quote:

Originally posted by Ishta:
Energy = ½ x Mass x Velocity2
or
Energy (ftlbs) = [(Velocity (fps))2 x Weight (grains)] ÷ 450,240

I've never been a big fan of KE for this kind of thing. KE is often misused (even by the mythbusters, example being the KE required to kill various sized animals... the chart they were using only worked for bow/crossbo type projectiles if I remember correctly, not bullets).

My preferred equation of 'pain' is F=MA, simpler, but easy to understand. If the mass is the same, but the acceleration is double, so is the force.

This equation explains why two cars travelling at 50mph hitting each other head on is the same as one car hitting a stationary one at 100mph. The acceleration is for all intents and purposes 'instant'. And it easily shows the force involved.

I've heard people go 'Wow!' at the amount of energy stored in a freight train being 80 times that of the Hiroshima bomb. Makes it sound like any contact with it would instantly vaporize you... but it doesn't. If it hits you at a fast enough speed, sure, it might send you flying and kill you, but if a train hits you at 10mph or whatever, its just going to bump you out of the way (or run you over ). Might hurt a bit, but nothing too serious. The force involved is tiny since on one side you have gigantic mass (train) with tiny deceleration (10 mph to 9.99999999999 mph heh), and the other size small mass (you) and a small acceleration (like being tacked in football on a kickoff return).

Eric:

The acceleration potential of a steamroller ain't that big, but I doubt you would like to be run over by one...

Being hit by a steamroller is far different than being crushed by one.

C'mon ericw, you're getting into semantics and losing the point. There is clearly not an outward "centrifugal" force on the projectile. The diagrams used in the graphics on the show illustrated an outward force on the projectile that was supposed to fling it away. That force does not exist. The way you are using the term centrifugal force is just an application of Newton's 3rd Law.

quote:

Originally posted by ericw66:
Being hit by a steamroller is far different than being crushed by one.

Depends if its stopping or not

quote:

Originally posted by jjacobs78:
C'mon ericw, you're getting into semantics and losing the point. There is clearly not an outward "centrifugal" force on the projectile. The diagrams used in the graphics on the show illustrated an outward force on the projectile that was supposed to fling it away. That force does not exist. The way you are using the term centrifugal force is just an application of Newton's 3rd Law.

Did you even read the link? There *is* a real force called 'centrifugal'... Its a reactionary force, but its real all the same (otherwise you'd not feel a thing when being pressed against the wall).

quote:

Originally posted by ericw66:
I love the complaints about the use of Centrifugal force.

As much as some physics <teachers> might want to deny it, it does "exist".

http://en.wikipedia.org/wiki/Centrifugal_force

"As a result, even students who master the physics curriculum may leave school with the false impression that it is never scientifically valid to speak about centrifugal forces."

Heh... Those who cannot do... teach.

quote:

Originally posted by jjacobs78:
C'mon ericw, you're getting into semantics and losing the point. There is clearly not an outward "centrifugal" force on the projectile. The diagrams used in the graphics on the show illustrated an outward force on the projectile that was supposed to fling it away. That force does not exist. The way you are using the term centrifugal force is just an application of Newton's 3rd Law.

If you are in a car and the speed is increasing, the car is accelerated by a force applied in the direction of travel. Easy

Inside the car, you feel a force is pushing you back in your seat toward the rear of the car. Also easy

Those two forces, forward and backward, are the straight line equivalents of centripetal and centrifugal force then in circular motion.

Constant speed in a circle is accelerating.
If the car moves at a constant speed, but travels around in circle, it is accelerating. Because velocity is changing, velocity is speed and direction. First car changes speed the other direction both accelerating. Force that is pulling the car towards the centre is centripetal force.

But inside the car, you feel the force pushing you from the centre and that is centrifugal force witch is the result of the two other forces.

Centripetal center seeking
centrifugal center fleeeing

It is the acceleration we feel as centrifugal force, in the car that drives in a circle at constant speed. Even though centrifugal is not one real force but a different name for something else when moving in circle dose not mean that we can say that it is a centripetal force we feel, so the pellets in the gun will fly out if spinning because of acceleration due to change in direction also called centrifugal force. The machine is held in place in the centre, that is the centripetal force and that force dose nothing to the pellets.

what do you mean by saying there is no force on the pellets, did they not spin, because the tube spins the pellets go through the tube so they must be spinning, or did it shoot then spin, then shoot, then spin
I must be missing something, I observe painted metal, others see rubber, I perceive spinning but was there none

Confederate steam gun... There is no doubt that the steam gun could be lethal. The problem was rotational speed/barrel length. If the barrel was 12" and they spun it at 2000 rpm the maximum fps the ammo could exit the gun around 200( 2x3.14x1=6.28 feet per revolution )( 6.28X33.33Rps=209fps ).. If the barrel length stayed the same the gun would need to spin at 8000rpm to achieve around 830fps( 6.28x133.33Rps=837Fps )( approx. speed of 9mm pistol round ). There is also one more matter, the fact is that every time a steel ball is dropped the inertial force of the gun will be slowed as the ball reaches the end of the barrel. This must be compensated by either adding a flywheel or the addition of rpm. Also at these speeds the gun would fire 8000 rounds per minute .Which means to make it fire an economically feasible 400 round per min. The ball drop mechanism would need to be a 20:1 gear ratio. Fulfill these specs and this is a deadly weapon. It's the same principal as a sling!

The balls kept hitting the shield correct?

Well, when they loaded multiple balls in they basically killed any remaining "science" in this myth. Being packed tightly together they probably mostly bunched up in the barrel until the first one was freed etc.

I guess the time constraints prevented them from actually putting any thought into getting the timing right.

The following is the statement of its principles by the inventor: ' As a triumph of inventive genius, in the application and practical demonstration of centrifugal force (that power which governs and controls the universe and regulates and impels the motion of planetary bodies round the sun),

this most efficient engine stands without a parallel commanding wonder and admiration at the simplicity of its construction and the destructiveness of its effects; and is eventually destined to inaugurate a new era in the science of war. " Rendered ball proof, and protected by an iron cone, and mounted on a four-wheeled carriage, it can be readily moved from place to place or kept on march with an army. It can be constructed to discharge missiles of any capacity from an ounce ball to a twenty-four pound shot, with a force and range equal to the most approved gunpowder projectiles, and can discharge from one hundred to five hundred balls per minute. "For city or harbor defense it would prove more efficient than the largest battery. For use on the battle-field (the musket calibre engine) would mow down opposing troops as the scythe mows standing grain; and in sea-fights, mounted on low-decked steamers, it would be capable of sinking any ordinary war-vessel. "In addition to the advantages of power, continuous action, and velocity of discharge, may be added economy, in cost of construction, in space, labor, and transportation, all of which would be small in comparison to the cost and working of batteries of cannon, and the equipment and management of a proportionate force of infantry. " The possession of this engine—ball-proof, and cased in iron—will give the powers using it such decided advantages as will strike terror to the hearts of opposing forces, and render its possessors impregnable to armies provided with ordinary offensive weapons. " Its efficiency will soon be practically demonstrated, and the day is not far distant when, through its instrumentality, the new era in the science of war being inaugurated, it will be generally adopted by the Powers of the Old and New Worlds, and, from its very destructiveness, will prove the means and medium of peace.

"BALTIMORE, May 1, 1861."CHARLES S. DICKINSON."

When I first saw this episode I thought they would adapt a Gatling Gun to run on steam.
http://en.wikipedia.org/wiki/Gatling_gun

quote:

Originally posted by physcrw:
I hope they can redo the test of the gun using Lead ammo (more period specific & more common during that time)... ... I would also like to see vented barrels used to reduce air pressure.

They should hae not only used period correct ammo, but they should have also tried smaller calaber ammo.

On the topic of centrifugal vs centripetal force.

The force that is excerted upon the balls is actually neither centrifugal or centripetal, but perpendicular to both those forces. A quick drawing of the forces show this quite easily. When a ball is in the steel tube, the tube exerts a force on the ball in the current direction of the spin. The direction of this force changes, but the velocity gained by the force does not, leading the bullet to gain a velocity that goes along the tube.

As the ball hits the safety thingish, however, a centripetal force will act upon the ball from the safety thingish. Supposing that the ball lies against this until it comes to the hole, what makes the ball go flying is the removal of the centripetal force, which lets the ball fly at its current velocity (perpendicular to the "line" created by the tube).

However, if the ball does not reach the safety thingish before it exits the tube (that is, if it is perfectly timed to exit the tube in the hole where it's supposed to), it will leave in a direction neither perpendicular to the tube, or parallell.

As for the existence of a centrifugal force, there is the 3rd law force that opposes the centripetal force, which is a perfectly legitimate force, and the pseudoforce which can be observed when in a spinning reference frame. There is nothing wrong with talking as if this pseudoforce exists, if this will help to ease the work you're currently doing, but it is important to remember that it is a pseudoforce.

As for the lethality of this gun, I can see some holes in what the MBs did, and I'd like to stress an earlier point somebody made: The goal in war is not to kill your opponent, but to incapacitate him. A hail of bullets breaking bones and doing quite nasty non-lethal damage does that quite well, if not neccecarily as well as lethal damage.

I really love the effort you guys put into proving/disproving myths but I do agree that it was WAY dangerous to use generic water heaters to produce the steam. Even REAL boilers are super dangerous and have killed and maimed large quantities of people in the past. Heck back'in'the'day they killed and maimed so many railroad employees that Congress enacted the "boiler inspection act" in 1908 to help protect employees from poorly maintained boilers. It worked so well that railroads to this day still have to adhere to it.

I just want to point out that with the gun, if they had it set higher as to aim for the head/neck area I'm sure it could fracture a skull or collapse a trachea. Also, a body shot would definitely leaved a soldier stymied and more vulnerable to attack, so it could still be a viable weapon to aid in battle.

As for the lie detector, I've often wondered if you could fool one by mentally replacing a question in your head. I'm sure it would take great concentration, but if you could mentally re-assign "Did you steal the money?" to "Did you drink soda today?" maybe that could trick it. Or even if you substitute it for something you morally object to and would never even consider.

Just my two cents

I agree with "bigwrm" and "steamer" that the cruxt of the matter is barrel length. With increased barrel length, at a given rpm, the resultant force of that projectile (lead, steel, hard platic) will increase dramatically- which is precisely why David could kill Goliath!

Just a few comments;

The projectiles were steel, not plastic. I'd assume steel ball bearings which were easy to obtain. Adam mentioned they were going to use steel balls just after Jamie made the barrel. The error of assuming they were plastic no doubt comes from the colour they where when loaded-This was most likely nothing more than MB painting the projectiles so they would be easier to see during the tests.

The boilers-MB used water heaters for the simple reason they could get their hands on them quickly, and from previous episodes already knew what pressure they could be brought up to safely. For the purposes of figureing out of the machine would work-and how well-it didn't matter how the steam was produced. A boiler more in keeping with the period would have required a lot of time and money to produce and required skills and experience to make safely-skills and experience that Adam and Jamie don't have. It also helped that the water heaters could be run off a generator rather than having to lug around a large quantity of fuel.

The size of the MB machine, compared to the orignial is misleading. Most of the originals size was down to two things-the size of the boiler and the need to be able to move it around. MB could load their machine into the back of a truck and load/unload it with the aid of machines. The original was placed on a waggon, and it also seems to have included some form of armour to protect the boiler and crew from hostile fire directed at it. Come to think of it this could be considered a form of early tank.

Conflicting reports of its effectivness would simply be down to propoganda from one side, and excuses for conduct from the other. In the first case you would not want to admit to spending all this time and money on a weapon that wasn't all that effective-since by this stage you are losing the war you would be trying to keep moral up by claiming the weapon was far more effective than it was. In the second case imagine advancing over a battlefield and suddenly catching sight of this large monstrosity that was beltching steam and bullets at you. Chances are most of the first soldiers to be on the wrong end of this thing would panic, and either hit the ground or run off. In either case they would then be prime targets for more conventonal weapons. If there was artilery in the area firing grapeshot at the troops as well it would be impossible to work out who was hit by the steam machine gun and who was hit by the grapeshot.

Design-The MB had acess to the original plans for the machine. As such it should be assumed that the details of the timing mechinisum, barrel length etc are either identical or near identical to the ones used on the orignial. However, the posibility that the weapon was modifyed in the field after it was first built should not be dismissed. For example they might have altered or replaced the timing system etc but not noted this down for the records were destroyed.

All in all I would say that they covered this quite well, they showed that the weapon in itself wasn't all that dangerous to troops. But I imagine that as a 'terror' weapon it would have been very effective.

I think there are some errors in the range of the steam gun. As the projectile is a sphere, it will either roll or bounce when it hits the ground, making the range seem longer. I would suggest a re-visit and try it on a sandy field so the projectile can land without bouncing off. Anyway, nice effort yeah! Keep up the good work!

quote:

The boilers-MB used water heaters for the simple reason they could get their hands on them quickly, and from previous episodes already knew what pressure they could be brought up to safely.

And exactly how did they "know" this? By blowing up "similar" ones? Water heaters are not certified pressure vessels. They are not build to a standard where they will or will not explode. The steel is not certified, the welds are not certified. The jacketing was not even removed to see if there were obvious defects to the welds or tank. I have no problem with 160 lbs of air prssure in a water heater tank, but 160 lbs of pressure on 25 gallons of water at 250 degrees, in an unknown pressure vessel, huge potential for mayhem. And to charge it inside their building, what were they thinking...

quote:

Water heaters are not certified pressure vessels. They are not build to a standard where they will or will not explode. The steel is not certified, the welds are not certified.

If you mean in regards something like a steam engine you would be correct. If on the other hand you are trying to say that Water heaters are not designed to handle high pressures you'd be incorrect. Water heaters would have to undergo saftey checks before they are allowed to go on general sale. Part of that testing would be to ensure that if the safety valves are incorrectly set the heater can withstand higher than normal pressures without exploding-and since the companies that build these things really don't want them to blow up any more than the people who's houses they are installed in they add a significant safety margin just in case.

Or in other words the manufactorers rate their heaters to be able to withstand a set pressure, information MB would have little trouble getting their hands on.