Stokemonkey Human Electric Hybrid Drive
Stokemonkey is an electric motor assist kit for Xtracycle® Sport Utility Bicycles. Xtracycle gives almost any bike amazing cargo capacity, and Stokemonkey gives you the power to haul it over mountains or swiftly across town.
Most electric bike products are designed for people who don’t, won’t, or can’t ride regular bicycles. Stokemonkey is different. We don’t believe in replacing human power with electricity; we believe in replacing cars for tasks that even the strongest cyclists seldom if ever choose to handle without a car. Developed in a car-free household, Stokemonkey is for fellow riders who want to become more completely independent of cars in their daily lives.
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It’s for people who want to transport their spouse, their child, and their camping gear a dozen hilly miles offroad and back. It’s for picking up a friend with two checked bags at the airport. It’s for your knees. And if there are thousands of vertical feet between your farmers’ market and your family kitchen, now you can pedal those couple dozen melons home without qualifying for charitable sponsorship.
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It’s for people who commute twenty-five miles each way, can’t shower at the office, and never want to sit in traffic. It’s for taking the lane without slowing motorists down.
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It’s for people who understand that vehicles heavier than what they carry are inefficient almost by definition; that fiddling with their fuels comes at sustainability problems from the wrong end, and ignores the social and health problems of car dependence in built environments altogether.
How it works
When you want help, you turn a variable-speed throttle on the handlebars to engage the motor. The motor drives the pedals, just like the stoker of a tandem bicycle helps the captain. You cannot use the motor without pedaling along, but you can pedal normally without any added resistance, and coast whenever you let go of the throttle. As you shift gears to maintain comfortable pedal speeds, you keep the motor operating between its most powerful and most efficient speeds, for more than four times the torque, higher top speeds, and better range than similar motors driving wheels directly.
Stokemonkey uses a brushless motor with no internal moving parts other than sealed bearings, for maintenance-free, cool, virtually silent operation. All drivetrain parts subject to wear are standard bicycle components for decades of service. Stokemonkey is powered by 36-volt rechargeable batteries you carry like any other cargo.
A patent is pending on the Human Electric Hybrid Drive™.
Performance
Top speed can exceed 30 MPH on level ground, and 20 MPH up modest hills, or be restricted to improve range and conform to local laws. Stokemonkey’s exceptional torque moves heavy loads off the line quickly, lets you walk your grocery-laden bike effortlessly up staircases, and enables you to haul adult passengers up grades exceeding 30% — the steepest streets in the world. Powered range is limited only by the amount of battery packs you carry, but to leave ample room for cargo and remain light enough for pleasant unassisted pedaling, Stokemonkey is generally most useful for trips up to 50 miles between recharges.
| Peak power | Peak efficiency | |
|---|---|---|
| High mode | Cadence 80 : 430W | Cadence 120 : 275W |
| Low mode | Cadence 60 : 340W | Cadence 90 : 190W |
It has two power settings or modes, high and low. Low mode offers the best range, and optimally supports pedal speeds (cadences) of about 60-80 RPM. High mode is for people willing to trade some range for more power; it’s best with faster cadences. Users typically set the mode to match their dominant style or performance goals, not changing it while riding.
Power figures are extrapolated from data supplied by the motor manufacturer, field experience, and physics models; they are cited as approximates in good faith. Extreme climbing examples assume suitable low gearing; 34T rear cog with 26″ wheel yields >100 foot-pounds of torque. Power output changes with cadence, not wheel speed like most electric bikes. At full throttle, high mode delivers 430 watts near cadence 80, tapering to 275W near 120. Low mode delivers 340W at 60, dropping to 190W at 90. For reference, it takes approximately 100W to ride a normal bike on level ground at 14 MPH, while Lance Armstrong can put out 500W for up to twenty minutes. But Lance weighs five times as much as Stokemonkey.
Stokemonkey adds 21 pounds to your Xtracycle before batteries, which start at about 12 additional pounds. Gross vehicular weights start well below 70 pounds, not unlike many loaded touring bikes.
Cost
Complete Stokemonkey kits start at $1350.00, with numerous options and upgrades. You provide the bike and the Xtracycle FreeRadical attachment; we provide the rest. Generally, we don’t sell kit components separately, but you may omit parts for which acceptable substitutes exist. See the Order form for more complete information.
Stokemonkey pays for itself every few months when used to replace a typical car. More importantly, you get to ride a bike more often, even when you need to haul your family, groceries, or just your unbearably smug self further or faster than you would on a regular bike.
Guarantee & warranty
Stokemonkey comes with a six-week money-back guarantee, and a two-year warranty against defects in materials and workmanship. Batteries are warranted separately for six months. We advise you to purchase an Xtracycle, set it up, and become accustomed to it before ordering, so you will have the full guarantee period to install and evaluate Stokemonkey.
