Chains above locomotive trucks?

Question

Chains are sometimes stored above the trucks on a locomotive, what is the purpose of these chains?

Answer 1

Hoghead gave you all the correct answers to your question.One set of chains he didn't mention are the short lengths of chain that connect the trucks to the car body(locomotive frame)Those chains keep the trucks with the frame in the event of a derailment.The trucks on cars and locomotives aren't bolted to the frames, the frames just rest on what is called a bolster and a center pin holds them in place.Sheesh Hoghead you've been around a while too  lol I don't think i've seen a set of blocking chains since the 80's!

Answer 2

They can be for several things.

If short lengths, joined end to end by a connecting piece of steel, joined with at the "ring" they are "blocking chains."  These are placed in front of and behind the locomotive wheels on top of the rail.. They are for extra security when leaving locomotives unattended, used in conjunction with the hand brake.

If considerably longer (which is probably the case as blocking chains are usually stowed behind the ladder/steps and are actually not used much these days), then they can be used to "chain up" to a car that has had the draw bar ripped out, so the car may be moved to the nearest spur or siding where the car department will come and effect repairs.  Found on some locomotive trucks, but these are usually carried in "tool boxes" that are built in to the catwalks along the sides of the engine, the top serving as a deck plate.

Additionally, in the case of a minor derailment, where the trucks of the car have derailed and remained close to the rail, these chains are used as "blocking material" (different from blocking chains) in conjunction with a "frog(s)", usually carried on the locomotive truck as well, to "walk" the car back onto the rail.

When used in this fashion, they are sort of piled up in the distance between the derailed wheel and the frog, so that the wheel will not dig into the ties and will climb up on the frog easier.  Wood blocking material is used as well in the absence of chain.

These types of minor contre-temps are actually pretty common.

Or, and with the greater probability, you are looking at the chain that runs to a brake cylinder as a part of the hand brake system.  When released and the brakes are released, there is sufficient slack to allow the cylinder to empty and keep the shoe off the wheel.  When leaving the engine unattended, the slack is taken up either via electrical or mechanical (manual) means so that if the air brakes release for any reason, the brake shoe will stay against the wheel preventing uncontrolled movement.  It is most likely that this is the chain you are seeing, being much, much more common.

Not all locomotives have these chains visible, such as is the case where the cylinders are "under slung" and outta sight.

Answer 3

Usually a locomotive has only one, if it has any chains at all.  By the operating rules, the only use would be in the case of the rear car having lost the use of its brakes, in which case that rear car would have to be secured to the second rear car, by use of that chain, to keep it connected to the train, should the coupler fail for some reason.  The car having no brakes would have to be set out for repair or switched to a position forward of a car with operational brakes as soon as possible (assuming the car still has continuity of the brake pipe, i. e. the brake pipe transmits air and doesn't leak).

In reality, the chain could be used as well to help align a coupler that might be "slewed" off-center.  Proper alignment is necessary before a coupling can be made.  Large web straps are usually used for this purpose, when available.

Answer 4

to hold up a torn out draw bar