Tooling around downtown on a personal electric vehicle is a lot of fun, but it is even better when you do like [James Dietz] and ride on your own 3D-printed electric scooter. As one of the entries for the Hackaday Prize, RepRaTS (Replicable Rapid prototyper Transportation System) has a goal of doing for scooters what the original RepRap project did for 3D printing: provide a user-friendly design base that you can extend, modify, and maintain. It doesn’t even require power tools to build, other than, of course, your 3D printer.
The design uses threaded rods and special plastic spacers made to hold a large load. The prototype is deliberately oversized with large hub motors, with the understanding that most builds will probably be smaller. As you can see in the video below, the scooter seems to go pretty fast and handles well.
The build is very much of the “parts laying around the shop” genre. An old skateboard deck was fitted with nice rubber scooter wheels and a set of handlebars thanks to a series of 3D printed parts. Unfortunately, the first revision had problems with flex in the skateboard deck, which isn’t designed to take the full weight of an adult human standing on one leg. Another skateboard deck was pressed into service, reinforced with a metal pipe for added strength.
From there, [Alexandre] set about creating a front-wheel-drive system using a power drill, several shaft extensions, and a right-angle drive. Clamped to the handlebar tube, the drill’s trigger is controlled via a twist throttle linked up by a string.
It’s not the easiest scooter to ride, with a bit too much torque from a standing start and somewhat scary handling characteristics at times. However, we’re sure with some practice and some tweaks, [Alexandre] will have a useful ride on his hands. If you prefer something wilder, however, consider this walking scooter build. Video after the break.
When [Vitor Melon] found out there was a custom firmware (CFW) available for his Xiaomi Mijia M365 Pro electric scooter that would increase his top end speed, naturally he installed it. Who wouldn’t want a little more performance out their hardware? But while the new firmware got the scooter running even better than stock, he does have a cautionary tale for anyone who might decide to ride their Mijia a bit harder than the fine folks at Xiaomi may have intended.
Now to be clear, [Vitor] does not blame the CFW for the fact that he cooked the control board of his Mijia. At least, not technically. There was nothing necessarily wrong with the new code or the capabilities it unlocked, but when combined with his particular riding style, it simply pushed the system over the edge. The failure seems to have been triggered by his penchant for using the strongest possible regenerative breaking settings on the scooter combined with a considerably higher than expected velocity attained during a downhill run. Turns out that big 40 flashing on the display wasn’t his speed, but an error code indicating an overheat condition. Oops.
Results of the PCB repair.
After a long and embarrassing walk home with his scooter, complete with a passerby laughing at him, [Vitor] opened the case and quickly identified the problem. Not only had the some of the MOSFETs failed, but a trace on the PCB had been badly burned through. Judging by the discoloration elsewhere on the board, it looks like a few of its friends were about to join in the self-immolation protest as well.
After a brief consultation with his graybeard father, [Vitor] replaced the dead transistors with higher rated versions and then turned his attention to the damaged traces. A bit of wire and a generous helping of solder got the main rail back in one piece, and he touched up the areas where the PCB had blackened for good measure.
A quick test confirmed the relatively simple repairs got the scooter up and running, but how was he going to prevent it from happening again? Reinstalling the original firmware with its more conservative governor was clearly no longer an option after he’d tasted such dizzying speeds, so instead he needed to find out some way to keep the controller cooler. The answer ended up being to attach the MOSFETs to the controller’s aluminum enclosure using thermal pads. This allows them to dissipate far more heat, and should keep a similar failure from happening again. You might be wondering why the MOSFETs weren’t already mounted this way, but unfortunately only Xiaomi can explain that one.
Before it was officially unveiled in December 2001, the hype surrounding the Segway Human Transporter was incredible. But it wasn’t because people were excited to get their hands on the product, they just wanted to know what the thing was. Cryptic claims from inventor Dean Kamen that “Ginger” would revolutionize transportation and urban planning lead to wild speculation. When somebody says their new creation will make existing automobiles look like horse-drawn carriages in comparison, it’s hard not to get excited.
Dean Kamen unveils the Segway
There were some pretty outlandish theories. Some believed that Kamen, a brilliant engineer and inventor by all accounts, had stumbled upon some kind of anti-gravity technology. The kids thought they would be zipping around on their own Back to the Future hover boards by Christmas, while Mom and Dad were wondering what the down payment on a floating minivan might be. Others thought the big secret was the discovery of teleportation, and that we were only a few years out from being able to “beam” ourselves around like Captain Kirk.
Even in hindsight, you really can’t blame them. Kamen had the sort of swagger and media presence that we today associate with Elon Musk. There was a general feeling that this charismatic maverick was about to do what the “Big Guys” couldn’t. Or even more tantalizing, what they wouldn’t do. After all, a technology which made the automobile obsolete would change the world. The very idea threatened a number of very big players, not least of which the incredibly powerful petroleum industry.
Of course, we all know what Dean Kamen actually showed off to the world that fateful day nearly 20 years ago. The two-wheeled scooter was admittedly an impressive piece of hardware, but it was hardly a threat to Detroit automakers. Even the horses were largely unconcerned, as you could buy an actual pony for less than what the Segway cost.
The last few years have seen a huge rise in the prominence of electric scooters. Brushless motors, lithium batteries, and scooter sharing companies have brought them to the mainstream. However, electric scooters of a variety of designs have been around for a long time, spawning a dedicated subculture of hackers intent on getting the best out of them.
One such hacker is yours truly, having started by modifying basic kick scooters with a variety of propulsion systems way back in 2009. After growing frustrated with the limitations of creating high-speed rotating assemblies without machine tools, I turned my eye to what was commercially available. With my first engineering paycheck under my belt, I bought myself a Razor E300, and was promptly disappointed by the performance. Naturally, hacking ensued as the lead-acid batteries were jettisoned for lithium replacements.
Over the years, batteries, controllers and even the big old heavy brushed motor were replaced. The basic mechanical layout was sound, making it easy to make changes with simple hand tools. As acceleration became violent and top speeds inched closer to 40 km/h, I began to grow increasingly frustrated with the scooter’s one glaring major flaw. It was time to fix the brakes.
Like many mechanically inclined parents, [Tony Goacher] prefers building over buying. So when his son wanted an electric scooter, his first stop wasn’t to the toy store, but to AliExpress for a 48V hub motor kit. Little did he know that the journey to getting that scooter road-ready would be a bit more involved than he originally bargained for.
She cannae take anymore, Captain
Of course, to build a motorized scooter you need a scooter to begin with. So in addition to the imported motor, [Tony] picked up a cheap kick scooter on eBay. Rather than worrying about the intricacies of cleanly integrating the two halves of the equation, he decided to build a stand-alone module that contained all of the electronics. To attach it to the scooter, he’d cut off the rear wheel and literally bolt his module to the deck.
[Tony] goes into considerable detail on how he designed and manufactured his power unit, from prototyping with laser cut MDF to the final assembly of the aluminum parts that he produced on a CNC of his own design. It’s really a fantastic look at how to go from idea to functional device, with all the highs and lows in between. When the first attempt at mounting the battery ended up cutting into the 8 Ah LiPo pack for example, and treated his son to a bit of a light show.
With all the bugs worked out and his son happily motoring around the neighborhood, [Tony] thought his job was done. Unfortunately, it was not to be. It turned out that his bolt-on power unit had so much kick that it sheared the front wheel right off. Realizing the little fellow didn’t have the fortitude for such electrified exploits, he went to a local shop and got a much better (and naturally much more expensive) donor for the project.
It’s here that his modular approach to the problem really paid off. Rather than having to redesign a whole new motor mount for the different scooter, he just lopped the back wheel off and bolted it on just as he did with the cheapo model. What could easily have been a ground-up redesign turned out to be a few minutes worth of work. Ultimately he did end up machining a new front axle for the scooter so he could fit a better wheel, but that’s another story.
[Adam Zeloof] (legally) obtained a retired electric scooter and documented how it worked and how he got it working again. The scooter had a past life as a pay-to-ride electric vehicle and “$1 TO START” is still visible on the grip tape. It could be paid for and unlocked with a smartphone app, but [Adam] wasn’t interested in doing that just to ride his new scooter.
His report includes lots of teardown photos, as well as a rundown of how the whole thing works. Most of the important parts are in the steering column and handlebars. These house the battery, electronic speed controller (ESC), and charging circuitry. The green box attached to the front houses a board that [Adam] determined runs Android and is responsible for network connectivity over the cellular network.
To get the scooter running again, [Adam] and his brother [Sam] considered reverse-engineering the communications between the network box and the scooter’s controller, but in the end opted to simply replace the necessary parts with ones under their direct control. One ESC, charger, and cheap battery monitor later the scooter had all it needed to ride again. With parts for a wide variety of electric scooters readily available online, there was really no need to reverse-engineer anything.
The motors in these things are housed within the wheels, and have frankly outstanding price-to-torque ratios. We’ve seen them mated to open-source controllers and explored for use in robotics.
