Year-round commuter E-bike
his is my first e-bike, which I built from scratch in 2020. I was inspired by endless-sphere.com and the Grin YouTube channel. Initially, I had planned to buy a ready-made e-bike, but every model I considered seemed too complicated and difficult to repair. So, I asked myself how much it would cost to build an e-bike with the best available components. A rough estimate showed that this would be only half as expensive as a conventional, ready-made e-bike – that was the impetus for my project.
My design specifications were:
• Simple mechanical and electrical construction
• Climbing ability of up to 12%
• Should not get stuck in streetcar tracks
These specifications limited the selection of components to be used. I decided on:
• A direct drive motor
• A frame without suspension
• Mechanical brakes (no hydraulics)
• No gear shifting
Since I wanted to use a direct drive motor, I looked for a frame that could accommodate not too big wheels, i.e. 26 inch. The Surly Troll, which is no longer in production, turned out to be well suited. It fits tires wide enough not to get stuck in streetcar tracks. I did some actual measurements, and it turned out that 2“ wide tires (or wider) will do fine.
After numerous simulations with the Grin motor simulator, the MXUS XF40 hub motor emerged as a suitable drive due to its relatively high efficiency at road gradients of 12%, despite its high weight of about 10 kg. However, if I had the choice today, I would opt for the Grin Fatbike motor, which offers similar performance to the XF40, but weighs only 6 kg.
Some problems only arose during assembly: Although the MXUS motor has a mount for disc brakes, it turned out that there was not enough space between the motor housing and the frame to install a brake disc without the caliper rubbing against the motor housing. This issue seems to be known many other users report similar difficulties in forums. Fortunately, I had ordered rims that were also suitable for rim brakes, allowing me to install a V-brake. In hindsight, I would say that this is even the better solution compared to a disc brake. Most braking is done through the regenerative motor brake anyway, and to come to a complete stop at a traffic light, I usually use the front brake. The rear V-brake is rarely used, and the brake pads have not needed to be replaced after 16,000 km – not to mention the rim itself.
Since non-existent components cannot break, I opted out of a gear shifter. The missing torque is always provided by the motor. I calculated on the website www.ritzelrechner.de that at a speed of 25 km/h – the maximum speed for non-registered e-bikes in Switzerland – and a desired cadence of 85 RPM, a chainring with 44 teeth and a sprocket with 17 teeth would fit well together.
From the mechanical diagrams of the motor and a BMX freewheel sprocket, a chainline of 48 mm was determined. To achieve this chainline at the bottom bracket, I combined a "John Wayne style" 3x chainring set with a relatively short bottom bracket. I kept only the outer chainring and mounted it in the middle position.
The electrical components include:
• Battery from EM3EV
• Phaserunner PAS and Cycle Analyst from Grin.
Now, almost five years and 16,000 km later, it’s time for an update. Although my e-bike was meant to be as low-maintenance as possible, especially after the first winter, some repairs and conceptual changes were necessary.
Initially, this concerned the brake levers. I originally installed brake levers with electrical contacts that could trigger regenerative braking support. However, this brought some disadvantages: The quality of the e-bike brake levers was nowhere near comparable to normal brake levers. They were wobbly, the lever arm was too short, and the brakes had to be adjusted very precisely. Additionally, there were winter problems with coupling mechanical and regenerative brakes. When I parked my e-bike outside for a few hours, the battery temperature dropped so low that the BMS prevented charging. This caused the electronics to stutter when braking. The solution came with the CA firmware version 3.2 beta in the form of a virtual backpedal brake. Now the mechanical brakes and the regenerative brake are decoupled, and as a welcome side-effect the cable from the brake lever to the Cycle Analyst is no longer needed.
Other changes concerned weather resistance. In Switzerland, aggressive potassium chloride is spread in winter, which caused my chain to be completely degreased after only one ride in the salt, and even the BMX freewheel was damaged. After various attempts to better protect the chain, I finally discovered a fabric chain guard. This type of chain guard has been common on Dutch bikes and already seemed old-fashioned to me in my childhood. However, old-fashioned does not have to be bad – quite the opposite. With a pair of scissors, this chain guard could be easily adjusted to expose the crank, the opening for the PAS, and the area next to the sprocket. Thanks to the fabric, the chain box does not form a resonance chamber, and the significantly reduced chain wear eliminates rattling or scraping noises.
Since front fenders are usually too short, I extended mine downward with a mud flap and forward with a cut plastic piece. Previously, rainwater always splashed onto the headlight and the bottom bracket housing – this problem has now been solved.
Another improvement concerns the handlebars: I originally installed a downhill handlebar with a 15-degree backsweep. It looked sporty but led to arm pain and cold fingertips in winter, A new handlebar with a 47-degree backsweep brought a significant improvement: no more pain, and thanks to better blood circulation and a better position against the wind, no more cold fingers.
Canadian
