Whats even cooler than the single ratio 'toughbox' series is the narrow and small enough for ebike mounting
$239 2-speed dog-shift spur-gear box with 2.56:1 ratio difference betweeen 1st and 2nd gear, and a final reduction ratio of 30.1:1 and 11.8:1 respectively. This gearbox weighs a manageable 4lbs and can handle
at least 4.84Nm of input torque given that it is designed as standard to accept two of
these at it's input. That's a tad over 3kW@6krpm!! Well sized for many RC eBike builds!
http://files.andymark.com/Super-Shifter-Assembly-Instructions.pdf
http://files.andymark.com/super-shifter-asm.pdf
So in conclusion this gearbox seems to tick all of the essential boxes that we have been looking for in an affordable 2spd eBike gearbox.
-It seems to be able to handle at least 3kW (@6krpm - typical RC motor speed)
-It's available off-the-shelf
-it's affordable for eBike use
-It's light enough for eBike use
-It's small enough for eBike use
-With a belt/chain input sprocket and inline parallel mounted motor, it has a narrow enough form factor to not foul with a bike's Q-factor (lateral crankarm spacing)
-It's available with a gear ratio spread that's about right (2.56:1)
-It's enclosed gears keeps dirt out and gears well lubed (it may be oil fillable when gasketed if it isn't already - I can't tell from the documentation/drawings)
-It's setup for servo gear shifting
-Replacement parts appear to be readily available
The only initial downside I can see is - due to using spur gears, its gonna be noisy....
So, who's gonna be the first guinea pig to try one of these with an RC build?