Huge wrote:
On 2012-01-02, Andy Champ wrote:
On 31/12/2011 08:34, harry wrote:
On Dec 30, 9:10 pm, Andy wrote:
On 30/12/2011 07:58, harry wrote:

On Dec 29, 4:48 pm, wrote:
On Thu, 29 Dec 2011 01:33:17 -0800 (PST),
wrote:
The weight of the on board capacitors would in itself be an energy
store (kinetic energy).
And how do they get up to speed - magic pixie beans?
Stupid boy. You don't get anything for nothing.
But storing kinetic energy is far more efficient than charging/
discharging batteries.
Kinetic energy stored as vehicle momentum is of no use for accelerating
the vehicle. At the time you need it it isn't there.

It's also of no use for climbing hills - the extra weight exactly
cancels out the extra KE.

In fact I can't think of a use for extra mass at all. Except in a road
roller.

Andy
But it can be used for charging batteries. Which is exactly what
happens in electric cars. In ICE cars, it is lost.
Bad news during cornering though.
Harry,

Lets take two examples, a 1000kg car and a 2000kg one. We'll give them
identical power trains.

Accelerate them to 10m/s (22mph, a traffic sort of speed) will take:

1/2 * 1000 * 10 * 10 = 50 kJ for the 1000Kg car
100kJ for the 2000Kg one.
Lighter is better.

We'll go along the road a bit. Air drag is the same, rolling resistance
slightly higher for the heavier one.
Lighter is better.

Come to a stop. Perhaps the recharge cycle is 80% efficient, so we get
back 40kJ for the lighter car, 80 for the heavy one.
The loss for the start-stop cycle is less for the lighter car.

As I say I can think of no case where heavy is better.

Armoured cars.


No, even there weight per se is no advantage, unless you want not to be
blown into the air.
But even that is arguable.

armour is not about weight, its about energy absorption.


They are not always connected. As anyone who has fired a 22 round into
a steel plate, and a straw bale will tell you. The straw bale wins
weight for weight.