Last summer, I built my very first ebike, and there were a ton of things to learn and consider, so I decided to make a detailed post about the build to hopefully help and inspire people who are getting started.
Here are pictures of the bike in its current state. Top speed is above 100 km/h, I never actually hit the limit because it’s just too fast for me. The range is around 100 km with a 72V 20Ah battery. Around 4 hours of charge time.
After deciding that converting my Tomos moped and getting it street legal was too difficult, this build started with a bike I got from Facebook Marketplace for 120 Euros. It’s a Decathlon Rockrider 520. L size, which is a little bit small for me, but I was happy with the price, so I took it. My only requirements were the disc brakes and front suspension. The bike was overall in good shape, and I was super excited to finally start building an e-bike.
I got a Flipsky FSESC75200 Pro V2 VESC with a Flipsky VESC Display. I mounted the Display to the bike to see how it fits.
At this point, I didn’t have anything else. The motor was on the way, and I knew that I needed to reinforce the dropouts so the frame wouldn’t crack. I took some pictures of the frame, which I imported into Fusion 360. After scaling the picture, I spent some time designing a pair of torque arms. At this point, I realized that this is probably the worst frame for a hub motor, but in the end, I got it sorted out.
I got a Surron Throttle from Aliexpress, and here I was test-fitting everything on the handlebars. I also got a thumb-style throttle, which I mounted on the left side, and it is used for regenerative braking.
A few more parts came from Ali. I got a push-button switch for the lights, a 12V buck converter, and I also got a solid-state relay, which I planned to use for switching the lights, but that thing blew up the second I connected it to my battery.
Here is a 3D printed prototype of the first torque arm design. The thing was way too thick to have any thread on the axle left, and I was designing around an M14 axle while the motor actually had an M16, but all of that was fixed later. I had to make these torque arms a little thicker than usual because I can machine aluminum only, and it is much softer than steel.
The motor has arrived! It’s an MXUS 3K Turbo. 135mm dropout to fit my frame. I got a 3T version, not knowing that this motor has too high a KV value for my 27.5-inch wheels. I didn’t know about the different winding versions at this point, and the seller didn’t ask me about the turn count, so I was stuck with the 3-turn version. I was a bit underwhelmed with the power when I installed it, but increasing the phase amp setting helped.
Of course, I couldn’t wait any longer, so I installed it on the bike the same day. I had to file the dropouts a little bit to make the motor fit.
I 3D printed another set of torque arms to confirm everything fits before I machine them. The design is a bit complicated, but I had to make it this way because of the frame's geometry.
Continuing the build in the comments since I can't upload more pics here.
Here are pictures of the bike in its current state. Top speed is above 100 km/h, I never actually hit the limit because it’s just too fast for me. The range is around 100 km with a 72V 20Ah battery. Around 4 hours of charge time.
After deciding that converting my Tomos moped and getting it street legal was too difficult, this build started with a bike I got from Facebook Marketplace for 120 Euros. It’s a Decathlon Rockrider 520. L size, which is a little bit small for me, but I was happy with the price, so I took it. My only requirements were the disc brakes and front suspension. The bike was overall in good shape, and I was super excited to finally start building an e-bike.
I got a Flipsky FSESC75200 Pro V2 VESC with a Flipsky VESC Display. I mounted the Display to the bike to see how it fits.
At this point, I didn’t have anything else. The motor was on the way, and I knew that I needed to reinforce the dropouts so the frame wouldn’t crack. I took some pictures of the frame, which I imported into Fusion 360. After scaling the picture, I spent some time designing a pair of torque arms. At this point, I realized that this is probably the worst frame for a hub motor, but in the end, I got it sorted out.
I got a Surron Throttle from Aliexpress, and here I was test-fitting everything on the handlebars. I also got a thumb-style throttle, which I mounted on the left side, and it is used for regenerative braking.
A few more parts came from Ali. I got a push-button switch for the lights, a 12V buck converter, and I also got a solid-state relay, which I planned to use for switching the lights, but that thing blew up the second I connected it to my battery.
Here is a 3D printed prototype of the first torque arm design. The thing was way too thick to have any thread on the axle left, and I was designing around an M14 axle while the motor actually had an M16, but all of that was fixed later. I had to make these torque arms a little thicker than usual because I can machine aluminum only, and it is much softer than steel.
The motor has arrived! It’s an MXUS 3K Turbo. 135mm dropout to fit my frame. I got a 3T version, not knowing that this motor has too high a KV value for my 27.5-inch wheels. I didn’t know about the different winding versions at this point, and the seller didn’t ask me about the turn count, so I was stuck with the 3-turn version. I was a bit underwhelmed with the power when I installed it, but increasing the phase amp setting helped.
Of course, I couldn’t wait any longer, so I installed it on the bike the same day. I had to file the dropouts a little bit to make the motor fit.
I 3D printed another set of torque arms to confirm everything fits before I machine them. The design is a bit complicated, but I had to make it this way because of the frame's geometry.
Continuing the build in the comments since I can't upload more pics here.
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