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Electric BMW R75/7
I've been kicking around the idea of building an electric motorcycle (EM) for several years. I got into Elec-Tracs to
get my feet wet on EVs. I hoped to build an EM based on a BMW and have been doing a low level search. I guess this is going
to be a low-tech blog.....
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| Donor Bike |
Jan 2008
A friend from the local BMW Vinatge group came though with a great donor; A '77 R75/7 that he wanted the motor and transmission
out of. It's in real good shape mechanically so I won't have to mess with the chassis too much.
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| Motor and Batter Mounts |
For a motor, I'm hoping to use one of the extras from my stash of Elec-Tracs. The obvious choice was a traction motor
from an E12S or E20, but it turns out the snowblower motor may be a better candidate as it is more powerful and it's a series
motor, which is probably better suited to my needs. I took it out of the blower and pulled it apart. It's in great shape.
For a controller, I bought an Alltrax AXE 4845 off ebay.
I'm starting to buy parts. I fabricated a motor-driveshaft coupling from a chain sprocket. This will determine where
the motor will sit. I also need to make a housing to cover from the motor to the end of the coupling. A rubber boot covers
between that and the driveshaft since the driveshaft tube has oil in it.
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| This is the first shot (right side) |
03feb2008
I finished the motor mount and battery lower frame. I was able to bolt it in without changing the original frame - just
in case. This will support 3 surplus Hawkers I bought to test things out with. Hopefully they will work well enough to get
data to figure out what I really want for batteries (and maybe motor).
mar2008
I got everything cobbled together and took it out. Definately under-powered. I need a bigger motor or gear reduction.
Since I don't have good data on what I really need, I'll find a (hopefully) cheap tranny to let me try out some different
gear ratios and get some real data.
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| Rearranged after adding transmission (left side) |
apr2008
I found an R65 tranny to try. I had to completely rethink the layout since the tranny takes up a lot of valuable space.
I threw this setup together so I can try it out. I've run it in first gear and it certainly starts up better. So, since 1st
gear is about 4:1, that means I need a motor with at least 4 times the power to run without a transmission; which is what
I really want.
AXE monitor software and manual
In order to get data from my test setup I wrote code for my Palm PDA to display and log the data availble from the Alltrax.
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| AXE monitor on Palm Vx |
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