A $1200 Mass Produced Electric Car

[Big Tea]

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

Does it have to break and regen through the drum?
For instance, can the motor not do both jobs for much of the time and the actual friction break just be for when needed or at times of full charge?

I mean as in rear end break via regen and front as hubs?.

I do see what you mean though, as in some earlier cars had a 'disk hand break' which breaked the axle

[coaster]

Could a system be devised to store braking and acceleration energy as pnuematic pressure?
Each wheel could have a pnuematic hub motor performing all functions.
No bulky copper windings or bulky magnets, surely electricity cant be the only solution?

[Zynerji]

Could a system be devised to store braking and acceleration energy as pnuematic pressure?
Each wheel could have a pnuematic hub motor performing all functions.
No bulky copper windings or bulky magnets, surely electricity cant be the only solution?

I think we discussed hydraulic drive here years ago (like cam-ring motors integrated into the wheel hub/upright). It was something about flow volume or something that made it unusabe.

I think pneumatic would fail for similar reasons to hydraulic.

[Billzilla]

I think pneumatic would fail for similar reasons to hydraulic.

I chatted with someone about this, maybe here, many years ago. Using compressed air to capture energy when slowing down isn't particularly difficult but (from memory) you only get back about 60% of that energy when using it to accelerate again.
Still worth looking at though I reckon, as pneumatic gear is quite a lot cheaper than battery packs .... for now at least.

[Greg Locock]

Compressed air storage has a big problem- temperature. When you pump the air into a tank it gets hot. That heat is a large part of the stored energy. If you let the air cool down then you have the opposite problem when you try to expand it again - basically your motor freezes up.

So you either thermally insulate the tank, or rely on using the stored air before it has time to cool down, which for regen brake seems quite likely anyway.

I doubt anyone is really working on this any longer, the industry is entirely consumed by BEVs at the moment. I'm slightly amazed we're even working on PHEVs, although there are some markets where they'll be allowed.

[Zynerji]

Compressed air storage has a big problem- temperature. When you pump the air into a tank it gets hot. That heat is a large part of the stored energy. If you let the air cool down then you have the opposite problem when you try to expand it again - basically your motor freezes up.

So you either thermally insulate the tank, or rely on using the stored air before it has time to cool down, which for regen brake seems quite likely anyway.

I doubt anyone is really working on this any longer, the industry is entirely consumed by BEVs at the moment. I'm slightly amazed we're even working on PHEVs, although there are some markets where they'll be allowed.

Is this a concern in an air bladder tank where hydraulic fluid is concerned? Its just compressing the bladder, not holding the energy in heat?

[coaster]

Maybe air over oil such as a shock cannister?

[Jolle]

Compressed air storage has a big problem- temperature. When you pump the air into a tank it gets hot. That heat is a large part of the stored energy. If you let the air cool down then you have the opposite problem when you try to expand it again - basically your motor freezes up.

So you either thermally insulate the tank, or rely on using the stored air before it has time to cool down, which for regen brake seems quite likely anyway.

I doubt anyone is really working on this any longer, the industry is entirely consumed by BEVs at the moment. I'm slightly amazed we're even working on PHEVs, although there are some markets where they'll be allowed.

Is this a concern in an air bladder tank where hydraulic fluid is concerned? Its just compressing the bladder, not holding the energy in heat?

Then the energy is stored in the rubber of the bladder. Any storage or release will produce heat. And there are better ways to store energy in rubber, then the use of hydraulics. A simple wind up thing would be more efficient.

[coaster]

Air over oil cancels this problem, hot or cold, the oil just pushes a piston around and the gas behind it deals with the temperature as pressure.
Oil cannot be compressed, air can, oil forms a mechanical barrier.

The transferral of continueous pressure might get tricky, the system could be plagued with frictional losses.

[Zynerji]

Air over oil cancels this problem, hot or cold, the oil just pushes a piston around and the gas behind it deals with the temperature as pressure.
Oil cannot be compressed, air can, oil forms a mechanical barrier.

The transferral of continueous pressure might get tricky, the system could be plagued with frictional losses.

Fluid friction? Like a viscosity thing?

[coaster]

At some point the fluid must transfer to gas pressure, it would be beneficial for 'work' to be handled by the oil side as fluid can carry away heat to another location, gas would be a good way of storing energy.
But the fluid side must be minimal and low friction, moving a large mass of oil and a friction laden pump would kill this approach.
It would require some canny design.

[gruntguru]

A car needs to have energy stored onboard just to get from A to B. Call this the primary energy store. If that energy store and the conversion system (motor) can be run in reverse, it makes sense to use the same system for regenerative braking.

Battery electric systems do both very well.
Pneumatic or hydraulic systems are hopeless as primary energy stores.
Combustion engines running off chemical energy stores are hopeless at regen.

[henry]

Around 2012 Peugeot-Citroen made an experimental city car with hydraulic regen. Here’s the first article I could find. https://www.extremetech.com/extreme/14 ... 80-mpg-car

I don’t think it went any further.

[coaster]

Thanks for that link Henry, i knew it had some potential, Peugoet system tried realise it using nitrogen cannisters to store the energy.
im only 8 years slow on the uptake hey, 2013?

[Zynerji]

Wasn't there a thing called the Hydristor that did something with the transmission fluid as the energy store?

https://en.wikipedia.org/wiki/Hydristor

Regenerative braking and hybrid vehicles
The Hydristor torque converter can also accomplish total hydraulic braking and energy storage. Once a cruising speed has been achieved with front and rear Hydristors at some appropriate relative displacements, hydraulic braking is achieved by first simultaneously reducing both front and rear to zero displacement, then leaving the front Hydristor at zero (thus hydro mechanically disconnecting the engine from the torque converter hydraulic circuit and finally beginning to increase rear displacement as a braking function with the braking pressure and flow being directed to a hydraulic accumulator pressure tank. The decaying vehicle speed (kinetic energy), the rising tank pressure and the desired rate of deceleration determined by the driver all are variables which are easily managed by the Hydristor system. The stored braking energy can then be re-used for subsequent re-acceleration. With hydraulic storage capability, the acceleration at highway speeds can result in wheel spin.

The installation of a Hydristor torque converter into a typical car or truck [7] already on the highways will create a hybrid vehicle which will out-perform the current crop of hybrids[citation needed], thus adding other alternatives to that technology. One benefit of this approach is that the existing fleet can be re-configured thereby incurring monetary and natural resource savings[citation needed].