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From: fish@ihlpg.UUCP (Bob Fishell)
Newsgroups: net.bicycle
Subject: Building a LOUD horn
Message-ID: <1119@ihlpg.UUCP>
Date: Thu, 22-Aug-85 18:42:03 EDT
Article-I.D.: ihlpg.1119
Posted: Thu Aug 22 18:42:03 1985
Date-Received: Sat, 24-Aug-85 18:23:52 EDT
Distribution: net
Organization: AT&T Bell Laboratories
Lines: 86

***     AC  T              YOUR     AGE ***

Some time ago I posted an article on how to build a LOUD horn,  mainly
out of components available at your friendly local Radio Hack.  With 
all the flack about obnoxious motorists lately, I thought I'd recap the
article.  A LOUD horn can help in traffic, believe me.  It's saved my
butt a couple of times.

Parts List:

2 12-V buzzers.  These are the round variety, made of steel, with one
wire and a bracket on the back.  The original recipe called for 6-V
buzzers, but Hack don't carry 'em any more (thanks to the netter who
pointed this out to me; sorry I clobbered your letter before I got a
chance to reply).  The 12-Volters work just fine.

2 9-V battery clips, like those used in cheap transistor radios.

2 9-V radio batteries, preferably alkaline.  The carbon variety are a
couple of grams lighter (for those who really care about that sort of thing),
but won't last as long.

1 normally open, SPST, momentary switch.

Electrical connections:


           __buzzer__
bike      |          |                                               bike
frame-----|          |---( - battery +)---( - battery + )---switch---frame
          |__buzzer__|


Mechanical assembly:

Depends on what you've got lying around.  I made mine out of chassis parts
from old TV sets, but any of several materials should do.  The buzzers
have clamps in the back that will admit a rectangular brace about the
size of a popsicle stick.  I made one such brace out of an aluminum
rail.  I clamped the brackets down on either side and drilled a  5/32"
hole on the middle.  This mounts the buzzer on the front reflector
tongue, but don't do it yet.

I made a little basket out of strips of sheet metal.  It's just the
right size so that the two batteries sit snugly side by side in it.
I taped the batteries together so they can be removed as a unit.
Another 5/32" hole is drilled in the center of the basket's front.
The basket goes behind the reflector tongue, and both the basket
and buzzer assembly are mounted with the same screw.

The parts I used are decidedly nonstandard, but I think you could use
mending plates quite satisfactorily.

Wiring:

The buzzers only have one wire coming out; the body serves as the
other connection.  These are automatically grounded to the bike
frame if you use all-metal parts, but you'll have to run a ground
wire if you use plastic.  Solder both the wires to the negative
pole of one battery clip.  Solder the positive pole to the negative
pole of the other one.  Solder the other's positive pole to a wire
about 20" long leading to one side of the pushbutton switch (see
drawing). Ground the other side of the switch to the bike frame.  
All connections should be secured with heat-shrink tubing.  
DON'T use electrical tape, because it gets gooey in a hot sun.

My button is mounted on the handlebars just to the right of the stem.

Tuning and operation:

The buzzers I used can be changed in pitch by turning a screw
in the back.  I chose two frequencies that beat together rather
unpleasantly.  The noise they emit is thin and metallic, but very
LOUD.  It is so obnoxious that I don't use it on joggers or other
bikes (unless they're wearing headphones) that I'm just trying
to pass, but it gets attention QUICK in an emergency.  The horn
is LOUD enough to be heard clearly by a teenager in a closed,
muffler-less Camaro with the radio blasting, and LOUD enough to 
hurt your ears if you blow it inside the house.  I use it mainly
on motorists, most of whom turn their heads in surprise at the
decibels this mother produces.  Serves 'em right, too.
 __
/  \
\__/
				Bob Fishell
				ihnp4!ihlpg!fish