[Galileu]

Hi all,

My name is Jose B. Almeida, I live in Portugal and I am a retired university professor; since I have a lot of spare time and some knowledge of car mechanics, electricity and electronics, I am considering a project for an EV conversion. I would like to do something which is a little challenging and saving money is not my primary motivation.

My idea is to start with a donor vehicle which has 2 rigid axles and a chassis, possibly a Suzuki Samurai, get rid of engine and transmission in order to fit 4 electric motors, one for each wheel. The converted vehicle won't have differentials, their action being replaced by electronic control of each motor's speed, with input from the steering.

At this stage I have only a very broad idea of what I will be doing, this idea being likely to change substantially in the course of the project. I will welcome all the help and suggestions that people can make and I intend to report as the project advances.

Best regards

[nimblemotors]

Hello Jose, welcome to diy.
That project idea sounds like about half of all that come here with the same idea, put a motor on each wheel.

If you are looking for a challenge,
I say that saving money is the greatest challenge!
i.e. building an EV cheaper and yet better than using off-the-shelf parts and proven techniques. Anyone can build an expensive EV.

What advantage are you trying to gain with 4 motors and no physical steering that is worth the expense and complexity? Save the weight of a steering column and rack? Do you plan to have the car steer itself, so a human doesn't have to steer it, i.e. Google's self-driving car.
The failure mode of this design can be disaster.

Not sure what suggestions you are looking for.

Originally Posted by Galileu

Hi all,

My name is Jose B. Almeida, I live in Portugal and I am a retired university professor; since I have a lot of spare time and some knowledge of car mechanics, electricity and electronics, I am considering a project for an EV conversion. I would like to do something which is a little challenging and saving money is not my primary motivation.

My idea is to start with a donor vehicle which has 2 rigid axles and a chassis, possibly a Suzuki Samurai, get rid of engine and transmission in order to fit 4 electric motors, one for each wheel. The converted vehicle won't have differentials, their action being replaced by electronic control of each motor's speed, with input from the steering.

At this stage I have only a very broad idea of what I will be doing, this idea being likely to change substantially in the course of the project. I will welcome all the help and suggestions that people can make and I intend to report as the project advances.

Best regards

[rwaudio]

Originally Posted by Galileu

Hi all,

My name is Jose B. Almeida, I live in Portugal and I am a retired university professor; since I have a lot of spare time and some knowledge of car mechanics, electricity and electronics, I am considering a project for an EV conversion. I would like to do something which is a little challenging and saving money is not my primary motivation.

My idea is to start with a donor vehicle which has 2 rigid axles and a chassis, possibly a Suzuki Samurai, get rid of engine and transmission in order to fit 4 electric motors, one for each wheel. The converted vehicle won't have differentials, their action being replaced by electronic control of each motor's speed, with input from the steering.

At this stage I have only a very broad idea of what I will be doing, this idea being likely to change substantially in the course of the project. I will welcome all the help and suggestions that people can make and I intend to report as the project advances.

Best regards

Welcome to the forum!
Sounds like a cool project, I've dreamed of a small awd EV that would do winter duty up here in Canada. I had a different idea though, using a vehicle with 2 rigid axles I would keep them and do a motor to the front and one to the rear. Or instead of an EV conversion you would need to redesign/build the entire suspension and drive line. Unless your design is for a replacement rigid axle with integrated motors/gear reduction, I think that would be a pretty heavy live axle though? If I were to do a 4 motor setup I would look to a vehicle with 4 wheel independent suspension so that I could simply remove the existing diff and drive each wheel separately through the existing axle shafts without having to mess with the suspension system.

Good luck with the project though, I'd love to see a small awd setup completed to see what kind of efficiency you got and your resulting wh/mile, and how well the awd system performs on electric.

Would you be looking at an AC or DC system? Lithium or Lead? Range and Speed? Terrain that you would be driving in?

[Galileu]

OK, I didn't know ny idea was so common, although I didn't expect it to be original; and surely it won't be self steering.

A 4 motor EV, totally electronically controlled is expected to behave as a 4WD with both diffs locked for low grip situations and ride normally on tarmac. The idea is to have a central controller that tells each motor what speed it has to rotate. In order to do this the controller receives input from the steering and calculates the optimum rotating speed for each wheel. The controller part doesn't scare me, it's the mechanical side that I feel uneasy about.

What I like about a car like the Samurai is that it is possible to completely remove the body to work freely on the chassis. I think this would probably be one of the best choices for proving the concept, after which it could be implemented in other cars.

[Woodsmith]

One issue with 4wd using 4 motors is that in conditions of poor traction there is only 1/4 of the power available to any wheel with traction.

If your conversion is for tarmac use and in good conditions then that would not make any real disadvantage. However if you wish to go off road then I would recommend a single motor driving though the transfer box, and possibly the main gearbox as well, and then adding limited slip or locking differentials to the axles.

You idea of electronically controlling the drive motors in lieu of the differentials may be over complicateing things. Two, or I guess four, motors on the same controller would have a degree of variability I would think. Certainly, from what I gather, series motors would do just that.

If you want to have individual wheel motors then it may be best to avoid series motors, especially when off road, as lifting a wheel would result in a series motor spinning to death.

Given that you have some knowledge, and want a challenge, it may be a good idea to start off with the simplest conversion, swaping the exisiting engine for a single series motor, and then learning the differences in the way it responds and can be controlled. As your knowledge on the control side is developed and proven through experiment switch to twin motors, one to each axle, to see how the varying speeds and torque requirements can be controlled effectively.

[Galileu]

Originally Posted by Woodsmith

Given that you have some knowledge, and want a challenge, it may be a good idea to start off with the simplest conversion, swaping the exisiting engine for a single series motor, and then learning the differences in the way it responds and can be controlled. As your knowledge on the control side is developed and proven through experiment switch to twin motors, one to each axle, to see how the varying speeds and torque requirements can be controlled effectively.

Very good advice; one step at a time. Thanks!

[nimblemotors]

The battery is usually the limiting factor for power, so as long as the motors are not undersized, they could use the reduced power to a given motor.

I think I misunderstoods Jose's design, I thought he was eliminating the steering, and steering using wheel braking like a tank/tractor, but I see it is just an input to adjust wheel slip, as you can force each wheel to rotate the same speed, but this would need to be adjust when turning,
although the difference is not much, locked differentials seem to work just fine in offroad, but I have no experience here.

If you keep the differentials, there is no control of each wheel speed, so not sure that helps.
The problem with removing the differentials is you have removed their gearing, so you'd have to replace it for each motor.

Maybe another design approach is to have a single big motor that feeds two open differentials, and then add 4 small AC motors that can slow the speed and use the braking effect to regen back to the pack, and thus effectively xfer that power to the other wheels. Of course, this is complicated and not inexpensive. (Excuse my crude drawings..

Originally Posted by Woodsmith

One issue with 4wd using 4 motors is that in conditions of poor traction there is only 1/4 of the power available to any wheel with traction.

If your conversion is for tarmac use and in good conditions then that would not make any real disadvantage. However if you wish to go off road then I would recommend a single motor driving though the transfer box, and possibly the main gearbox as well, and then adding limited slip or locking differentials to the axles.

You idea of electronically controlling the drive motors in lieu of the differentials may be over complicateing things. Two, or I guess four, motors on the same controller would have a degree of variability I would think. Certainly, from what I gather, series motors would do just that.

If you want to have individual wheel motors then it may be best to avoid series motors, especially when off road, as lifting a wheel would result in a series motor spinning to death.

Given that you have some knowledge, and want a challenge, it may be a good idea to start off with the simplest conversion, swaping the exisiting engine for a single series motor, and then learning the differences in the way it responds and can be controlled. As your knowledge on the control side is developed and proven through experiment switch to twin motors, one to each axle, to see how the varying speeds and torque requirements can be controlled effectively.

[Galileu]

Originally Posted by nimblemotors

The battery is usually the limiting factor for

I think I misunderstoods Jose's design, I thought he was eliminating the steering, and steering using wheel braking like a tank/tractor, but I see it is just an input to adjust wheel slip, as you can force each wheel to rotate the same speed, but this would need to be adjust when turning,
although the difference is not much, locked differentials seem to work just fine in offroad, but I have no experience here.

Right! On turns the wheels must turn at different speeds but the beautiful thing about electronics is that it does complex calculations. With steering input one can workout the turning circle for each wheel and hence calculate it's turning speed.

[Woodsmith]

Originally Posted by Galileu

Right! On turns the wheels must turn at different speeds but the beautiful thing about electronics is that it does complex calculations. With steering input one can workout the turning circle for each wheel and hence calculate it's turning speed.

Does that mean that you are planning on having a live feedback loop to ensure that the controller knows where each wheel is and how fast it is turning?
I think this is overly complex and not really necessary.
You could still prove the functions with a much simpler set up first though. Do it with two motors, one for each axle and if that works then take it further.

[Galileu]

Originally Posted by Woodsmith

Does that mean that you are planning on having a live feedback loop to ensure that the controller knows where each wheel is and how fast it is turning?
I think this is overly complex and not really necessary.
You could still prove the functions with a much simpler set up first though. Do it with two motors, one for each axle and if that works then take it further.

I'm not rejecting this suggestion completely, although it is very likely that the 2 motors used for the trial cannot be used for the 4 motor setup. I guess for the latter I'll be considering four 7KW induction motors or perhaps a little less for the front axle, while for a 2 motor setup I would be talking about something on the region of 10KW to 15KW.
As I wrote earlier the controller doesn't scare me and designing it is part of the challenge; furthermore I expect the 4 motor setup to outperform a similar powered ICE 4WD, particularly off-road, whereas the 2 motor version should perform on a par with the ICE.