How to build an electric vehicle.
Electric, Solar, Hybrid and Human Powered Vehicles designs by Frank Didik.
How to Build an Electric Vehicle
Design and Prototyping
By Frank Didik
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NOTE: Many people have requested information on how to design and build an electric car. The following is an outline of a seminar which I conducted at the Cooper-Hewitt National Design Museum of the Smithsonian Institute on July 9, 1998. This may be of use to those interested in designing or building an experimental electric car. How many people build their own electric vehicles? The exact number is not known, however over 3500 people per day read this page. This fact seems to indicate the high level of interest in self made electric vehicles.
ELECTRIC VEHICLES – Designing and Prototyping
Cooper-Hewitt National Design Museum
Summer Design Institute
July 9, 1998
By Frank Didik
DIDIK SUN SHARK at the Smithsonian Institute National Design Museum
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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.
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.
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?
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
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
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
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.
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
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.
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DIDIK Design Electric Vehicle Pages of
Interest to the Electric Car Builder:
Didik Main Menu for alternate vehicles
How DIDIK Vehicles are Designed
Didik Muscle Car
Foldable Didik Muscle Car
Didik Shooting Star
Didik Sun Shark – Safety Motorcycle
Didik Arctic Exporer
Didik Long Ranger
Worlds Lightest Bicycle
DIDIK Human Powered Bus
Licensing Information for Manufacturers and Resellers
PRESS KITS (only available to members of the press)
Electric Vehicle CD-ROM
How Build an Electric Car (Smithsonian Institute Talk) Also go to Didik Turtle which covers how to quickly build a small 2 person EV
History of Electric Vehicles from 1834 to 1987
The Horseless Age The first car magazine in the USA from 1895. Information on every early electric car. Fascinating!
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Other DIDIK EV and Energy Related Menus:
Electric Car Owners Club Main Menu
Solar Energy Research Main Menu
Also go to Didik Turtle which describes how to build a 2 person electric vehicle in only 14 hours.
Critical and accurate assessment of electric vehicles Covers questions and answers regarding electric vehicles, including conversion, are they safe, are the practical, are they good for the environment and are they less expensive to run then gasoline powered vehicles. Who Killed the electric car? The answer is simple. No one. If anything, one can perhaps argue that the electric car tried to kill itself! The answers become more apparent when you read the technical issues regarding electric vehicles. The fact is that the electric car is alive and getting better. For the conspiracy theory types, it is interesting to note that in the turn of the last century, there were people who claimed that the electric conglomerates were trying to prevent gasoline cars from becoming popular! No one is holding back this technology.
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Copyright 1998 by Frank Didik. Certain Rights Reserved. Information, text and photograph contained on this page may be freely reprinted in full or part provided that credit is given to author/copyright holder. It is requested that a copy of any quotation be sent to the author by conventional postal mail or electronic mail.
Didik, Didikmobile, Muscle Car, Foldable Muscle Car, Shooting Star, Sun Shark are registered trademarks of Frank Didik. Various USA and foreign patents approved or pending.