1000 km

Other numbers:

• 99 hours, 42 minutes (total time)
• 10.1 km/h (average speed)
• 202 days (ownership)
• Several hundred trips enabled by the Firefly
• Dozens of friendly compliments
• 1 significant mechanical issue:
• Shims for the wheelchair attachment are slippery.  If used, inspect them regularly.
• 1 tip over accident
• while going around an illegally parked truck.  Always cross drop-offs at a perpendicular angle, even when annoyed.
• 1 worn out front tire
• 1 flat rear tire (from a thumb tack)
• 0 collisions
• 0 empty batteries

Need for speed

Speed kills, but it also thrills.  The converse is also true:  Slow is safe, but oh-so-frustrating.  My manual wheelchair travels slowly because steering is problematic, shoulder power is limited, and obstacles abound.  Amazingly, the Firefly electric front wheel attachment solves these problems.  Power at the wheel is up to 350 Watts, similar to a professional bicyclist and over 10 times more than most people can get out of their shoulders.  The handlebar allows for proper steering, and the longer wheelbase improves handling on non-ideal surfaces, which are almost all of them in my city.  It brings out the joy of riding something fast, which must have been etched into our DNA long ago.

With speed and power comes danger!  Go too fast through a turn or cross a drop-off at an angle, and you gain a new appreciation for the tippiness of high center-of-gravity tricycles.  Someone more adventurous than me has maybe perfected the technique of balancing on two wheels to corner fast without the need for body English.  Hopefully they were wearing elbow pads.

Credit: Martin Pettitt originally posted to Flickr as Race Of Champions (CC BY 2.0)

But even straight-line speed is fun and helps eat the miles if you're going somewhere.  My first impression of the Firefly was that it's pretty darn slow.  Releasing the wheelchair's rear brake locks helped (duh), as did reading the instructions to understand that the device starts in 1st "gear", which has a low speed limit.  Setting the "gear" to 5 raises the top speed to 20 km/h (12 mph), already pretty fast if you're travelling on a sidewalk.  That's still an artificial restriction, which can be removed by adjusting the LCD controller.  Then the limit comes from the motor and battery voltage, and a fully charged battery reaches 24 km/h (14 mph).

There is a saying about all-wheel-drive cars, that they just get you to your accident faster.  Be that as it may, it would be nice to go faster than 24 km/h on smooth and clear pavement.  One option is the Phaserunner motor controller whose manual describes "Field Weakening for Speed Boost".  Apparently, the motor coils can be energized in a tricky way to gain 15-20 % in speed, at the expense of battery drain and maybe motor stress.

The Firefly's motor controller is a circuit board inside the battery base that is connected to the wiring harness.  All of those connections will make it hard to replace.  In the end, it might be more effective to replace everything (motorized wheel, the battery and maybe controller) with higher voltage parts that can go faster.  Update:  internet comments claim that most 36 V motors can operate with 48 V batteries.  I'm curious if anyone has done this already.  This could be a good project for the winter when I'm snowed in.  The cat's meow would be to also drive the rear wheels.

Parking brake

My Firefly came with a button on the right brake lever that you could press to hold the brake for parking.  This feature is great, because you can stand the Firefly up in a corner when not in use, or set the brake at a traffic light and use both hands for your phone, to dig in your bag, etc.  This is also a safety feature, because once the parking brake is engaged, accidental throttle activation has no effect.  But after about 500 km (300 miles), the button broke, and all of the parts scattered around!

What's left of the original brake-hold button.  The spring is missing and the bottom head broke off.

So I contacted the manufacturer (Rio Mobility), and they wrote that others were having the same problem, and their "solution" was to remove the brake-hold feature!  No warranty fix is possible.  I can sympathize, since the company probably doesn't want to be in the brake-lever engineering business.

But I have an affinity for mechanics, and giving up on this little bit of sweetness was not so satisfying.  Clearly, the button breaks because every time you release it, a spring causes it to pop up and smack into the brake housing with large peak forces.  The poor button can't withstand the repeated violence, and the part fails.  This seems like a design flaw, but most users of these brake levers are on bicycles or recumbents, and they won't use the brake-hold enough to cause failure during the warranty period.

After some experimenting, I ordered a replacement brake lever (Sun BL46K) for $13 that includes a brake-hold button.  This has a slightly higher quality feel than the original, but the brake-hold mechanism appears to have the same not-so-good design.

Fortunately there is a simple fix!  You can take a small cushioning washer like McMaster 93650A100 and stretch it over the bottom of the brake-hold part like a rubber band.  Now the brake lever can last a long time, because the peak forces that caused the part to fail are much lower.  Feature restored!

The red oval shows where the cushioning washer (which is transparent) was stretched over the bottom of the brake hold button.

Update (October, 2021):  Over 6000 km later, the brake-with-rubber-washer works as well as ever.  This page will be updated if a problem develops.