From: ahahma@polaris.utu.fi (Arno Hahma)
Newsgroups: rec.pyrotechnics
Subject: Re: Paper Tubes, rockets, fuse
Message-ID: <1991Mar12.164437.17748@polaris.utu.fi>
Date: 12 Mar 91 16:44:37 GMT

In article <22810062@hpcvaac.cv.hp.com> billn@hpcvaac.cv.hp.com (bill nelson) writes:

>>while they dried, but the tubes were not very strong. What kind of paper?
>>What kind of paste. Should the paper's bias run lengthwise, or horizontally?

Kraft paper is the strongest and best. Xerox paper works, too, with small
tubes. You'll get the strongest tubes, is the
bias runs lengthwise, i.e perpendicular to the tube (I hope I understand
that "paper's bias" right, i.e. the orientation of the paper as it was
made). Rolling such tubes is not easy. You'll have to have a jig to
get the paper evenly tightened on the tube, otherwise voids will be left
between the layers. Rolling tubes is laborsome, that is why I soon began
searching for a better alternative.

There are industrially made kraft paper tubes, that may even fulfill
mil-specs. These also have the nozzle assembly industrially made for you,
all you have to do is to ram the moistened meal black powder in, close the
tube and drill a burning channel into the powder or use a spindle
to make the channel. Usually these tubes even cost nothing. The answer is:
paper shotgun shells, empty of course ;-). The primer cup works as a nozzle,
just drill a hole trough it and press it back to the base. Naturally, the
"nozzle" is not an ideal one ;-), but the rocket works - that's the most
important point, isn't it? Needless to say, these are no high-thrust-
motors ;-).

>Do people still make rockets?  They tend to be more work than they are
>worth for pyrotechnic displays.  It is much easier (and safer) to use
>mortars.

I do not agree. To be able to use mortars you'll have to build the shell
strong and use some kind of a pressure resistant delay fuse. With
rockets the shell can be a plastic container, a piece of spiral
paper tube (not very strong), etc, since the acceleration will be
much smaller. Also, you need no additional delay fuse, the rocket itself
acts as a delay.

If you are shooting big shells, then the mortar is better, it consumes
much less propellant.

Yes, I have used rockets, since they are easy to make and use. I had to
develop those shotgun shell rockets - I always had a shortage of paper shells
but plenty of plastic ones. So I made some composite fuel of sodium
chlorate (YES! Isn't that dangerous!) and polyurethane resin. The fuel is
strong enough to hold the pressure and it is possible to use it in the plastic
shells, actually, it does not work in the paper ones at all. The nozzle is a
piece of stainless steel tube (6 mm or 1/4"). The other end of the nozzle is
broadened to make the nozzle conical. The burning channel is either cast
using a spindle or drilled before assembling the nozzle.

The ignition goes either electrically or with a fuse, the electrical method
is much better, since the nozzle can be plugged to raise the operating
pressure faster.

An ideal load for these rockets is 200 grams, that will fly about 200..250
meters high. The engine itself weighs about 50 grams with about 40 grams
of fuel.

>If no one else posts instructions, I will look in my old books and see
>what I can find.

These are not intended to be instructions, I only told I have made some
rockets.

About fuses:

Let's imagine it is saturday evening and you run out of fuse. You need
some, but you can't buy it. How do you make some of you own? Some additional
requirements: it has to run through a 2 mm hole - the safety fuse
wouldn't do anyway.

ArNO
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