A $1200 Mass Produced Electric Car

[gruntguru]

The "car expert" calls the Chanli's front beam axle a McPherson strut???

[Cold Fussion]

Carmakers are dictating what we should drive instead of consulting the public,

Surely the automotive trends show it is the opposite that is happening. What is the engineering justification for any crossover to exist? From what set of logical requirements would a "sporty" SUV be the optimal solution? People are irrationally attracted to the idea that their car can do anything, even when it does pretty much everything sub optimally. If people bought bikes the way they did cars, the cycle-way in an inner city park would be littered with downhill bikes

[Pat Pending]

If people bought bikes the way they did cars, the cycle-way in an inner city park would be littered with downhill bikes

And every city centre office bike-park would be filled with carbon framed road racing bikes. Oh, hang on...

[Cold Fussion]

If people bought bikes the way they did cars, the cycle-way in an inner city park would be littered with downhill bikes

And every city centre office bike-park would be filled with carbon framed road racing bikes. Oh, hang on...

I have marginal gains tattooed to my thigh so I'm perfectly ok with this.

[Martin Keene]

Drum brakes are lighter, easier to package, guarantee zero drag, and self-servo. They have some very significant disadvantages of course. If you are using regen then they become emergency brakes.

The biggest advantage of disks is anti-fade with repeated heavy use. If this car is regen, there will not be much heavy use, and with the intended use there will not be high speed stops either repeated or not.

As an 'eco' aside, the dust is retained in the drum too.

Also, with regen braking the rear's do very little work, and with a disc the moving parts are open to the environment, where as with a drum they are enclosed insode the drum that protects them from the elements.

This was covered by Johny Smith, aka Car Pervet, on one of his videos discussing this very subject with a brake manufacturer.

[henry]

Drum brakes can also self servo, so the servo unit could be dispensed with saving cost and weight.

[Big Tea]

Drum brakes can also self servo, so the servo unit could be dispensed with saving cost and weight.

Its a trade off of self assisting or having the 'advantage' of assisting anti-rollback on hill starts. But with an electric drive I don't know that would be relative.

[Jolle]

Drum brakes can also self servo, so the servo unit could be dispensed with saving cost and weight.

Its a trade off of self assisting or having the 'advantage' of assisting anti-rollback on hill starts. But with an electric drive I don't know that would be relative.

Drum brakes are ideal for light electric city cars with re-gen. Disk brakes don’t do well when salt is used on roads and they don’t get used (especially with rotating aluminium and stuff around).
As re-gen becomes stronger on big cars and brakes more a backup, my guess we will see a new type of covered inverted disk brake or something.

[Greg Locock]

Women affect 80% of new car purchases in the West. One of the things they like is to sit high in the car when driving. Hence CUV. I'd like to see the actual report on that rather than anecdote, but there you go.

[Tommy Cookers]

Drum brakes can also self servo, so the servo unit could be dispensed with saving cost and weight.

Its a trade off of self assisting or having the 'advantage' of assisting anti-rollback on hill starts. But with an electric drive I don't know that would be relative.

Drum brakes are ideal for light electric city cars with re-gen. Disk brakes don’t do well when salt is used on roads and they don’t get used (especially with rotating aluminium and stuff around).
As re-gen becomes stronger on big cars and brakes more a backup, my guess we will see a new type of covered inverted disk brake or something.

does ABS with drum braking exist ?
how does ABS fit with regenerative braking ?

ABS seems to be the enabler of the 21st century novelty the 'town car'
ie the car with a body that ends where the rear wheel envelope ends
(the car with a 70/30 weight distribution - and related ride issues)

no BEV will have 70/30 weight distribution

[Jolle]

Its a trade off of self assisting or having the 'advantage' of assisting anti-rollback on hill starts. But with an electric drive I don't know that would be relative.

Drum brakes are ideal for light electric city cars with re-gen. Disk brakes don’t do well when salt is used on roads and they don’t get used (especially with rotating aluminium and stuff around).
As re-gen becomes stronger on big cars and brakes more a backup, my guess we will see a new type of covered inverted disk brake or something.

does ABS with drum braking exist ?
how does ABS fit with regenerative braking ?

ABS seems to be the enabler of the 21st century novelty the 'town car'
ie the car with a body that ends where the rear wheel envelope ends
(the car with a 70/30 weight distribution - and related ride issues)

no BEV will have 70/30 weight distribution

It does. Most small European city cars have drum brakes at the rear and ABS. On the control side drum and disk brakes don’t differ, it’s simply adjusting the hydrolic pressure. As for ABS and regen, that’s even simpler. Just modulate the regen. Don’t even need a valve and pump system (because it’s brake by wire).

[Tommy Cookers]

....As for ABS and regen, that’s even simpler.
Just modulate the regen. Don’t even need a valve and pump system
(because it’s brake by wire).

I don't believe that's what they do in most road EVs
though the descriptive material out there all seems poor

can anybody link some good material ?

[Greg Locock]

AFAIK all EVs have hydraulic brakes as well as regen. You can't rely on using the motors as brakes in high speed/high g situations, you'd kill the batteries, and unless you have one per wheel you can't use them only for ABS. It takes 8-16 minutes to get Tesla's battery ready for a 1.2 g drag takeoff, that waiting time might be a bit of a disadvantage in 1 g emergency stop.

[henry]

Most BEVs are single motor, single axle drive so the opportunities to manage wheel lock by re-gen don’t really exist.

For those cars that do have individual wheel control the power is an issue, as @Greg Locock points out. For a 2000kg car in a 1g stop the instantaneous power at 30m/s (60mph ish) is 600kW. High powered cars like the Taycan and Model S Plaid have 2 high performance motors at the rear which doesn’t help when trying to prevent locking on the steered wheels.

I wonder if there might be some mileage modulating traction by powering the locking wheels during braking to keep them rotating perhaps linked to steering inputs. So using the electrics to modulate the hydraulic braking which could be done at lower power levels.

[Tommy Cookers]

.... there might be some mileage modulating traction by powering the locking wheels during braking to keep them rotating perhaps linked to steering inputs. So using the electrics to modulate the hydraulic braking which could be done at lower power levels.

afaik
that characteristic is inherent to any type of EM or EM system used in a BEV
and most systems will anyway have an inner 'speed' (rpm) control loop supervising the torque control

ie if during driver-commanded regen both driven wheels hit an ice patch ....
the generation torque will collapse and may even be replaced briefly by motoring torque
the system is a continuous one between max motoring torque and max generating torque

ie for stability the system must have a relatively low frequency response eg lower than the ABS's frequency response


there's arguments for having the EM inactive when braking demand requires mechanical braking
some articles seem to imply this (saying when mechanical braking starts the brake pedal 'steps down')

my guess for the typical EV is that max regen torque is about 0.2 g
significantly it seems to be driver-settable