Air Trajectory B/C

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ImNotSmart
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Re: Air Trajectory B/C

Post by ImNotSmart » February 28th, 2015, 5:07 pm

bernard wrote: The threaded end (left side) of the brass hose barb is screwed into the PVC end cap (which I've drilled a hole into). The bike pump head fits onto the barb end of the brass hose barb and is tightened.

The ball is inserted into the PVC so the outermost tip of the ping-pong ball is flush with the PVC pipe. It's a tight fit.
Even with the adapter, the ball barely launched. I think I might be screwing something up with the connection. My bike pump is airtight - I've felt around the whole area leading from the pipe to the barrel and haven't felt any air leaks. Could you post a picture of your connection and barrel? Thanks again, and sorry for bothering you so much.

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bernard
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Re: Air Trajectory B/C

Post by bernard » February 28th, 2015, 5:12 pm

ImNotSmart wrote:
bernard wrote: The threaded end (left side) of the brass hose barb is screwed into the PVC end cap (which I've drilled a hole into). The bike pump head fits onto the barb end of the brass hose barb and is tightened.

The ball is inserted into the PVC so the outermost tip of the ping-pong ball is flush with the PVC pipe. It's a tight fit.
Even with the adapter, the ball barely launched. I think I might be screwing something up with the connection. My bike pump is airtight - I've felt around the whole area leading from the pipe to the barrel and haven't felt any air leaks. Could you post a picture of your connection and barrel? Thanks again, and sorry for bothering you so much.
I can post a picture later. Is your bike pump releasing air? Are you tightening your hose head over your brass barb (which usually involves flipping a mechanical switch)? If you take a video of your setup working, I can try to diagnose your issue.
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Re: Air Trajectory B/C

Post by ImNotSmart » February 28th, 2015, 5:53 pm

bernard wrote:
ImNotSmart wrote:
bernard wrote: The threaded end (left side) of the brass hose barb is screwed into the PVC end cap (which I've drilled a hole into). The bike pump head fits onto the barb end of the brass hose barb and is tightened.

The ball is inserted into the PVC so the outermost tip of the ping-pong ball is flush with the PVC pipe. It's a tight fit.
Even with the adapter, the ball barely launched. I think I might be screwing something up with the connection. My bike pump is airtight - I've felt around the whole area leading from the pipe to the barrel and haven't felt any air leaks. Could you post a picture of your connection and barrel? Thanks again, and sorry for bothering you so much.
I can post a picture later. Is your bike pump releasing air? Are you tightening your hose head over your brass barb (which usually involves flipping a mechanical switch)? If you take a video of your setup working, I can try to diagnose your issue.
My bike pump is releasing air - I'm just pretty sure that its not enough. Just to give you an idea, if I take out the adapter and connect the hose directly to the barrel, the ping pong ball does not budge when I pump down the handle. I have been putting the hose head over the barb but it hasn't seemed to do much good.

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Re: Air Trajectory B/C

Post by bernard » February 28th, 2015, 8:18 pm

ImNotSmart wrote:My bike pump is releasing air - I'm just pretty sure that its not enough. Just to give you an idea, if I take out the adapter and connect the hose directly to the barrel, the ping pong ball does not budge when I pump down the handle. I have been putting the hose head over the barb but it hasn't seemed to do much good.
If you don't put your ball into your PVC barrel and put your hand over the end of the barrel, do you feel air coming out?
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Re: Air Trajectory B/C

Post by ImNotSmart » March 1st, 2015, 6:52 am

bernard wrote:
ImNotSmart wrote:My bike pump is releasing air - I'm just pretty sure that its not enough. Just to give you an idea, if I take out the adapter and connect the hose directly to the barrel, the ping pong ball does not budge when I pump down the handle. I have been putting the hose head over the barb but it hasn't seemed to do much good.
If you don't put your ball into your PVC barrel and put your hand over the end of the barrel, do you feel air coming out?
A little bit but definitely not enough to launch the ball.

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Re: Air Trajectory B/C

Post by bernard » March 1st, 2015, 12:41 pm

ImNotSmart wrote:
bernard wrote:If you don't put your ball into your PVC barrel and put your hand over the end of the barrel, do you feel air coming out?
A little bit but definitely not enough to launch the ball.
I'd like to see a video because I'm not sure what is wrong from your descriptions.
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Re: Air Trajectory B/C

Post by goodcheer » March 1st, 2015, 2:21 pm

dhdarren wrote:Does anybody have a good alternative to a soda bottle for the air chamber? Is there a compressable bellows that somebody has bought? If so, could they please link me to where it can be purchased? Thanks! :D
We started with a soda bottle, but could not get enough air out of the small opening for the projectile. We then switched to a laundry detergent bottle with much success. We used 2 inch pvc pipe inserted into the bottle opening and duct taped it. Then connected a 45 degree elbow and another short piece of pvc. Inside the pvc, we inserted a short piece of 1.5 inch metal pipe, duct taped. A ping pong ball fits inside the metal pipe and plenty of air is produced by the laundry bottle. As mentioned elsewhere, a ping pong ball might not be as consistent as a plastic golf ball, but that is what we are going with. Good luck.

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Re: Air Trajectory B/C

Post by ImNotSmart » March 1st, 2015, 3:04 pm

bernard wrote:
ImNotSmart wrote:
bernard wrote:If you don't put your ball into your PVC barrel and put your hand over the end of the barrel, do you feel air coming out?
A little bit but definitely not enough to launch the ball.
I'd like to see a video because I'm not sure what is wrong from your descriptions.
I think unfortunately I'm going to have to abandon the bike pump design - my bike pump is simply not producing enough pressure to ever be able to launch a ball 8 meters, but thanks for all the help and patience.

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Re: Air Trajectory B/C

Post by actionpotential » March 1st, 2015, 3:33 pm

Yikes yikes goodcheer! Just curious, where do you test your device, and did you ever have to transport your device and test it somewhere else?
Inside the pvc, we inserted a short piece of 1.5 inch metal pipe, duct taped. A ping pong ball fits inside the metal pipe and plenty of air is produced by the laundry bottle.
At one point we used a 1.5 inch metal pipe with a plastic practice golf ball- we were ecstatic because the golf balls fit perfectly into the metal pipe and we were getting nice consistency. All the testing was in the warm comforts in someone's house.

We were really happy, designed and built the wooden frame, then brought our device to test for the long-range shots in our school gym. But when we launched, the ball didn't go anywhere. We examined the connections, looked for leaks...

Then we felt the metal pipe. It was freezing cold. Bringing our device straight from outdoors apparently made the metal contract, causing the inner diameter to be slightly bigger, allowing for the air to flow around the ball instead of launching it. When we got home, we had to put the metal pipe in front of a heat lamp for 15 minutes before it would launch again, and the distances were very different from the first time we tested it.

I would recommend to avoid using metal parts especially for the launching barrel since it is so sensitive to temperature changes (unless of course you tested it extensively.) We at one point were thinking of bringing hairdryers or something, but it took too long to heat up the pipe. Ya never know what the competition conditions will be like :P

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Re: Air Trajectory B/C

Post by actionpotential » March 1st, 2015, 3:36 pm

But goodcheer I see that you're putting the 1.5 inch metal pipe inside a PVC pipe, so that may minimize temperature sensitivity. Definitely test your device if the cold will matter. You could just bring your device outside for a few minutes, bring it back inside, and test it again.

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