If the car is in dedicated service there could be a contract between the railroad and shipper to keep all loading supplies with the car or cars. For an example the PRR had a contract to supply the DOD/ US Navy with F22 gun flats. The RR was responsible for the return of all the rigging used to fasten the gun barrels to the flats in good working order. They even reused the Do Not Hump signs.
If the cars are not in dedicated or contractual service then I would surmise that new blocking would be used in loading. Most blocking would be lagged or nailed to the floor to resist movement. There were even cars with nail-able steel floors. Once the blocking is pulled up it is pretty much destroyed and not good for reuse. Another good reason for not reusing old blocking is insurance. Weigh the cost of a chunk of 8x8 oak to the cost of the load it is supposed to support or hold from movement. When we loaded military equipment on European rail roads we used all new material and chains were not allowed. Cables and turnbuckles were considered safer then chains. Chains are only as strong as the weakest link.
Pete
I pray every day I break even, Cause I can really use the money!
I started with nothing and still have most of it left!
Search on 'load blocking for rail cars' - You will find on-line loading information for UP/BNSF/KCS and ARR on the first page alone. A 'Google' search will find a lot of free information!
Jim
Modeling BNSF and Milwaukee Road in SW Wisconsin
Try to find Volume 20 of the Railroad Prototype Cyclopedia. It is alas out of print.
http://www.rpcycpub.com/v20.html
It has complete coverage of freight car loading rules and practices. here is their description:
Flat Car Loading Practices (85 pages) by Patrick C. Wider
The article contains 46 diagrams that show how many types of loads are restrained and tied down to flat cars. Also included are 126 photos of flat cars with all types of loads such as various steel products including pipe, auto frames, road construction and farm machinery, transformers and circuit breakers, boilers and vessels, rolling stock underframes, trucks and wheels, forging presses, locomotives, damaged freight cars, street cars and busses, lumber products, stone, containers, military equipment, and trailers on flat cars. Captions describe the flat cars photographed including the cars' histories (car number series, builder, and build date). Additional text details the A.A.R. rules for securing the various commodities. This article was several years in the making!
I refer to that text often. I also have dog-eared copies of two AAR booklets from circa 1950 with even more information on the rules for bracing loads. That brings up another point -- those rules are the minimum the railroads will accept for safe transit of the load. A given shipper, or receiver, may have more stringent load rules to protect the condition of the load.
In my experience most loads are secured and braced with new materials and there is often quite a burn pile of good looking wood where cars are unloaded (a lumber yard for example would have little reason to be a shipper, just a receiver, so the usual shipper would not have the chance to get the bracing material returned for re-use).
Exception: A flat car in dedicated service which is sent back empty may well retain at least some of the specialized bracing for a very particular load. But lumber loads are rarely that kind of specialized load.
At our local NMRA divisional meets we often hear clinics from a fellow who is an FRA inspector and he touches on other rules, such as loads on a flat car without bulkheads (or loads in a gondola higher than the end of the car) should not be coupled next to a tank car, and other such rules. That is an additional level of prototype practice that can add challenge to an operating session. When that FRA fellow had an open house on his layout he ran a freight train and circulated a quiz asking if you could see every FRA violation he had worked into the train. Loose loads near a tank car were the easy ones. Some cars had broken or damaged grab irons, and some tank cars lacked placards. That was a very educational layout tour.
Dave Nelson
Oak used most of time. The shipper must furnish the blocking as he is responsible for proper loading, blocking and securing (cables, banding, etc).
The following is from the Alaska Railroad Load Manual. While it does not say that new material must be used, I doubt that most used material could be considered free of defects since it would have holes in it and could have been otherwise damaged in use and during removal:
Blocks should preferably be made of hardwood such as Ash, Birch, Cypress, Elm, Maple or Oak.
Blocks must be free of defects such as large knots and splits.
Blocking must always be wider than it is high
Blocking less than 5 inches tall must be solid
Blocking greater than 5 inches tall may be constructed by securely nailing multiple pieces together
Two nails should be evenly spaced, equal to the thickness of the blocking, from the end. Additional nails must be applied less than ten inches apart for the full length of the piece.
Nails must be at least 11/2 inch longer than the thickness of the piece being added.
I tried to sell my two cents worth, but no one would give me a plug nickel for it.
I don't have a leg to stand on.
In my opinion, most blocking and supports are considered expendable items and are disposed of when the car is unloaded. The exceptions might be loose blocking left in a gondola, or blocks nailed to the floor of a flatcar. The railroads don't like loose stuff that can fly off a car.