

I think that you need to keep it simple. 1 1/2 schedule 40 PVC pipe is a perfect fit for the ping pong ball. Any burs at the end of the pipe need to be sanded off. The pipe needs to have the bore cleaned of "refuse" periodically. We use a microfiber shop cloth wrapped around a 1" dowel. You repeat this until there is nothing in the tube.
You allude to having joint leaks. Where??

slapyou512
Member
Member
Posts: 3
Joined: September 25th, 2014, 7:51 am
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by slapyou512 » November 14th, 2014, 7:54 am

So is it okay to blow up my device with a breath? its at ambient pressure because the air reservoir is not pressurized. It only takes one breath to fill my reservoir, I just wanted to double check that its okay to do this before launch

User avatar
chinesesushi
Member
Member
Posts: 259
Joined: September 17th, 2013, 4:57 pm
Division: C
State: CA
Has thanked: 0
Been thanked: 13 times

Re: Air Trajectory B/C

Post by chinesesushi » November 14th, 2014, 11:36 am

slapyou512 wrote:So is it okay to blow up my device with a breath? its at ambient pressure because the air reservoir is not pressurized. It only takes one breath to fill my reservoir, I just wanted to double check that its okay to do this before launch
I believe it has been mentioned before that as long as you can show that the reservoir is open to the atmosphere, it should be at atmospheric pressure no matter what you put into it. If anyone gave provide a website/link/physics/etc. that could back this up maybe that could serve as "verification" at tournaments XD.
Never argue with an idiot, they will drag you down to their level and then beat you with experience.
Before you criticize a man, walk a mile in his shoes. That way you'll be a mile away and he'll be shoeless.
You should only create problems, that only you know solutions to.

mej710
Member
Member
Posts: 24
Joined: September 15th, 2013, 2:48 pm
Division: C
State: NY
Location: Ithaca, NY
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by mej710 » November 15th, 2014, 2:44 pm

So under "construction" in the event manual, it says the triggering device "must extend out of the launch area, allow for competitors to remain at least 1m from the launch area, and does not need to return to the launch area after launch." When is says "does not need to return to the launch area" are they referring to the triggering device or the competitors? I'm wondering if we are allowed to return to the launch area between launches to put our mass back to where it was at the beginning of the first launch.

retired1
Member
Member
Posts: 676
Joined: July 25th, 2012, 5:04 pm
Division: Grad
State: FL
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by retired1 » November 15th, 2014, 4:27 pm

They are talking about the firing device. Many people will attach a lanyard to a pin the when pulled out will drop the load.
Obviously, you have to go back to the device to reload and re aim/adjust.

mej710
Member
Member
Posts: 24
Joined: September 15th, 2013, 2:48 pm
Division: C
State: NY
Location: Ithaca, NY
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by mej710 » November 16th, 2014, 3:56 pm

Ok great. We were thinking of making our device with two pistons. Something like this: https://www.physicsforums.com/proxy.php ... ed2d5ce7ff
Is anyone else doing something similar? If so, what are you using to make the pistons?

zarnold16
Member
Member
Posts: 8
Joined: November 19th, 2014, 8:16 am
Division: C
State: MI
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by zarnold16 » November 19th, 2014, 8:19 am

I have read the rules at least 3 times. Can I do a catapult like design or what is a good way to make one like a stomp rocket.

iwonder
Admin Emeritus
Admin Emeritus
Posts: 1115
Joined: May 10th, 2011, 8:25 pm
Division: Grad
State: TX
Has thanked: 0
Been thanked: 0

Re: Air Trajectory B/C

Post by iwonder » November 19th, 2014, 9:10 am

I would suggest that you read rule 3.b. a 4th time :P

If that doesn't answer your question, how does a catapult create air movement or pressure that's used to move the projectile?
'If you're the smartest person in the room, you're in the wrong room' - Unknown

Locked

Return to “2015 Build Events”

Who is online

Users browsing this forum: No registered users and 1 guest