On 12/11/2013 10:38, Apellation Controlee wrote:
On Mon, 11 Nov 2013 11:56:02 +0000, John Williamson
wrote:

Apellation Controlee wrote:
On Sun, 10 Nov 2013 21:58:11 +0000, gremlin_95
wrote:

On 10/11/2013 18:12, Adrian wrote:
On Sun, 10 Nov 2013 17:32:21 +0000, SteveW wrote:

Indeed we allow 44 (or is it 48 now) ton trucks to travel at 56,
knowing they haven't a hope in hell of matching a car's stopping
distance.
http://www.youtube.com/watch?v=ridS396W2BY
Quite impressive. I travel by bus to get to work and the journey
involves a lot of NSL A-roads, I was quite impressed how quickly and
smoothly the buses come to a complete stop when going down hill at full
pelt (56-62mph). The auto box seems to drop down gears as it slows down
to increase the braking effect.
I don't know if they caught on but, about 30 years back, I was on a
bus that was fitted with a magnetic arrester device. The braking, even
from the device alone, was breathtaking.
Retarders. Some of them use electromagnets to energise what is,
effectively, a shorted out generator.

http://www.telma.com/

Others use a pump in the gearbox to force oil through an adjustable
hole. When working and used correctly, they replace about 90% of the
friction braking. Hybrid buses use the motor and recovered energy to put
some charge back into the batteries, too.

They're fitted to the vast majority of large buses and coaches, and are
beginning to catch on in the lorry world, too. They are also a legal
requirement in Germany, and come in very handy on some of their long,
steep, motorway hills.
Retarders - yes, I knew I hadn't got the correct term. Thanks.

That's the one, they are apparently built in to the gearbox on these buses.

Probably something like this: http://www.youtube.com/watch?v=bXai8z99lUg

It seems to control the 18 tonne bus from 'running away' down hills
whilst making all manner of strange noises in the process.

--
David