My homemade bicycle motor, version 1

Lebowski

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beautiful Zurich, Switzerland
Since I was pulling apart my motor anyway I thought I'd make some pictures to show how it's built.
The motor is meant to power a bicycle. Here in Switzerland the limit for electric bikes is 250 W, above
that it doesn't count as a bicycle anymore and it gets messy in the legal department (you need a
licence plate, insurance etc etc). The motor will be mounted on the bikes luggage carrier (so above the
rear wheel) with a chain running down to the left side of the wheel. In the wheel I plan to attach a
sprocket to the spokes.

This is the assembled motor:DSC00299_scaled.JPG

The motor consists of two 'magnet plates' sandwiching a 'coil plate':DSC00300_scaled.JPG

The coils are embedded (using expoy glue) in a tough 5mm thick acryllic glass plate:DSC00302_scaled.JPG

The magnets plates are rotating on a standard Shimano Deore rear axle. This is an easy way, if you don't have a lathe
and top mechanical building skills, to build an axle for a motor as it provides the bearings for the motor to run on, it
has a freewheel and the standard splines so its easy to attach a (low-tooth) sprocket for chain-drive:DSC00304_scaled.JPG

Here you can clearly see that the rotor is attached to the axle with 3mm screws through the spoke holes:View attachment 2

With the top magnet plate removed:View attachment 1

With the coil plate removed:DSC00308_scaled.JPG

This last picture shows the 25mm diameter magnets stuck to a 5mm thick iron backplate. The iron backplate is actually
a bunch of wedge shaped pieces cut (with a hacksaw, lots of blood sweat and tears) from a bar. The wegde pieces are
attached with screws to the aluminium holder.

The engine was built using simple tools, a drill press, a jigsaw and a hacksaw. When mounted to the bike it will need around
60V for 25 km/h. Coil resistance per phase is 0.65 Ohm, inductance 300 uH. It has 14 magnet pairs over 12 coils, coils
are Y-connected. The plastic coil plate is the most difficult bit to make, I had to make a small winding rig and clamping the
coils soaked in glue was messy. The plastic looks feeble but is actually very tough and can stand temperatures up to
190 degrees Celcius (way past the de-magnitising temperature of the magnets). The attachement of the coils to the plastic
is also very solid, the glue is rated at 1200N per cm^2, each coil is attached over 6 cm^2.I tried pressing out a coil on a test
pieces but (using just my thumbs) it's impossible. Test runs upto 1000rpm showed no explosive deconstruction type of behavior.
Power required to spin at 800 rpm: 11 Watts (60V 0.18A).

At the moment I finished my (also homemade) sensorless motor controller. I'm now busy with the actual power controller, for this
I need to mount the motor on my bike and then onto my Tacx home trainer. Then I start pushing power through it to see whether
my constant-current based power controller is any good :D
 
Finally got the thing strapped to my bicycle and managed to put 175 W through
it :D this is however the limit of my laboratory DC power supply :( Need to get
my hands dirty with batteries now
 
Hey I finaly found this thread. Can you fix the pictures? As Well I want to know what you meen when you have it turning the 3 wire motor into a 2 wire motor?
 
I'm currently busy glueing together a second coil plate for my motor. This one will have a slightly
different coil-setup than the first one and will have added hall sensors. I plan to use this one for
the development of my sine wave controller (see 'not simple bldc controller' thread). This one will
be star connected but at the star point I plan to use 3 0.1 Ohm resistors to perform the current
measurement necessary for the current control and the automatic timing advance.
The glueing is rather messy and stuff but lots of fun, I feel like in kindergarden :D
The highly advanced rig at the bottom is for winding the coils, it uses an opto-coupler to count
the number of windings (49 per coil).
Note the stack of paper in the top middle of the picture, this is (only part of) the datasheet
of a PIC 18F processor :shock:
 

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Lebowski said:
I'm currently busy glueing together a second coil plate for my motor. This one will have a slightly
different coil-setup than the first one and will have added hall sensors. I plan to use this one for the development of my sine wave controller (see 'not simple bldc controller' thread).
BadAss Sweet. 8) Boohahaha... Version 1 :shock: :twisted: :!:

Did you finish this part yet? Shoot pics & video & post when/if possible. :D

This IS sooo very kool. 8) 2012 will be an e-cream-dream on ES with awesome projects like this! :twisted:
 
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