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Registered Member #190
Joined: Fri Feb 17 2006, 12:00AM
Location:
Posts: 1567
I am planning on making a blast shield with lexan. After doing some reading I think 1/2" will work well. I also plan on taking a small piece to a gun range and shot it with a 9mm and .357 and assess the damage.
Has anyone built a blast shield? Any comments?
I plan to have this between me and my tubing which will be pressurized to 3000 psi.
Registered Member #207
Joined: Sat Feb 18 2006, 05:14PM
Location:
Posts: 45
It's all going to be crude, but such is the nature of shielding oneself from blasts.
There seems to be plenty of resources online where people have shot miscellaneous things at Lexan sheet. If I were you, I would use their results as a crude benchmark for the material's reaction to objects with different kinetic energies. Use a rough estimation of the round's velocity and mass.
Next I'd take a look at the tubing you plan on pressurizing. Do some conservative estimations on average flying particle size/mass that you'd expect in the event of a failure. Figure some realistic velocities given your proximity to the source of the explosion. Then, correlate everything back to the original performance of a somewhat equivalent bullet. Finally, double the thickness you think is safe.
My only other comment is do some soul searching. Figure out whether you really need to witness the thing live. Maybe spend the money on a CCTV system as opposed to Lexan.
Actually, what am I talking about? Chicks dig scars.
Registered Member #65
Joined: Thu Feb 09 2006, 06:43AM
Location:
Posts: 1155
Synthetic sapphire laminates with bonded transparent metal infused co-polymers are not consumer equipment.
Bury whatever you plan to test below the local frost line in a pit, and use a mirror to peer 90' from behind a reinforced concrete wall with an earth roof. A few dozen Kevlar "drapes" hanging around a camera will stop most shards that would pass through a regular car frame.
Taking shrapnel in the face hurts, bleeds like a punctured garden hose, and makes people stare at you like you have a second ass. Even a shield wont stop a "curve ball" with a spiraling trajectory... please consider a camera looking on a plastic dollar store mirror instead.
You should also take a ticket certification course to learn about safety.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
You may have better fragment or round stopping power with several thin sheets, with airspaces between.
ABS (Lexan) has high tensile strength but is easy to cut, PMMA (Perspex, Lucite) shatters easily.
A sheet of PMMA backed by a sheet of ABS works in an interesting way. The PMMA shatters, and a piece comes off and stays ahead of the fragment, effectively blunting it. The ABS then has an easier job to stop it. "One way" "bullet-proof glass" has been demonstrated using this principle.
If tube bursts are the main cause for concern, wrapping them with a textile bandage will stop fragments, letting the working fluid through. Just add more layers until you think you have enough.
Of course wrapping the apparatus and a shield in front of the operator is belt and braces.
Registered Member #509
Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329
Dr. Slack wrote ...
You may have better fragment or round stopping power with several thin sheets, with airspaces between.
ABS (Lexan) has high tensile strength but is easy to cut, PMMA (Perspex, Lucite) shatters easily.
A sheet of PMMA backed by a sheet of ABS works in an interesting way. The PMMA shatters, and a piece comes off and stays ahead of the fragment, effectively blunting it. The ABS then has an easier job to stop it. "One way" "bullet-proof glass" has been demonstrated using this principle.
If tube bursts are the main cause for concern, wrapping them with a textile bandage will stop fragments, letting the working fluid through. Just add more layers until you think you have enough.
Of course wrapping the apparatus and a shield in front of the operator is belt and braces.
IIRC lexan is polycarbonate, not ABS, but the principal sounds right, as polycarb is a lot easier to scratch than acrylic (which seems like it would be related to cut resistance)
However, for equal stopping powers, I'd suspect steel would end up much cheaper then a polycarbonate sheet, so minimize the area you need to see though, unless you have other considerations to worry about.
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3140
I believe that a significant factor is how the sheet is mounted, e.g. all-around support in an elastic medium is best I think, such as a (synthetic) rubber gasket around the edges which is clamped between rigid beams etc. is tougher than drilling a hole near each corner and using screws.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
IamSmooth wrote ... ...THe tubing is rated for 7000psi with a safety factor of about 3x The fittings are also rated over 5000psi. These are based on yield values for stainless. The failure values are much higher.
Here are a couple of points.
1. The hazard from a bursting tube depends as much on the length and diameter, as on the pressure. Of course you already knew that.
2. Strictly speaking, "blast" effects (e.g. from explosion of a munition) are just the damage from overpressure. They don't include damage from fragments, even when fragments are the primary kill mechanism.
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Blast shield construction
