How to determine projectile velocity with a phone book

A place for general potato gun questions and discussions.
MRR
Specialist 3
Specialist 3
Posts: 361
Joined: Tue Feb 17, 2009 2:29 pm

Wed Mar 21, 2012 4:48 pm

A fellow YouTuber posted on one of my videos that he has build an air gun that is capable of 2000 fps. I told him that this figure is more than unlikely but he insisted on that number.

His calculations are like this....
300 fps pellet gun penetrates 9 pages
homemade gun penetrates 92 pages
= 10x as strong/fast

10 x 300 fps = 3000 fps (yes he even did the basic math wrong)

:lol:

[youtube][/youtube]

Please don't troll this guy, this is just an example how not to do it.

PS.: about 15min of the 21min video is him counting pages :roll:
User avatar
wyz2285
First Sergeant 2
First Sergeant 2
Austria
Posts: 2381
Joined: Sat Mar 06, 2010 7:50 am
Location: Porto, Portugal
Has thanked: 1 time
Contact:

Wed Mar 21, 2012 5:11 pm

:lol: :lol: :lol:
I have seen other fails, but not this level yet :lol: :lol: :lol:
CpTn_lAw wrote: :D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
User avatar
killerbanjo
Specialist 2
Specialist 2
Posts: 245
Joined: Fri Jun 18, 2010 6:56 pm

Wed Mar 21, 2012 6:11 pm

GAHHH MUST.... NOT.... TROLL.... URRR
User avatar
Crna Legija
First Sergeant 2
First Sergeant 2
Posts: 2333
Joined: Sun Jul 20, 2008 5:14 am
Location: australia

Wed Mar 21, 2012 11:43 pm

ahahaha lol does it work for golf ball cannons?
'' To alcohol... The cause of, and solution to, all of life's problems.”
--Homer Simpson

Add me on ps3: wannafuk, 8/11/11 cant wait
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 25792
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 109 times
Been thanked: 64 times

Donating Members

Thu Mar 22, 2012 3:27 am

Oh dear.

Image

This is what happens when you let the marketing department sell on the basis of feet per second.
hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
pneumaticcannons
Specialist 3
Specialist 3
Posts: 392
Joined: Sat Oct 30, 2010 9:45 am
Location: shite country in asia
Contact:

Thu Mar 22, 2012 8:47 am

thats pretty hilarious :lol: :lol: :lol:
But why was the video for "adults only"? maybe there was a porno scene at the end , I was too bored to watch the full video so I wouldn't know :D
ramicaza <- My Youtube Channel
User avatar
D_Hall
Staff Sergeant 4
Staff Sergeant 4
Posts: 1883
Joined: Thu Feb 07, 2008 7:37 pm
Location: SoCal
Has thanked: 1 time
Been thanked: 19 times
Contact:

Donating Members

Thu Mar 22, 2012 9:14 am

Why can't we troll him?

Anyone THAT misguided NEEDS to be brought back to Earth. I mean, this is a harmless bit of stupidity, but what happens when his stupidity starts to wander into the realm of dangerous?
Simulation geek (GGDT / HGDT) and designer of Vera.
User avatar
wyz2285
First Sergeant 2
First Sergeant 2
Austria
Posts: 2381
Joined: Sat Mar 06, 2010 7:50 am
Location: Porto, Portugal
Has thanked: 1 time
Contact:

Thu Mar 22, 2012 12:17 pm

I´m sorry :lol: :lol:
I went to troll him, because I couldn´t stop laughing when he said:"if you are under 18, don´t make any questions, I will NOT answer you"
LMFAO :lol: :lol:
CpTn_lAw wrote: :D "yay, me wanna make big multishot pnoob with 1000 psi foot pump compressor using diamond as main material. Do you think wet bread make good sealant? " :D
User avatar
MrCrowley
Moderator
Moderator
Posts: 10078
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand

Thu Mar 22, 2012 2:32 pm

i promise this gun is the best in the world, i made it and i know what i did to it, i discoverd something that you add to the barrel to double the speed, and by the i did not lie a bit about it, i believe my calculation is correct, air gun that shoots 300fps with the one i made very simple calculation, and dont be a fool like the other guy and tell i shot with a nail, i shot with same caliber as the marksman air gun its a BB
I'm with D_Hall on this one. Misinformation should be sought out and removed from the public sphere in this case.
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 25792
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 109 times
Been thanked: 64 times

Donating Members

Thu Mar 22, 2012 3:43 pm

Looking at his other videos, he might not be completely "there" so go easy with the trolling, just be polite and back your claims with data.

KE = 1/2 x m x v x v

It's kinetic energy that causes the penetration, not the velocity alone.

Assuming (tenuously...) a linear relationship between energy and penetration, and his creation is penetrating 10 times more that a 300 fps BB gun, then the KE is 10 times greater.

As mass is constant, we can say that v x v is 10 times bigger. Therefore to find the velocity, √(300 x 300 x 10) which gives us 948 fps.
hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
MrCrowley
Moderator
Moderator
Posts: 10078
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand

Thu Mar 22, 2012 3:45 pm

jackssmirkingrevenge wrote:just be polite and back your claims with data.

KE = 1/2 x m x v x v

It's kinetic energy that causes the penetration, not the velocity alone.

Assuming (tenuously...) a linear relationship between energy and penetration, and his creation is penetrating 10 times more that a 300 fps BB gun, then the KE is 10 times greater.
That's more or less the route I took with him and I gave an estimate of 800fps+ but he still ignored me and wouldn't comment on the physics. He thinks his design is so brilliant he can ignore everything else.

No idea how he expects 200PSI of air to propel a projectile 2700fps.

Edit: Only having just realised where he is actually from, it probably wasn't a good idea for me to quote David Hume's famous "what is more likely..." remark in a comment reply to him.
User avatar
jackssmirkingrevenge
Five Star General
Five Star General
Posts: 25792
Joined: Thu Mar 15, 2007 11:28 pm
Has thanked: 109 times
Been thanked: 64 times

Donating Members

Thu Mar 22, 2012 4:01 pm

MrCrowley wrote:wouldn't comment on the physics
I don't think physics means much to him:

[youtube][/youtube]

:roll:
hectmarr wrote:You have to make many weapons, because this field is long and short life
User avatar
MrCrowley
Moderator
Moderator
Posts: 10078
Joined: Fri Jun 23, 2006 10:42 pm
Location: Auckland, New Zealand

Thu Mar 22, 2012 4:05 pm

Oh wow, he is special.
User avatar
SpudBlaster15
First Sergeant 2
First Sergeant 2
Seychelles
Posts: 2397
Joined: Wed Oct 18, 2006 11:12 pm
Has thanked: 2 times
Been thanked: 4 times

Thu Mar 22, 2012 4:38 pm

I wonder if he is related to (former) YouTube user dawson01912.
People should not be afraid of their governments. Governments should be afraid of their people.
Post Reply