Dual-Tone Car Horn for Bicycle

A Super LOUD Horn for your Bicycle!

I have an electric bike and use it for commuting all over town. That means sometimes I have toattempt to share the road w/cars. I have tried all of the"horns" on the market for bicycles and they have all been terrible for communicating with cars. None of them sound like a horn and while they tout 120+dB output, they couldn't compete w/road noise.

I started the project with aREAL car horn and built around that. While researching battery options, I wanted a simple battery/swap solution with an easily accessible/cheap battery.... and found the Dremel/Bosch/similar form-factor very appealing with it's "slide in/lock" interface.

For the weight-conscious, here's the weight of the assembly:

*703 grams - w/3500mAh battery installed *549 grams - w/o battery

Here's a couple short videos of the horn in action, however it doesn't do it justice... it's LOUD!!!!!!

Thanks to @topias5 for his model of the Bosch Battery Pack. This helped greatly in the design process.

Print Settings

Resolution:

.2mm

Infill:

33%

Filament: any PETG

Notes:

The following parts need to be printed at 70%+ infill, as they will have directed heat applied to them so they can be expanded to allow mounting to the bar.

*extender_bar_mount *button_bar_mount

The following parts will need support:

*horn_mount_front - (for fan cutout slots) *horn_mount_back - (for fan cutout slots) *button_bar_mount

Bill of Materials

Printed Parts

• 1xhorn_mount_front.stl
• 1xhorn_mount_back.stl
• 1xhorn_mount_battery_connector.stl
• 1xbutton_bar_mount.stl
• 1xhelper_battery_terminals.stl
• 1xextender_bar_mount (attaches to handlbar extender)

Hardware

• 12mm Momentary Button
• 12v Dremel Battery
• 12v 77mm Disc Horn Kit

(optional)

• Carbon Fiber Handlebar Extender

The extender is optional, but is required to use the included mount that attaches the assembly to the bike.

Vitamins

• 16 - 18AWG silicone wire
  • • not required to be silicone... it's just much nicer to work with.
• Automotive Quick-Connect Crimp Spade connectors
• 5 minute 2-part epoxy
  • 4x Female connectors (connect to horns)
  • 2x Male connectors (connect to battery)
• 1x (Male & Female Tamiya Connectors)[https://smile.amazon.com/Pairs-Tamiya-Style-Connector-Unwired/dp/B00XQ91C18/]
• 2x M5x20mm screws
• 2x M5 nuts
• 4x M3x30mm socket-cap screws
• 2x M3x50mm socket-cap screws
• 1x M3x14-16mm socket-cap screw
• 5x M3 nuts

Note: The type of connector used (from battery-to-button) is flexible. You can use anything you have laying around... or don't use a connector at all... I used it so it made it easier to install/etc.

Assembly

Wire up Battery Terminals

• Cut 2 lengths of wire, about 12 inches long each.
• Remove all the outer nylon protector of the 2 male spade connectors
• Crimp each spade connector to one of the wires.
• Pull the wires thru the bottom of the printed parthorn_mount_battery_connector and assure that the connecters are pulled into the notches.
• Insert the printed parthelper_battery_terminals to hold the connectors in place & tape to hold.
• Flip over to expose the terminal-ends + wire. Notice the notched opening is wider than the wire/terminal... this is where we will glue the terminals in place.
• Mix a small amount of 2 part epoxy and fill the 2 notched areas.
• Allow to cure and then remove thehelper piece.

Before moving on, make sure the battery can cleanly slide onto the battery terminals.

horn_mount_battery_connector (with male terminals in place) & helper_battery_terminals

Bottom of horn_mount_battery_connector with terminal spade connecters epoxied in-place

Assemble the body

• Install 2x M3 nuts into the back ofhorn_mount_battery_connector
• Assemble thefront,back, and _batteryterminal parts and insert 2x M3x50mm screws
• While holding in place, make sure the battery can slide cleanly into place. Depending on the quality of the print/etc, you may need to clean the parts before assembly.
• Insert each horn into the slots and attach w/M5 screws/nuts

Note: I used aliquid rubber on the faces of the parts that connected, as a "first pass" in the process offully water-proofing the design.

The body is now assembled and ready for wiring

Wiring Up the Horn

The horns have no required polarity, meaning you can connect POS/NEG to either terminal on an individual horn and it'll honk. They are wired in parallel, supplying 12v to each horn.

Negative

• Cut a length of wire that will reach from the NEG terminal from 1 horn to the NEG on the other horn.
• Crimp a female connector to one end of that wire (optionally: add shrink wrap)
• Take the NEG wire from the back of the battery and the previously crimped wire and insert them into a female connector and crimp (optionally: add shrink wrap)
• Connect all NEG female connectors to the horns

Positive

• Cut a length of wire that will reach from the POS terminal from 1 horn to the POS on the other horn.
• Crimp a female connector to one end of that wire (optionally: add shrink wrap)
• Cut another short length of wire and the previously crimped wire and insert them into a female connector and crimp (optionally: add shrink wrap)
• Connect all POS connectors to the horns.

Button connection

• Use a Tamiya (or which ever connector you want to use) connector and attach to the POS wire out of the battery and the short POS wire crimped to the horn.

Note: Once installed and tightened, I added a dab of silicone into that area to keep out water.

Install and Wire up the button

• Install M3 nut into the bottom of thebutton_bar_mount printed part.
• Screw the 12mm push button in
• Adjust the button so that the screw terminals face towards the wire opening
• Cut 2 lengths of wire, long enough to reach the horn to the area you want to mount the button.
• Strip/expose enough wire to allow them to be inserted into the screw terminals. I used insulated ferules to make this easier
• Once the wires are inserted, flip the mount over to expose the terminal post screws and tighten.
• Connect the other end of the wires to the matching Tamiya connector to complete.
• See the section belowInstalling Handlebar Mounts for getting the mount over the handlebar. Once on the handlebar, use the 14-16mm M3 screw and tighten.

Installing Handlebar Mounts

The Handlebar mounts (extender_bar_mount andbutton_bar_mount) are printed as 1-piece. Because of this, we have to soften the plastic to make it temporarily flexible so we can stretch it to fix over/around the handlebars.

To do this, you can use a blow dryer (or heat gun) on the area of the part that wraps around the handlebar.

Hints/Tips for using heat:

• Setup/use the heat gun near the bike so you can put it in place before it cools down too quickly.
• Use low heat and keep the heat moving around the area -- Even PETG requires very little heat to become pliable enough

Attaching it to the Handlebar Extender

• Install 4x M3 nuts to back ofextender_bar_mount
• Once heated/attached around handlebar extender, insert 2x M3x30mm screws towards the top of the mount until the screws catch the nuts (don't tighten completely)
• Align the horn assembly into mount slot and insert 2x M3x30mm screws and tighten
• Adjust the entire assembly until it is at an ideal angle and tighten the top screws

Water Proofing

The following pieces are water/splash resistant:

• Horns
• Button

The following are NOT:

• Battery
• Assembly for battery

An easy solution is to take plastic/water-resistant material and wrap the battery area to keep water out (not completely water proof).

Category: Sport & Outdoors