Just as February is winding down, electric bicycle industry leader Justin Lemire-Elmore made a couple of big announcements on the home page of their website. First, the “Edgerunner” cargobike that they designed in a partnership with Naked bikes and also Xtracycle is now finally for sale to the public (including an optional rear hub-motor).
At the same time, they gave the public a peek at the electric drive system that they have been developing as an option, and as anyone who has ridden a loaded cargobike knows, cargobikes and NON-hub electric-assist go together like apple pie and ice cream. Here’s the news release:
“Stokemonkey Kit Update:
We mentioned the 2nd generation Stokemonkey motor last year thinking it would just be a short while before getting the remaining hardware piece sorted out with CleverCycles in order to re-release the kit. But then something unexpected happened. Partway through this process we worked out an elegant use of the motor on a right-hand drive with a Patterson crankset in a way that doesn’t force the cranks to turn.
So the complete Stokemonkey kit is now getting a hardware redesign in order to accommodate both classic left side AND freewheeling right side installations. We don’t expect the full package to be ready until late March or early April now, but we have listed the motors only for sale for people either making a DIY mount or replacing the motor on an existing Stokemonkey setup.”
For those of you who are unfamiliar with the “Stokemonkey” kit, it was a ground-breaking design from Clevercycles.com that took a de-spoked hubmotor and mounted it as a non-hub. The original kit used a Crystalyte 407 (40mm wide stator coils, 7 turns of copper wire per stator tooth), which is considered a fast winding (providing high RPMs from low volts). A motor like this would normally be mounted in a small 20-inch wheel, because in a larger diameter wheel, it would have a tendency to bog down. By using this motor as a non-hub, it could be spun very fast, and then use external gearing to reduce the RPMs down to wheel speed.
As to the memorable name, a Stoker is someone who shovels coal into a steam engine, and as a result, a two-person tandem bicycle in the late 1800’s designated the front cyclist as the “captain” [of the ship], and the rear cyclist is the stoker, since he didn’t steer, but simply added power.
The Stokemonkey used off-the-shelf components where ever they could, and as you can see from the picture, the motor drives a chainring that’s attached to the left side of the bottom-bracket. This leads to one of the only complaints of the original kit. The pedals must be moving when the motor is on, and some customers would have preferred for the pedals to have the capability of being still when under power.
This past year, freewheeling cranksets have become more well-known (like on the GNG and the EGO). Although the non-freewheeling cranks on the Stokemonkey would be very robust and long-lasting, many customers still want a freewheeling crank option, even if it means occasionally replacing a worn freewheel.
One clear benefit to the original Stokemonkey kit was that the 407 was known to be one of the quietest motors ever used by an E-bike kit. geared hubs of the same size (like the MAC that we are currently developing here) has a slight whine from the internal gears. The popular large diameter direct-drive hubs have a slight rumble when under acceleration. I believe that this is due to the square sine wave of the common controller pulses (it causes a sudden on/off to the power pulses), and also due to the large side plates of common hubs (such as the common 9C) acting as a resonator (like the box of an acoustic guitar). But…for whatever reason, no other motor that we know of will be as quiet on a bicycle as the 40X-series.
The one place where the Stokemonkey really shined, was that…it gave the motor the ability to use the bikes gears!, and that meant that it could always be kept in the upper range of its RPMs. You would have to downshift to a lower bicycle-speed on a steep hill with a heavily loaded cargobike, but…this compact motor could do it easily without overheating. Even if you don’t have any steep uphills on your commute, giving the motor some gears to use will provide a greater range to whatever battery you are using. And a low peak amp-draw doesn’t just provide longer range each day, it also provides a longer battery life measured in many more months before needing to buy a new battery.
On a recent forum post, Justin said this about the improved motor:
” It’s actually one of the newer generation of Stokemonkey motors based on the semi-generic 154mm [diameter] Chinese hubs. Similar the Crystalyte ‘G’ series but with 40mm wide stator and magnets rather than 25mm [like the G-series]. They’re about the same overall size as the old 40X series but are more efficient and smoother running”
The long chainline and serpentine path of the Edgerunners new motor configuration, may seem odd at first, but I believe there are benefits to it. Most current bottom-bracket (BB) drives use a trials-bike freewheeling crank, where a BMX freewheel is attached to a threaded protrusion on the right crankarm, and two chainrings are attached to the FW. The motor drives one chainring, and the other chainring drives the rear wheel. This creates twisting side-loads inside the FW that it was not designed to handle. Their lifespan is acceptable when used this way, but when used in their normal mounting at the rear wheel, they last many years.
The long and odd chainline means the freewheeling BB will not experience any sideloads and will last many years. The Patterson crankset is a fully housed and lubricated planetary gearset that provides two speeds at the BB. Their website doesn’t mention the crankset as freewheeling, but Justin clearly states that the system (as he has configured it) can be powered without the pedals moving.
Endless-sphere member Rassy experimented with a similar configuration back in May of 2010, and it definitely caught my interest. The large 9C that he used was a real hot rod in the way he configured it. I was inspired by it, but I recognized that the slightly smaller MAC geared hub would be much easier to find the space to mount it on most conventional frames.
ebikes.ca states that they plan to offer the E-Edgerunner with the option of a NuVinci transmission in the rear wheel, or a 9-speed external gear cluster. You can specify a 36V or a 48V battery. Available color options are listed as “Black, Blue, or Mocha [suede]”. Depending on options chosen, prices range from $3695 for the 36V kit using an eZee rear geared-hubmotor, or $3995 for the new Stokemonkey, with the Patterson crankset and the NuVinci transmission.