Building Your Own Electric Mini Bike: A Step-By-Step Guide

Building your own electric mini bike is a great way to get a feel for engineering and physics while creating a fun mode of transportation. The first step is to decide whether to build the bike from scratch or use an existing frame. If you're starting from scratch, you'll need to design the structural elements and cut them out from a material like plywood. If you're using an existing frame, you'll need to prime it and apply paint before assembling the frame and handlebars. Once the frame is ready, you'll need to add a motor, battery, and electronics. The type of motor and battery you choose will depend on the desired speed and power of your bike. Finally, you can add extra details like lights and custom flourishes to make the bike your own.

Choosing the right motor

Firstly, you need to decide on the type of motor: brushed or brushless. Brushless motors tend to be more efficient and require less maintenance, as they don't have brushes that can wear out over time. They also offer higher torque and speed capabilities. However, they might be more expensive and complex to control. On the other hand, brushed motors are simpler and more cost-effective, making them a good choice for those on a budget.

The gear ratio of the motor will impact the bike's performance. A lower Kv value will result in lower top speeds but higher torque, providing better acceleration. For a pocket bike, a Kv of less than 200 is recommended. Consider your desired speed and torque when selecting the gear ratio.

Voltage and current requirements are also important considerations. Ensure that the motor can handle the voltages and currents you plan to use. Most motors can surpass their ratings, but it's crucial to stay within safe limits. Check the motor's specifications and choose one that aligns with your voltage and current setup.

Additionally, pay attention to the physical size and weight of the motor. It should be compact enough to fit within the frame of your mini bike while being powerful enough to drive it effectively. Consider the weight of the motor as well, especially if you intend to carry your electric mini bike or include it in a lightweight design, such as plywood construction.

When choosing a motor, it's advisable to seek advice from online forums and communities dedicated to electric mini bikes or similar projects. They can provide valuable insights, recommendations, and tips based on their own experiences.

Preparing the frame

Building an electric mini-bike is a fun project that can teach you a lot about engineering and physics. The first step in the process is to prepare the frame. You can purchase a ready-made frame or build one from scratch. If you choose to buy a frame, Azusa Parts is one option. If you want to build the frame yourself, you can design it using software like Autodesk Fusion 360 and then cut it out from plywood using a CNC router. If you don't have access to a CNC router, you can print templates and do the routing by hand.

Once you have the frame, the next step is to prime it. Choose a primer that suits the final look you desire for your bike. After applying the primer, you can paint the frame in your chosen colour. It is recommended to allow ample time for the paint to dry before proceeding to the next steps.

After the paint is dry, it's time to assemble the frame. Start by taking the handlebars assembly and greasing the connecting bolt or rod. Securely attach the handlebars to the body frame. If you're using a ready-made frame, ensure you have all the necessary parts, as sometimes certain components like the chain or driving sprocket may be missing.

The next step is to mount the motor to the bike frame. You'll need L-brackets for this. Mark the motor mounting points on the L-brackets, and if necessary, drill holes to match the frame. Position the motor and bracket into place on the body of the bike. Depending on the motor, you may need to create a custom-sized chain.

Finally, you can mount the battery and other electronics to the frame. The ESC and battery can be mounted underneath the seat, and you can use duct tape or more professional methods for this step. You can also add extra details like shred lights or other LED lights to illuminate your bike rides in low-light conditions.

Adding propulsion

Now that you have the frame of your mini-bike assembled, it's time to add propulsion to bring it to life. This is where the electrical components come into play, so let's go through the steps to ensure a smooth process.

Firstly, you'll need a motor to power your mini-bike. A brushless motor is a popular choice, and you can source one from a hobby store or online. Keep in mind that the motor's Kv rating will impact your bike's performance. A lower Kv will result in a lower top speed but higher torque, providing better acceleration. Consider your desired speed and the weight of the rider when choosing a motor.

Next, you'll want to mount the motor to the bike frame. Using L-brackets, mark and drill holes to attach the motor securely. Ensure the brackets are sturdy and that the motor is positioned correctly.

Now, let's connect the motor to the electrical system. Add 5mm bullet connectors to the motor's wiring, making it compatible with the rest of the system. The specific wiring will depend on your motor type, so refer to its instructions. You'll also need to connect a throttle to the motor controller, allowing you to control the speed.

The battery is another crucial component. A 24V LiPo battery is a standard choice, but you can explore other options depending on your budget and performance goals. Consider the battery's placement, ensuring it's secure and doesn't affect the bike's balance. You might want to put it in a box and mount that box to the frame, providing extra security with zip ties.

Finally, you can add some finishing touches, such as lights. Mount LED headlights and a rear light to the frame to enhance visibility during evening rides. With these steps complete, your electric mini-bike will be ready for testing!

Mounting the battery

Firstly, decide on the location for your battery. A popular option is to mount the battery underneath the seat, as this can provide a secure and discreet location. If you opt for this location, ensure you have sufficient space and that the seat can still be comfortably accessed and used.

Another option is to use a rear cargo rack to mount the battery. While this is a frequently used method, especially for affordable kits, it can affect the handling of the bike, particularly at higher speeds, so it may not be the best choice for a mini bike.

If you have a full-suspension frame, you may encounter the challenge of having a shock absorber in the middle of the frame triangle, which can hinder your mounting options. In this case, a backpack battery could be considered. While this option ensures you don't forget to remove the battery when away from your bike, it's important to note that the weight distribution of the bike will be affected.

Once you've decided on a location, it's time to secure the battery. One method is to use a universal mount, such as the Electrify Bike Flex Mount Bracket, which can accommodate various battery shapes and be attached to almost any bicycle frame. This option provides flexibility in choosing the perfect spot for your battery.

Another approach is to create a custom mount by building an interfacing plate. This involves mounting a plate to both the controller and the holes in the frame. For added security, you can place the batteries in a box that fits snugly and then mount the box to the frame using zip ties.

When mounting the battery, it is essential to treat it with care as it is a fragile and expensive component. Ensure you provide ample support and padding to prevent physical damage to the cells. Additionally, consider using materials like duct tape or rubber mats to protect your bike's paint job during the mounting process.

Final touches

Now that you've assembled the frame, added the propulsion, and mounted the battery and electronics, it's time to put the final touches on your electric mini bike.

First, consider adding some lighting to your bike. Shred lights or other LED lights can be mounted to the frame to illuminate your path when riding at dusk or dawn. You may also want to install a rear light to enhance your visibility to others when riding in the dark. These lights can be powered by the same battery as your motor, so be sure to account for this extra load when sizing your battery and wiring.

Next, give some thought to the bike's aesthetics and comfort. You can paint the frame in your favourite colour or design, and perhaps add decals or stickers for a unique touch. If your seat is uncomfortable, consider swapping it out for a more ergonomic option. You could even add a small basket or storage compartment to the front or rear of the bike, depending on its design.

Finally, take your bike for a test ride and make any necessary adjustments. Check that the handlebars are tight and the wheels are securely attached. Ensure that your brakes are functioning correctly and that the throttle responds smoothly. Fine-tune these components until you're happy with the performance and feel of your electric mini bike.

With these final touches, your electric mini bike is ready to hit the road. Remember to follow any relevant laws and regulations regarding the use of electric bikes in your area, and always wear appropriate safety gear when riding. Enjoy your custom creation and the fruits of your labour!

Frequently asked questions