Guy Wilber

Bill Pardie asked:

"It seems that most brake systems in the 20's and 30's used a regular 'TEE" fitting to route
the air flow to the KD or AB brake system. Later (in the 40's) a special "TEE" was used
that routed the air off the topside of the air line and angled it down to the AB brake
system. Does anyone know when the latter came into widespread use?"


The "Improved Branch Pipe Tee" was an integral part of the "AB" brake system. All cars built new after September 1, 1933 would have been so equipped as well as rebuilt cars after August 1, 1937.

Early on, many roads likely used the existing "K" brake branch line tee, but it was less expensive to purchase the entire "AB" kit which would have included the new tee. After September 1, 1942 all new and rebuilt cars were also required to be equipped with extra heavy 1 1/4" pipe (trainline) which was also a product of the original "AB" system.

It was "recommended" that cars built prior to September 1, 1933 when receiving new "AB" brakes receive the heavy train line as well, but the use of the existing lighter pipe and tee was probably more prominent due to cost and shortage of the heavy pipe throughout the war and for several years thereafter. The shortage of pipe of all sizes was one of the factors considered when the requirement for "AB" brakes was extended after the war.

The new tee was machined with flanged unions which were designed to reduce air leakage due to train vibrations. The heavy pipe allowed both nipples and other connections to be tightened without distorting the pipe which also led to leakage problems within older "K" systems.

Guy Wilber
Sparks, Nevada

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