[N&W] Re: brake schedules

[nw-mailing-list at nwhs.org]

 >In part 2 of N&W Dieselization in the September/October issue of the Arrow,
 >there are references to brake schedules 24RL and 26L. What are these? I
 >need some education.
 >
 >Ross Hunter

The 24RL and 26L are two different types of automatic brake valves. The 
24RL is the older of the two and on N&W units was equipped with a (brake 
pipe) pressure maintaining feature. The big difference between the two is 
that the 24RL is not self lapping where the 26L is self lapping. The brake 
handle on the 24RL had to brought around to a certain point, service, to 
make a reduction on the equalizing reservoir, then turned back to the lap 
position to stop this reduction. The brake pipe would then fall to match 
this pressure reading. Each further reduction meant that the handle needed 
to be brought to the service position and then back to lap.

The 26L introduced this self lapping feature and also has the pressure 
maintaining feature. On the 26L, after the 1st service position 
(6-8lb.reduction), you can bring the handle around to make almost any 
reduction you want on the eq. res. and leave the handle there. It will lap 
itself.
The pressure maintaining feature was an important advance in train 
handling. Whereas, when brake valves had no pressure maintaining and a 
brake application was made to control the speed of a train, if the brake 
pipe throughout the train had an air leak, the brakes on the cars would 
continue to apply at a rate relative to the air leak.

On long grades where the brakes need to be used for a long period of time, 
any air leak may cause the train to slow too much and eventually stop 
unless the brake is released. This on-off cycling of the automatic brake is 
not a situation that you want to be a part of as it takes much longer to 
fully charge the brakes than it does to put them on and continuing to "Fan" 
the brake will ultimately result in a loss of brakes as the pressure in the 
aux. reservoirs becomes lower and lower with each application. I have been 
with engineers that have done this and believe me it can get very scary.

With the pressure maintaining feature, an engineer makes a brake reduction 
to control the train, lets say 10 lbs. When the brake pipe equalizes at 
this 10lb. reduction the pressure maintaining feature will keep the brake 
pipe at this pressure despite any leakage throughout the trainline. There 
are limitations to this. The 26L can handle about a 25lb./min. leak. The 
24RL not quite that much. The Power Brake Law only allows a max. 5lb/min 
leak, otherwise the offending car must be set out of the cause of the leak 
fixed.

Some engineers liked the 24RL better than the 26L others like myself prefer 
the 26L. In my opinion the 26L is the best brake in use today. The electric 
brakes are asking for trouble and are not as safe nor can you do as much as 
with the 26L.

26L Forever!
Jimmy Lisle
________________________________________________________________
The brake schedule numbers are Westinghouse Air Brake Co. model numbers.
The 24RL was a large assembly mounted on a pedestal with, of course, an
automatic brake handle and an engine brake handle.  The cutout valve and
feed valve (brake pipe pressure regulating valve) were mounted close to the
floor, as was another valve used to cut the pressure maintaining feature in
or out.  The 24RL was a development of the late '40s, I believe, and was
seen on EMD cab units - Wabash E's and F's had 24RL; it was an evolution of
Westinghouse's Schedule 6 and 8 brakes (each of which had subletters to
denote various versions).  N&W steam power built before the development of
the 24RL was usually equipped with Schedule 8ET (Engine & Tender); it's
possible that older switchers were equipped with a Schedule 14 brake.  N&W
desired to modernize older Y5-6-6a, pre-24 As and Js and the rebuilt
streamlined Ks with the 24RL brake with the pressure maintaining feature;
the airbrake mavens modified the pedestals from the old #8 brakes and
mounted the 24RL accouterments on top of these pedestals. Post-24RL N&W new
power was equipped with it from birth.  N&W may have been the only railroad
with steam power equipped with the 24RL brake; the pressure maintaining
feature was a tremendous help in handling long and heavy trains.  Wabash and
NKP both had Geeps equipped with the old #6 brakes.  Wabash air brake gurus
had devised a pressure maintaining system for a 6BL brake; it worked but
required considerable shop attention.  (After the engineer sets the brake
with the automatic brake valve, pressure maintaining admits a small quantity
of air to the brake pipe to maintain the pressure level to that called for;
for instance, if the engineer set the brakes by making an 8-pound brake pipe
pressure reduction, the pressure maintaining would keep the brake pipe at
that level.  Without it, when a brake pipe reduction was made and the brake
valve handled returned from the application position to lap {which cuts off
the brake pipe from everything}, leakage in the brake pipe could increase
the amount of the reduction, causing the brakes to apply harder than the
engineer desired.)

The 26L system was a totally new brake valve that used diaphragms and
O-rings where the older brakes had used machined metal surfaces connecting
ports in the pedestal.  It is much smaller and lighter and easier to
maintain; it was developed in time to be applied as I recall first to all of
N&W's 620-699 series GP9s.  It had pressure-maintaining built in, and was
easier to operate, although the 24RL would make a brake-pipe pressure
reduction quicker and thus put the brakes on the train more rapidly.  The
26L automatic brake valve was self-lapping; in other words, when the
engineer moved the handle to the position that gave him the application he
wanted, he could leave the handle in that position and the valve would lap
itself after the application was completed.

When 611 and 1218 were overhauled they were equipped with the 26L brakes,
which helped maintenance greatly.

Ross, I hope this helps; there have been many books written about the answer
to your question, and I may have just muddied the water more for you.

EdKing