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By Bill Drinkwater / EVMaine.org
I want an electric car, so I have decided to build one from scratch. So you can follow the design decision-making processes, if you like through the construction stages as they occur. There are many photos included. Expect a lot of rambling statements and opinion-changing until the dust settles on the final design decisions along the way. Much will change as I build it because I design-as-you-go. That means backtracking occasionally, and redoing some things as I change how to proceed.
First I will decide on the basics of my vehicle.
Design Criteria
Purpose: A one-person car that I can use to run local errands, drive for fun and to take to schools and car shows, It will have a range of about 40 miles per charge, and will have a top speed of around 45 mph.
Spring/Summer/Fall driving only/therefore no heater needed. A hardtop design which may be a 110 watt Mitsubishi solar panel.
Although I can garner some very good design ideas from solar powered racers, my vehicle will weigh hundreds of pounds more than any of them because of its steel frame and six 12 volt lead/acid batteries that will weigh about 40 pounds each. My car should cost no more than five thousand dollars by the time it is finished.
I’ll include one small solar panel to trickle charge the auxillary battery that feeds the lights and horn.
My car will have to be highway-legal. I live on a highway with a speed limit of 45 mph where I live, so I cannot drive a Low Speed Vehicle out my drivevay, also known as a Neighborhood Electric Vehicle, to get to town (5 miles away) because they cannot be driven on roads with a posted speed limit higher than 35 mph.
A 3-wheeled vehicle would weigh less than a 4-wheeled vehicle. Since vehicle weight is extremely critical in electric vehicles because they must run on very little energy, my choice is to build a 3-wheeler. Any enclosed cab 3-wheeled vehicle must be registered as an ‘autocycle’ in Maine even though it will look more like a 3-wheeled soapbox derby racer with two wheels in front and the single drive wheel in back. Toad and Delta are the two shape names for 3-wheeled cars. A toad has the two wheels in the front, while a delta shape has the two wheels in the back. Mine will be a toad design because the two wheels on front design has proven to be more stable, especially on corners.
Photos of over 160 3-wheelers are found at this URL: http://www.3wheelers.com/projgall.html Although most of them are gasoline-powered, they demonstrate many interesting and innovative body and running gear designs.
My car will have a safety glass windshield, and a windshield wiper. It will have LED taillights and turn signals to reduce consumption of electricity, and two headlights with both high and low beams.
I want the vehicle to be unique enough to attract attention to the EVMaine.org logos that will be on its sides, so I cannot buy a kit car because that would look too much like all of the other kit cars. Instead I will build a vehicle from scratch with a totally unique design.
Why not just buy some books on how to build an electric car? Because they tell how to convert a standard car to electric, which is very different from building a simple, usable, small electric car from scratch. For starters, a standard car has a very heavy steel frame and a heavy steel body that requires a powerful motor and expensive electronics, and therefore needs lots of very heavy batteries to move it. Mine will have a smaller and more lightweight steel frame.
My little peawee car will be much simpler to build, and I think it will be a lot more fun to drive, than a larger electric car.
The ill-fated Sinclair C5 (British). Once touted as THE great personal tranportation breakthrough for the UK, it proved to be too small, too weak and too dangerous in traffic.
http://www.speedace.info/sinclair_c5.htm
Safety Features to be Included
Safety is a major concern for me, so it will have disk brakes on all 3 wheels, a horn, a steel roll bar, a seatbelt, break-away side mirrors on both sides, a recessed door handle, a rear view mirror, a backup light, a backup alarm, a passenger-side door only, and a hand-operated parking (emergency) brake.
Safety bumpers front and rear with air-filled boat bumpers.
Inertia switch (cuts power automatically in case of an accident)
A high voltage kill switch.
It will have larger diameter wheels than are found on some small cars which will make it safer and more comfortable when negotiating potholed roads.
The relatively low speed and proper front end geometry should prevent ‘scrubbing’ or sliding (loss of traction) of the narrow front motorcycle tires on corners.
I also have designed a shock-absorbing front bumper that I plan to install.
I will also include some foam side panels on the sides of the cockpit for energy absorbsion in case of a side crash.
I like this basic design
http://www.youtube.com/watch?v=2hX7DWtnLBc
I will use six flooded lead/acid deep cycle marine batteries for 72 volts total.
The car frame will have between nine and twelve inches of ground clearance, but must have a center of gravity as low as possible to deter rollovers, so the batteries will be placed as low as possible on the frame.
The driver’s seat is a very comfortable passengers seat from a junked ‘99 Dodge Caravan.
It will have all-wheel suspension so the vehicle won’t be bone-jarring to drive on mostly side roads in the real world.
The two front wheels must have fenders of some sort, either steel or plastic.
Wheels: 26.5 inch sturdy spoked wheels with Kevlar belted tires on front and a slightly smaller diameter, but wider single motorcycle tire in the rear, which is the back end of a motorcycle frame with a highly modified fork. Relatively narrow tire treads on the front end will reduce rolling friction and thereby help to increase the vehicle’s range per charge.
This is a 3-wheel design that I like, but mine will be much taller.
My vehicle will have a top speed of about 45 mph, with an electronic bicycle speedometer that holds the odometer mileage. It won’t have a transmission since small electric motors have plenty of torque at all speeds. That will help keep the vehicle weight to a minimum. I will be running a 72 volt, DC system. That translates to six, 12 volt, 125 amp/hr lead/acid deep cycle batteries onbooard. It’s a lot of weight, but necessary.
DC motor systems tend to be much simpler and cost less than AC motor systems, so I’ll have a DC system. Despite what many experts recommend, I have decided not to have regenerative braking in my vehicle, which is more easily implemented with an ac motor anyway.
I will include a small solar panel to keep the extra (motorcycle) battery for the car lights and horn topped off.
The dash will have an electronic speedometer (bicycle-type), a Curtis battery ‘fuel gauge’, an ammeter, high and a blue high beam indicator light and whatever other instrumentation and switches are deemed necessary. The high/low beam headlight switch will be on the floor, operated by my right foot.
I will put some lightweight, noise-reducing foam between the driver and the motor/chain drive. The chain should not be too noisy anyway because it will not be travelling over 1,000 rpm, which is when it gets very loud.
The car will have a square steel tubing frame.
The body material will be standard bathroom wall material over a steel square tubing frame.
http://www.mit.edu/activities/solar-cars/flash/vehicles/present.shtml
A link to an absolutely superlative solar car blog with LOTS of useful information is below:
http://www.stanford.edu/group/solarcar/equinox.html
A lockable compartment for groceries and an onboard charger for opportunity charging in public will also be included.
The car will be painted bright (safety) yellow, a Rustoleum paint color, so that it will be more visible in traffic for safety. I will paint it myself using a good quality brush.
Here are two quirky 3-wheeled designs from Italy that are somewhat appealing, to me at least.
www.3wheelers.com
My car will be tall enough that people in regular vehicles will know that I am in the traffic mix. I will sit upright in the car over the battery box, so the car will be much taller than recumbent driver vehicles.
Wheelbase: Looks like around ten feet because of the stretched out battery box and long fork on back. That will leave plenty of room for groceries.
Width of Body: The body is only 24 inches wide at its narrowest, but the front wheels are over five feet wide for lots of stability.
In/Out: A grab handle on the dash. Curbside door only is safer for a one-person vehicle. .
Ignition: A key switch and contactor. I’ll run all wires in plastic conduit with no grounds to the frame - too much voltage involved.
Although this will be a one-person vehicle it will also include enough room for at least a couple bags of groceries in a locked compartment, so the car has real utility.
It will have an extension cord and charger onboard for “opportunity charging” wherever possible in any standard 110 volt grounded AC outlet.
The groceries compartment might be replaceable with either a small pickup truck bed, or a rear-facing passenger seat. They would also be protected by the roll bar.
Trailering: I have a ten foot long trailer for taking it more than 20 miles from my home, such as to car shows. .
Towing: I will attach sturdy tow hooks on both ends of the frame for emergency use.
Here’s a somewhat similar design concept:
http://www.mcn.org/a/omni/elite/elite.html
This is the Pod One 3-Wheeler from www.gaiatransport.com
Other Considerations
Where will I build it?
I am building it in my backyard and (soon) in a small shop that I am building..
How will I pay for this project?
I sold my 250 cc, 2003 Honda Reflex scooter. That was a lot of fun, but it is time to move on to this new project.
Do I have adequate skills for this project?
I have done much mechanic-type work and repairs on my own vehicles over the years (before vehicles became too high tech to work on), and have designed and built many of my own projects, including several RVs. I had a job building prototype safety cars many years ago, hence my preference for lots of safety features. I also was an arc and oxy-acetylene welder for many years. I have only a few hand and power tools left, but I won’t need many for this project. I got a smalll cored wire-feed welder at Home Depot to use on this project.
However, I am NOT using any exotic tools or techniques on this car that anyone who can hold a hammer in their hand cannot easily do. Also, no oxy/acetelene torch is required.
What is my budget for this project?
$5,000 maximum, hopefully less. The electronic motor controller and other electronics jack up the price considerably, putting it closer to the $4,000 mark, unfortunately.
Next Page: I have selected the many components needed after much research and studying on the Internet.
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