I have been absent from the forum for awhile. I have been waiting for Astro 3205 motors, which are now here, and I have been getting a 1000 watt midrive, with a true double freewheel, into production. The 1000 watt midrive is out of the machine shop and in assembly. I will publish that drive in a separate post.
First, the great news! Josh Kerson successfully climbed Pikes Peak with the 750 watt system mounted on a Yuba Mundo cargo bike. He renamed the drive system, " The Rocha Mountain Drive " (my last name ). I think I will adopt that name. His story:
http://endless-sphere.com/forums/viewtopic.php?f=3&t=31490
Note the 60 amp hour, 24 volt, batteries from Elite Power Solutions.
I was very concerned about the motor overheating at altitudes above 9000 ft. The air is considerably less dense at that altitude, and air cooling less effective. I asked Josh to keep the motor operating at high rpm, and limit power to 500 to 600 watts ( you can do both because of the thru the gears drive system). In this operating region the motor is at the upper end of the maximum efficiency range. Josh reported that the motor never got over "warm to the touch".
Some other news, Josh has run the system, quite successfully at 36 volts. With a 52 tooth chain ring (the largest readily available) on the primary drive side of crank, the max cadence is 105 rpm. The result is a top speed of 30 mph. Note that you will need a battery capacity of at least 20 amp hour.
A complete system, including motor, gearbox, structure, freewheeling crank set, bottom bracket, primary chain ring, and primary chain, is now available for $1850.
