Issue Six - Spring 2013 - Electric Bike Magazine

+E-BIKE BASICS
ELECTRIC BIKE BEGINNER GUIDEI
More types: motors
As well as the main distinction
between torque sensing and
rotation sensing, it’s also
useful to know about the two
main motor types.
Second
You really should test ride the two
basic types of electric bike:
A bike with ‘torque sensing’
control. This means that rather like
power steering on a car, the electric
assistance amplifies any effort you
put into the pedals, making you feel
like you have superhuman legs. This
type feels just like a normal bike, but
with a tailwind. You do need to be
putting some effort (which generates
torque, which the sensor measures)
through the pedals, though, before
you’ll get any assistance from the
motor. So you can’t just sit there and
let the motor pull you along: instead
you’re definitely going to be getting
some exercise, but without the strain.
Often favoured by people who have
done a fair bit of unassisted cycling,
or those looking for fitness benefits
from their electric ride. Prices start
around the £1000 mark, however.
A bike with ‘rotation sensor’
control. This means that the motor,
when it kicks in, does so at a set
level, and it continues until you stop
pedalling or squeeze the brakes. It’s
the rotation of the pedals which
controls when the motor operates.
You don’t have to be actually putting
an effort into pedalling, you can just
be waving them round. Many of these
bikes also have a throttle, so you can
just sit there and be pulled along,
ideal as a ‘get me home’ mode if you
run out of puff. You can pedal too,
of course, and get quite a workout,
especially if the motor assist is set at
a low level – but this can take a little
discipline! This type of machine is
available at all price points.
This is the key distinction in how
bikes operate, and the ride sensation
is so different between the two that
I really would recommend trying
both. If not, and you don’t try the
type which grabs you, you’ll be really
missing out.
It’s always puzzled me, incidentally,
why no manufacturer has a model
which offers both modes, so the user
could switch between them. Maybe
next year?
PHOTO: Batribike
Geared motors are used in
most hub motors and all (I’m
fairly sure) crank drives. A
fast-spinning motor (usually the
‘brushless DC’ type) is geared
down within the hub or drive unit
so that the output matches the
speed of the wheels or cranks.
This helps the motor operate at
an efficient speed, and the motor
can be smaller, too.
The downside is that there’s
inevitably some noise from
the meshing of the gear teeth.
Hubs are usually more noisy
than crank drives, but in recent
models the noise level is really
pretty low for both.
Gears can, of course, wear
out, but this doesn’t seem to
be much of an issue in modern
drives. Good ones are well sealed
and the gears run in internal oil
baths or long lasting grease.
Direct drive motors don’t
have any gears involved at all.
There’s a ring of magnets inside
the hub shell, and a ring of
coils attached to the axle, with
just a small air gap between
them. As the coils are energised
they pull the magnets round.
There’s no physical contact
and so these drives tend to be
completely silent.
One possible drawback is that
at very low speeds they can have
limited power, although modern
control systems are getting
ever better in this respect. They
also tend to require large hubs,
which can be problematic when
building small wheels, and have
typically been a little heavier
than geared hubs (but again
development is reducing the
weight). Finally, they tend to be
at the higher end of prices.
Examples include systems from
BionX, Falco, Storck-Raddar, BH
Emotion ‘Neo’ and others.
36 Electric Bike Issue 6