Drunkskunk said:
dogman said:
I've often wondered about a stokemonkey setup of a gearmotor for climbing extreme hills. With lots of big vent holes in the covers, and maybe a blower.
Stokemonkey(tm) doesn't get notably warm even after extended loaded climbs (don't know about "stokemonkey type setup"). The motor doesn't operate any less efficiently climbing than on the flat. No need to compromise weatherproofness with vents, and how are you proposing to power the blower? Motors that are forced to operate below half of their unloaded speed tend to get hot, especially if they are low mass. The variable gearing is there to prevent the motor ever from needing to chug along at these low, inefficient speeds.
Drunkskunk said:
I've woundered the same thing. A Stoke monkey type setup would be ideal for a trike project I've been considering So I went and looked up the specs.
Cyclone's 500 watt can be found here:
http://www.cyclone-usa.com/500w_chart.htm
I can't find good specs for the stoke monkey, or rather I've found them to be conflicting. What I have learned is essentualy it was at one time a Clyte 404, but it may now be a 5302 or a clone of it. I'm going to use the math from the 404 as an example. I think you'll see it really won't matter which it is.
Stokemonkey has never used any of those motors. Where are you getting this?
Drunkskunk said:
Numbers are rounded:
If we limit these motors to 36 volts, 20 amps, the Clyte 404 makes 20 footpounds of torque on a 26 inch wheel at 600 rpm. a normal 408 makes 25 footpounds of torque at 300 rpm. As a Stoke Monkey, the 404 with a 2:1 gear reduction would have an RPM of 300, but 40lbs of torque! Nearly double the 408.
Stokemonkey roughly triples (not doubles) the motor torque to the cranks (again, don't know about "stokemonkey type setup"). With common MTB gearing, where the granny gear might be 22:34, the torque can again be multiplied for about 4x the motor torque to the wheel. You can get about 500W mechanical power at slow walking speed, where keeping the bike upright in a straight line is the biggest problem -- not whether your windings are going to melt, not even on a hot day.
Drunkskunk said:
Now, under the same conditions, the cyclone runs at 3000 rpm, and makes roughly 20 pounds of torque. Turned through a reduction of 10:1, thats an output of 300 rpm and 200 foot pounds of torque. 5 times what the Stoke monky does.
Now a few other comparisons. a 404 weighs roughly 15 pounds. the 5302 weighs roughly 25 pounds. the cycclone weighs roughly 5 pounds.
the Stoke Monkey has 3 to 5 times more mass for keeping cool, but the cyclone has 5 times more torque, meaning it will be working 5 times less hard as the Stoke monkey, and generating 5 times less heat.
This is all way, way off. Cyclone's gearmotors (AFTER the noisy gearbox) put out similar amounts of torque as the direct drive motors used in Stokemonkey. Again like Stokemonkey, that torque is roughly tripled to the cranks, or rather the single 44T chainring. But because you can't shift to a smaller chainring (or a bigger), you can't access as wide a gear range as Stokemonkey this side of a $1500 Rohloff (or SRAM DualDrive). Depending on operating conditions (load and grade) this might not be a problem. But if your grade and load get hard enough to force the Cyclone to operate below half its unloaded speed, (pulling big amps if 24V by the way), lots of heat and a loss of power will result. The 1-2% lower gross vehicular weight of the Cyclone v. Stokemonkey will become a liability.
I went ahead and ran the numbers for the 500W Cyclone with the stock 44T chainring and assumed a 34T big rear cog. With that gearing you hit peak power at about 60 crank RPM and 6 MPH, ~600W. That's enough to take a 170lb rider up a 20% grade assuming (only) 50lb. for the bike+batteries+motor. Add an adult passenger or equivalent cargo and you can take only a 10% grade. With Stokemonkey I've pulled 480lbs gross up a 31.5% grade. No place for an adult passenger or equivalent cargo on your e-bike after the battery? Few >20% grades in your charge radius? Then 500W Cyclone kit will likely be fine! On the other hand, if you ride a regular bike when not carrying cargo up steep hills, and you expect your assisted rig to move just about anything you can load up any grade, then Stokemonkey is made for you. We don't offer Stokemonkey for non-cargo bikes because it's highly unlikely you need that much torque without heavy cargo! A short-wheelbase bike will flip over backwards on the kinds of grades (or heavy enough trailer loads) that Stokemonkey can provide torque enough to handle.
Not slamming the Cyclone: it's a lot less expensive and may provide more than enough torque/speed variability for people who will use a car or truck for more serious hauling, plus many people don't want to have to pedal (and will accept the reliability hit of multiple freewheels). Any variable motor gearing is better than none. But Stokemonkey on a cargo bike gives families living in hilly areas more to work with in terms of torque/speed flexibility, quiet and cool running, all-weather ready: it's still the only motorized vehicle we've ever owned (after the hot-rodded Giant LaFree (a lot like Cyclone in drivetrain layout) blew up after ~5K miles in 2003: http://clevercycles.com/bike/cp/scale.html ). It's paid for itself many, many times over in never needing to own a heavier motor vehicle for our family's needs, not even in San Francisco. Here in flatter Portland, frankly, we ride assisted for fewer than 2% of trips: only the really big provisioning or passenger hauls more than 10 miles.
