|one stage reduction for a second |
stage reduction to the drive wheel
Washington state e-bike laws are not adequate for heavy duty cargo bicycles.
This means that your electric bike may need a speed sensor to turn off the motor if using a gear fast enough. ie: the human powered gears on the bike when using a Mid Drive kit, or just a Hub motor, or any motorized gear ratio, in conjunction with the motor's maximum RPM, that is enough to move the bike faster than 20mph on flat land.
“The electric-assisted bicycle's electric motor must have a power output of no more than one thousand watts, be incapable of propelling the device at a speed of more than twenty miles per hour on level ground, and be incapable of further increasing the speed of the device when human power alone is used to propel the device beyond twenty miles per hour.”
And while your at it you may as well install a sensor on the crank arms to activate the motor to make sure they don't classifie your bike as a Moped.
See State electric bicycle laws on Wikipedia.
Remember, electric motor power specifications are in terms of 'rated power' not the actual power you run it at. So a 500W MAC can easily be run at 1500W although it will heat up and eventually overheat with this overrated operation. But legally, it's still only a '500W' motor. Do not be confused by comments about testing the output of a motor - the traffic statutes are written to facilitate field enforcement - so many rated Watts - not the actual hp output of a motor which an officer could not possibly measure. He needs to be able to make a decision based on only a quick look at a motorcycle model plate or wattage sticker - hence the way the statutes are defined (of course there are some really confused state statutes out there, but that's another matter...)
Two speed gear boxes for bicycles