DIY Gear Indicator

It can be difficult to know what gear you're in on a motorcycle.

It's easy to see what gear you're in when you're driving a car. Some motorcycles, such as a 1984 GS550ES, had gear indicator displays. Many motorcyclists have considered how to add this feature to their bike. Mechanically, counting the up-shifts and down shifts doesn't always work because you can miss a gear or accidentally hold the clutch in so the gear doesn't engage -- throwing a mechanical indicator off. There is a solution using a microchip and electronic and magnetic sensors that will indicate, without error, what gear you are in.

Things You'll Need

• Digital bicycle speedometer
• Electrical pulse sensor
• Programmable microprocessor

Instructions

1. Mount the magnet from the digital speedometer to the primary drive sprocket. You will need to drill a hole through the sprocket to secure it, making sure the mounting screws are the same diameter as your hole, so it fits very snuggly. Use thread-locking adhesive tape when you install the magnet.

2. Fabricate a bracket to hold the digital reading device such so it's pointed at the magnet, counting each revolution of the primary drives sprocket. Route the wires carefully so they they do not get caught in the chain during operation.

3. Use an electrical pulse sensor like those used in multi-meters and timing lights to mount to either the ignition coil wires or wires that send ignition commands from electronic ignition systems to capacitors. This will count every spark ignition, from which you can extrapolate engine revolutions. There will be one full revolution per spark in a two-stroke motor and two full revolutions per spark in a four-stroke motor.

4. Integrate the primary drive magnet sensor data with the ignition sensor data in a single microprocessor/display unit. Programable micro-controllers that can do this are available in the robotic hobbyist community.

5. Program the microprocessor with your gear ratios. These devices will feed the microprocessor the revolutions of the crankshaft and the revolutions of the primary drive sprocket. The ratio between these two will correspond to your gear ratios. Your program must display the gear that corresponds to the ratio sensed by the sensors. For example, 4:1 might be first gear and 3:1 might be second gear. All your program will do is calculate the gear ratio, match the ratio to the correct corresponding gear, and display that gear on a digital LCD display.

Tips & Warnings

• Look for easily programmable and extensible components.

• This project requires thorough understanding of electrical engineering and basic understanding of software engineering.

References

• Expert Advice from REI: How to Choose a Bike Computer
• Ikalogic: Infra Red Sensors Applications and Construction
• Robot Room: Electronic Analog and Digital Counter
• MotorCycle Anchor: Understand Motorcycle Sprocket Math