Another Electric Scooter Project

This project was started by 3 friends then working in a particular company as a means of transportation to lunch and back to office (since this particular company with > 1000 employees has surprisingly no canteen ...).

The basic idea behind the "Another Electric Scooter Project" was to convert a cheap $70 Kick Scooter into an electric motorized version by replacing the mechanical front wheel with a hub electric motor. We decided to purchase an off-the-shelf solution in the UU Motor electric scooter conversion kit for the speed controller, hub motor as well as the necessary accessories such as the throttle, brake and auto-cruise.

The main early challenges we faced were mostly mechanical modifications starting with how to modify the fork, then how to fit and fasten the aluminum hollow bars to the kick scooter base, etc.

Later on the challenges were related more to electrical issues, especially the selection of type of battery to use, the required Ampere-Hour rating we needed and also to find the most corresponding 42 volt charger which seemed almost impossible to find at one point.

Anyway here's our version of another electric scooter project, maybe it will inspire you to build one too :-)

Step 1: ​Parts and Tools

Parts

• Plywood (thickness = 10 mm, length and width at least 20 mm border from the edge of selected scooter base)
• Hollow Aluminum bar for sides (thickness = 2 mm, length = 220 mm, width = 2.5 mm)
• Hollow Aluminum bar for rear (thickness = 2 mm, length = 80 mm, width = 2.5 mm)
• Hub Motor Kit
• Battery Holder (10 pieces, each holds 3 cells (18650) each 3.6 volts, 3000 mAh)
• Lithium Polymer (18650 type LiPo) Batteries (30 cells, each 3.6 volts, 3000 mAh)
• Battery Heat Shrink wrap (large enough to fit all battery holders stacked in 5 x 2 arrangement)
• Battery Charger (42 volts)
• Water proof 3 way switch
• Battery Monitor System (BMS)
• Charging port
• Water proof charging cover
• Wires
• Bolts
• Nuts
• Rivets

Tools

• Hand held drill
• Riveting tool
• Hacksaw
• Flat metal file
• Electric jig saw
• Spanner
• F-Clamps
• Soldering Iron
• Hair dryer (for heat shrink wrap)
• Adjustable spanner

Step 2: Fabrication of Plywood Base

1. Instead of directly marking the cut out lines on the plywood, it's a good idea instead to make a template out of cardboard which can be reused to mark out other bases.

2. Transfer the base template outline to the plywood with a pencil.

3. Using a jig saw with a wood cutting blade, cut out the base carefully moving the jig saw blade on the outside of the outline.

4. After completing cutting out the base, use a flat file to remove any splinters or sharp edges.

Step 3: Modification of Kick Scooter Fork

The original Kick Scooter we used in this project had a front fork that was slightly too narrow to fit the UU Motor Hub motor. We had to either modify the existing front fork to widen it enough to fit in and install the UU Motor hub wheel motor. An additional problem was that the original front wheel was mounted via an axle shaft to the fork which was inserted via a single hole on each side of the fork.

This made it also impossible to insert the UU Motor into the fork since the only way to get the UU Motor mounted was to pry open the fork outwards, slide the motor in then bend the fork inwards and secure the motor axle to the fork. However this was not practical since the bending and unbending of the fork would most likely weaken the fork joints and eventually snap the fork at the joints.

The other option would have been to fabricate a custom fork, however this would have taken much more time and blown the budget :-)

We therefore decided to make a simple modification to the existing Kick Scooter fork by making a slit from the bottom of the fork up towards the existing mounting hole.

Steps to modify Kick Scooter front fork

1. Using a permanent ink marker, mark out the cut lines from the bottom of the fork upwards to the original mount hole.

2. Using a hacksaw, carefully saw along the marked out lines up towards the original mount hole on the fork.

3. Once the sawing has been completed, file away any sharp edges but be careful not to widen the cut out edges too much as this will affect the mounting of the UU Motor which might be too loosely mounted.

4. After finishing filing, try to slide the UU Motor axle into the modified front fork and check that it fits in smoothly.

5. If the UU motor axle does not fit in, carefully file the fork edge to remove access metal, then repeat step 4.

6. Slowly iterate between Steps 4 and 5 until the UU Motor axle fits snugly into the cut out slot.

7. Once the fork has been modified with the cutout on 1 side, make a template on a piece of cardboard which can be reused to mark out on the other side of the fork or on other scooters.

Step 4: Modification of Kick Scooter Base

Main modification of the original Kick Scooter base is the attachment of 3 aluminum hollow bars at the 2 sides (10 cm each)and at the back (10cm) of the base as the main supporting structures for the plywood base to the original metal base of the kick scooter.

Modifications on Kick Scooter Metal base

1. Place the 3 aluminum hollow bars on the metal base of the kick scooter

2. Using a pencil, trace the outline of the hollow aluminum bars onto the metal base of the kick scooter.

3. Remove the hollow aluminum bars and check that the pencil outline of the bars are clearly marked on the kick scooter base.

4. For each of the 2 side aluminum bar outlines, mark out a centre line and mark 2 points about 2 cm from the ends.

5. Using a centre punch, mark the 2 points then drill pilot holes using a 2mm metal drill bit, then proceed to drill the final sized holes to fit the mounting bolts.

Modification on Aluminum hollow bars

1. After all the holes have been drilled on the metal base of the kick scooter, place the aluminum hollow bars one at a time onto the metal base of the kick scooter to line up exactly with the pencil markings.

2. Using an F-clamp, secure the hollow aluminum bar to the metal base of the kick scooter then using a pencil or marker mark the positions of the holes drilled in the metal base onto the aluminum hollow bars.

3. Check that the markings on the aluminum bars are located along the middle and not too close to the edges (as this would lead to problems when mounting the bolts in the next steps).

4. Repeat Steps 2 and 3 for the other aluminum hollow bars.

Mounting of Aluminum hollow bars to Kick Scooter metal base

1. Once all the holes have been drilled on the metal base of the kick scooter and the aluminum hollow bars, double check that the holes are all aligned.

2. If the holes are not aligned, possible remedies are to widen the hole but be careful not to widen the holes too much that the bolt would be too loose.

3. Once all the holes have been aligned between the bars and the metal base, insert the bolt from the beneath the metal base upward and through the aluminum hollow bar.

4. Then place the spring loaded washer first, then the nut and fasten until finger tight, the use a screw driver and spanner to hold down the nut and fasten the bolt tightly.

5. Repeat Steps 1 to 4 for the remaining aluminum hollow bars.

Securing wood base to aluminum hollow bars

1. Position the cut out plywood base onto the aluminum hollow bar and check that the wood base covers all the aluminum hollow bars with sufficient margins all around.

2. Once the wood base is in position, with a pencil mark out the outline of the hollow bars onto the underside of the wood base.

3. Using a pencil, mark out the center line of the aluminum hollow bars and select positions to drill the mounting holes.

4. Drill pilot holes, then drill the final hole for the 3 mounting holes (1 hole per aluminum bar).

5. Position the wood base back onto the aluminum bars using the pencil outline from Step 2.

6.To avoid any slippage, use an F-clamp to fasten down the wood base to the aluminum bars and then using a center punch, punch a marking for each mounting hole onto the aluminum hollow bars.

7. Drill the mounting holes onto the aluminum hollow bars, first a pilot hole and then the final mounting holes.

8. Next step is to attach the "screw holder" onto the inside of the aluminum hollow bars.

9. Position the "screw holder" on top of the aluminum hollow bar by aligning with the mounting screw.

10. Using a center punch, punch the positions of mounting holes of the "screw holder" onto the top of the aluminum bar, then drill holes to match the mounting holes.

11. Secure the "screw holder" inside the aluminum hollow bar aligned with the mounting holes, then secure with the screws.

12. Finally place the wood base over the aluminum bars and install the mounting screws and check that everything is correctly aligned and that the mounting screws can be fully screwed in flush with the wood base.

Step 5: Fabrication and Installation of Side Skirting

Step 6: Electrical Installation

The battery management system consists of 2 main components
1. BMS controller
2. Battery pack

The BMS is responsible for battery charging and to protect the battery from getting over discharged. During normal discharge operation, the battery is pack supplies the motor controller via the BMS. The hub motor has a rated voltage of 36V. As such, we have opted for a 10S3P configuration for the battery pack. This works out to a capacity of 42V (full charge)

Max battery pack voltage = 4.2V * 10 = 42V

Total mAH rating = 3000mAH * 3 = 9000 mAH

Using the 3-way switch, the system is able to have 3 configurations
1) Battery charging

2) Battery discharging

3) Neutral (Open circuit)

Step 7: Charging the Batteries

Step 8: Test Ride

After months of hard work, finally the scooter is ready for a test drive.

Before heading out for a test drive, the following checklist could be useful :-)

1. Fully charge the batteries and double check the voltage with a multimeter.

2. Do a bench test, lift the hub motor wheel off the ground and check that the throttle, brakes, auto-cruise controls are working.

3. Bring along the following set of basic tools in cases some thing goes wrong on the test drive :-(

- Allen keys

- Screw driver

- Multimeter

- Duct tape (if all else fails this usually helps)

- Spanner

- whatever else that might be needed ...

4. Step onto the scooter and ride it, if in doubt use protection gear :-)

Test ride 1

Test Ride 2