On 26/04/14 11:25, Dave Plowman (News) wrote:
In article , The Natural Philosopher
wrote:
You don't need massive steel disc brakes for moderate retardation.
What you do need them for is a panic stop from 90 mph. And
regenerative braking ain't going to do that.

Oh yes it is.

you put a short across a leccy motor and it stops dead in its tracks
mate.

No it doesn't. The braking effort can't exceed the maximum torque the
motor can produce.


Oh yes it does.

You risk of course burning out the windings doing it, because you are
WELL over the peak current its rated for and it WILL get bloody hot of
left doing that for any period, but for an emergency stop, yes its
possible to do a lot more than normal peak torque. AND in the end you
are ONLY talking about torque up to tyre slippage. Once you lock the
wheels, the torque vanishes, and you end up in a partial slip mode.

The trains that use that system have the disc brakes there largely to
achieve the final stop, but not to absorb the bulk of the energy.



the disc brakes are there to get to to a final stop, not to absorb the
bulk of the energy.

Nonsense.

more twaddle from the man with his head up his arse.

Regenerative braking torque is entirely down to the peak current you can
let the motor generate without burning out. do a 10 second burst, its
the same as a disc brake, that is a hell of a lot more than it can in
general dissipate if you are on a racing track, dong it every few
seconds unless its a Porsche. Do 5 emergency stops from 140mph in a
Jaguar saloon, and like as not the brakes are gone. You need a Porsche
and vented disks to do that.


--
Ineptocracy

(in-ep-toc-ra-cy) €“ a system of government where the least capable to
lead are elected by the least capable of producing, and where the
members of society least likely to sustain themselves or succeed, are
rewarded with goods and services paid for by the confiscated wealth of a
diminishing number of producers.