<h2>Make a Vortex Cannon.</h2>

<p>This is a device for firing a coherent torus-shaped vortex across a room.  If it is made with a degree of care, it will extinguish the flame of a candle from some distance.</p>

<h3>What you will need</h3>

<ol>
<li>An empty Pringles can.  This is the cylindrical foil-lined cardboard tube which originally contained Pringles potato chips.</li>
<li>A party balloon.</li>
<li>Some strong parcel tape.</li>
<li>A hole punch capable of making a clean hole of about two centimetres (three quarters of an inch) in diameter.</li>
<li>A small drill.</li>
</ol>

<h3>What to do</h3>

<h4>Step 1:</h4>

<p>Drill a small hole in the metal end-plate of the Pringles can.  This hole needs to be large enough to accommodate the threaded portion of the hole punch.</p>

<p>The hole needs to be as close to the exact dead-centre of the plate as you can make it.</p>

<p>Use the hole punch to make as clean as possible a hole as accurately as possible.</p>

<p>Here in the UK it is possible to obtain a hole punch called a Q-Max punch from Maplin, the supplier of electronic and hobby parts.</p>

<p>I am sure they are available from other sources.</p>

<p>It is very important that this hole is:</p>

<ul>
<li>As close to the centre of the end-plate as is humanly possible</li>
<li>Has edges which are clean and crisp.  Hence the use of a hole punch.</li>
</ul>

<p>It is these two factors more than any other that will effect the efficiency of the cannon.</p>

<h4>Step 2:</h4>

<p>Cut off the mouth-piece end of the balloon.</p>

<p>Stretch it over the open end of the Pringles can and pull it as tight over the end as you can.</p>

<p>When I say the open end I mean the end from which you removed the lid and chomped on the chips.</p>

<p>Use the parcel tape to wrap the balloon tightly around the circumference of the cylinder, anchoring it in position so that the open end of the can is now like a drum formed by the stretchy membrane of the balloon.  Nice and tight.</p>

<p>The cannon is now ready to fire.</p>

<h3>Firing the cannon</h3>

<p>Pinch the centre of the balloon membrane and pull it back as far as you can.  This might be easier if you push some kind of (blunt ended) rod into the can from the hole end and push out the membrane until you can pinch it.</p>

<p>Some other stretchy latex device which has a little bulb at the end might be easier to get hold of, but I can't think of such an item, can you?</p>

<p>When you let go of the membrane with it stretched out as far as you can go, what happens?</p>

<p>Well, if you made the small circular hole at the metal-plate end of the cylinder nice and clean and central, the cannon fires a coherent vortex of air.</p>

<p>What do I mean by a 'vortex'?</p>

<p>Imagin a ring doughnut compromised of air shooting out of the end of the tube like a smoke ring out of a Hobbit.</p>

<p>The vortex is spinning.  Not like the bullet fired from a rifled barrel, but as if it is constantly trying to turn itself inside-out.</p>

<p>This spinning keeps the torus (this is what the shape of a ring doughnut is called) coherent and intact for several feet.</p>

<p>If you made the hole in the metal plate end of the tube nice and clean, and you stretched the balloon membrane out as far as you possibly can, the cannon is capable of blowing out the flame of a candle at about ten feet (three metres) in the still air in a room.</p>

<p>As soon as it leaves the cannon, the vortex will begin to degrade and fall apart.</p>

<p>A word of warning</p>

<p>This little toy might only be firing a torus of air, but do not be tempted to shoot yourself or the cat in the face at point blank range.  It hurts.</p>

<p>Mike</p>

