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jeremy13
05-20-2010, 09:37 PM
We did some testing with some lead. I had to pour two of them. One for a control and one for the test. Dimensions wear 20cm X 20cm outside with a 25mm hole 125mm deep. They came out weighing just over 155 pounds. Man these things are deceiving. A first I thought it was stuck to the table when I went to move it. The first block we set a blasting cap in the bottom of the hole and backed it with sand. Popped it and then metered the amount of water it took to fill the hole. The next one we put 10 grams of our explosive in the bottom of the hole and then a cap. And back filed with sand and made the shot. Then back to the amount of water to fill the hole. And subtract the amount of water it took to fill the first one. This is what it looked like in side the hole after I cut it in half.
http://i47.tinypic.com/35nar13.jpg
The hole had a flat bottom. And is now just over 2 1/2" (65mm)wide at the widest point.

Boucher
05-20-2010, 10:27 PM
I did some work years ago where we were trying to contain the explosive output in some H shaped housings designed to restart a second redundant leg in an explosive train that involved linear shaped charge. Turned out that dead soft aluminum worked better than anything else. They sure swelled up but they contained everything. Seems like it is good for like 20% elongation before it fractures.

Evan
05-20-2010, 10:52 PM
Lead has the major advantage of providing much greater inertial containment.

I am very curious how you cut the block.

hojpoj
05-20-2010, 11:01 PM
I am very curious how you cut the block.

If I were to venture a guess, I'd say that was done with a bandsaw. The cut pattern seems to be consistent with a bandsaw, anyhow.

Evan
05-20-2010, 11:08 PM
Cutting lead with a bandsaw is extremely difficult.

jeremy13
05-20-2010, 11:24 PM
Not with this one and some lenx stick lube.
http://i45.tinypic.com/2wg697p.jpg

Northernsinger
05-20-2010, 11:41 PM
Lead seemed to band saw cut quite easily for me using blades for wood cutting. I think I remember 3 TPI, no sticking no problem at all, just cute lead sawdust all over the floor.

Evan
05-20-2010, 11:53 PM
The first time I tried cutting a lead block on my horizontal I was using a 14tpi blade and WD-40. It went ok until the blade was well buried and then it ate the blade. I still haven't freed that blade from that block. I will have to melt it out.

Doc Nickel
05-21-2010, 12:00 AM
14 teeth is a bit too fine for anything over thin sheet, and WD is too "thin". You need, as Jeremy noted, a wax stick lube.

I used an old Craftsman wood bandsaw many moons ago to chop up some long bars of linotype so they could be melted down in a small bullet pot. I was told wood speeds were fine, but I needed big, open teeth and keep the wax stick handy. Worked like a charm.

What I'm wondering is what the explosives are for. I saw an earlier post about popping a hole in some thick plate, but I seem to have missed the reasoning behind the testing.

Unless, of course, it's just the "I get to play with explosives" type of testing, whose chief hypothesis is usually "let's see what happens when we try to blow this thing up!" :D

Doc.

hojpoj
05-21-2010, 06:43 AM
What I'm wondering is what the explosives are for. I saw an earlier post about popping a hole in some thick plate, but I seem to have missed the reasoning behind the testing.

Unless, of course, it's just the "I get to play with explosives" type of testing, whose chief hypothesis is usually "let's see what happens when we try to blow this thing up!" :D

Doc.

I think the explosives are just a perk. No self-respecting redneck I know uses a control in their tests. :D

Jeremy, were you trying to quantify something? I can see the parameters you were measuring, but not sure what sort of conclusion you were trying to draw.

Evan
05-21-2010, 07:29 AM
I suspect that they are trying to quantify the energy density of the explosive. Explosives are obviously a very non linear form of energy conversion and this makes it possible to determine how much mass was moved and how quickly. Incidentally, most high explosives have a very low energy density compared to other forms of chemical energy. Comparing by the BTU heat released a gallon of gasoline equals about 60 sticks of 70% dynamite.

jeremy13
05-21-2010, 02:38 PM
While we do get to do some lets see what happens.( ok a lot) This was to compare the power of the explosives to a known explosive. In this case it was TNT. Looks like we are in the 82% range of the power of TNT. Not bad for a binary explosive. That you mix on the job sight. The other tests with the holes are for destroying unexploded ordnance. Like air dropped bombs and artillery shells that did not go off. Or when you clean up a bombing range. And you can not determine if the round is a concrete filled round. You would shoot a hole in the casing and if it was live it would go off. Or you would expose the concrete for proof of a dummy round. I most cases you can just put a charge of explosives on the side of the round and knock a hole in it or knock out the fuse and expose the in side. But on the high explosive rounds the wall is much thicker and a shape charge is needed to put a hole in the round for inspection.

BobWarfield
05-21-2010, 04:04 PM
Not with this one and some lenx stick lube.
http://i45.tinypic.com/2wg697p.jpg

ROFL!

Evan's gonna have to get a bigger bandsaw ala Crocodile Dundee:

That's not a bandsaw, THIS is a bandsaw!

Having just gotten a much bigger one myself (20" Rockwell Delta), I love having one around. Indispensible. Not sure why I waited so long. I just got tired of having things I couldn't cut with my chopsaw or my "little" bandsaw.

RE lead for inertial confinement and binary explosives...

Man, the D.H.S. gets hold of this thread and we'll all be staggering onto airports with lead shoes to prevent foul play.

Cheers,

BW

dfw5914
05-21-2010, 05:12 PM
We did some testing with some lead. I had to pour two of them. One for a control and one for the test. Dimensions wear 20cm X 20cm outside with a 25mm hole 125mm deep. They came out weighing just over 155 pounds. Man these things are deceiving. A first I thought it was stuck to the table when I went to move it. The first block we set a blasting cap in the bottom of the hole and backed it with sand. Popped it and then metered the amount of water it took to fill the hole. The next one we put 10 grams of our explosive in the bottom of the hole and then a cap. And back filed with sand and made the shot. Then back to the amount of water to fill the hole. And subtract the amount of water it took to fill the first one. This is what it looked like in side the hole after I cut it in half.
http://i47.tinypic.com/35nar13.jpg
The hole had a flat bottom. And is now just over 2 1/2" (65mm)wide at the widest point.


You have a really cool job!

Black_Moons
05-21-2010, 07:28 PM
Wow, im amazed evan droped the ball on lead machining.

Evan: Considering what a low temp lead melts at, Might of you of started melting the block (or the swaff) due to too many teeth engaged and not enough chip room in the blade causing excessive heat and fusion around the blade? How thick was the peice you where cutting evan?

14TPI does sound too fine for any signifigantly thick block of lead without a very light feed rate considering how fast lead would cut under minimal pressure and fill up the space in the blade.

Would I be right to assume lead should be machined like a soft plastic?
Low tooth count if its thick to maximize chip room, low to moderate SFM and medium/high feed rates to minimize heating?

It should cut great with even a dull tool, Just don't want to melt it.

Evan
05-21-2010, 07:45 PM
The lead doesn't melt when sawed but it is so soft it smears out in the cut and jams the blade. As for dropping the ball, I don't have any coarse tooth blades for my horizontal. The piece I was cutting was about 3"x4".

jeremy13
05-21-2010, 10:23 PM
Well we did some more playing O!! I mean testing to day. First was a 12" H beam with 1/2 web. And the next was a round we filled with concrete to simulate a dummy round.
http://i47.tinypic.com/2psooxs.jpg
One pound in middle of web.
http://i46.tinypic.com/1zx1vlc.jpg

http://i48.tinypic.com/2elyz2g.jpg
Two pounds on nose of round if it had a live round it would have went off but we exposed the concrete so we can see it was a dummy.
http://i50.tinypic.com/w8xfnd.jpg

Optics Curmudgeon
05-21-2010, 11:46 PM
Interesting test methodology, the lead, I mean. Relatively accurate, too, apparently. 82% of TNT is close to the actual value of 88.6% for Kinepak and it's relatives. Major test labs shy away from aerosolizing lead in more than tiny amounts but it looks like you're not hampered by those sorts of restrictions. There's still a place (a growing place, actually) for this sort of entrepreneurship.

Joe