[PRCo] Re: The final brake

[Fred Schneider]

Brakes are unaffected by loss of 600 volts except that you cannot  
release them again.

1.   You can apply brakes.   The battery will spin the pilot motor  
backwards which will maintain steady dynamic brakes as the car slows  
down.

2.   When the dyanics made, the lock out relay (32 volts) will allow  
the drum brakes to come on.

3.  If you need them in emergency, the track brakes can be energized  
from the batteries as always.

4.  But you need 600 volts to release on the windings of the drum  
brake release solenoid.   With the pole off the wire or a substation  
down, you cannot release the brakes.   However, you can manually wind  
off the brakes and push the car off the street with the truck.

5.  If the battery is stone cold dead, pray for something soft in  
front of you.   Not only will none of the relays work but the pilot  
will also not work to notch the accelerator backwards to cut out  
resistance.  I suspect pushing the reverse bar all the way forward  
will buck the motors with no resistance and maybe the car will get  
down to 1 mph before you burn out or flash over a motor.   I've been  
told it is the trick of last resort.

Sufficient answer?



On Sep 1, 2007, at 5:55 PM, ROBERT R ROCKWELL wrote:

> So, in the case of a complete  power failure on an ALL electric  
> car,  which is the last resort ? A motor drum brake spring loaded  
> (reduction type brake), or a magnetic track brake fed from 32 v  
> batteries ?
> Robert Rockwell
> w3syt1 at msn.com<mailto:w3syt1 at msn.com>
>   ----- Original Message -----
>   From: Boris Cefer<mailto:westinghouse at iol.cz>
>   To: pittsburgh-railways at dementia.org<mailto:pittsburgh- 
> railways at dementia.org>
>>>> followed by a mechanic brake,
>   wheel tread brakes operated by air on earlier PCCs or motor drum  
> brakes controlled electrically on most postwar cars.
>