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ELECTRIC
VEHICLES -
How they work Electric
vehicles are probably the simplest form of self propelled mechanical
transportation. In it most basic form, the drive train of an electric
vehicle consists of a battery attached to an off and on switch which
is attached to an electric motor. The electric motor drives the
wheels. Most electric vehicles have a more elaborate method to
control the amount of electricity going to the motor as well as a
system of gears to drive the wheels in a most efficient manner. In
addition to the above, "solar powered" vehicles incorporate
a solar collector which converts solar energy into electricity which
is used to slowly recharge the battery.
WHAT
THEY CAN AND CAN NOT DO
: Many
people have the impression that electric cars are pollution free and
will eventually replace fossil fuel powered engines. This
understanding is rather inaccurate. The fact is that at the present
time, electric vehicles can not compete with main stream gasoline,
diesel, compressed natural gas and other vehicles in terms of speed,
range and overall safety. In addition, electric vehicles create
pollution in a number of
different
ways. First, most of the electricity we use in the United States is
from fossil fuel burning power plants which creates pollution, though
usually away from the urban centers. In some cases, electricity
produced at nuclear power plants, though
these
also pose potential risks. Solar power plants are in their infancy,
though they may be useful in sunny, areas with little cloud cover. If
everyone was to have solar arrays on their property, some people may
object to them, similar to how people objected to the early 10 foot
satellite dishes. Wind power may also offer some potential to
generate electricity, though windmills pollute in terms of visual as
well as noise pollution. In January of this year, I drove from
Hamburg Germany north towards Denmark and passed a large array of
modern windmill electric generators. The first thing that struck me
was the loud and continuous wiring sound they put out. Here in New
York City, there have been several attempts over the past 25 years to
harness wind power. There were windmills on East 10 street between
Avenue A and First Avenue, East 5 Street between Avenue A and Avenue
B and on East 9 street and the Bowery. In every case, the owners
abandoned
the windmills after a year or so presumable since they were not cost
effective. Nevertheless such a system may be useful in remote areas.
Many of the materials used in electric cars today are toxic. For
example the lead, which is the most common element used in
conventional deep cycle electric vehicle batteries can be a serious
health hazard. In the case of solar panels, many of the panels are
manufactured using highly toxic chemicals and the panels themselves
can, under the wrong circumstances, pose a health
hazard.
Many people are concerned about power lines and the possible health
effects. In an electric car, you are surrounded by massive amounts of electro-magnetic
radiation. To this date,
health
hazards of this has not been proven. The primary obstacle facing
electric vehicles today is the limited storage capacity of
economically viable batteries. The most common and probably the best
compromise battery is the "deep cycle" lead acid
battery...the same type of battery that has been in use for electric
vehicles since the 1880's. There are other batteries that do offer
greater electrical storage capacity but at either a much higher
price, or less overall life or low power output (though higher total
storage capacity). Today, most electric cars have a range of about 40
miles per charge at a speed of about 35 to 45 miles per hours. Most
smaller electric cars use between 6 and 12 6 volt deep cycle, lead
acid batteries. The recharging time is normally 8 hours and once per
week, the charging time is 12 hours to even out the charge among the
battery array. Deep cycle lead acid batteries, with proper care, can
last about 3 years or about 600 charge-discharge cycles. Factors such
as ambient temperature, moisture in the air, terrain and how a person
drives can substantially decrease these figures. Overall,
conventional batteries are not are predictable in terms of range and
speed as say, a gallon of gasoline. To increase range, many car
companies have experimented by building lighter or smaller vehicles.
Generally a lighter or smaller vehicle can hold less passengers and
in most cases, does not offer the safety of a larger vehicle. Solar
panels have been used to recharge electric vehicles, though there is
not enough energy from sun light per square foot to directly propel a
conventional 2500 pound car. It is possible to slowly store solar
energy in the batteries to allow the car to move for a limited time.
SO
WHY BOTHER WITH ELECTRIC VEHICLES? Electric
vehicles offer a unique driving experience. With their low center of
gravity, most
electric
cars, offer superb handling as well as rapid initial
acceleration.
Electric motors offer almost continuous torque even
at
lower speeds. This allows a vehicle to do things that
conventional
fossil fuels vehicles can not do. For example, if you were to drive
up to a street curb with a conventional gasoline
powered
car, stop and then try to climb the curb, you would have to rev up
the motor and only then would you be able to drive over
the
curb. With an electric vehicle, you would be able to climb the curb
with out any real effort. Today, most railroads around the
world
use diesel electric locomotives with the diesel engine generating
the electricity to power the electric motors which actually turns the
wheels. American military tanks use the same technique. Electric
vehicles are also ideal for use in areas that have very high gasoline
costs or where conventional fuel is simply
not
available. During world war two, many countries started to produce
electric vehicles for the population. Electric cars were
manufactured
during the war in Spain, Belgium, France, Japan and others. In 1946,
my father had seen several electric powered and steam powered private
vehicles in Tokyo that clever citizens had converted from gasoline
when gasoline was no longer available.
Presently,
I support multi-powered or hybrid cars which utilize a combination
of gasoline and electric motors. In such vehicles, the electric power
can be used at low speeds or in cities limiting the amount of
pollution in urban areas, while at higher speeds, the gasoline engine
can take over. This configuration was actually first tried in 1901
and a number of times thereafter, but did not take hold partially
since there is a double cost involved to manufacture the vehicle.
Electric vehicles will probably have a limited niche market for the
foreseeable future. |
DESIGN CONSIDERATIONS
Electric
vehicles are fascinating to build and drive, even taking into
consideration the limitations as outlined above. Electric vehicles
are so simple in overall construction that they can easily be built
by people with basic construction skills. In the simplest form, such
as in a high school class, a very basic electric go cart can be built
that can consist of a simple wood frame built out of 2" x
4"s, basic wheels, an electric motor, a car battery and a
momentary electrical switch to turn the electricity on and off as a
gas pedal. A more sophisticated system would use a go-cart body made
out of steel (or perhaps converted from an existing gasoline
go-cart), with the same elements as the wooden cart would use. Simple
electric vehicles as just described can probably be built in two
weeks with minimal skills.
![[IMAGE]](shark4.jpg)
Basic
frame of the Didik Sun Shark being welded while clamped to a basic jig.
DESIGNING: As
with all design projects, it is essential that the designer has a
clear understanding
of what the function of the final vehicle will have. For example,
how many passengers will the vehicle carry? Will there be storage
space? Where or how will the vehicle be recharged? Will it be parked
on the street? What are the local regulations pertaining to electric
vehicles? If the vehicle will be charged from the power grid, is the
available outlet adequate for charging the vehicle?
![[IMAGE]](shark5.jpg)
Once
everything of the final vehicle has been written down and
considered, you can start to design the vehicle. With the limited
storage capacity of batteries, it is important to design the vehicle
using as much light weight materials that can be safely incorporated
into the vehicle with cost and skill considerations in mind. It
should be noted that many light weight materials are particularly
difficult to work with and often times a person who is not acquainted
with the particular engineering of the material will actually build a
vehicle that is heavier using the light weight materials, than if
they had used heavier, but easier to use materials. I have seen
college student constructed solar powered racing cars using much
touted, though still questionable, carbon fiber that probably weighed
more then if they had used aluminum or steel tubing. Steel,
particularly thin walled steel, is the easiest to work with.
Aluminum, while weighing about 60 percent less then steel, is very
difficult to weld and requires
![[IMAGE]](shark6.jpg)
considerable
engineering in order to fully take advantage of the wight
difference. Wood can often be used for some components, though in an
accident, it usually does not offer the same protection that metals
offer. Steel and wood are by far the cheapest materials to work with
and this should be taken into
consideration
if cost of the finished vehicle is a factor.
After everything is considered, then and only then should the actual
design phase proceed. In a classroom environment, I think that it is
important for a professor to summarize to the students what materials
can be used and then, with out suggesting a design, let the students
individually design their vehicle on paper as a homework assignment.
At this point, each member of the class
![[IMAGE]](shark7.jpg)
As
seen in this photograph, it is much easier to finish all mechanical
and electrical aspects of the vehicle prior to installing the body.
In the case of the DIDIK SUN SHARK, about 500 feet of wire and over
100 moving mechanical components were installed prior to the
body being built.
should
review every other design and then redesign a vehicle using the new
ideas gained by seeing what other have designed. This way new ideas
can be incorporated into the design. Who can predict what can be
developed this way? Again everyone should compare notes and then a
final design should be decided on, perhaps by paper ballot. Safety is
a very important element that should be incorporated into the design.
In my vehicles, I make it a point to have as many lights and
reflectors on the vehicle as possible so that conventional car
drivers can see the vehicle from a distance. I also paint the
vehicles bright colors for added visibility.
SKILLS: In
building a prototype vehicle, one must consider the skill of the
builders. Probably any shop class or machine shop
could
build a reasonably high quality electric powered car. The basic
skills that will be needed using off the shelf components or surplus
components includes welding skills, metal cutting skills,
drafting
skills and general design skills. Welding is essential if the frame
of the vehicle is to be made out of steel. Surprisingly, it is very
easy to master basic welding, particularly
if using a wire fed "mig" type welder. Such basic mig
welders can be purchased from mail order companies such as Harbor
Freight Tools, out in California for as little as $129 though prices
can also be substantially higher. It will also be necessary to have
access to a metal cut-off saw. A cut off saw capable of using 12 or
14 inch blades is ideal. Once basic welding techniques are mastered,
many seemingly hard projects will look much easier. If
the
vehicle is to have a body, it is useful that someone with auto body
repair skills be involved in the project. Such a person with auto
body and painting skills can make a basic body look like a big
three
fantasy car. |
MATERIALS: The
basic materials needed to build a steel framed,
electric
vehicle with a body includes:
Steel
tubing. I
prefer to use basic 1/2" to 1" EMT electrical tubes. They
are light weight, easy to cut, easy to handle and are very
inexpensive. For example, a 3/4" x
10
foot EMT tube at Home Depot costs about $2.50 in New York City. If
you prefer, you can also purchase standard square steel tubes from
steel distributors such as Eastern Steel in New York City for very
low prices. The standard length of steel tubes form distributors is
20 feet or 24 feet.
Electric
Motor. Though
some people have used ac motors, I
much
prefer to use DC motors. One to three HP DC motors can
be
purchased in scrap yards (not to be confused with auto junk
yards)
for under $100. They can also be purchased from a
variety
of surplus outlets throughout the country.
Drive. You
can use a number of systems to couple the
electric
motor to the wheels including sprocket gear and
chain,
pulley and belt or similar. The pulley and belt system
is
probably the easiest system to use.
Body. There
are several ways to shape the body. One way
is
to use a very large styrofoam block that can be sanded
using
an electric sander to the correct shape and then covered
first
with Elmers type white glue and then covered with
fiberglass.
Another, cheaper and less messy way is to use
chicken
wire mesh to shape the body over a basic metal frame.
You
can then cover the wire mesh with fiberglass sheets,
though
I usually cover the mesh first with very thin layer of
plaster
and fabric strips to give the mould strength and then
cover
it with the fiberglass. The finish can be made perfect
with
the help of an auto body expert who will smooth out
imperfections
and then paint the resulting vehicle to high
standards.
Windshield.
The windshield should be made out of a substance with safety in mind.
While conventional car windshields are useful, I have found them to
be generally too heavy for my vehicles. Instead, I prefer to use
"unbreakable" Lexan type plastic. I normally use the
1/16" thick lexan and for strength, design the windscreen so
that it is curved. It is also possible to mould the windscreen using
either a vacuum or compression system, though this requires a rather
high degree of construction skill.
![[IMAGE]](shark2.jpg)
When
designing an electric vehicle, it is important to consider exactly
how the vehicle will be used. In the case of the DIDIK SUN SHARK, it
was designed to be able to go through a standard 28" doorway.
Electric
wiring and switches can be purchased at most electrical supply houses.
CONSTRUCTION:
After the vehicle has been designed on paper, and the components
purchased, you can proceed with the actual construction. Safety
should never be compromised. Always wear ear plugs, face shield,
proper protective clothing and work in a well ventilated, properly
lighted room.
First
cut out the immediate metal frame parts and weld them together. I
have found that a department store type rolling coat rack can be
utilized as a welding jig with the use of vice grips to hold the
metal that is being welded together. After the frame has been welded
together add the steering mechanism and electric drive
components. Before the body can be incorporated on to the
vehicle,
it is essential that the vehicle is in complete working order. After
the body has been built, it is normally more
![[IMAGE]](shark1.jpg)
DIDIK
SUN SHARK without the solar panel installed.
difficult
to make possible modifications to the mechanical components. Initial
test drives should not be conducted on public
roads
but rather on private property, at the slowest possible speed. As
with all prototypes, it will probably be necessary to made minor and
possibly major modifications before the vehicle is ready for general
use. No matter how much preparation is made in
designing
the vehicle, one can never predict the effects of every possible
design feature.
Construction
of a basic vehicle, capable of holding two people should not take
more than 60 hours of actual construction time, though it may take as
little as 25 hours.
LEGAL
REQUIREMENTS The federal
government as well as all states have strict rule for motor vehicles
manufacturers. Almost all states have special provisions for electric
cars. Further, most states allow human powered vehicles with power
assists to operate on local roads without having to be registered.
Further, some
states
have special regulations that are easier to conform to for slow
moving vehicles or specialty vehicles such as snow mobiles, or all
terrain vehicles. These provisions may be useful to know when
designing the vehicle.
Also
go to Didik
Turtle
which describes how to build a 2 person electric vehicle in only 14 hours. |
![[IMAGE]](shark3.jpg)