A penetration test "Standard"

[boyntonstu]

1> We all use the same distance for the test, say 20 feet.

2> Target:

a. Plywood
b. Yellow pages
c. ?

Suggestions?

BoyntonStu

[Ragnarok]

My suggestion would be to NOT set up any spudding standards.

As far as penetration goes, there's far too much projectile/target matching for the results to mean anything serious.

I've got a project that's looking to punch holes through a half inch thick steel plate a quarter mile away - and I've explicitly designed the projectile to do that specific job. Try to test the same projectile on a different target*, and its results might be alright, but likely below average.

*Layered wood would stop it particularly well. It's expressly designed to become highly unstable after penetrating its target (or whatever it happens to have hit) as a way of minimising the risks of "over-penetration"

We can judge on an individual basis whether a shot is good, average or poor penetration using common sense and experience.

[inonickname]

Plywood varies. As do phone/info books.

The projectile really has the biggest bearing on penetration.

[jackssmirkingrevenge]

When it comes to gauging performance, a chronograph and a good set of scales are much more useful tools, depth of penetration is as stated above highly subjective.

[Technician1002]

1> We all use the same distance for the test, say 20 feet.

2> Target:

a. Plywood
b. Yellow pages
c. ?

Suggestions?

BoyntonStu

A ream of paper is pretty consistent. If we standardize on a type such as 20 lb high speed photocopy, multipurpose, or ink jet printer paper. 5 or more reams of paper against a solid backstop such as a huge rock, wrecked car, sandbag pile, etc should be reasonable.

[Moonbogg]

I've got a project that's looking to punch holes through a half inch thick steel plate a quarter mile away - and I've explicitly designed the projectile to do that specific job.

Alright Ragnarok, thats a huge claim. Now its out and we are waiting for result

[Ragnarok]

@Moonbogg: That's the objective (along with achieving a respectable 5 shot group). There is no guarantee of meeting it - although I'd very much like to.

But, expect to be waiting a while. Neither the cannon nor anything else I'll need to build to do it is finished. Most importantly, it's also dependent on finding somewhere to do it. I'm not even going to invest the time or money into the projectiles (and let's face it, the target) until I have a confirmed location.

[Moonbogg]

Just pull a NASA and shoot the moon.

[jackssmirkingrevenge]

Just pull a NASA and shoot the moon.

Looking at the moon now, it would seem that an alien race of consierably larger proportions than us are into the hobby of "asteroiding"

[qwerty]

A ream of paper is pretty consistent. If we standardize on a type such as 20 lb high speed photocopy, multipurpose, or ink jet printer paper. 5 or more reams of paper against a solid backstop such as a huge rock, wrecked car, sandbag pile, etc should be reasonable.

20 LB! dont you think that would cost quite alot? well it would in england i think 500 sheets of a4 costs about £8 and that weighs about 4 lb.
As for things to shoot, i have no idea maybe something like the milkbottle challenge but with coke cans.

[Technician1002]

A ream of paper is pretty consistent. If we standardize on a type such as 20 lb high speed photocopy, multipurpose, or ink jet printer paper. 5 or more reams of paper against a solid backstop such as a huge rock, wrecked car, sandbag pile, etc should be reasonable.

20 LB! dont you think that would cost quite alot? well it would in england i think 500 sheets of a4 costs about £8 and that weighs about 4 lb.
As for things to shoot, i have no idea maybe something like the milkbottle challenge but with coke cans.

The 20 lb in the USA is a reference to the thickness of the paper, not the weight of a sheet. Index cards are 110 lb, thin copy paper is 16 lb, presentation cover stock is 65 lb etc.

[qwerty]

ohh !!! we use gsm like a piece of printer paper is 90 gsm my mistake im not american

[velocity3x]

[quote="Ragnarok"]I've got a project that's looking to punch holes through a half inch thick steel plate a quarter mile away - and I've explicitly designed the projectile to do that specific job.
quote]

Surely this can not be a pneumatic launched projectile...can it? If so, wouldn't you be required to spend many, many thousands of dollars on machine shop services to produce a launcher that will produce that kind of excessive energy at 1/4 mile?

[Ragnarok]

Surely this can not be a pneumatic launched projectile...can it?

It will be pneumatically fired, from Project 3vo.

There are two ways to get sufficient energy at that range. Start with a huge amount of energy, or lose as little of it as possible to drag. I'll personally be trying to get drag as low as possible.
There are also several ways to minimise the energy needed for the job of punching through the target. Unfortunately, these aren't necessarily the same things as will produce the best aerodynamics.

So, there is a sliding scale between a projectile which carries as much energy to the target as possible, and one that needs as little energy to pierce as possible. For any given range, there will prove to be a best compromise somewhere on that scale.

Alternatively, there's another option, where the projectile has a destructible nose which is of the best aerodynamic shape (and which is destroyed on impact), and under that a nose that presents the best penetration shape.

I've got a design for both ideas, and at some point, I'll need to do some tests on both to see which is of greater merit.
(While the destructible nose projectile will be "better", I need to decide if it's enough of an improvement to be worth the extra resources needed to build it.)