Explanation of lemonade bottle rockets
Mon, 25 Feb 1991 00:54:12 PST
Just had a letter from Dave requesting further info on the lemonade
bottle rockets. In case there are others amongst you who haven't got a clue
what I am talking about, here is a brief description.
A couple of months ago, Bob one of the other scout leaders on
this side of the pond, who also works for Rank Xerox, described to me, how his
scouts make lemonade bottle rockets.
Basically what they do, is to get a litre size or larger, plastic
lemonade bottle. They 1/3 fill it with water, and then push a bored rubber
bung with a car tyre valve fitted into it, into the neck of the bottle. This
should be a tight fit. Three bamboo canes are pushed into the ground in the
form of a triangle. These are to hold the bottle in an upright position prior
to launching. The bottle is then inverted so that the bung is pointing towards
the ground, and the air hose from a pump is fitted to the tyre valve. When the
air supply has been connected. The bottle is placed within the bamboo launch
stand. When air is pumped into the bottle, the space above the water becomes
pressurised and eventually the friction of the bung is overcome. The bung
shoots out and the bottle is launched into the air.
I made one of these up and was pleasantly suprised at the height that
was reached by the bottle. This basic design has a few minor problems though,
1/ Pressure is limited to the holding power of the bung.
2/ Person launching the rocket can get a little wet.
3/ Flight pattern can be a bit erratic.
4/ Damaged bottles could explode.
I wrote a note to Ken, one of the scout leaders on the Dl in the
States. He supplied me with some sketches and notes, explaining a similar
device he had seen used by some American scouts. Ken says that they had
overcome most of the problems that I have described.
In the model described, two "U" shaped brackets are fitted to a base
board. To one of these is fitted, two hinged bars or rods. These clamp around
the neck of the bottle just behind the thick flange. This flange is found on
most types of these bottles, it is probably used in the filling factory.
Spring tension is applied to the bars with a couple of elastic bands. A simple
latch at the other end of the bars, with a long length of string attached,
enables the rocket to be launched outside the wetting range of the rocket. The
bars could either be adustable up and down so as to hold the bung against the
base board, or there could be an adjustable stop fitted to the base board.
This could then be wound up until it contacts the bung. The bottle can now be
pressurised, far beyond the holding power of the bung.
Thick plastic drainpipe or tube could be used as a launch tube, as an
addition to this set up. This would stop any shrapnel should a bottle explode.
Plastic fins can be stuck at the lower end of the bottles to increase
stability in flight. Most of these bottles come with a stuck on base, this
enables them to be stood upright without falling over. If this base is
removed, then the rounded base of the bottle proper is exposed. This also make
the rockets fly better.
Ken tells me that he saw a write up on these rockets in an American
boys magazine. If anyone has a copy of this article, or has any further
information to what Ken has supplied me with, I would be very pleased to hear
from you. We are at present experimenting with different methods for attaching
parachutes to the nose of the bottles.
Cheers for now
Terry Howerton Sakima Group, Inc. SCOUTER Magazine Kansas City