Ok lets start with the WARNING in this instructable we are dealing with HIGH PRESSURE AIR and of course archery equipment so proceed at your own risk.
Step 1: What You Need
Thick Tape (I used a heavy duty plastic masking tape but PVC Isolation tape works )
Rubber Sheet (for this I used an exorcise stretch band/Strip but anything with a smooth surface and not to thick 0.5mm ish should do )
0.75mm drill (not shown)
Baby Powder (Not Shown)
POP Bottle tops
POP Bottles (not shown)
I want to emphasise the POP for the sake of safety only use bottles from Carbonated drinks as they are thicker and are designed to withstand air pressures unlike the much thinner bottles used for mineral water or cordial etc.
Step 2: Choosing Your Bottle Tops
This may prove to be the trickiest part of this ibles
What you are looking for is a bottle top with as smoother inside as possible the Green cap on the left is a perfect example of what you are looking for the blue one can be used but with a bit of modification that I shall expane as we go on
Also steer away from the shorter tops the more threads onto the bottle the better.
Step 3: Preparing the Lid
First inspect the inside of the lid and make a note of any makers marks as you will have to ovoid these.
Now from the outside of the cap make a small hole no bigger than 1mm (0.04") about 10mm (0.4") in from the edge into plane area of the top .
When making this hole its important to leave a clean hole free from any fraize or burs this is to make a good seal against the rubber valve this is why I found it better to drill from the outside with as little pressure as possible.
Its also works if you can melt it through with a hot pin or if you have access to one a laser cutter.
Step 4: The Valve
This is in effect a simple flap valve
To make the valves start by cutting a strip of rubber long enough to make the required number of valves Ie 20mm per valve
Then cut two strips of tape.
Place the first strip of tape sticky side up on a flat surface then place the rubber onto it only covering half of it making sure not to stretch the rubber as this will cause ripples in the tape ( first pic ).
Then place the remaining piece of tape onto the exposed part of the first piece making sure not to overlap onto the rubber. The object of this second piece of tape is to keep the surface of the tape level with the surface of the rubber.
The next step is to cut the valve to fit inside the bottle top this can be a little tricky to hold so I stuck the strip to a piece of waxed paper the type you would find on the back of a bumper sticker cut it and then peal it off that .
If you couldn't find a cap with a flat surface you might have to cut a recess in the valve to accommodate these raised sections the important bit is to have the valve sit flat inside of the cap.
As mentioned earlier I have access to a laser cutter so once I had perfected the valve I used this to cut the pieces and to make the hole I have included a picture of the template in case its of interest
Step 5: Fitting the Valve
When fitting the valve its important to make sure the rubber lies flat to the bottom of the lid and is not touching the sides .You can see by the second picture the position of the valve to the hole you can also see where the air pressure has tried to push the valve through the hole this is why I recommend that the hole should be no bigger that 1mm (0.04")
Step 6: FillingThe Bottles
Again this can be a bit tricky
SAFETY FIRST DO NOT EXCEED 80PSI
Adjust your air compressor up to 80psi
Ive been making these a while now and have tried different ways to fill them the most effective was to flatten the end of my blow gun push this firmly over the hole and while making sure not to have your face over the top of the bottle let the air in until you cant hear it any more.
Note the blue item was an attempt to make an adaptor to help with filling but It acted like an air cylinder and would lift me off the bottle
Step 7: Notes
If you put some baby powder in the bottle it gives an impressive white cloud when it is hit
When these bottles go off they are loud and have a reasonable amount of energy so don't use them in an indoor range and don't use your favourite arrows as they have been known to shread an arrow from time to time.When placing these bottles I found that if you put them just over an arrows length away from the boss (archery back stop not your employer) this will minimise damage to the arrows
With that said they are loads of fun