Introduction: Electric Vehicle - a Simple Lightweight EV Platform

Picture of Electric Vehicle - a Simple Lightweight EV Platform
I've been looking forward to the arrival of electric car technology. Not just for the smooth quiet power, wide torque range, cheap running costs and minimal maintenance, but to design and build cars to take advantage of the simplicity and flexible packaging offered by electric technology. Some new knowledge and skills of battery and electric drive systems are required, but once you have an understanding of this, putting it all together is much simpler and quicker than using a petrol or diesel drivetrain. Why? The motors and controllers come ready to bolt on and plug together and all the sensors required are usually built into the motor.  Cooling systems, fuel storage and pump, gearbox, differential, exhaust system and complex wiring harness are not required. There are a few more components required to deal with high voltage electrical power, but other than this, it is really not much more complex than building a radio controlled electric car. With less complex mechanical systems to worry about, building your own car has become more achievable and more fun.
Electric car components have been available for a while now.  A friend converted his first electric car 10 years ago then changed it to lithium batteries 6 years ago. The technology is now becoming more readily available, costs are coming down and performance is increasing and this trend is set to continue.
Why build your own? Because you can and it is great fun to build a very light, simple car reasonably inexpensively.  It is a heap of fun to drive and has excellent performance because of the light weight.  Buggies, gokarts, grass roots racers and kit cars such as Lotus 7 clubman style car that is still going strong since the 60's have spurned their own industries.  Electric cars bring new opportunities for a fresh look at homegrown performance.
Concept and Design
This Instructable provides a summary of a basic layout for an EV platform that suits a wide range of applications and can be easily tuned with different size motors, batteries, gearing and size. It demonstrates a simple and compact system with a low centre of gravity that is strong, stiff and straightforward to build. The Instructable does not go into the design and fabrication of bodywork, I will leave this to others and your imagination. It is pretty easy to see that this rolling chassis is very flexible in the bodywork it could accommodate, but keeping the body light will maximise performance and range.
Key Design Parameters
When designing a new car platform from scratch, there are a lot of choices. A lot of thought and design effort has gone into keeping the design as simple, light weight and very easy to build - simpler than a Locost or clubman style car.
I will get straight to the point here and outline some of the key design features and why.
Drive - Rear wheel drive, one electric motor powers each rear wheel. Eliminates the need for a differential and CV joints.
Motors - AC Induction. Have good torque over wide speed range. Simple and robust with a motor controller for each motor. Mounted inboard.
Batteries - Large lithium cells. I used 45 Lithium cells for a total of 148V and 100Ah. This needs to be matched to the motors and controllers. This is a relatively small pack compared to production EV's vehicles but is ample for a car that is light and is not used for long range driving. Keeping the battery pack size down helps keep down the vehicle weight and cost. My large lithium cells are good for a peak current draw 3 to 5 times the rated hourly figure above (3C to 5C). Lithium polymer cells are available that have a higher energy density and will do much higher peak currents than this and they are commonly used in model cars and planes, but at present the large lithium cells are a lot more economical for larger packs and the 3C peak current is not a major limitation unless you need a high peak demand such as for drag racing.
Chassis - Folded aluminium box. The batteries are contained in the box which also handles all the vehicle loads. This is the key to a simple, light and very easy to construct car. It provides a high level of strength and stiffness from a very simple and light structure.
Suspension, Steering and Brakes - Double wishbones were used and they are the best choice for a number of reasons including lower height for maximum flexibility in body design, height adjustable again for flexibility in body styles and optimum handling performance. There are numerous vehicles that can be used to source suspension and steering components. I used parts from a Mazda MX5 (Miata) which has front and rear wishbone suspension and rear wheel drive so all the parts could be obtained one source. It also has 4 wheel disc brakes and a straightforward steering rack. Using mass produced parts helps streamline the project, keeps costs down and ensures that these important items are robust and reliable.
Gearbox - Nil. The electric motors have such a wide torque range that they will operate effectively with one fixed gear. I use a toothed drive belt at a ratio between 1:3 and 1:5 for smooth quiet and maintenance free transmission. A chain drive would also be ideal and would be lighter and cheaper but a little noisier.
Weight - The weight of the EV platform including motors and batteries is approx 500kg. Major components of the weight come from the batteries (150kg), wheels and suspension (140kg) and motors (118kg).
Vehicle Platform - A vehicle platform is basically rolling chassis with drivetrain installed. It is drivable and just needs some bodywork to complete the package. I avoid any body styling discussion in this Instructable and rather present a very flexible platform that will suit a range of body styles.
Driving the Car  -  With one gear and heaps of torque (300Nm from the twin motors) Driving is simple and effortless and the car rapidly gains speed and without a body the sensation of speed is greatly exaggerated.

Step 1: The Chassis

Picture of The Chassis

The chassis is one of the few items you need to fabricate. The majority of items are sourced and attached to the chassis. We use a pressed aluminium box from 3mm thick aluminium sheet that doubles as the main structural spine and the battery box. The approach keeps fabrication very simple, maximises rigidity, keeps the weight low down and concentrated in the centre of the car and keeps the battery pack away from damage in impacts.

One of the disadvantages of using a thin walled box section is that large concentrated loads cannot be applied directly to the aluminium walls. This is easily overcome by using tubular steel subframes or bulkheads to spread loads. The tubular steel subframes are relatively small and are not difficult to fabricate.

Aluminium Box
The chassis box requires a large press to bend up. Because it's a simple box, your local metal roofing supplier should be able to supply the material cut and pressed to size.. I sourced a 3m long box, 270mm high x 300mm wide made from a single 1.2m x 3m x 3mm sheet complete with lid for $300.
The width of the box is wide enough for 4 batteries across plus a thin ply lining. The ply lining helps to protect the batteries, stop any drumming noise being transmitted through the chassis, ensures rivet heads don't rub on the sides of batteries. Attach the lining to the aluminium chassis using sikaflex automotive or marine polyurethane flexible sealant/adhesive.
Note that the lip on the aluminium box serves not only as a place to fix the lid, but also strengthens the structure when the lid is not fixed in place.

Inside the chassis box, a series of bulkheads, either aluminium or ply plates are fitted. The bulkheads have a number of functions. They support the chassis box against buckling, support batteries from acceleration and deceleration loads (including an impact) and provide reinforced mounting points for heavy components such as motors and seat frames or floor.

The box also needs a lid that can be opened to access batteries, but it needs to be securely fastened as an integral structural part of the box. While riveting would give a quick and strong attachment, it is not suited to testing and development requirements of a custom vehicle. A suitable alternative to using rivets is using rivnuts and socket screws. 6mm to 8mm rivnuts and screws are suitable. They should be spaced reasonably close and stainless rivnuts and screws are not recommended as the threads tend to bind. I have used 6mm socket screws at a spacing of 50mm. I do not recommend using stainless socket screws and rivnuts, having learned the hard way when several of the socket screw threads binding and needed to be drilled out and replaced.

A drawing showing dimensions for a chassis box is shown above along with an Autodesk Inventor rendering showing the basic chassis layout. The chassis box design is optimised 45 CALB 100Ah lithium cells fitted four wide.

Suspension Subframes
External subframes that slide over the box section are used to mount the suspension. The subframes are welded up from 25mm x 1.6mm steel box section. They are attached to the aluminium box using structural rivets from inside the box. An angle attachment for your drill or a right angle drill is essential for drilling the rivet holes this and a pneumatic riveter is needed to apply sufficient pressure to set a structural rivet as you will not fit a large manual style riveter inside the box.

Structural rivets such as Megalock Rivets should be used for attaching subframes. In Australia they will probably need to be sourced from a specialist supplier such as Profast. At the time of writing there was limited availability of structural rivets on Ebay, but suppliers such as Profast will post out supplies. A pneumatic riveter is available online starting from under $100 and is needed for the higher pressures required to set structural rivets, particularly in confined spaces.

The front and rear subframes mounted to the chassis box are shown above. The suspension mounting points are visible in the photos. The angle of the outer members matches the suspension mounts.

Step 2: Electric Drive

Picture of Electric Drive

The car uses two electric motors mounted on a subframe that sits on the chassis, driving the rear wheels via belts. There is one fixed speed and keeping the belts (or chains) inside the chassis box keeps them clean, minimises maintenance and protects fingers.

This platform is easily adaptable to virtually any motor, either face or foot mounted.
I have used AC motors which are 58kg each. They are a good price for their size and have excellent torque over a large rev range. BLDC or permanent magnet AC motors will give a higher power to weight but are more expensive for an equivalent power output at this size due to the cost of large rare earth magnets. My AC induction motors were sourced from EV Power and came with controllers. Brushed motors are an even more economical option and an Etek / Mars style motor such as the Motenergy ME0709 are available from around $600 each.

The motors also require a motor controller. I won't go into detail about motor and controller selection here as there are other good resources available, however most motor suppliers will offer a motors either with a controller, or will recommend suitable controller options. A purpose built motor controller for a vehicle drive system is designed with forward and reverse and often regen programs. They typically also have switch inputs that will be compatible with a 12V ignition switch to switch the controllers on and off. Connecting up a motor controller is about as complex as fitting an aftermarket stereo to a car, although you need to be very particular about not making any errors or there could be smoke and tears.

The motors transmit power through a toothed belt to the rear wheels. A 30mm wide Gates GT3 will transmit up to 30kW peak power and run smoothly and silently. Chain drives can be cheaper and lighter and provide a higher torque rating. The use of a belt or chain drive eliminates the need for a gearbox as the electric motors have more than adequate torque for single speed operation, particularly with a light weight vehicle.
I am using two AC motors put out a combined 300Nm of torque and with a 1:3 gear ratio from the motor to the rear wheels and while the acceleration from a standing start is excellent, it is currently geared for a very high top speed, thus even better low range performance could be achieved with lower gearing.

Rear Axle
The rear axle comprises two half shafts bolted to the original mazda drive shafts. A large pulley is mounted directly on each half shaft and is driven from a small pulley mounted directly on the motor.  The half shafts are supported by a basic bearing each end, approx 20mm inner and 30mm outer bearing size with a pulley mounted keyed onto the shaft.  The diagram above illustrates the rear axel arrangement.  The half shafts have an outer flange welded to the shaft and machined to match the rear drive shaft flanges of the MX5 / Miata.

There is no interconnection between the two driveshafts or motors - each drives completely independently of the other. The torque characteristics of the electric motors inherently distribute torque between the driven wheels, thus there is no requirement for any differential.  This arrangement will also facilitate simple development of true control systems in the future (torque vectoring) 

HOW TO....
Order your selected motors and controllers
Order small pulley or sprocket with hole and keyway to match electric motor
Order drive belts or chains
Order rear pulleys with a ratio between 1:3 and 1:5. Ratios can easily be changed and experimented with and the best ratio needs to consider the motor selection, target vehicle speed and acceleration characteristics. The larger rear pulley will typically require a taperlock bush. This makes it easy to fit the pulley firmly onto the driveshaft and to change pulley ratios in the future.
The only specially machined items in the drivetrain are two half shafts that have a flange at one end to suit the drive shaft flanges from the suspension donor parts. A large rear pulley or sprocket is mounted on each half shaft and the half shaft is supported with a bearing each end attached to the chassis box and rear suspension subframe.

Step 3: Seating

Picture of Seating

A pressed aluminium floor box is riveted on each side of the chassis box and a 25mm x 1.6mm square hollow steel tube extends across the chassis at the front and rear of the floor box to assist in spreading loads across the chassis so the riveted joints on each side work in unison. Alternatively a frame for the floor boxes hangs over the chassis box and sits on rubber pads making fabrication more suited to interchangeable modular components and providing additional shock absorption for a smoother ride.

It is critical that the passenger cells are well attached to the chassis as considerable loads are encountered in the event of an impact. For the direct riveted floor, loads are shared across a large number of rivets, providing considerable shear strength. Where a floor box subframe is used with a couple of attachment points to the chassis box, reinforcement of the chassis box will reduce the risk of any localised buckling or tearing of the chassis box at the subframe attachment points in the event of higher speed impacts.

The photographs show a ply finish to the top of the floor box. In this example a ply and aluminium composite floor box has been used. The composite panel is constructed by riveting and glueing a ply and alumium sheet over aluminium ribs and a foam core. This increases stiffness, reduces any 'drumming' of the floor and provides a nice finish. It requires more time to fabricate but can reduce the cost of materials as ply is quite cheap and it permits a lighter gauge of the more expensive aluminium to be used.

The seats shown are Jaz Pro blow moulded poly seats. They are light weight, economical and ideal for outdoor use.


Step 4: Battery

Picture of Battery
Batteries need to be selected to suit the peak motor current draw, operating voltage of the motor and controller and a capacity that will provide the required range.

The motors and controllers that I am using operate at 144 volts so I have used 45 lithium cells in series. The peak current draw is 600 amps for brief periods with a maximum rated current for longer periods of 300 amps so I have used 100Ah cells to limit current draw to between 3C to 5C. This gives a 14kWh battery pack which is a bit more than half of the capacity of Nissan Leaf's 24kWh battery pack.
Each cell is 3.3kg giving a total battery weight of 150kg.

A battery pack of this voltage is enough to do some serious damage if you drop a tool across the terminals and can give a dangerous electric shock. A qualified electrician with experience in DC power circuits should complete work on the battery pack.

An essential part of the battery pack is the battery management system. The battery management system is required to ensure individual cells are not over or under charged. A good battery management system will also provide information about the battery state of charge and the current draw in or out of the battery. The cells sourced for this project were CALB 100Ah cells from EV-Power, ordered and supplied complete with EV-Power's own battery management system and a compatible single phase battery charger. The individual cell and battery pack installed in the car is shown in the photos above.

Some background on lithium cells for electric vehicle use from the battery supplier...
LFP batteries have many advantages over Lead Acid, half the weight, higher voltage under load, double the usable capacity and ten times the cycle life! The total cost of ownership is less for LFP batteries than for lead acid.
  • Voltage: 3.2-3.4V nominal, 2.5V min, 3.9V max
  • Cycle life: 2000+ to 80% DOD, 3000+ to 70% DOD, measured, not just claimed.
  • high discharge rate
  • Consistently low internal resistance. (=longer life)p
  • Safe LFP chemistry, proven performance in EVs.

Step 5: Suspension and Steering

Picture of Suspension and Steering

A vehicle platform with double wishbone suspension on each wheel and rear drive has been developed. Wishbone suspension provides maximum flexibility both with body design and ride height as wishbones give easy height adjustment and typically require lower height above the wheels than strut type suspensions. Wishbones also provide optimum handling performance while driving the rear wheels is a little simpler, avoids the need for CV joints on the steered wheels and provides more entertaining handling. Rear wheel drive is also suited to more central placement of the electric motors for optimum placement of the heaviest components closest to the vehicles centre of mass.

The cheapest and easiest way to obtain suspension components is to source from a wrecking vehicle, however there is a limited number of vehicles with front and rear wishbones and rear wheel drive. Two fairly light weight vehicles are the Mazda MX5 / Miata and Honda S2000. I have used a wrecked Mazda MX5 as they are more commonly available in Australia. The suspension from a MX5 is conveniently attached to subframes that can be detached from the car by removing a few bolts. The subframes include all of the suspension mounting brackets so they could be reused, but the chassis box would need some work to cut and fit around the original subframes, so a simpler (and lighter) approach is to fabricate your own front and rear subframes and attached the suspension, wheels, hubs, brakes, springs etc. complete onto the new subframe.
Photographs: The front and rear wheel and suspension after removal from an MX5 is shown in the above photos along with the original front subframe and a rear subframe. Note the front suspension subframe is reasonably heavy as it also incorporates the front engine mounts. The new fabricated subframe can be easily seen on the car in the last photo.

Even though the MX5 is a light weight vehicle, there is still significant unsprung weight, with the four wheel, brake and suspension assemblies weighing a total of approx 140kg, which is nearly 1/3 the weight of the car. For lighter weight (but more expensive and more fragile) aluminium racing wheel uprights and hubs with fabricated wishbones and rod ends can be sourced eg from Formula Ford parts suppliers.

HOW TO.....

Firstly if you need to disassemble the host car to get the components out, refer to a useful guide such as how to remove an MX5 body from the makers of the exocet kit car, although suspension components can easily be removed just by removing wishbone pivot bolts and driveshaft flange bolts at the rear and wishbone pivot bolts at the front.

Secondly press up brackets for the suspension pivots from 50mm wide x 3mm thick steel plate. The bracket widths need to match the width of the suspension bushes on the inner ends of the wishbones. They may need to be slotted to cater for camber angle adjustment. The Mazda uses a simple offset washer to position the suspension mounting point in the slotted hole for camber adjustment.

Thirdly attach the brackets to the suspension arms in the middle of their adjustment range. With the suspension and wheel still assembled, clamp the brackets onto the suspension mounting subframes and check the position and alignment of the wheels. Clamp long lengths of tubing to the wheels to assist in aligning them. Once the wheels are in position and aligned, tack the mounting brackets onto the suspension subframes with a welder, then remove the suspension arms and weld into place.

The steering rack sits at the front of the chassis and two tube or angle arms are welded to the front suspension subframe to mount the rack. The angle of the steering shaft and column needs to be determined to suit the seating position in the car. Placement of a pivoting joint on the steering column mount caters for a height adjustable steering wheel.

3d CAD drawings of Mazda MX5 / Miata suspension assemblies are available online from grabcad and can be used with free 3d CAD programs such as Autodesk Inventor Fusion for development of the suspension design.

The mazda steering rack with power steering has a higher (faster) ratio than unassisted racks. With the lighter weight of this vehicle design, hydraulic assistance is not required and the assisted rack can easily be depowered. Instructions for depowering an MX5 steering rack are available online on MX5 / Miata community forums.

Step 6: Driving Experience

Picture of Driving Experience

The experience of driving and fine tuning a light weight EV designed around a central battery box has been a lot simpler than a petrol powered car. Basically it was plug everything in and check that the motors are running in the right direction, fine tune the two throttle pots, tighten the drive belts and very little else to do.

The concept of twin motors independently driving the two rear wheels has worked perfectly and the motor torque and speed characteristics automatically distributes power to the two rear wheels without the need for an "electronic differential". There has been some drifting in the adjustment of two separate throttle pots that send signals to their respective motor controller. This doesn't cause problems in normal driving and in the future will be addressed by going back to one throttle pot with an electronic splitter.

The EV is being used around a farm with a small tray and is proving convenient, smooth and quiet and with the short range trips typical around the farm, the battery pack does not get discharged below about 85%.

The large section size of the chassis box provides excellent stiffness and there is no discernible scuttle shake and the design will continue to be tested over rough farm roads to prove the strength and reliability of the concept and to expose any weaknesses.

The level of performance of the motors far exceeds that which can be explored on gravel farm roads and some track time will need to be booked in the future for further performance testing. The gravel farm tracks do provide an excellent testing ground for testing torque vectoring systems to get the best performance on slippery gravel roads and a future project to develop an Arduino based torque control system is planned, although not in time for the current Arduino challenge.

Range, Speed and Recharge Time

Update May 2014 typical energy consumption 0.74Ah/km (106wH/km), normal driving, gravel roads.
It uses around 1% of the battery's charge per kilometre on unsealed farm roads and off road, so that equates to 100 km or 60 miles per charge.
For my application and testing, the range is a lot more than required around the farm and the pack was sized more to ensure safe peak current draw than range. The advantage is the extra pack capacity gives a mobile power source around the farm.

Speed is excessive for farm tracks and haven't explored the upper end of the speed range, this will have to wait for track time. On the tree lined farm tracks I wouldn't go more than 100km/h or 60mph. Estimated top speed is around 160km/h or 100mph but dependent on the aerodynamics of the body as the car good low end torque geared for a top speed of 200km/h (1:3 motor to drive ratio, 6000 rpm motor speed) although it will not be able to reach speeds this high without a low drag, streamlined body. A lower gear ratio is planned and will increase acceleration to 100km/h which is faster than needed.

The recharge time is about 5 minutes per 1% of charge or 8 hours for recharge from fully discharged using a 10amp 240 volt single phase battery charger. The charge rate is not linear and as the battery approaches fully charged, the charge rate drops off.

Step 7: Resources

BotEV Chassis Platform November 2013 2D CAD file (dwg)
Chassis Box cross section CAD file (dwg)

3D CAD model information

Suppliers & Parts
Motors, Controllers, Batteries and Battery Management - EV Power (Australia)
     Smaller motors for light weight EV projects also check out Cyclone Motor, Golden Motor and Kelly Controls
Drive pullies and belts - Gates GT3, Busselton Bearings
Aluminium Pressings - Combined Metal Industries
Seats Jaz Pro - Ebay, Sydney supplier

I would like to thank Rod Dilkes from EV Power for his encouragement, support knowledge and assistance. Rod is the brains behind the electrical setup for this project.


goldenshuttle (author)2014-02-02

This is a great post indeed. You probably want to try this book which shows you how to make your car run forever without recharging the battery. It really works:

If you are working against the principles of the Law of conservation of energe ,then you will definately end up wasting your time,energy and money.

SirCooksalot (author)DIY KING 002015-06-04

I believe there is a motor in existence that runs on hydrogen, and refuels from hydrogen present in the atmosphere. My dad and I debated whether or not that falls into the category of perpetual motion, but regardless, mechanical failure aside, it could 'run forever' without the user physically refueling. It does require fuel, but it auto-refuels- sort of like if your gas car could draw petrol from the ground while you drive!

Ganhaar (author)SirCooksalot2015-06-06

The amount of hydrogen in the atmosphere is about 0.00005% so you would need 2,000,000 litres (or gallons) of air to extract one litre (or gallon) of hydrogen. It you were using 10 litres per hour and and your extraction efficiency was 50%, you would need to process 40,000,000 litres of air per hour or 11,000 litres per second.

Tahquitz (author)Ganhaar2017-03-30

That 11k l/m would make a terrible sucking sound and I would not want to operate that ride.

tkddms225 (author)Ganhaar2015-08-24

Or... Use water electrolysis... But that would just defeat the whole purpose since it would probably take more energy to do water electrolysis than just use the energy directly.

Grimm123 (author)tkddms2252015-10-03

yup, an efficient way to separate water into H H O is still not likely to happen. if it took less energy to separate it than the energy you are getting, it would be in violation of thermodynamics. if there was simply a low loss method, then at some point hydrogen could be a viable fuel but from what i have seen, its still a ways from being a reality.

Grimm123 (author)tkddms2252015-10-03

yup, an efficient way to separate water into H H O is still not likely to happen. if it took less energy to separate it than the energy you are getting, it would be in violation of thermodynamics. if there was simply a low loss method, then at some point hydrogen could be a viable fuel but from what i have seen, its still a ways from being a reality.

loki2012 (author)goldenshuttle2015-06-05

Make an R/C version first as proof of concept. I highly doubt it will work, but no harm trying.

I'm pretty sure that if this worked, it would be breaking one of the fundamental laws of nature, the Law of Conservation of Energy.

Suffice to say, I'm skeptical.

Michael013 (author)BeefDivision2015-06-04

According to Stephen Hawking, all you need to beat conservation of energy is a Big Bang. Should be simple enough.

valveman (author)goldenshuttle2015-06-04

I am 100% positive that the Fueless Motor you describe is bogus. No it does not work because devices which power themselves would fall into the category of Perpetual Motion and as a previous poster said, it would contradict the Law of Conservation of Energy.

Tomas Jansen (author)2017-02-27

The only problem i see with this is the motors are not protected against dust and dirt. it could effect the motors

RonQ2 (author)2017-01-08

.. could the two motors be wired in series - motors with half the voltage rating? Then a single speed potentiometer would suffice ...

Ganhaar (author)RonQ22017-01-10

That won't work with brushless motors - each motor needs electrical pulses sent to the coils in the motor synchronised to the rotation of the motor. In addition you need to keep the voltage up to minimise amperage to get the maximum power from a given size motor and reduce cable sizes, improve efficiency etc.

ANIRUDHT (author)2016-12-09

Hi Ganhaar, youhad mentioned that the use of two motors will eliminate the differential. How will you the car perform well in the corners. Won't the two motors run at slightly different speeds.

MakerN1 made it! (author)2016-09-19

HI, it's a cool project and I agree with your opinion about ev opinion and we do a similar open source vehicle(which is simpler than your). I attach the picture of my OSV. could we contact deeply through email ( .I has some new views about this vehicle ,and I want to get guide from you.

Ganhaar (author)MakerN12016-09-19

Hi MakerN1,
Thanks for the picture, I love your work on the 3d graphics modelling. Much more advanced than my humble attempts. I will send an email and happy to discuss ideas further,

74khart (author)2016-04-09

This is a good project, thanks!

I have an idea I have been considering, but one which I have not been able to find discussed on any forums... Could it be possible to use one electric motor in the same fashion as what you have shown here, going to only one rear wheel of a car that has FWD, with manual transmission ??

The elements I am trying to accomplish here is an economical and simple feasibility.

Electric motor would be set up just like yours, direct drive & half shaft, belt driven, no transmission.

Electric motor could be used for maintaining constant speed in city driving. I.e 50 Km/hr. While the combustion engine and manual transmission would do the initial work.

This way the electric engine has a narrow enough bandwidth to remain efficient, and I could still make use of of transmission, without over complicated design.

I can not afford the 15 thousand to do all of this, but to do one engine only, maybe, if I can network with some other people who have some experiences firsthand. This is the reason I am glad to find this project you have built.

Please mention any concerns that may come to mind with this idea mentioned here, or email

Thanks again for nice project posting!

Ganhaar (author)74khart2016-09-19

Hi, How is the project going. Sorry I missed your post before. I can't see any reason why just driving one wheel won't work. A couple of issues that may arise but shouldn't be too significant are limited traction in more slippery situations particularly unsealed or wet roads, going over a large bump affecting only the undriven wheel will tend to lift the driven wheel off the road. This will affect a vehicle with a higher suspension roll stiffness more than one with a low suspension roll stiffness and finally driving only one side of the car will induce a turning force on the vehicle. For a lower power vehicle this could be easily counteracted by the wheels of the car but it may create a noticeable pull on the steering and contribute to uneven tyre wear.

If you are converting an existing car, a better ploy may be to put the drive of the electric motor onto the engine driveshaft, gearbox output or differential input.

I have thought for some time now that an electric motor providing a torque boost to the engine driveshaft would be a great mod that would not only improve efficiency but also be able to boost power and torque as well and would make a much better performance upgrade kit than the turbocharger or supercharger kits that some companies offer.

OogieMustBoogie (author)74khart2016-05-13

interesting idea, sounds like you are considering hub motors, which work well if properly done. with that said, using half shafts would not be direct drive, but hun motors would be. your first issue would not be cost, it would be gearing. a hub motor going straight into a wheel (even one already spinning) would not have any reduction. this idea could potentially work, but I'm not sure your price would be as high as 15k. a manual tranny donor vehicle (maybe a civic, etc) would set you back less than 3k and a two motors/controllers would be another 5-6, I think it could be done for under 10k

andymenon (author)2016-07-24

This is awesome! Years ago when Tesla displayed it's platform at a showroom in a local mall, I came to know from the people there that the entire frame, suspension and drivetrain comprised of approximately 168 components.

Electric cars are truly open source, but to make them road worthy, the safety features and certifications required will need to be figured out by we the common folks!

Great project! Someday, I will need to give this a shot!

OogieMustBoogie (author)2016-05-04

ganhaar, I'm in the middle of a single seat electric car project. I have a similar transmission setup with single speed but in my case, it is connected to a FWD ifs differential. since there are not multiple gears, I saw you were using AC induction motors because they have a wide range of torque, great for single speed setups. I was planning on using the warp 9 DC motor in this configuration. do you think a DC motor will have enough torque range to serve this purpose? thanks

Ganhaar (author)OogieMustBoogie2016-05-11

It's been a while since I've looked at brushed DC motors so I don't recall how their torque curves differ, but there are plenty of examples out there using warp9 motors and they still have a much better torque range than a petrol motor.

Some considerations will be how heavy is you vehicle, how hilly is the terrain you operate on, what top speed do you want and how fast do you want to accelerate. If you only drive around town and don't need high top speeds then it will probably be much easier. If you want good acceleration at low speeds as well as a high top speed, you may be better off with a gearbox.

OogieMustBoogie (author)Ganhaar2016-05-12

thanks for the reply, vehicle will weight around 900 lbs with a ifs diff with a ratio 1:2.9, i'm thinking that from the warp 9 will be a decent balance of top speed/torque

if you want, check out the build here

msh1353 (author)2016-04-25

well done .

i think that it is a bit wide !

Ganhaar (author)msh13532016-05-11


Yes it is wider than it needs to be, however I choses to go slightly wider instead of shortening the driveshafts from MX5

ChristianL72 (author)2016-03-22

hey could you tell me where you got your steering system? I'm currently building an EV with my school for a solar car competition, and would love it if you could recommend a steering kit or where you got your steering kit.

Ganhaar (author)ChristianL722016-03-22

steering rack came from an MX5 and the instructable mentions that the power steering is disabled. How much will your car weigh? you may be able to use direct steering similar to a gokart or quad bike. You may even be able to pick up parts for next to nothing from an old quad bike.


steve000 (author)2015-06-06

Hey mate, I have seen this before.

  • 45 x CALB CA100FI cells with CM090 cell modules and BCU-PEV-45C
  • Dual GLE IM15 AC induction motors, 150V 300A 6000rpm each
  • Belt driven rear wheels
  • vehicle weight < 500kg
Ganhaar (author)steve0002015-06-07

Where abouts? Do you have a name or a link or somehow I can follow this up, I would be interested to see other similar projects and what sort of performance they are achieving.

mragan3 (author)Ganhaar2016-03-04

plan not available

Ganhaar (author)mragan32016-03-14

Thanks for the heads up.

If you message me your email address I can send them by email. Probably only a handful of people chasing plans at this point so probably easier just to email out now.



fstedie (author)2015-06-04

You would not be able to license it for road use in the US though, you'd have to make it a 3-wheeler

Grimm123 (author)fstedie2015-10-03

that is not entirely true, people scratch build cars all the time, its a matter of getting the proper rules for your state. in Idaho, you have to bring the major component receipts to the sheriffs dept to prove you didnt get them from stolen vehicles/parts. then they give you the papers to go to the DMV to finish the licensing and roadworthiness inspection.

things like crash ratings are only subjected to vehicle manufacturers, not home builders.

Ganhaar (author)fstedie2015-06-04

From what I have seen i agree it would be easier to license as a three wheeler, but it doesn't make a lot of sense that it is easier to license a less stable, i.e. less safe vehicle.

Grar Varg (author)Ganhaar2015-08-17

I see you are only using the rear wheels as powered wheels, why not use all 4 wheels as powered wheels? If you combine that with the use of an alternator connected by a belt to each rear wheel to help keep the batteries charged you would extend the distance you could drive.

Ganhaar (author)Grar Varg2015-09-01

powering all 4 wheels is ideal, but I haven't done so here to keep the drive train as simple as possible and to reduce cost. There is added weight, cost and complexity for powering the front wheels with CV joints and motors. The motors can also act as alternators so they do charge the batteries in regen which is more efficient than a separate alternator being driven constantly driven from the driveshaft.

fstedie (author)Ganhaar2015-06-05

What I'm saying is that in the US (and more specifically in California), it is extremely difficult to license a home-built vehicle due to all the safety restrictions, no matter what kind of body you put on it. A 3-wheeler is registered as a motorcycle in many states.

As for the stability and safety issues, you simply have to look at other production 3-wheelers to know that a 1R2F vehicle like the T-Rex or the new Polaris Slingshot are just as stable as 4 wheel car. Now put the wheels the other way around and you're asking for trouble...

leonthedruid (author)fstedie2015-06-05

Or use an existing platform as in DC Plasma Fiero and a Hybrid Fiero converted in 2009. But this project is a grounds up proof of concepts and do it yourself all the way fun project.

Ganhaar (author)fstedie2015-06-04

This was not intended to be a completed car ready for licensing, rather it is the mechanical platform for a car complete with chassis, motors, batteries, steering and brakes ready for a body to be fitted. I have deliberately published without the body as I want the focus to be on the design of the chassis and drivetrain rather than how the body looks.

SirCooksalot (author)2015-06-06

What if the engine took moisture from the atmosphere and then extracted the hydrogen from the water? And also how do you know how much hydrogen it needs to run... You say 'it would take x amount of air' but to calculate that you'd need to know the consumption rate of hydrogen. Ive seen what appear to be genuine examples of powerful engines running on pure h2o, assuming they're real, and the hydrogen is the fuel, one can imagine some super efficient condensermajiggy that can collect atmospheric moisture and keep you running. I gueeeeess if I had to top it off with a gallon of Poland Spring before I left the house, that'd be ok lol. Anything that runs on any kind of fuel has the potential to run out of that fuel so it can't be 'perpetual', but the idea of an engine equipped with a system to 'gather' it's own fuel is interesting. I think I read somewhere that one of the electric cars out there uses the friction created by braking to recharge the electric battery. If you could do that efficiently enough, you could have a self charging electric car that basically fueled itself. Probably gives oil stockholders nightmares!

tkddms225 (author)SirCooksalot2015-08-24

That's so awesome! I've recently been looking into hydrogen fuel cells used in cars, and the best one so far is Toyota's Mirai. Although it's not a vehicle that can refuel itself with resources around it, once we have hydrogen refueling stations around the country, I think hydrogen fuel cell cars are the best they can come up with. That's probably why I like your idea... Have any thoughts about going in the industry? Hahaha

ToolboxGuy (author)2015-06-07

I think you meant "spurred" not "spurned" when talking about the spinoff companies...?

wanton (author)ToolboxGuy2015-06-16

Think he means "spawned" (created/caused to be created)

aassad (author)2015-06-15

Would be cool to install a MultiSoundBomb on it :)

kweigant (author)2015-06-11

How would you like unlimited battery? I have the solution and it is 18 years old. Car factories watch out, I got even tesla beat on this.

Driver69 (author)2015-06-10

I'm still looking for some one to come up with a electric handycap van for my wife.

Blaise_Gauba (author)2015-06-07

Wow...that is really cool. I've always wanted to have an electric car. There's nothing more satisfying than driving right past the petrol station...and the minimum maintenance is a super plus. I live in southern California...and don't have access to a place where I could build an electric vehicle. But I can dream...right? Nice car guys.

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