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| jwpaine |
 Posted: Sun Jun 01, 2008 6:15 pm Post subject: A few of my projects.. |
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Forum Freshman
Joined: 01 Jun 2008
Posts: 2
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Hello all - this is my official introduction. I'm going to be posting on this forum quite often, from now on, so I thought I might introduce myself and share a few projects that I have done.
I am an engineering physics student at the University of Maine.
My most resent project is my pneumatic air cannon made out of PVC parts, chemically welded, giving me an air chamber by which air is released by a solenoid into the barrel - the initial velocity of the projectile can make any boring Sunday, into a FUN-tastic time!
He is my cannon introduction vid: http://youtube.com/watch?v=Ah5LNBifOWo
Below are three destruction videos:
http://www.youtube.com/watch?v=eSaPC8uszmc
http://www.youtube.com/watch?v=SDgsCedBf3k
http://www.youtube.com/watch?v=kiPRfDtz_3s
Next is my garage-door spring powered trebuchet:
http://www.youtube.com/watch?v=ATSQAuxcHU8
That is my little trebuchet that I made a few years back. Traditional counterweight acceleration due to gravity is too low, so I decided to put on some heavy garage door springs.... I think this is around 250 lbs of pull at full extension (that is a **** load of energy) When adjusted correctly, I remember throwing apples almost a foot ball field. See how fast the end of that arm is going? Now think how fast the end of the sling is going, and that is the initial velocity when the pin slips out... that is one fast apple.
Besides those two projectile projects, most of my time has been put into high voltage research:
Here is my High voltage ion-wind lifter that I made to present to a few groups of students: http://youtube.com/watch?v=ibW_x8lWWFM
As my description says: This is my compound lifter prototype I made for a High school physics class. I am applying a high voltage charge around 25kv ~1mA from the flyback transformer of a standard 14" CRT. Essentially what is happening is the emitter wire is attracting electrons from nearby air molecules. This creates a cloud of ionized air which is then attracted to the nearest ground potential, being the foil skirt electrically connected to ground, as a source of electrons to regain it's neutral charge. This effect is know as ion-wind. There are other factors such as the biefeld brown effect which is less substantial at lower voltages. The lifter is being held down from going to high with monofilament on each corner.
I've also built a Tesla coil, electrostatic generator and a few other things but I am too lazy to find the pictures of them.
Cheers - John |
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| Cat1981(England) |
| Posted: Mon Jun 02, 2008 11:02 am Post subject: |
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Forum Ph.D.
Joined: 09 Sep 2006
Posts: 925
Location: Mind your own business
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Hello and welcome to the forum.
_________________
When we talk to God it's called a prayer. When God talks back it's called schizophrenia. |
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| Pendragon |
| Posted: Thu Jun 05, 2008 2:57 am Post subject: |
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Moderator
Joined: 07 Jan 2005
Posts: 1160
Location: Nederland
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Omg I love those homemade guns, hehe you don't wanna know how much time I've spent watching such videos 
Btw about the Trebuchet, would it be technically possible to build a functioning one without springs on this scale? Or is a large scale necessary to get enough energy from the counterweight? (tell me if this doesn't make sense, I'm a noob in anything technical)
And welcome btw  |
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| jwpaine |
| Posted: Fri Jun 06, 2008 10:03 am Post subject: |
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Forum Freshman
Joined: 01 Jun 2008
Posts: 2
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| Pendragon wrote: |
Omg I love those homemade guns, hehe you don't wanna know how much time I've spent watching such videos
Btw about the Trebuchet, would it be technically possible to build a functioning one without springs on this scale? Or is a large scale necessary to get enough energy from the counterweight? (tell me if this doesn't make sense, I'm a noob in anything technical)
And welcome btw |
Yes, of course. You could indeed build a counterweight trebuchet at this scale, which is what most people do. Counterweight is not as efficient as spring, as you would have to scale up the trebuchet to account for counterweight, in order to achieve the same performance as a smaller scale, spring-powered, trebuchet. Remember, when the projectile in the sling, your counterweight will be dropping somewhere between 0 < a < 9.8m/s^2
For a given arm length, if counterweight is dropping at 9.8m/s^2, than the sling speed can only be increased by adjusting length of sling and or adjusting length of arm, giving more length to the throwing part at pivot, and less arm at pivot where counterweight is attached
If you want the trebuchet powered by counterweight, you should make the trebuchet a bit wider that mine. although you can't see that dimension in my video.
Cheers - John
Last edited by jwpaine on Sat Jun 07, 2008 8:19 pm; edited 1 time in total |
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| Pong |
| Posted: Fri Jun 06, 2008 1:17 pm Post subject: |
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Forum Professor
Joined: 08 Apr 2008
Posts: 1192
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Jwpaine, you've inspired me to build a trebuchet! 
I'm in the building trade and often have a site cluttered with 24' 2x10's and such for erecting largish structures. So I'm gonna design a trebuchet that two guys can bang together of standard house framing materials then knock down before the police arrive. Trash bins filled with water for counterweight?
Maybe you can help perfect and explain the physics? |
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