46 replies to this topic

[sasman]

eh

Edited by sasman, 25 October 2010 - 09:38 PM.

[pymp]

I'm in a similar situation regarding a blast shield. Nobody would happen to have any spare polycarbonate sheeting sitting about would they?

[ProfHawking]

I picked up a load of lexan-type offcuts via ebay a while back. Unfortunately its not very thick. Some is 12mm, but most is only 8. I've not had too much success so far, but it should be possible to laminate it somehow into something plenty thick enough.
If anyone knows how to do it properly please let me know! In which case i should still have some spare if you are interested Pymp.

[pudi.dk]

Would sticking two 8 mm together be a bad idea? else try it

[pymp]

Several posts on rec.pyro suggested 1/4" (6.4mm) was sufficient, but that more should be used if possible. If two 8mm sheets were layered, and bolted to the press (as pudi.dk suggests), would this suffice?

Edited by pymp, 08 May 2007 - 01:49 PM.

[cooperman435]

My local council are curently upgrading all my bus shelters.

If anyone wants some Ill go down to the depot and ask if the old stuff is available.

anyone?

[Gavin]

1/4" lexan holds up in this experiment-

http://www.thecalder...lastShield1.htm

So as it suggests using 2 or 3 sheets should give added safety.

There was a discussion on rec.pyro recently and the general opinion was that sheets should be layered with no gaps between them. The logic being having gaps makes the setup weaker much like a karate chop can break a stack of planks with gaps but not without. I'm sure I've read somewhere ages ago that the opposite was true and with lexan sheets it's better to have gaps between the sheets. Also not to drill bolt holes as this introduces weak points. Does anyone have any hard information, rather than the karate example, which is better - gaps between sheets or not?

[pymp]

Was looking at that experiment just yesterday, interesting stuff.

If bolt holes weaken the structure too much, what is the best method of securing it? A clamp of some sort perhaps?

[barra69]

Used to use riot shields made of lexan. As a rule when they broke it was at the point of greatest flex, i.e. half way between the bottom and the arm grips. They did not break where they were drilled for the hand/arm grips.
The abuse they could take was amazing. Just think of a fit 96kg man jumping at a shield with his feet. They just bounced off.

Edited by barra69, 02 May 2007 - 07:39 PM.

[portfire]

Hi all.I'v just bought some 4mm plexiglass from B&Q.If i laminated this to 24-28mm,will this give me enough protection????? Or have i just wasted my money.

[ProfHawking]

Plexiglass? Like acrylic? If so, it is nowhere near as strong as polycarbonate based lexan or similar.
You might need to check what you have is strong & shatterproof.

[portfire]

Sorry should have been more specific.This is there website

http://www.arielplas...rene/index.aspx

Its clear polystyrene.

[portfire]

Found some tech specs,i cant make my mind up whether to use it or not,if it save's me once thats fine,but i'd rather not find out the hard way if it wont


http://www.boedeker.com/polyst_p.htm

Edited by portfire, 09 June 2007 - 06:45 PM.

[Frozentech]

Sorry should have been more specific.This is there website

http://www.arielplas...rene/index.aspx

Its clear polystyrene.

Too brittle, and liable to fragment into shrapnel instead of acting as a shield. Polycarbonate is the only way to go.

[portfire]

Oh well,i'm sure i'll find another use for it,but just to add,it wont be stopping metal,like from a sleeve.I'll only be making small rockets,fountains and dont think i'll be using a sleeve (just watch for the case bulging) so it will be just bits of carboard tube it stops,surely 28mm will work



regards
dean

Edited by portfire, 09 June 2007 - 07:50 PM.