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Help With Spud Gun

A place to ask general spud cannon related questions.
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Unread postAuthor: jrrdw » Fri Jun 26, 2009 8:24 pm

Tap on your pressure gauge as your filling your chamber. Gauges can really suck!
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Unread postAuthor: THUNDERLORD » Fri Jun 26, 2009 11:10 pm

Forgot to mention: Usually when people modify the valve, they plug or fill the solenoid with epoxy (JB weld, other two part epoxy).
But It also works to leave the solenoid and wrap the wires around.
That's what I usually do, so it can still be activated electronically
(for a future experiment ?).
There's "sticky's" and hubbo17 has a pdf in "pneumatic cannon discussion"

I usually use a short piece of threaded lamp pipe, drill hole in cover, put lamppipe in drill chuck (thread it into plastic), adjust it flush with inside of cover above diaphram (doesn't need to be center), Little JB-weld each side(and on lamppipe threads) ,
screw valve screws back together, very short pneumatic hose, hoseclamps(2) 1 onto lamppipe and 1 onto hose barb , teflon tape on threads (not mandatory) into Husky blow nozzle (which usually work one directional only).
Pretty simple to do. The main thing is being careful not to break the plastic.

Well If worse comes to worse, you could strap on the chest plate and say something like "there's virtually no felt impact using THIS chest protector"
Something like This crazy vid .
There's a better one (can't find now) with a .44mag, soft vest and owner of company does [something against rules to discuss] to himself :shock: 8)
Oh, also, I realized later if the barrel is lubed the ball would need to be wrapped so it doesn't absorb random weight. :oops: 8)

BTW, I disagree with the info in vid because he states the same force affects the rifle as impact, but seems like the bullet is only putting force on rifle the fraction of sec. it's in the barrel, while coming to a complete stop against an object...could absorb it's full energy practically. (Not sure though, and difficult to explain). :roll:
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Unread postAuthor: THUNDERLORD » Fri Jun 26, 2009 11:11 pm

EDIT: Page froze up and tripled...WTF???
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Last edited by THUNDERLORD on Fri Jun 26, 2009 11:24 pm, edited 1 time in total.
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Unread postAuthor: THUNDERLORD » Fri Jun 26, 2009 11:11 pm

EDIT: sRRY, Clicked submit..nothing happened...Triple WTF???
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Unread postAuthor: Technician1002 » Fri Jun 26, 2009 11:57 pm

THUNDERLORD wrote:EDIT: sRRY, Clicked submit..nothing happened...Triple WTF???


Spudfiles had a couple hickups tonight. I noticed it in chat. Sending photos had random errors including SQL server errors. If that happens, just wait, reload the page and see if it posted.

BTW, I disagree with the info in vid because he states the same force affects the rifle as impact, but seems like the bullet is only putting force on rifle the fraction of sec. it's in the barrel, while coming to a complete stop against an object...could absorb it's full energy practically. (Not sure though, and difficult to explain). Rolling Eyes


The force of impact and the force of launch are related and well known in physics. There is an online physics lecture where a (real) gun is fired into a block of wood. Both the gun and block of wood are the same weight. When fired, both the gun and block of wood have the same recoil. The peak impact force is greater, so it makes a hole in the wood, but the duration is shorter.

The foot/lbs of force is the same.
Found it.. The gun, bullet, energy recoil force.
The lecture is about an hour. The series is great if you are into physics.
Look at about 35 minutes.

[youtube]http://www.youtube.com/watch?v=fLjaVL26hzI[/youtube]
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Unread postAuthor: THUNDERLORD » Sat Jun 27, 2009 1:03 am

Thanks Tech, I'll have to check that out when I have time tommorow.

Here's a vid that seems to demonstrate impact being greater. Here, and IIRC the pistol broke into a couple pieces even. Course when he flinched it added, but still seemed like greater force than recoil. Seems Confusing.

I am interested to see a concrete type of test.
Got to get up too early though :(

BTW, off topic but I noticed 4500psi hose for hydraulic grease gun $5.97 at home depot! My pressure washer hose is 3700psi...
Thanks.

EDIT: dANG!!! Now I can't sleep until I get my idea for a recoil vs. projectile energy test out:
Take a .308 cal. rifle, drill a .308 diameter hole in the stock,
Insert a .308 diameter rod into stock,
place the .308 rod against a 3/8" thick plate steel,
place a 3/8" plate steel in front of muzzle...
Never tried it, but I am willing to bet there's not a chance in heck the rod will penetrate the steel and the projectile will...so How is the energy the same then???
I Can't figure it out... :roll: 8)
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Unread postAuthor: Technician1002 » Sat Jun 27, 2009 3:18 pm

THUNDERLORD wrote:Thanks Tech, I'll have to check that out when I have time tommorow.

Here's a vid that seems to demonstrate impact being greater. Here, and IIRC the pistol broke into a couple pieces even. Course when he flinched it added, but still seemed like greater force than recoil. Seems Confusing.

I am interested to see a concrete type of test.
Got to get up too early though :(

BTW, off topic but I noticed 4500psi hose for hydraulic grease gun $5.97 at home depot! My pressure washer hose is 3700psi...
Thanks.

EDIT: dANG!!! Now I can't sleep until I get my idea for a recoil vs. projectile energy test out:
Take a .308 cal. rifle, drill a .308 diameter hole in the stock,
Insert a .308 diameter rod into stock,
place the .308 rod against a 3/8" thick plate steel,
place a 3/8" plate steel in front of muzzle...
Never tried it, but I am willing to bet there's not a chance in heck the rod will penetrate the steel and the projectile will...so How is the energy the same then???
I Can't figure it out... :roll: 8)


Put the steel on roller skates. Hit it with the heavy rod at slow speed and the bullet at high speed will roll the skate at the same speed. Same energy transfer. (generally) slower launch may actually pick up more energy and transfer more weight to the block, and mass changes need allowed for.

Impact force is higher but a shorter duration. Total energy transferred is the same. Same recoil from impact.
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Unread postAuthor: jimmy101 » Sat Jun 27, 2009 4:59 pm

Technician1002 wrote:The force of impact and the force of launch are related and well known in physics. There is an online physics lecture where a (real) gun is fired into a block of wood. Both the gun and block of wood are the same weight. When fired, both the gun and block of wood have the same recoil. The peak impact force is greater, so it makes a hole in the wood, but the duration is shorter.

But not well known in movie making. :D

The maximum recoil of a target hit by a round is equal to the recoil the shooter felt when he fired the gun, fudged by the relative mass of the shooter and the target. The force on the target can be no greater than the force on the shooter, and usually it is a fair amount less since the round is slowing down in flight.

In the movies, any round that knocks a person over would have knocked over the shooter even worse. In real life, people tend to fall straight down when shot. They don't get blown through a conviently located window by the round's impact.
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Unread postAuthor: mark.f » Sat Jun 27, 2009 6:05 pm

jimmy101 wrote:
Technician1002 wrote:The force of impact and the force of launch are related and well known in physics. There is an online physics lecture where a (real) gun is fired into a block of wood. Both the gun and block of wood are the same weight. When fired, both the gun and block of wood have the same recoil. The peak impact force is greater, so it makes a hole in the wood, but the duration is shorter.

But not well known in movie making. :D

The maximum recoil of a target hit by a round is equal to the recoil the shooter felt when he fired the gun, fudged by the relative mass of the shooter and the target. The force on the target can be no greater than the force on the shooter, and usually it is a fair amount less since the round is slowing down in flight.

In the movies, any round that knocks a person over would have knocked over the shooter even worse. In real life, people tend to fall straight down when shot. They don't get blown through a conviently located window by the round's impact.


Been watching "Lethal Weapon" lately, have we? :wink:
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Unread postAuthor: THUNDERLORD » Sat Jun 27, 2009 6:22 pm

I understand, Just got back from long day of labor...(bright side, I love to work)...(haven't watched vid tech linked to yet)...

Anyhow, I still see no response to my version of the test....(besides roller skate addition)...
Perhaps the energy is not "maximized" would be the best way to put it...(???)

We are not closed minded "monkeys", I believe in keeping an open mind so the "truth" we seek can be determined above all... Is what I am getting at.

So what about the duration of energy transfer, similar to an object being able to withstand it's combustion temp. for a moment being diffferent to exposure to that temperature for duration???

Similar to recoil vs. impact pressure or no??
Sure there are glancing blows etc., but I've NEVER seen impact energy much less than recoil "head on".

Ragnarok had a program on it, but I probably P'd him off royally two days ago... Hope it's just a phase (since he seems pretty gifted). :twisted: :roll: :( 8)

EDIT: So what do you fellas think of the old body armor? There's all sorts of new stuff...?
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Unread postAuthor: spudtyrrant » Sat Jun 27, 2009 7:01 pm

THUNDERLORD wrote:I understand, Just got back from long day of labor...(bright side, I love to work)...(haven't watched vid tech linked to yet)...

Anyhow, I still see no response to my version of the test....(besides roller skate addition)...
Perhaps the energy is not "maximized" would be the best way to put it...(???)
its like the professor explained in the video carrying a bullet to space will take the same amount of energy as shooting one to space the difference is shooting a bullet to space is a lot faster than carrying one just like shooting a .308 will transfer the same amount of energy to your shoulder as it will to your target the difference is the transfer to you shoulder is over a much wider area and a much longer period of time but in the end the same energy is transferred thats why they put shock dampeners in stocks the spring they have is compressed and energy is transferred over a long period therefore you don't feel so much shock from the recoil exactly as you said its all about duration
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Unread postAuthor: THUNDERLORD » Sat Jun 27, 2009 7:21 pm

spudtyrrant wrote:.... just like shooting a .308 will transfer the same amount of energy to your shoulder as it will to your target the difference is the transfer to you shoulder is over a much wider area and a much longer period of time but in the end the same energy is transferred thats why they put shock dampeners in stocks the spring they have is compressed and energy is transferred over a long period therefore you don't feel so much shock from the recoil exactly as you said its all about duration


You haven't read or pondered my test method.
The same area per square inch applied, as well as another impact plate in front of muzzle...I gaurauntee you there will be MOAR damage at the muzzle side...WHY??? (A.308" rod extended from the stock will NEVER = the projectile impact energy/damage/carnage) Why??? (if this theory is correct). :roll:
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Unread postAuthor: Technician1002 » Sat Jun 27, 2009 7:22 pm

We are not closed minded "monkeys", I believe in keeping an open mind so the "truth" we seek can be determined above all... Is what I am getting at.


That is the essence of true science. Well put.

Another example I can cite is breaking cinder blocks on the belly with a sledge hammer. The impact force is high and very short duration. The transfer of energy to the belly is slower, but still the same ft/lbs of force.

http://www.youtube.com/watch?v=cGu8lXqJs0I
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Unread postAuthor: KineticAmbitions » Sat Jun 27, 2009 10:18 pm

Momentum is conserved between the gun and the projectile + gases, but the gun DOES NOT recoil with the same ENERGY that the projectile hits with. Kinetic energy is proportional to velocity squared, and momentum is directly proportional to velocity. The heavier part of the system, the gun, will have equivalent momentum to the bullet, but (far) less energy, as it is much heavier and thus moving much more slowly. If the gun recoiled with the same energy that the projectile impacted with, firing a .30-06 would give similar results to a fistfight with a 600 pound gorilla.

There will be more damage at the muzzle side because there is more energy at the muzzle side, and because higher speed impacts are less hindered by cohesion forces in the target - which is why you hammer nails instead of pressing them with a constant force.

In a gun, momentum of the entire system will always equal zero, but the kinetic energy of the system will change because of the conversion of potential energy in the propellant to kinetic energy of the propellant gases (and then to kinetic energy of the projectile).
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Unread postAuthor: Technician1002 » Sat Jun 27, 2009 11:26 pm

KineticAmbitions wrote:Momentum is conserved between the gun and the projectile + gases, but the gun DOES NOT recoil with the same ENERGY that the projectile hits with. Kinetic energy is proportional to velocity squared, and momentum is directly proportional to velocity. The heavier part of the system, the gun, will have equivalent momentum to the bullet, but (far) less energy, as it is much heavier and thus moving much more slowly. If the gun recoiled with the same energy that the projectile impacted with, firing a .30-06 would give similar results to a fistfight with a 600 pound gorilla.

There will be more damage at the muzzle side because there is more energy at the muzzle side, and because higher speed impacts are less hindered by cohesion forces in the target - which is why you hammer nails instead of pressing them with a constant force.

In a gun, momentum of the entire system will always equal zero, but the kinetic energy of the system will change because of the conversion of potential energy in the propellant to kinetic energy of the propellant gases (and then to kinetic energy of the projectile).


I only lightly touched on that topic by stating "and mass changes need allowed for. "

In a typical combustion spudgun, the mass of the air and shot of propane is quite low in relation to the spud. In a rocket and a gun, the propellent mass in relation to the projectile mass is higher, but a blank starter pistol has much less kick than a 22 ejecting a round.
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