Very Mild Hybrid
 

I have a 2004 Smart Roadster Coupe, it weighs just 800kg(1800lbs), is only 1.2m(47" or whatever weird completely random uint of measurement you use for car height) tall, has a 60KW 3 cylinder 700cc rear-mid engine mated to an absolutely awful 6 speed automated manual driving the rear wheels.

I love this car, but the transmission shifts incredibly slow, combined with the fact that the tiny engine NEEDS revs and boost to accelerate sensibly, I crave a little electric boost sometimes. When I make a turn the transmission takes a couple secs to shift, then the engine takes its time to make power resulting in basically having 0 power while turning, which isn't nice. If I had just a little power that would be much nicer, also during gear shifts a little extra power, so I don't loose speed, would be greatly appreciated.

I would like to add small (2-5KW) motors to the front wheels and a very small battery (~5kWh), just enough to drive ~15km pure electric.
The whole system shouldn't be to heavy, since you really feel every kg in such a light car. Ideally the electric motors should have enough torque to start the car from a standstill, if it can do that it could replace the reverse gear, the alternator/battery and the starter.

Reverse gear: simple just reverse the polarity of the motors and you have reverse.

Alternator/battery: use the motors as regenerative brakes. I don't need much power anyway, I don't use the ac, stereo or any other unnecessary stuff. If the power gets to low just use the motors like a normal alternator.

Starter: the motors should be able to push the car to ~10kph meaning I can bump start the engine like LMP cars.


The question is just what motors should I use and how to mount them. my car is currently on 25mm spacers but 30-35mm should be easily possible. mounting them directly onto the rims seems the most solid to me. I habe a CNC so making a mounting plate shouldn't be a problem.


What motors should I use? I saw some scooter motors which are rated up to 120kph (would be really nice) although they are probably not slim enough to fit.

Serial hybrid, with an altermotor and serpentine toothed belt system, controller and battery, starter delete.

An exemplar would be the GM eAssist.

Keeping an eye for some wrecked Fiat or Jeep with a mild-hybrid version of that 3-cyl 1.0L GSE engine and swap it into your car could serve you quite well.

Firstly I should've specified that my goal isn't 100% to reduce consumption, I want to improve drivability, offsetting any weight gains in the front by removing parts (which this system makes redundant) in the rear.

I thought about something like this, but this wouldn't help me with the whole "no power during shifting" situation, when turning the engine would build power faster but nothing else.

The system should be behind the transmission and ideally on the front wheels.

you most likely can't swap a normal engine into this. It is still a smart car, it has a tiny engine, which is 60° tilted and the engine bay is cramped as hell, there are some engine swapped Smart Roadsters out there and all to motorcycle engines, which is also what I would do.

Easiest would be to find OEM components. But now I can't change my vote.

So if you want to put a hub motor on the rim, I'd look to the eight-bolt Pontiac aluminum drums.

https://live.staticflickr.com/4055/4...aac86c31_b.jpghttps://live.staticflickr.com/4055/4...aac86c31_b.jpg

But machine them to use VW/Porsche wide-fives or similar.

Traditionally, electric motors are axial flux or radial flux, but good results have been shown for transverse flux.

1968 The Generator You Have Never Heard Of - Transverse Flux

I live in Germany, US car companies never did to hot here, if there are any here they will be really expensive.

but the concept of using the motor as part of the rims doesn't seem bad, I have a set of steel rims which I won't drive again, so they are perfect to experiment on, maybe I will do something similar

With the wide-five bolt circle you could have a fat hub sticking through the wheel. With fins.

My 2020 Ram has a system called etorque that accomplishes something similar but without any extra drive motors. The alternator is a motor/generator and can drive the drive train through the conventional engine. So it never really does it without the engine also running at least at an idle, but it does regen braking, auto start stop, and adds 16hp and 130 ft-lbs of torque. Has a very small battery 48 volt, 430 watt hour. Oh and the whole system adds 90 pounds total
https://www.popularmechanics.com/car...-1500-etorque/

Doesn't sound bad at all. Sometimes I still lurk about a Honda CB 500 engine swap into some econobox, yet it wouldn't be so easy to import an auxiliary gearbox to provide reversing, such as those manufactured by Quaife in England or by Rito in Portugal.