|
Rupert, the specifications varied by era, and can be found in the Post Office Publication 19 "A Publication of the Post Ofice department" "Specification for the Construction of Fulll and Apartment Railway Post Office Cars". "Structural requirements" are quite lengthy, and vary from era to era, and prior to 1912 (? - have to find the exact date) - there was little standardization. Mail cars often were in the middle of a car with Express on one side and Baggage on the other, with a passageway between along one side of the car, and the mail apartment against the other wall, with a door to the passageway. That changed to be no through door, although there was a crawl through for emergency purposes. OTW, the car apartment could not be entered from a non-mail portion of or complete car. Several cars were "grandfathered" in including the wood cars built for the D&RG narrow gauge (and the C&S predecessors). Also some branch line cars. Regardless, after that point, they had to have a certificate of construction to verify certain points. Live Loads - by 1956, the loads had to be (at least) 20,000 pounds for a 60' full mail car, and 10K & 5K for 30 & 15' apartments respectively. Stresses had a table for tension, compression, shear, rivet sheer and bearing - for center & side sills and bolsters. The buffing static load ranged from 50,000 to 400,000 pounds depending upon the total weight of empty train (pounds). There are pages of formulas and calculations related to the variety of materials, train size and other concerns. Basically though, a mail car was expected to be the strongest car in a given train (per foot). This in an effort to prevent telescoping and other such events that would impair the mail crew. Unfortunately (for the purposes of the question), by 1956 truss rods (as referenced) were a thing of the distant past (although, still in use on the D&RGW NG cars and odd branchline uses). Even at that, if the cars were touched beyond normal maintenance (strictly defined), they would have to be totally reconstructed to meet the latest specifications. There were a variety of cars that had to have applications to the AAR or ARA (or MCB - depending on era) for modifications to the specifications in order to fit in the design. It is interesting to note that companies are always far more concerned for their employes' (correct alternate spelling, as used by Pullman amongst others) safety when said employes were in another company's conveyance. And example is the Pullman company's concern for their porters and wait staff when ensconced within another builder's cars. This was trumpeted fairly loudly after the Naperville crash, as Pullman (quite correctly as it turned out) had been reluctant (?) to allow their porters to staff Budd sleepers and other cars fearing for their safety. As it turned out, the largest loss of life in said wreck was in the Budd diner - including some Pullman employes (not working the diner). This resulted in the welding of a larger center sill adjunct to existing (Budd pre-war) cars (which one can see on the Nebraska Zephyr cars at IRM). The purlines also were an issue as they connected similarly to collision posts in the body as opposed to the corners of the car. Pullman had not been as concerned in the past with wood cars, or in composition cars. Basically, once the Post Office Dept. started publishing specifications, the requirements were for the best practices and materials then in existence and certified by the AAR (or ARA, MCB). At 08:47 PM 6/2/2013, you wrote: Re. truss rods and RPO?s. I?ve had a quick look on the internet but can?t find anything specific other than - __._,_.___
Your email settings: Individual Email|Traditional
Change settings via the Web (Yahoo! ID required) Change settings via email: Switch delivery to Daily Digest | Switch to Fully Featured Visit Your Group | Yahoo! Groups Terms of Use | Unsubscribe __,_._,___ |