Electric
motor-assisted human power vehicles (eHPV) have the potential of
providing an alternate to both overpowered internal combustion engine
(ICE) driven vehicles and underpowered bicycles (when less than fit
humans are pedaling them) for intra-city or short-trip personal
transportation. The dream of human only powered vehicles replacing
cars has long be held by those valuing efficient, sustainable,
environmentally responsible, and just plain sensible transportation,
but cars remain dominant. Perhaps the HPV dream needs a boost.
Practical
HPVs, velomobiles being an example, offer streamlined weather protection,
cargo carrying capability, safety features, full suspension, and other
amenities not often found on light weight bicycles. Bicycles tend to lack such
features because adding them adds evermore weight requiring evermore muscle power
to pedal. Vast numbers of people already feel that the effort needed to pedal
even an ultra light bicycle is too great, so doubling or tripling the
weight insures that only a few ultra fit humans can pedal them (except on flat
land).
An aerodynamic fairing more than compensates for the extra weight
when operated on flat ground, but performance rapidly declines as the slope
increases. Apart from a few flat regions, such as the Netherlands, practical
HPVs have proven to be impractical.
Most velomobiles are trikes, which have the considerable advantage of not falling over
at a stop. The down side is that on roadways lacking a paved shoulder where cyclists
must ride the white line or be run over, trikes stick out into passing
traffic more, either obstructing the flow of traffic or increasing the risk
of being clipped (or worse) by passing cars and trucks. Trikes weigh more
than bicycles, and the scant sales of velomobiles makes them very expensive. While
adding power-assist would make them practical for average humans, the added
price makes them even more impractical from a financial
perspective.
Part of being practical is being comfortable. Imagine
taking the seat off a racing bike, mounting it on a stool, and
putting it in among the other seating offered by a large
furniture store. Just how many customers would look at the bike seat and say,
“Yeah, that's what I want to sit on after a hard day at work.” More than likely no one would choose to sit on an upright
bike seat no matter how much gel it had.
There are, however, bicycles without bicycle saddles. Such bicycles are called recumbent
bikes or bents. They've been around a long time now, and absolutely
every one can agree that they are more comfortable to sit on.
Recumbents also have a safety advantage: if you run into something,
would you rather it be feet first or face first? Like velomobiles,
however, bents tend to be expensive due to low production.
The Cruzbike is a full suspension recumbent front-wheel drive bicycle that
uses mass-produced mountain bike (or other) frames, and standard bike
shop available parts. This allows a quality bent to be made at
a comparatively good price. In a Cruzbike conversion the
mountain bike's front wheel becomes the rear wheel, but if instead
another geared rear wheel is added and an electric motor used to drive
it, then the result is an all-wheel drive bicycle. By not trying to combine
human and motor drive trains, the design of both can be much simpler
as no freewheels are needed to allow pedaling without using the
motor, or motoring without forced pedaling.
While the Cruzbike doesn't
need an electric assist motor, turning it into a practical HPV by
adding fairings, cargo carrying ability, trailer towing ability,
lights, horn, fenders, etc., pretty much necessitates also turning it
into an eHPV. The Cruzbike is ideally suited to being converted into
an ebike as both motor and batteries can be mounted so as to keep the
center of gravity low.
One use for the otherwise unused bottom bracket is as a mount for what might be called a “wheelstand” to replace the
kickstand. The wheelstand acts as a landing
gear, allowing the bike to remain upright at stops without the need to take
a foot off the pedals. This design has the advantages of
the trike without the disadvantages. With four wheels down it
is stable at rest and at low speed, yet pop the wheelstand back and on two
wheels the bike can lean into corners, go down narrow paths, and stay on or to
the right of the white line.
For clarity the batteries are shown mounted as low as possible,
good for lowering the center of gravity, but for improved aerodynamics it would probably
be best to mount them slightly higher on either side of the motor.
The rod on the rear fairing would support the upper part of the soft fairing and
would be fiberglass. It could extend higher to carry a pennant for
improved visibility. Lights, horn, fenders, electronics would also be
added. Another addition would be a retractable head cover to provide
shade when needed. The cover could be a small solar panel
to provide power for onboard electronics such as a meter, bike
computer, lights, AA/AAA battery charger for GPS, iPod, cell phone,
whatever. Having a separate 12V system might be simpler that stepping down
voltage from the motor battery pack. While solar powering the ebike may
not be practical (unless solar panels are part of a recharging station),
powering the bike's electrical system using solar would make sense.
A gearhead motor is shown,
but there are two other approaches. One is the use a
rear hub motor mounted on a short fork. The
entire motor turns to drive the rear wheel. These slow turning motors
are heavy, but without gears, they make little noise, which avoids the major objection
to gearhead motors. To be small and efficient a motor has to turn
at high rpms, about 2800 rpm or higher. The
problem is to gear the motor down efficiently without generating a
lot of noise (think electric drill). One way would be to go with a
5:1 belt drive reduction, then a 5:1 chain drive reduction. Belt drives
are not as efficient as chain drives, but are quiet--a chain drive directly
off the motor would be very noisy.
Wal-Mart has an Ultra-lite folder (Kent
International) for $150. Removing just the front wheel of the folder and
hitching it on to the eTrek turns it into a tandem bike. Striped down it would
make a cheaper trailer than the B.O.B. trailers. Using a front fork trailer hitch allows old bikes to be easily turned into a variety of utility trailers on the cheap. Add a solar panel to the trailer and extra batteries (even motorize the trailer), and more power will be available for towing, or touring. The eTrek concept is starting to evolve into a practical EV. More heads are better than one, so anyone interested in developing ebikes along a practical line should join the Yahoo! group mentioned below. The ultimate goal and proof of concept is a cross-country ebike tour. Anyone want to go for a ride?
Practical
HPVs, velomobiles being an example, offer streamlined weather protection,
cargo carrying capability, safety features, full suspension, and other
amenities not often found on light weight bicycles. Bicycles tend to lack such
features because adding them adds evermore weight requiring evermore muscle power
to pedal. Vast numbers of people already feel that the effort needed to pedal
even an ultra light bicycle is too great, so doubling or tripling the
weight insures that only a few ultra fit humans can pedal them (except on flat
land). 
Part of being practical is being comfortable. Imagine
taking the seat off a racing bike, mounting it on a stool, and
putting it in among the other seating offered by a large
furniture store. Just how many customers would look at the bike seat and say,
“Yeah, that's what I want to sit on after a hard day at work.” More than likely no one would choose to sit on an upright
bike seat no matter how much gel it had.
