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.
Stop Me If You’ve Heard This One Before
The Razor E300 comes stock with a band-brake, akin to an inside out drum brake. When the brake lever is pulled, the brake cable pulls on a lever which tightens the band around a drum attached to the driven wheel at the rear of the scooter.
Band brakes are cheap to make and can be effective in some applications. Unfortunately, the cheap stamped metal shell used on the E300’s brake is prone to deformation, causing misalignment between the band and drum. Simply riding carelessly up and down bumpy footpaths is enough to cause problems. Typically the brake ends up either scraping continuously on the drum, wasting power, or is unable to effect enough friction to slow the scooter down. Either way, it usually can’t lock the rear wheel for doing awesome skids and that’s a shame. With electric scooters having a somewhat uncool vibe akin to the Segway, the impact of not being able to do the aforementioned awesome skids cannot be understated.
Stepping Up to Disc Brakes
Like all variants of drum-type brakes, the band brake pales in comparison to the superior disc technology. For automotive and large-scale applications, this is primarily due to improved heat dissipation and easier maintenance. In our case, other factors are more important — bicycle disc brakes are cheap and readily available on eBay, and with the right installation, shouldn’t suffer the same issues with rubbing or lack of stopping power. A series of discs in various sizes, along with calipers and mounting brackets were sourced for under $50 AUD. The calipers can be mounted out of the way of obstacles, and the right sized disc should also be safe from impacts.
Despite going through years of formal engineering training, I’ve never been one to enjoy drawing up a design before getting down to work. Instead, after letting the parts marinate in their shipping boxes for 18 months, I finally took them out on a sunny winter’s day and began staring at the back of the scooter until a plan came together.
Rather elegantly, the drum for the band brake serves nicely as a mounting surface for the brake disc. By removing the friction surface with an angle grinder, I was left with a nice flat plate attached to the axle, to which I would bolt on the brake disc. With a slight modification to the disc’s mounting lugs to clear the centre of the axle, it slid on to the hub and was attached with three M4 bolts.
A ruler was used to check that the disc was perpendicular to the axle and aligned properly. Spacers were required to be added to the rear assembly to make up for the missing width of the original band brake assembly; in this case, a series of three half-inch washers did the trick.
The caliper was more difficult, requiring the fabrication of a custom bracket to marry the caliper mounting hardware with the frame of the E300. A piece of steel L-angle was massaged into the right shape to bolt to the rear frame upright. Plate steel would probably have sufficed, but a hacker often uses what falls first to hand. Getting the mount right was crucial to ensure the brakes worked effectively, as misaligning the caliper to the disc would cause the pads to wear prematurely and slow the scooter down. Thankfully, the mounting hardware that ships with the calipers allows some adjustment of the final position, meaning the bracket doesn’t have to be made to a particularly high level of accuracy.
With everything bolted up, all that was left to do was replace the original brake cable with one long enough to reach the rear caliper, which was mounted further aft than the original band brake. The original brake lever was also of cheap construction and was replaced with a nicer all-metal unit also sourced from eBay.
How Does It Perform?
After some initial headaches with the original plastic brake lever falling to pieces, the new disc brake setup performed brilliantly. Thick, fat, high speed skids are now easy to perform even on grippy asphalt surfaces. There is little to no noise from the brake when not in use, which is a huge improvement over the continually screeching band brake. This has the side effect of greatly improving the scooter’s stealth capabilities. Dynamically, it’s a much better experience, though the lack of a front brake is still felt when descending slippery muddy hills.
The scooter is now a joy to ride, and it’s an upgrade I wish I’d completed much sooner. Anyone handy with a power drill and grinder should be able to complete the switch in a weekend. Hopefully this hack inspires you to mod your own vehicles for ever greater performance, and to those that get stuck in, I look forward to seeing you on the trails!