“If
anyone can build these street legal they can sell a lot more of
them”
This
is the most heavy duty “looking” cargo bike that I have seen made
in the industrialized world. Unfortunately they used two hub motors.
Making this street illegal in Washington state, and a number of other
places.
People
are so obsessed with speed they think that even a large heavy duty
cycle truck should be able to drive as fast a motorcycle. Yet they
refuse to consider that there are good reasons that motorcycles have
really powerful brakes and very heavy duty tires.
Not
only are hub motors a waste of energy, but they use more energy than
is needed to climb steep hills.
I
am going to have to stop writing this blog, people just don't care.
But if you want to sell these vehicles use your brain by reading
these pages.
Two motors with two controllers will give you more speed with a larger use of power. But an extreme gear reduction would use less power, and just not because of the lack of speed.
Here's
the simulation for dual MAC8T motors assuming equal sized wheels with
identical controllers. As you can see the motors are out of the
controller-limited region (after the peak inflection point of the red
motor curve) and so are not bound by the controller amp rating and
are running at near peak efficiency even though they are climbing a
9.5% grade. This requires about 54 battery amps which should not be
difficult to achieve (you want to run a single battery - avoid the
control and monitoring complications of using two).
Here's
the simulation for dual MAC8T motors assuming equal sized wheels with
identical controllers. As you can see the motors are out of the
controller-limited region (after the peak inflection point of the red
motor curve) and so are not bound by the controller amp rating and
are running at near peak efficiency even though they are climbing a
9.5% grade.
This
requires about 54 battery amps which should not be difficult to
achieve (you want to run a single battery - avoid the control and
monitoring complications of using two).
This
technique is essentially a graphical analysis that gives viable
results given the constraint of equal sized wheels and identical
motors and controllers:
Set
up for one motor/controller/wheel and run the simulation
Scrub
the cursor back and forth, until the required load power is twice
the delivered motor power (for 2 motors)
In the above example, you need 1600W to climb the grade and each motor will be loafing and supplying only 800W.
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| for 20 inch wheels |
If
you run equal wheels/motors/controllers, you can use simple Infineon
trap controllers and will get optimum efficiency under almost all
circumstances using a single throttle with no special tuning.
Recommend,
would be a CA3 to drive the two controllers to get the throttle
ramping, and current throttle for smooth operation + 2WD PAS and/or
auto-cruise if you wish... Since the drives are the same, you can use
the CA to monitor the temperature of either motor and assume the
other motor is about the same temperature. This gets you automatic
thermal power rollback to avoid cooking the motors if you try to
overtax them.
Remember,
electric motor power specifications are in terms of 'rated power'
not the actual power you run it at. So a 500W MAC can easily be run
at 1500W although it will heat up and eventually overheat with this
overrated operation. But legally, it's still only a '500W' motor.
Do
not be confused by comments about testing the output of a bike - the
traffic statutes are written to facilitate field enforcement - so
many cc's or so many rated Watts - not the actual hp output of a
motor which an officer could not possibly measure. He needs to be
able to make a decision based only a quick look at a motorcycle model
plate or wattage sticker - hence the way the statutes are defined (of
course there are some really confused state statutes out there, but
that's another matter...) But a label that says 500w would help.
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| dual controler assembly |
