I am very happy to find the initial design gives me about 16 watts (11.3 Volts DC @ 1.4 Amps) at the max speed my power drill can run the alternator. I’m not sure how fast that is in MPH or RPM, but I estimate it to be between 15 and 20 MPH! These measurements were taken with the rectifier and filter circuit and an 8 Ohm load. And with 1″ standoffs, it’s got an air gap of about 1/2″ (the magnets are 1/4″ thick), which leaves lots of space between the magnets and coils.
I spent some time optimizing the air gap to get it as small as possible without risk of rubbing the magnets against the coils. Once again I am thrilled! After removing about 7/64″ from the air gap, I’m now getting 
26 Watts (14.4 Volts DC @ 1.8 Amps) out of the alternator. That’s a 39% increase in output from just shoring up the extra space! Most importantly, this means I’ve met or possibly exceeded my design goals for output power.
I fashioned a new fork assembly for the alternator and attached it to the Version 1 mount. It fits nicely and stays centered.
The real-world test results are in and I’m getting 20 Watts/12 Volts at 16 MPH. This could not have worked out better! It powers my halogen bike light perfectly.
I finally had a chance to ride with a load and multimeter on the output of my alternator. I was able to sprint up to about 30 MPH (it’s a mountain bike with street tires!) and read 23 volts DC into the 8 Ohm load. That’s more than 66 Watts! Holy…! I couldn’t feel the alternator drag very much. And I got up to the fastest speed I could pedal on flat ground. I measured the output at a number of speeds up to 30 MPH and with 8 Ohm and 20 Ohm loads. I need to test at 40 and 50 MPH on a major downhill run to see the highest possible output levels.
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