I'm a dedicated cycling commuter in a city that is not particularly bike friendly. I've been a devoted fan of the AirZound bicycle air horn (http://www.airzound.co.uk/) since I first encountered one about 15 years ago. They are wonderful if you ride a mountain or hybrid bike but they really do not work well on a modern drop bar road bike. I've successfully modified two AirZounds for road bikes using different approaches and have documented them both here. Both methods require splicing in an air valve between the bottle and the horn.
Version 1: Auxiliary Valve Using Schrader Stem (this document)
Version 2: AirZound Valve Relocation (see my other posting(s))
Step 1: Acquire the Parts
After failing to find a small, light and inexpensive normally closed "air switch" valve available in Canada, I decided to make one. The operation was simple but a bid fiddly.
- 1 Schrader valve - ideally scavenged from a dead inner-tube
- 1 Schrader valve cap - potentially from the same dead inner-tube. If possible, choose a relatively long cap with as high a dome on top as possible.
- 1 circle of flexible rubber about 1/4" in diameter - You can slice this out of the out the same inner-tube to complete the theme
- 1 small brad or nail - the brass ones that come with picture hooks have rounded heads that are perfect for this job but almost any small nail with a decent head will do
- 1 eraser from the top of a pencil
- Epoxy - I love epoxy
Step 2: Assemble the Valve Head
Drive the brad into the top of the valve cap. Being ever-so-slightly off center and off vertical is actually an advantage, especially if you have a round-head brad.
Drill a 9/64" hole on the side of the cap as close to the top as possible and, in any event, as clear of the threads as possible. Pull out the brad, poke it through a 1/4" disk of inner-tube rubber then insert the assembly back through the cap so that the head of the nail is inside the cap and the rubber disk is able to act as a gasket when point of the brad is pulled all the way up. After carefully considering where you will be installing the bottle and the auxiliary valve on your bike, cut the AirZound hose and thread the section running to the horn through the hole that you drilled. Once you've confirmed fit, remove the hose and glue it into place with epoxy, being careful not to get any epoxy into the hose or the valve cap and being sure that the hose does not interfere with the placement of the brad. Spread a good dollop of epoxy on the outside of the cap and form a belt around the circumference and the hose. Cut the brad so that it extends about 1/2" above the cap when the brad is fully retracted. You are actually aiming to have it extend about 1/4" above the cap when the head is eventually put in contact with the Schrader valve pin). Drill a hole smaller than the diameter of the brad the eraser to about half depth. Stuff the hole with some paper or aluminum foil to act as wadding and poke some epoxy into the hole with a toothpick. You can then insert the blunt end of the brad to make a nice button.
Step 3: Assemble the Valve Base
Connect the section of the hose attached to the bottle to the bottom of the Schrader valve. This can be done by wrapping rubber flashing from the inner-tube around the hose, securing with a twist-tie and sealing the assembly with a blob of epoxy. I had a stem with a barb and ferule (from an old AirZound as a matter-of-fact).
Step 4: Test the System
Once the epoxy is fully cured, screw the cap onto the Schrader valve to complete the "air switch".
Pressurize the bottle by depressing the new auxiliary valve while filling the AirZound normally.
If your valve is working, pressing on the eraser will push the brad head into the Schrader valve opening it and allowing air to flow into the bottle.
Test the system by holding down the trigger on the horn assembly then pressing the auxiliary valve. Again, the brad will open the Schrader valve and allow air to move from the bottle into the horn assembly.
If everything works, you can mount the system on your bike. Use a heavy elastic to hold the original trigger (on the horn assembly) in the activated position. You will still need to use this valve to refill the bottle (remember to press the new auxiliary trigger when refilling!)
I'll leave it to you to figure out where and how to mount the components as every bike is different.
I hollowed out the large diameter mounting bracket using a Dremel tool, nestled the new valve between the sides and secured the assembly with a zip-tie (see intro picture).