[PRCo] Re: Brake Shoes

[Phillip Clark Campbell]

Thank you.


Phil



----- Original Message ----
> From: Fred Schneider <fwschneider at comcast.net>
> To: pittsburgh-railways at dementia.org
> Sent: Saturday, May 17, 2008 1:07:50 PM
> Subject: [PRCo] Re: Brake Shoes
> 
> None of the low-floor cars got dynamic braking.   They did, however,  
> get a different brake lever ratio to improve brake performance at  
> higher speeds. And they got brake lights worked by pressure switches  
> in the air brake pipe.   In this case, improved performance only  
> meant improved force on the brake shoes.
> 
> And Phil, you just touched on another subject regarding why those low- 
> floor cars would be absolutely inferior on the streets today.
> 
> Let's assume you have a nine inch diameter brake cylinder and you  
> have a six inch piston travel, then you need 381 cubic inches of air  
> to fill that cylinder.  You need to fill it using a 1/2 inch pipe  
> that runs from the air reservoir under the car all the way to the  
> brake valve on the platform and back to the cylinder, a distance of  
> about 45 feet or 540 inches.   It takes a hellish long time to charge  
> that cylinder moving that volume of air that distance.  You will  
> begin to feel a brake response roughly two seconds after you move the  
> brake valve into apply.
> 
> But you automobile, because hydraulic fluid does not compress, give  
> you an instantaneous response.  Dyanmic brakes, because electricity  
> moves at 186,000 miles per second, is, for all practical purposes,  
> also instantaneous.
> 
> But air brakes on conventional streetcars SUCKS.
> 
> The first time I was on one of those Gomac-built replica Birneys in  
> Tampa I was astonished at how fast the air brakes applied.   It  
> seemed almost instantly, like a bus or truck brake.  And the air  
> tubing from the brake valve looked too small to actually work the  
> brakes.    Later, when I was in their shop, I asked the  
> superintendent if those cars used some sort of a relay valve to work  
> the brakes.   His answer was yes, and he took me down in the pit to  
> look at it.   The 1/2 pipe went directly from the air reservoir to  
> the relay valve to the brake cylinder, a distance of perhaps not over  
> two feet.   The relay valve was controlled for the platform valves  
> through very small pipes about the size of soda straws.   Only a very  
> small amount of air had to be moved to make the relay valve work and  
> therefore it moved almost instantly, and the large volume of air  
> needed for the brakes only had to move a couple of feet instead of  
> charging a 1/2 pipe 45 feet long.   So the brakes applied almost  
> instantly and they released almost instantly.   BUT, PHIL, I HAVE  
> NEVER HAD THE PLEASURE OF RUNNING SUCH A CAR IN A MUSEUM.   I do not  
> know that we ever built such a critter for street operation because  
> we quit making cars with straight air systems in this country in the  
> 1930s.
> 
> Now, what do trucks and buses use.   Good question.   Glad you  
> asked.   I've driven buses.   I've even driven tractor-trailer  
> rigs.   But I've never bothered to investigate.   I guess it's time I  
> do.   But the response rates are incredibly fast so I suspect that  
> they also use some sort of a relay valve system.
> 
> ++++++++++++++++LIFE OF BRAKE SHOES ++++++++++++
> 
> How often did brake shoes have to be changed.   I have never seen a  
> chart that shows what is normal.   I remember John Horachek writing  
> on the Electroliners on the Chicago, North Shore and Milwaukee  
> Railroad.   John wrote that they changed out one truck truck every  
> night in Milwaukee.   There were two trains and one got to Milwaukee  
> every other night.   That meant that they had completely replaced all  
> shoes every eight days.   They made two round trips per day ... that  
> 4 one way trips x 95 miles  x 8 days or = 3,040 miles per shoe.
> 
> You do not change all shoes the same day or you need a parachute to  
> stop the car or train.   Why?   If you buy shoes for 26 inch wheels  
> and you put them on wheels that have been in service for a while and  
> they have worn down to 25 1/2 inches, then those brake shoes are only  
> going to touch the wheel along from side to side across the middle of  
> the shoe.   The rest of the shoe from top to bottom will not even  
> touch the wheel.   It will take quite a few stops until the shoe  
> wears enough that it contacts the wheel over it's entire surface  
> area.   That is why the CNS&M changed out only 1/4 of the shoes every  
> day every second day.
> 
> I remember going to work in Harrisburg one morning on a Penn Central  
> or Pennsy or Amtrak schedule using City of Philadelphia or PSIC or  
> SEPTA Silverliner that some dufus in Wilmington shops had changed  
> brake shoes on the night before ... the ass hole had changed all the  
> shoes at once.   You couldn't even stop that car with an emergency  
> brake application.   The engineman was not particularly enthralled  
> with the idiots in the shop.   How did I know?   Well, they all knew  
> that I was also working for the Strasburg Rail Road.  I often rode up  
> front with the engine crew.   In fact one night one of the engineman  
> slapped my hand on the controller and backed off before I could stop  
> him and I ended up running for 36 miles from Harrisburg to  
> Lancaster.   (Sheee-it, I just went into Yellow Book.com to see if I  
> could find that engineer ... no listing ... wonder if he died?)
> 
> City street service?   Have no clue.   I've heard Ed Amrhein bitching  
> about shoes he put on the Peter Witt at the Baltimore Streetcar  
> Museum a year before already needing changing but I think they were  
> buying a very soft cast iron shoe.   If we wore one out in a museum  
> environment in a museum, that would not have lasted a day in a service.
> 
> The best person to ask would be Elmer Van Dullen who is the retired  
> shop superintendent of New Orleans Public Service / New Orleans  
> Regional Transit Authority.   I cannot find the number in Yellow  
> Book.com under New Orleans.   Lives somewhere out in the city's  
> western suburbs.   Or maybe you can find his successor in the RTA  
> shops.  You probably want to know how many car miles they operated  
> last year and how many sets of shoes they used.   And if you find  
> out, post it.   I want to know too.
> 
> The multiple unit single end low-floor cars (3750s, 5000s, 5100s and  
> 5200s had dynamic brakes that could be energized in emergencies by a  
> separate controller.   The reason is simple.   In order to stop a car  
> with drum controller (type K as in K-35 K-8, K-63, etc.) in an  
> emergency if you have lost your air, you pull the reverse key in the  
> direction opposite to the way you are going, kick the canopy switch  
> (breaker) off, and then notch the controller up through the points.    
> A four motor car will go into dynamic braking on point 1, a 2-motor  
> car will not develop a brake loop until it is in the parallel  
> points.   However, cars with remote control (GE type M, GE PC, GE  
> PCM, Westinghouse AL, AB, HL, HB, VA) will not do this because the  
> reverser is under the car and will only throw when you pull power.    
> Because you have thrown off the canopy switch, you have no power.    
> So you cannot create emergency dyamic braking.   The normal emergency  
> procedures with such cars is to use power to buck them in reverse,  
> i.e. put it in reverse and pull a point of power if you loose air.    
> But Pittsburgh put a special dynamic brake controller on them for  
> emergencies.   But they were not used in normal service.
> 
> ++++++++++++++++++++++SPECIAL SAFETY FEATURES++++++++
> 
> Pennsylvania required required safety appliances like those on a  
> Birney car after 1938 for anything operated in one-man service.   All  
> of the low-floor cars still in service in 1938 had dead-man  
> controls.   They did not, however, have the doors incorporated into  
> the brake valve like the M28D valve used on a Birney and I'm not sure  
> that the doors balanced if you went into emergency.   Some day when  
> I'm running 4398 or 3756 I'll have to deliberately dump the air to  
> find out.
> 
> fws
> 
> 
> On May 17, 2008, at 2:46 PM, Phillip Clark Campbell wrote:
> 
> > Hello;
> >
> >
> > Many of the low-floor cars were re-worked for faster speeds.  Did  
> > they get dynamic braking or did they rely solely on brake shoes?  
> > How often would brake shoes need replacement?  Were there any  
> > special safety features on these cars?
> >
> >
> > Phil
> >
> >
> >
> >
> >