Date: Thu, 18 Oct 2001 08:48:05 -0700

Author: Ron Ebert

Subject: Re: Liquid Nitrogen Demos


At 08:35 AM 10/18/2001 -0400, John McIntyre wrote:
>Ron Ebert wrote:
> > Ice bomb - Take a galvanized piece of coupling with two end caps. Fill it
> > completely with water (best to do this in front of the audience). Tighten
> > it as tight as you can with two wrenches. Put it in an empty milk carton.
> > This milk carton sits on a protective wood board (so that the table isn't
> > damaged) and there is a metal shield you will place over the carton. Place
> > the shield. This shield has an open top so that you can pour the nitrogen
> > in - use a full liter. Place a lead plate or other heavy piece of metal
> > over the top. The bomb will explode after 2-5 or so minutes. DO NOT DO THIS
>In an attempt to economize compared to the costs of the Cenco ice bombs,
>we tried
>using coupling and end caps, but we had no success. Did we just use the wrong
>hardware store?

Maybe. Use 1-1/4 inch galvanized pieces. The coupling is 2 inches long and
is ribbed. Use teflon tape on the end cap threads. Make sure that there is
not even one little air bubble inside after filling it with water and
before capping it. You can hand tighten it in the water, but once you take
it out of the water, use two large wrenches to tighten it more. Put as much
torque in tightening as you can. Don't let it sit for more than half a day
before using. For reasons I don't understand, they don't work if they sit
around a long time. In any case, it's more spectacular to fill it with
water and tighten it before your audience.

We've never used those wimpy Cenco devices in the past 15 years.

Ron Ebert
"The facts will eventually test all our theories, and they form, after all,
the only impartial jury to which we can appeal." - Jean Louis Rodolphe Agassiz