To Don Valentines' question:

 

That, however, dose not explain the necessity of the extra layer of

wood over the metal sheathing in any way that has ever made sense to me.

 

As well as in the observance of well established methods, such as

We Always Do It That Way, I've understood that reefers were clad

 with wood over steel body sides and roof tops on some theory that

wood provided an additional insulating capacity and insulation layer.

 

Mal Houck 

I have done this twice using .010 x .060 Evergreen styrene strip. One was for a Sunshine pattern for his BREX and WFEX truss rod kits and a NYC stock car roof for Speedwitch to replace the roof on the Westerfield kit. In doing so I built in some weathering effects into the roof i.e. a few boards buckling or slightly twisted, small breaks/chipping/nicks at the ends of the boards, and the like. To my eye using grooved styrene sheet does not cut it for this kind of roof.

Hutchins was still showing their "plastic" car roof (in this case plastic likely refereed to bitumen impregnated paper - tar paper) for use between layers of roof boards, so it's impossible to tell from photos how many roofs were actually built this way, but this material had the same problems as sheet metal; when the roof racked it either tore or the nail holes elongated, causing leaks.

The problem wasn't torsional stiffness; it was shear forces, and no arrangement of sheathing made of parallel strips is really effective at resisting shear. That is why, before the days of plywood, houses were built with sway braces let into their framing to help resist wind loads..

The one serious effort I'm aware of to resist this racking caused by the weaving of the carbody was the Robertson patent on what we know as the NP "circular" roof. Mr. Robertson's patent doesn't make any claims on the actual roof covering, rather the system of keying the individual boards of the diagonal sheathing into one structural shear panel that is gently curved to shed water, but will still resist racking. This was patented in 1924, IIRC, and by that time the various flexible roofs had won most of the market, and Mr Robertson's system didn't gain much acceptance, but it was a step in the right direction. However, it was labor intensive, and the Murphy "solid steel" roof, which was the real solution to the problem, was already being shown in the 1922 CBC, so Robertson's design was just a bit too late.

Dennis Storzek

On Apr 26, 2014, at 1:59 PM, Brian Carlson wrote:

I need to reweigh a few C&I hoppers. Does anyone know if the railroad had their own facilities for this and what the code is?

Brian,
Several photos of C&I hoppers have "CR" reweigh stencils, which stood for Colver, Pennsylvania, that was home of C&I's shops.
Regards,
Ed Hawkins

      Good summary. But several Cycs from early in the 20th century show a fourth type of roof, with some kind of waterproof membrane sandwiched between the two board roofs, either roofing paper, or oilcloth, or metal sheet. From the outside, as Dennis says, none of these are easily distinguishable. I feel sure that the torsional stiffness of a double-board roof was considerably better than a single wood roof, which would help protect the inside metal (or other material) roof sheet from damage.

Some of the statements in the recent discussion about wood roofs on FGE reefers show a not total understanding of the challenges faced by builders of freightcars in the late nineteenth and early twentieth century, and maybe some general discussion is in order.

The wood roofs we can see in photos can be one of three general kinds, which are virtually indistinguaishable from their outer appearance. These would be:

1.) Single layer roofs, which were just that, a single layer of T&G boards laid over purlins supported by the carlines. These roofs were not very waterproof; they leaked between the boards, but were suitable for some classes of freight, such as livestock.
2.) Two layer, or "double board" roofs were an improvement. Both layers of boards ran the same direction, from roof peak to eave, the joints being staggered  by one half the board width. The boards on the lower layer had channels milled in their surface, their purpose was to collect the water that leaked through the joints in the upper layer and direct it out to the eves. Unfortunately, capillary action would still cause some water to migrate to the joints in the lower layer, where it then dripped on the contents of the car.
3.) Single layer wood roofs applied over an "inside metal roof" that consisted of light gauge sheet metal panels. The wood roof kept the light gauge metal from being damaged by trainmen walking on the roof; the purpose of the sheet metal was to capture the water that leaked between the boards and direct it out to the eaves. These roofs can be spotted by the rather boxy fascia that covered the drainage opening.

The ideal roof would seem to have been a single waterproof membrane, but it wasn't, for one simple reason; the freightcars would "weave" as they moved down the track. Unlike a building, which sits on a solid foundation, freightcars were supported at two points,one near each end. If dips in the track at opposite ends of the car were severe enough, the entire car structure would twist. The effect on the roof can be easily illustrated by taking an Accurail kit box, grasping one end in each hand, and twisting. While each of the five panels that make sides, ends, and floor remain rectangles, the open top of the box becomes a parallelogram, angled alternately one way, then the other. The car builders of the day were unwilling to to add the weight necessary, and expend the headroom, to build a roof structure capable of resisting this, and this weaving motion would literally tear the roof membrane to shreds. Sheet metal would crack and tear, nail holes would wear into slots,  interlocking joints would spring open, and the roof would shortly be no more waterproof than a wood roof. The multiple iron clasps one sees in illustrations of metal roofs from the early years of the twentieth century were an unsuccessful attempt to deal with this constant motion, as was the inside metal roof mentioned above, with its floating panels.

By the 1920's, the sucessful outside metal roof systems all had words like "pivoted" and "flexible" in their names; in these systems the panels were designed to accommodate the movement of the roof structure, having pinned connections at relatively few points.

The true solution was the Murphy "solid steel" roof, which was finally strong enough to resist weaving, while being light enough to be acceptable to the railroads. This roof design became the basis for the roofs used on the AAR standard boxcars of the mid century; these were so effective that they drive all competing roof systems from the market.

Dennis Storzek

Given that the roof of a freight car main purpose is to keep the lading dry, "quite trustworthy" seems like a relative term here if they also had a "tendency to leak."

Hi Don...

 

For an explanation of the problem with double-board roofs and the solution provided by the introduction of the combination wood/sheet metal/wood roof, see page 227 of The American Railroad Freight Car by John White, Jr.

 

Richard Bale

 

In a message dated 4/25/2014 7:49:30 P.M. Pacific Daylight Time, riverman_vt@... writes:

Hi Tony,

 

     Wiyh eight CBC's here from 1919 through 1953 I have seen that many times. That, however, dose not explain the necessity of the extra layer of wood over the metal sheathing in any way that has ever made sense to me.

 

cordially, Don Valentine

On Apr 25, 2014, at 4:25 PM, John Barry <northbaylines@...> wrote:
John, the ORERs aren’t helpful here because these cars retained their original numbers until ca. 1945 and were then only gradually renumbered into the 210000-214549 series.  The first cars with extended roofs were rebuilt in 1941 with only a 6” increase in interior height.  Those with the taller extended roofs and 10’6” interior height followed soon afterward, however, perhaps in late 1941 and certainly by 1942, and the rebuilding program continued for at least two years until the car builders began delivering new cars again (classes Bx-43 and Bx-44) and the Santa Fe was able to get the materials to rebuild former Bx-8/-9/-10 class wood sheathed cars with new steel bodies (classes Bx-41/-42/-45/-46/-49).

I am trying to find the dates of the roof extensions on the
Bx-11/12 classes. The ORER listings seem to indicate a prototype in 1944 and production coming on line in small numbers by Oct 45. I have the Dobyne box car book, but it is buried in storage.

John Barry

On Apr 25, 2014, at 2:09 PM, <fgexbill@...> <fgexbill@...> wrote: