[PRCo] Re: The final brake

[Boris Cefer]

You do not need 600 V to release drum brakes. The actuators are fed brom the 
battery and everything you need to release the brakes is to have the MG 
control switch or a fusetron ON and release the brake pedal.

Some General Electric actuators used 600 V to release drum brakes, but this 
was, I believe, an earlier design.

The LO (lock out relay) has two operating coils - one is a low voltage coil 
operated by the brake pedal and the other coil is placed directly in the 
dynamic brake (600 V) circuit and works as a "low or no dynamic brake 
current detector".

Boris

----- Original Message ----- 
From: "Fred Schneider" <fwschneider at comcast.net>
To: <pittsburgh-railways at dementia.org>
Sent: Sunday, September 02, 2007 12:46 AM
Subject: [PRCo] Re: The final brake


> Corrected copy
>
> On Sep 1, 2007, at 6:22 PM, Fred Schneider wrote:
>
>> 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 FADE, 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?