Location of brake cylinder on EMD trucks?

Question

Why do some EMD SD-series models are they brake cylinders placed at the bottom of the truck between two of the wheels instead of the normal position at the top corners of the truck?

Answer 1

I never did like those under slung brake cylinders.They are a pain in the butt.More than one engine has rolled off because of them.I never had it happen to me though!

Answer 2

Ah yes, the good ol' under-slung brake cylinders.

Usually they are part of an earlier design found on older loco's, such as the SD40s and SD45s.  They both function the same way, with the main difference being found in the application of the "hand brake."

When the chains that run to the cylinders, whether above or below, are tighten by either the brake wheel or ratchet, the chain keeps the brake shoes against the wheel even if the unit is shut down with no air.  The difference is, with the under-slung cylinders, when the chain becomes taut the first time, it actuates a lever that will automatically release the air from the cylinder, with the chain keeping the shoes against the wheel.  This is done so when you continue to tighten the chain, it is known for sure that the brake will operate as intended.  If the "bleeder" lever fails to release the pressure in the brake cylinder, then the brakes on the truck must be cut out before tightening the chain all the way.  If left running and the engine dies and the air is lost and this procedure has not been followed, then the hand brake will not keep the shoes against the wheel and the unit could move uncontrolled.

This is not necessary with hand brakes with the chain running to the cylinder above the trucks because it can be seen that the brake is applied properly.

Hope I didn't confuse you, but that is the real difference between the two.