Building Your Own Electric Bike: Frame Essentials

Electric bikes, or e-bikes, are a popular choice for commuting and outdoor adventures. Building your own e-bike frame can be a fun project, but it can also be a challenging and expensive endeavour. To build an e-bike frame, you will need to start with a bare frame and add all the necessary parts, including a motor, battery, controller, throttle, and various tools such as wrenches, screwdrivers, and zip ties. It's important to select a sturdy e-bike frame that can handle a wide range of uses and terrain. Additionally, you will need to consider the cost of batteries, which can be the biggest ongoing expense in owning an electric bike.

E-bike conversion kits

There are several reputable companies that offer conversion kits, such as E-BikeKit™, Dillenger, and Swytch. These companies provide kits that include all the necessary components, from the motor and battery to the small parts required for installation. The E-BikeKit™, for example, boasts of being the world's most complete electric bike kit, offering hand-built wheels, an LCD dashboard, and instructional videos to guide you through the conversion process.

When choosing a conversion kit, it's important to consider the compatibility of the kit with your bicycle. Ensure that the kit fits your bike model and that it provides the desired torque and speed you're looking for. Some kits, like the Swytch Kit, offer a compatibility checker on their website to ensure that their product will work seamlessly with your bike. Additionally, consider the range and power of the battery, as well as any additional features you may want, such as an LED display to track your battery level and unlock extra power modes.

The installation process for e-bike conversion kits can vary in complexity, but many users report that it is relatively straightforward. The Swytch Kit, for instance, only requires you to click a 2-part magnet disc onto your pedals and stick a sensor to the frame to detect your pedalling. The kit also includes detailed instructions and worldwide delivery, making it a convenient option for those looking to dip their toes into the world of e-bikes without breaking the bank.

Converting your traditional bicycle into an electric one using a conversion kit offers a cost-effective and flexible solution. With a wide range of kits available on the market, you can find one that suits your specific needs, whether it's for commuting, trail riding, or simply enjoying the great outdoors without breaking a sweat.

Choosing the right frame

Frame Material

The most widely adopted frame material for electric bikes is aluminium due to its lightweight, affordable, and durable properties. It is a good choice for those seeking a cost-effective option without compromising performance. However, aluminium is less stiff than other materials. If stiffness and strength are a priority, steel offers a more robust option, making it ideal for heavier riders or off-road use. While steel is heavier, it provides durability and superior performance on rough terrains. For those seeking a high-performance ride, carbon fiber is the lightest and stiffest frame material available, but it is more expensive and requires careful handling to avoid damage.

Frame Geometry

The geometry of the frame plays a crucial role in optimising performance, comfort, and handling. The relationship between the handlebars, saddle, and seat height, along with the length of the frame tubes and resulting angles, determine the overall riding experience. A narrower (slacker) head tube angle provides enhanced stability, especially during descents and cornering, while a wider (steeper) head tube angle facilitates more direct steering and easier shifting when climbing. Additionally, consider the height of the bottom bracket, as a lower height can provide better stability by lowering the centre of gravity, but it may also increase the likelihood of pedal shocks on rocky paths.

Rider Height and Frame Size

Your height is a critical factor when choosing an electric bike frame. Manufacturers often provide size charts based on rider height to help guide your decision. The goal is to select a frame that allows you to easily straddle the top bar with at least an inch of clearance. Traditional frame designs have a higher top bar, requiring you to lift your leg over the bar when mounting, while step-through frames offer a lower top bar for easier mounting and dismounting. Additionally, consider the stack height, which is the vertical distance from the bottom bracket to the top of the head tube. More height is advantageous for steep ascents, while a lower stack height provides better weight distribution during climbs and steering.

Riding Style and Terrain

Consider your riding style and the type of terrain you plan to ride on. If you primarily ride on trails, an electric mountain bike with a narrower head tube angle and a more upright position may be preferable for stability and shock absorption. On the other hand, if you ride mostly on roads or engage in racing, opt for a frame that positions you in a more forward-leaning posture for improved aerodynamics and comfort during longer rides.

Installing the motor

First, select the right type of motor for your needs. There are two main types of electric bike motors: mid-drive motors and hub motors. Mid-drive motors, such as the popular Bafang kits, replace the crankset and usually have a single chainring. They offer excellent performance and torque but may wear out your drivetrain faster. On the other hand, hub motors are housed inside the hub of a wheel and can be installed in the front or rear. Rear installation is usually recommended for more powerful motors.

Once you've selected your motor type, it's time to prepare your bike frame. If you're using a conversion kit, follow the manufacturer's instructions carefully. You may need to remove the cranks or the bottom bracket, and in some cases, you might need to use an extractor tool. For instance, the LIFT-MTB electric bike kit offers video instructions for installing their motor.

When installing the motor, ensure that the cable is on the left side of the bike and left loose for now. You will run the cable along the bike frame later in the process. Securely tighten the nuts to avoid any issues. Consider reinforcing the fork area, as the added force from the motor can potentially cause damage over time.

Next, you'll need to select and install a battery pack. The motor will specify a voltage range, so choose a battery pack that falls within this range. Also, consider the amp-hour (Ah) rating, which will determine how far you can go on a single charge. Panasonic and Samsung offer popular high-quality battery cells. You can install the battery pack in a drink bottle mount or inside the frame, depending on your preference for discretion or ease of removal for charging.

Finally, make any necessary adjustments to the motor's settings via the display mounted on your handlebars. You can adjust the max speed, acceleration, and regenerative braking to suit your preferences. Test your electric bike on a short ride to ensure everything is functioning properly and make any final adjustments as needed.

Building your own electric bike can be a rewarding experience, and with careful installation, your motor will provide smooth and efficient power for many rides to come.

Battery options

When it comes to electric bikes, the battery is one of the most important components. The ideal battery size for your electric bike will depend on several factors, including your personal needs, bike specifications, and riding conditions.

Battery capacity, typically measured in watt-hours (Wh) and ampere-hours (Ah), is a critical aspect of your e-bike's performance. A battery within the 400Wh to 700Wh range often offers a good balance, providing sufficient power for extended rides without adding excessive weight. A 400 Wh battery is a great choice for those on a budget or for short commutes and leisurely rides. However, it may not be powerful enough for longer rides or hilly terrain. A 500 Wh battery is a popular choice as it strikes a balance between power and affordability, making it suitable for both short and longer rides. For riders planning to take on long rides or steep hills, a 700 Wh battery is the largest and most powerful option available.

If you're planning on going on longer, multi-day adventures, a 48V+ battery will be your trusty companion, offering enough power for 50+ mile days and tackling various terrains. Additionally, consider the type of battery you choose. Lithium batteries are a popular choice due to their good capacity, weight, and performance. Within the lithium family, Lithium Iron Phosphate (LiFePO4) offers longer lifespans, while Lithium Nickel Manganese Cobalt Oxide (NMC) provides higher energy density in lighter packages.

It's also important to understand how your e-bike works. If you pedal without using power, your battery remains fully charged until you need it. By using power sparingly, you can ride a whole day on a single charge. However, most people ride with the throttle at maximum power, and in this case, a 6 to 8 lb battery will typically last about an hour for 20 miles on most bikes.

To calculate the ideal battery capacity for your needs, you can use the following formula: Battery Capacity (Ah) = (Power Consumption (W) / Voltage (V)) x Time (h). For example, if your electric bike has a power consumption of 500 watts and operates at 36 volts, and you plan to ride for 2 hours, you would need a battery with a capacity of approximately 27.78 ampere-hours.

Lastly, don't forget to consider the cost. A good Lithium battery pack can be expensive, sometimes costing more than the rest of your electric bike kit. Lead-acid batteries are a more affordable option, but they are heavier and may not provide the same performance as lithium batteries.

Tools and safety equipment

Building an electric bike requires a variety of tools and safety equipment to ensure a successful and secure assembly. Here is a detailed list of the essential items you will need:

Tools:

• Wrenches and screwdrivers: For assembling and tightening various components.
• Allen keys: Essential for working with screws and bolts.
• Zip ties: To secure cables and wires neatly.
• Electrical tape: For insulation and securing wires.
• Wire cutters and strippers: To cut and strip wires during installation.
• Torque wrench: To apply precise torque when tightening bolts.
• Multimeter: For measuring voltage, current, and resistance in electrical circuits.
• Bottom bracket tool: Specifically needed for removing the e-bike's bottom bracket.

Safety Equipment:

• Gloves: Protect your hands from dirt, grease, and potential injuries.
• Goggles: Essential eye protection when working with tools and electrical components.

Additionally, it is important to prioritize your safety during the building process. Always be cautious when working with electrical components, and ensure you have adequate ventilation when working in enclosed spaces. Before beginning any assembly, carefully review the instructions and identify any specialized tools or safety precautions unique to your electric bike kit.

Frequently asked questions