Vir Campestris wrote:
On 21/05/2021 13:19, The Natural Philosopher wrote:
...its almost impossible to break the 100mpg mark for anything
remotely car shaped, and even 70mpg is doing well. Car development is
pretty much mature - there aren't any more great gains to be had.
The fact is that when you drill down through the crap what is left is
that you need a certain amount of energy to push a car shaped car on
tyres on tarmac at a given speed, over a given distance, and that the
bigger battery you carry the heavier the car and the more energy it
takes....

It does not help that fashion is pushing cars away from nice streamlined
shapes into things with the aerodynamics of a brick.

Andy

There are some which are OK.

https://arstechnica.com/cars/2020/05...odynamic-cars/

This one is the one with Cd=0.045 . The guy inside is pedaling.
The shape of this one, shows you what it would take to make the Cd
really low.

https://en.wikipedia.org/wiki/Eco-Ru...o-Runner_8.jpg

Because a BEV doesn't need quite as much air intake, there's room
to improve it over an ICE vehicle. If you put more of the junk in the
back of the car, the front profile can be improved. Of course, done
to extreme, it might throw off the handling. But with the battery
pack being centered and down low, that does a lot to reduce the
impact of the rest of it.

BEVs are all about wind resistance, whether frontal or side resistance.
The above article mentions "wheel covers" several times. And
regenerative braking makes this a bit more feasible. The Taycan
for example, has almost full regeneration and can brake mostly
electrically. Other cars don't achieve quite the same level of
regen braking. You cannot eliminate friction brakes, but you can
reduce their usage, a lot. And that might help, in
situations where a stupid wheel cover is in place (less
effective brake disc cooling).

Since I have spent a lot of money on brakes over the years,
I feel the presence of friction brakes is a horrible idea,
and will be a revenue generator for somebody. I doubt any
car manufacturer has put effort into extending BEV brake life.

Since range anxiety is all the rage, expect to see a lot of
wheel covers and the like, to give better mileage numbers.
Things that an ICE car would not care about (as nobody really
cares about ICE MPG any more - reducing car emissions is more
important than MPG).

Musk thinks the Cybertruck will be Cd=0.3, whereas some
others are about 0.4. The devil is in the small details
(putting a cover on the bottom of the vehicle, which
doubles as intrusion prevention to the battery pack).
Expect some tradeoff of additional mass, for better Cd.

Paul