SpudFiles

Well, I guess we proved Jack's girlfriend wrong.



I still haven't tried the one inch barrel.

We had a major flood event here, and a power outage. So I have been taking care of other matters. But I did finally get some damage shots in today.

Here is the damage shots from the half inch barrels.

The short barrel is 2 feet long. The long barrel is 3 feet long. The short barrel was used for the shot on the left, and for the AA battery.

The short shot went about halfway through. With the AA battery doing about the same.

The longer barrel put the shot only a bit further in.




Here are two shots with the 3/4" barrel. That barrel is 34 inches long.

First a shot with a glass marble.



That marble would have gone right on through, if I hadn't had some metal about 3/4" behind the plywood.

And here is my last shot. Done with the same 3/8" steel shot that I was using for the half inch barrel.



I aimed higher, so I would miss the steel behind the plywood.

The steel shot did go all the way though. But not as cleanly as I'd hoped for.

As you can see, it tore a gash in the plywood that is 8 inches long.

Selador wrote:Well, I guess we proved Jack's girlfriend wrong.

Which one

jackssmirkingrevenge wrote:

Selador wrote:Well, I guess we proved Jack's girlfriend wrong.

Which one

The one that said size doesn't matter.



I might try the one inch barrel tomorrow.

If I do, one of the shots will be with the following:

I figured it was something along those lines

When it comes to penetration though, it really is not the size of the hammer, it's how fast you throw it.

It's an old debate, there is a rather lovely study done by a W.H. Noble of the Ordnance Select Committee in 1863 (referenced here but sadly it's poorly scanned text with no illustrations and jumbled up tables) which is quoted in Ian Hogg's "A history of artillery":

A 68 pounder smoothbore and a 7 inch Armstrong gun firing 200 lb shot had been fired at 4.5 inch plate backed by 18 inches of teak. The 68 pounders had penetrated the target, while the 200 pounder had made hardly any impression on it. Noble showed that the answer lay in the relative velocity of the two projectiles. The 68 punder had been moving at 1,425 feet per second when it struck, while the 200 pounder was loafing along at a mere 780 feet per second. On the face of it, the 200 pounder with 156,000 foot-pounds of energy should have out performed the 68 pounder with 96,900, but the low velocity of the heavier projectile allowed the plate to deform and resist the blow, whereas the higher velocity of the 68 lb shot tore through the plate before it could begin to absorb the blow.

As Noble said in his paper, "What is wanted is velocity; if you sacrifice it to weight you will only be able to keep knocking at the door without entering."

There are other aspects to penetration - projectile hardness relative to the target and sectional density for example, but bigger is not necessarily better when it comes to making a deeper hole

Looking forward to that buckshot round, be sure to film it!

jackssmirkingrevenge wrote:I figured it was something along those lines

When it comes to penetration though, it really is not the size of the hammer, it's how fast you throw it.

Yeah, she did say that you were rather, erm, 'fast' as well.

Whooda thunk you'd be bragging about it, though.

jackssmirkingrevenge wrote:It's an old debate, there is a rather lovely study done by a W.H. Noble of the Ordnance Select Committee in 1863 (referenced here but sadly it's poorly scanned text with no illustrations and jumbled up tables) which is quoted in Ian Hogg's "A history of artillery":

As Noble said in his paper, "What is wanted is velocity; if you sacrifice it to weight you will only be able to keep knocking at the door without entering."

There are other aspects to penetration - projectile hardness relative to the target and sectional density for example, but bigger is not necessarily better when it comes to making a deeper hole

Thanks for the links. I'll read the spudfiles thread as soon as I post this.

But goodgawdamitey !! I don't have a couple years to read through that offsite tome of tedium, trying to sift the pertinant from the trivial. I think I aged six years just reading the first three feet or so, of it.


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So now the next thing I need to suss, is how a larger barrel provided more velocity than the smaller one.

Just seems like the smaller barrel would have given more "force" to the steel shot. Like water streaming farther out of a crimped hose, than an open hose. But it's obviously not that simple.

Guess I'll have to go and meditate and repeat over and over again... Tech's mantra... "Force = Pressure times Area" I know there's a secret in there somewhere.

jackssmirkingrevenge wrote:Looking forward to that buckshot round, be sure to film it!

I don't have a video camera. You'll have to settle for still shots like I have already shown.

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As a parting thought... Tonight, I feel like I may finally be 'getting it'. (Actually, just beginning to.)

Like what I have done so far is just learn the mechanics of it. And now that I have had some small success, I'll start learning the theory of it all.

I really like this forum. And that has more to do with the community than the subject matter.

I have always liked tinkering with things. And spudguns gives me that 'fix'. (Plus, it's something I can tinker with, indoors, during the cold wet winter here.)

But there's something about a good, supportive community, which takes an 'interest' and easily turns it into an addiction. LOL

Selador wrote:Tonight, I feel like I may finally be 'getting it'.

Is that what she told you

jackssmirkingrevenge wrote:

Selador wrote:Tonight, I feel like I may finally be 'getting it'.

Is that what she told you

Yeah, but then, she told you that size don't matter.

So, on second thought, I guess the only thing I'll be 'getting', will cause more hair to grow on my palms...

Instead of loading up a shotgun shell, due to the limited power of the chamber/valve combination, try a single shot in a low mass sabot first, then add mass to slow it down if power is good.

With added mass of multiple shot, the energy on each pellet may be low for poor impact energy.

Technician1002 wrote:Instead of loading up a shotgun shell, due to the limited power of the chamber/valve combination, try a single shot in a low mass sabot first, then add mass to slow it down if power is good.

With added mass of multiple shot, the energy on each pellet may be low for poor impact energy.

I did a single shot.

It penetrated the plywood.

See pic above...



I will do a single shot from the one inch barrel, as well, though.

Selador wrote:I will do a single shot from the one inch barrel, as well, though.

Some foam or similar to keep the projectile centred as Tech did will serve you well.

If you use foam, use a hard shell on it. The sudden change in presssure will shrink the foam. Each time the pressure doubles by 1 atm, the volume of the foam shrinks in proportion due to the compression of the trapped air.

I have shot foam sabots right past golf balls in a 2 inch barrel.

jackssmirkingrevenge wrote:Looking forward to that buckshot round, be sure to film it!

I finally got the time to put the one inch barrel on the gun, and give it a try.

Here is the gun setup.



I like this setup. Now I may spend the rest of the winter making it look better.

Maybe an imitation of a "district 9" gun. Maybe steampunk. Who knows.

~~~~~~~

Here are the first two rounds that I tried in the one inch barrel.



They both use pill bottles as sabots.

The one on the left is a single steel shot 'stuck' to the bottom of the sabot, using candle wax.

The one on the right is the buckshot style. With paper towel wadded into the pill bottle on top of the shot.

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Here is the "buckshot" damage.



None of the steel shots went through the plywood.

Pretty much each, the same damage as was done by a single steel shot from the half inch barrel.

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Here is the entry hole from the steel shot that was stuck to the sabot with wax.



If you look closely, you can see the impression made by the bottom of the pill bottle, when it hit the plywood.

The shot penetrated easily. It went through the plywood. Through a piece of pipe, about 4 feet behind that. Through a fiberglass window cover. Through the window. And through the side of a cabinet about 7 feet further on, after the window.


The pill bottle sabot was destroyed in both cases. I'll have to start making sabots from cardboard, or heavy paper, or whatever. Because I'll run out of pill bottles real quick.


I was actually aiming for the knot. So the gun is fairly accurate. There are no sights, so I was just roughly sighting down the barrel.

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The next shot was a marble. This was wadded with paper towel. No sabot. Just wad the paper into the barrel, saving one small flap to lay the marble under. Once the marble is placed, stuff the whole thing to the bottom of the barrel with a ramrod. Ram it solid.

That is wadding a shot, not sabboting.



This pic shows the holes made by both the steel shot, and the marble.

The marble penetrated the plywood just as easly as the steel shot did.

Both made entry holes that are as clean as they could be, given the fact that the plywood is still wet.

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After shooting the marble, (and recovering the wad. Making the wadding from a paper towel that is thick and is like a cloth rag. It is actually recoverable, and re-useable.), I wondered what would happen if I shot my ramrod, instead.

The ramrod is 42 inches of 3/4" wooden dowel.

I stuffed the wadding in the barrel again, and rammed he rod in there solidly.

It penetrated the plywood by more than 12 inches.

Here is the rod sticking out the front of the plywood..




Here is the rod, in a side-on view.



I aimed at the same knot, that the steel shot went through. But the rod flew off to the left, erratically.

There was a lot more kick to that shot, as well. LOL

In the side-on view, I took the pic from the right side of the plywood. The rod is actually through the left side of the plywood.

There was no apparent damage at all, to the rod itself.

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And now, a pic of the rear of the plywood. Showing the damage from the steel shot, the marble, and with the rod still stuck through the plywood.



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Bottom line, size does matter.

Bore size makes more difference, than barrel length.

And.. I really like this setup.

After the flood cleanup, I tried the gun again with the 3/4" barrel, but for some reason the valve had developed a leak. And not a tiny one, either. There was too much leakage, to put anything in the barrel. It would just blow back out, well before you were ready to take a shot.

I rebuilt the piston itself. Making sure that everything was flat and square. Now it seals to the barrel and stays that way.


I have noticed that even though it triggers just fine with the blowgun... (And all the above damage was done with the gun triggered by the blowgun.)

If I trigger it by leaving the ball valve open, and disconnecting the compressor quick-connect fitting, it seems to fire even harder.

So I may work on a different triggering system.

Sprinkler valve is out, because it is too bulky.

Nice job. That is the kind of results I was getting.

Size does matter.

You could always go for a basic check-valve design in the piston to improve performance further, instead of using a pilot valve with higher flow.

saefroch wrote:You could always go for a basic check-valve design in the piston to improve performance further, instead of using a pilot valve with higher flow.

You know, in time I just might do that.