iten 1,5 in the wp&y rulebook states
Engineers are responsible for determining
the need for retainers. When used retainers
must be turned down after passing m.p.5.0
on southbound trains. when retainers are
used trainmen must observe the train carefully
for sliding wheels
An elementary question…What are retainers?
Retainers are a valve that retains pressure in the brake cylinder after the brakes are released. With the reatiners set the brakes stay “on” after the engineer releases the brakes.
Here is a quick and dirty high level overview on how the train brakes work.
Trains use air brakes. An air compressor charges air tanks on each car through a pipe/hose running the length of the train called the train line. A valve in the locomotive controlled by the engineer can reduce pressure in the brake line. The brake valves on the cars see that the pressure in the train line is less than the pressure in the cars air tank and use the air in the air tank to pressurize the car’s brake cylinder and apply the brakes on the cars. When the engineer uses his valve to restore the pressure in the train line to normal the brake valve in the car sees the pressure in the line is higher than the pressure in the air tank on the car and releases the pressure in the cylinders and, this is critical to the reatainer discussion, allows the train line to charge up the air tank on the car.
If you are going down a big hill and using the brakes a lot you will keep using up the air in the cars’ air tanks and since you never release the brakes, the train line would never recharges the air tanks. Eventually you run out of air in the tanks and your have no more brakes.
The retainers keep pressure in the cylinders so when the engineer releases the brakes, they are still applied but the trainline can now fully charge the air tanks on the cars. The engineer can keep the brakes applied on the train and keep his brake system fully charged.
Dave H.
To: DAVE
A very clear answer. Thanks Dave
If you have ever had a ride on the WP&Y railway like I have you would surely appreciate the need for retainers…that is one really nerve racking ride!
took the wp&y ry. five years ago. It was a mild day in Skagway
on May 22nd. When we started up the big hill the conductor
lit up the pot belly stove in the middle of the car ??? Got
to the top of the mountain and about five feet of snow on either
side of the train. They only clear up the winter snow just before
the summer cruise liners arrive. Got out of the car for a few
minutes, but glad to get back in from the freezing weather.
An excellent commentary throughout the trip from the guide
who told about the gold rush, building the railway and the
present operations