[PRCo] Re: Drum__Brakes

[Jim Holland]

Good Morning!

>> fschnei at supernet.com writes:

>> Whether or not they were air applied and spring released, or
>> spring applied and air released is something on which I never collected
>> any data.  Both designs were feasible and may have been built.

> HRBran99 at aol.com wrote:

	Absolutely excellent explanation, Herb!
		Never paused to consider this!

> Very easy to determine, if you can look inside one of the cars. If there is
> an emergency hand brake then the brakes are air applied. If there is no
> emergency hand brake then the brakes are spring applied. The emergency brake
> is necessary in a car which has air applied brakes do to the fact that a loss
> of air pressure means a loss of brakes.

	That means the PRCo 16s had air-apply drums, correct?   They did have a
handbrake if I remember correctly.   This is interesting because the 16s
had extended-range dynamics like the 17s.   The 16-series interurbans 
*seemed*  sluggish in the brake department but I never got to operate one
of those to know first hand.   The city 16s, on the other hand, seemed
better than the 16-interurbans in braking.

> Also, a car with spring applied
> brakes requires a method to "pull" (or release) the brakes manually. If there
> is a loss of air pressure on a spring applied system then the brakes are set
> "on" until the air pressure is restored. If the car must be pushed or pulled
> to the car house then the brakes must be manually released to accomplish
> this. The PRCo/PAT (original numbers) 1700 series had to have the brakes
> "pulled" before towing. This was done by taking the switch iron and using the
> hand grip to pull open a small hook located above the track brakes. After
> pulling the four hooks (one above each track brake) the car was ready to be
> towed or pulled to the car house by another car.

	The pull hook is actually on the bottom of the WAB actuator and was very
easy to pull by hand which is what we did here in SF.   Using the
track-switch iron would be better from the standpoint that it can be done
from a standing position.
	The ex-St.Louis cars in SF (and all St.Louis cars) might be considered
transitional all-electrics.   All St.Louis cars were all-electrics while
air-electrics were still being ordered and built for many years after.  
The GE drums had a crank to wind-off the drums.   Doubt these cars had
extended range dynamics because the brakes were spring applied and came on
with a bang.   Air cars generally had dynamics which faded about 3.0-mph.

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James B. Holland

Holland  Electric  Railway  Operation....... 
___"O"--Scale St.-Petersburg Trams Company Trolleycars and...
______"O"--Scale  Parts  mailto:pghpcc at pacbell.net

______Pennsylvania Trolley Museum http://www.pa-trolley.org/
___Pittsburgh  Railways  Company  (PRCo),   1930  --  1950
N.M.R.A.  Life member #2190; http://www.nmra.org

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