Post
by John Werner » Sun Jun 26, 2011 12:56 pm
An Exercise In Deflageration to Detonation
Copyright © 2011 By John Werner
This is a method to produce a detonation using empty food
cans.
The first thing that may come to mind is the "TennisBall
Cannon" Where empty food cans are taped together and fire a
tennis ball up into the air. It takes a little more then
this to produce a detonation as you will see.
Without getting into a long winded discussion I'll cut to the
chase on how to produce detonation. This model will get you
started and at your own risk you can carry it further.
The materials you will need are:
1) a ream of 8 1/2" X 11" 110 weight cardstock
Sams Club, Office Max
2) 1/2" masking tape and packing tape 2"
Office Max
3) one butane barbecue lighter
Home Depot
4) one pint of S-L-X brand denatured alcohol
Home Depot
5) two empty enchilada cans
Super market
6) one empty green bean can
Super market
7) Sharp nail used as a punch
What this model will do, it will show what a baffle will do
to increase combustion pressure and I'm really surprised that
no one in this forum has ever tried this with pulsejets.
In scouring the US patent office there are several patents
that use the baffel system in combustion.They are:
1) The Brown Patent awarded to Samuel Brown Jr 1972
#3,745,691
This patent now expired will allows anyone to build and sell
combustion devices using the baffle system.
2) December 28, 1982 #4365471 Joseph S. Adams
3) E. B. Meyers 1946 #2647365
The baffle is not as apparent in the Meyers jet engine but
it's there.
The baffel used in these patents is similar to the shchelkin
spiral which is still a baffle.
All of the PDE patents use some form of the shchelkin spiral.
OK back to the model. What it won't do with the three cans is
detonate, for that you need several more stages! And
electronic ignition with 20 feet of wire so you can get
behind a barricade. It will blow the cans into shrapnel.
Building the Model
Tape the two enchilada cans together end to end to form a
mandrel. Cut 4 pieces of the card stock 5 1/2" X 8 1/2 then
tape them to form one long piece 5 1/2" X 68".
Cut a piece of tape 3/4" long and tape the card stock to the
mandrel so that 3/16" holds the cardstock to the mandrel with
the rest on the cardstock. Start rolling to the end. It will
most likely be crooked, just clamp with your hand the roll
against the mandrel and twist against the direction you
rolled. This will loosen the roll so you can straighten it
then twist in the direction you rolled to make the tube nice
and tight and tape the seem with masking tape. Cover the
masking tape with a piece of the packing tape.
Dismantle the mandrel and punch a hole with the nail in the
center of one of the enchilada cans then enlarge it to 1/4".
In the other enchilada can punch a hole in the side 1" up
from the closed end, this will be the igniter can. No holes
are punched in the bean can.
Fueling the Model
Get an empty jam jar or any small jar with a lid and pour in
about 1/4" of alcohol. Pour a small amount of alcohol into
the igniter can, rock the can back and forth to cover the
bottom then pour out ALL of the alcohol back into the jar
for this first test.
Push the empty compressor can into the tube (center hole can)
then follow it with the igniter can (side hole can).
Orientate the cans so the compressor can with the center hole
is against the open end of the igniter can. Both cans should
stick out from each end of the tube. The cans must be
against each other. Place a tennis ball into the open
compressor can and ignite with the barbecue lighter at the
side hole with the cans standing on the igniter can.
Not much will happen, the ball may not even shoot out of the
cannon. Remove the cans and this time fuel both cans. Hold
the compressor can at a 45 degree angle when you pour in a
little alcohol then hold it over the jar as you rock it to
catch any spill through the center hole.
With both cans fueled place them back into the tube and add
the tennis ball and ignite. The ball should go up 50 feet or
more.
Now for the third and last test fuel the enchilada cans as
before and also the bean can and be sure to always pour out
to the last drop of alcohol, all you want is to coat the
bottom of each can.
Place the enchilada cans in the tube then place the bean can
over the open end of the tube, this should be a snug fit and
stand the tube on the igniter can and fire.
The bean can will shoot up 100 or more feet straight up and
you can calculate the height by timing with a stopwatch from
the time of the explosion till the can comes back down and
hits the ground. Divide the total time by 2 then multiply by 9.8
which gives the height in meters. Be sure to wear a hard hat to
protect your head from the falling can.
It takes a longer tube which must be reinforced with steel
and multiple stages of compressor cans to get a true detonation.
Do this at your own Risk!!