Another post? Wow!
While I was researching hopper rosters I was looking at the various ways John Nehrich has broken down the 1949 fleet of freight cars on the RPI site. Among this data was an interesting tidbit - in 1949 there were approximately 60,000 36' cars on the railroads. Of those, nearly 2/3 are CN and CP Fowler Patent single sheathed box cars. Leaving just 20,000 or so 36' double sheathed cars. About 5,000 of those are ACL and SAL ventilated box cars.
So not many 36' double sheathed cars at all.
Chris pointed out that there would have been more in 1947. So I was curious, and rather than keeping this between the two of us (and also so this info is someplace where I can find it later...), here's what I've compiled (with much thanks for John's research).
RPI Data
The percentage of composite to all steel box cars went from 56% in 1940 to 44% in 1945 and 31% in 1949.
This amounts to about 106,000 cars of a total box car roster of about 700,000+. And that's assuming all of those cars were 36 footers.
There were still 26,000+ all wood box cars in 1945, with about 7,500 'other' box cars in 1949, so that reduction was most likely all double sheathed cars since I'm not aware of any single sheathed car being made without a steel underframe. And I'm not aware of many 40' all wood cars.
In 1949 there were 60,000 of 223,0000 composite cars were 36' box cars, or about a 1/4. But of those, 40,000 were Fowler patent single sheathed cars. Leaving about 20,000 double sheathed plus the 7,500 'other' cars. That amounts to about 3% of the total box car fleet being under 40' and double sheathed.
So if all of the difference was double sheathed, and the number of Fowler patent cars remained constant, then 36' double sheathed cars would account for about 120,000 of 160,000 composite cars, plus most of the 'other' cars, which amounts to only 19% of the fleet as 36' cars.
Most likely the drop off accelerated instead of being linear. So it's somewhere between 19% and 3%, so 10% of the entire box car fleet as 36' double sheathed cars sounds reasonable. But I'm guessing it's lower.
In 1949, the roads with more than 1,000 cars (not including the CN and CP since they were all single sheathed) - Southern, L&N, NC&StL, D&H, ERIE, and Nationales de Mexico. Adding local roads that had at least 500 there's BAR and DL&W.
ORER Data from 1947
Comparing a few roads between 1947 and 1949:
SOU - 9,228 - 3,928
L&N - 7,438 - 2,829
D&H - 1,751 - 1,560
ERIE - 1,275 - 1,005
BAR - 1,099 - 903
DL&W - 832 - 538
RDG - 2,135 - 223
LNE - 190 - 183 (but these are 39' 10")
NYC - 752 - 156
In 1947 5,407 of these cars were ACL or SAL ventilated box cars.
So obviously some roads were retiring cars faster than others. But I think that up to 10% of box cars being 36' is reasonable.
Models
So how many 36' double sheathed cars do we need? Well, I think that the NH cars being home road cars don't count. We'll need a couple of them for revenue service, and a few more for MOW service.
I think that specialty cars like the ventilated box cars also don't count, provided we're modeling a season when they would be in use as ventilated box cars. If they are in use as regular box cars then they would be treated as such.
So I think the must have cars are those for direct connections with a decent percentage of 36' double sheathed cars (CV and RDG are both around 25% in 1947). The SOU SU design is also one that was such a large class of cars, and the Southern had the largest number of 36' double sheathed cars even in 1949.
As for other cars I think it depends on whether we identify commodities coming for other roads. Assuming there's a model available, then it's a question of how those cars relate to their larger box car fleet. But these would be low priority cars.
So for Chris' layout this amounts to, well, one 36' double sheathed box car. He's got two trains with 20-25 cars each, and perhaps 30ish cars on the layout. So less than 100 cars.
In my case, I've got 8 trains of 15-25 cars each, plus another 50 or 60 on the layout. So at any given time I'm probably looking at 2-3 36' double sheathed cars in any given session. Of course, on some days there could be more, others less.
F&C has the most 36' double sheathed car models. I've got the CV, NH and NYC
I also have SOU (Westerfield, but F&C makes the same prototype).
The NYC car is a great example of a rare car. Their 1947 roster of 752 36' cars is only 3% of their USRA design steel box cars (25,000+), just one class of steel box cars on the road, or about 1% of their 60,000+ box car fleet.
Roster vs Operating Session
Having said that, I go back to my assertion that there's a difference between your model roster, and the cars you run during a given operating session. I'll use Chris's layout as an example. Until he has an operating Shore Line, he needs about 100 cars for an operating session, probably less. So by our calculations he needs a single 36' double sheathed box car. And that's assuming (as we will for now) that all 100 cars per session are box cars.
So looking at the choices, he decides he likes the CV one. If he has an industry that is directly serviced by an industry on the CV then this is a good choice. I might even argue that it's no longer a rare car, as that industry would have about a 25% of receiving this type of car based on the CV roster (assuming they never use a foreign road car).
Problem is, if this isn't a car in semi-captive service, then this 'rare' car becomes 'common' if we choose to run one 36' car per session and that's the only car available.
So I think that it's worth modeling at least a handful of cars. This is why your roster should be larger than what you'd run in an operating session (or a couple of sessions).
Instead of running one 36' double sheathed box car per 100 cars per session (which would be a statistical anomaly anyway), these cars would simply fall under the 'rare' category. Rare cars could make up 10-20% of the cars used in the session. If we go with 20% then 2 cars of his 100 would be rare. Sometimes one would be a 36' car, sometimes none, sometimes two. In that mix are other rare cars.
One of the main reasons I like this approach is that I like freight cars. It allows me to have more cars, and more unusual cars, than most people would choose to model. But I also think it means that from session to session the mix of cars is good, and individual rare cars continue to be rare.
My initial approach was to model one car per 'x' number of a given car on the prototype. But for large classes of cars (PRR X29 for example) this would require 20+ cars. These are cars that belong in pretty much every ops session. But I can make that happen with far fewer cars. Folks won't remember car numbers from session to session, but they will remember unusual cars.
So now I'm working on finding an upper limit to the number of cars needed for any large class. This will probably vary depending on your prototype (you might need 25 X29s if you model the PRR). It's important to have enough common cars, whether a specific class, or a specific design used by many roads (1937 AAR Standard Box Car).
I suppose that's a next step - figure out what a representative mix of cars is for each session. That's for another post.
Hmmmmm. How is it that a number of us over the past year have independently stumbled onto the importance of double sheathed cars of the 36 ft. length? In my case part of it was from concluding that their use makes a train "look" longer because it may be a car or two longer but still be the same actual length as one with fewer 40 ft. cars.
ReplyDeletePart of what led me to the 36 ft. cars was recognition of the fallacy in John Nehrich's and Jeff English's orignal conclusions about the percentage of each car type we should all have in our freight trains. The fallacy is that they provide a good starting point but one that probably fits very few roads. In modeling northern New England roads years of viewing good action photos, where good portions of a train are shown rather than only the locomotive, has taught me that the vast majority of through freights in the region were composed of roughly 80% house cars, mostly box cars but with blocks of reefers as well, at least in the late 1940's period I am interested in. The same seems to be true on New Haven lines. I suspect the reasons for this are due to the way products were handled. Coal, for example, came in a few cars at a time with those cars being amongst the other 20% of the cars in each through freight. We must remember, however, that there were very few unit coal trains, if any, in New England in those years. Study has also shown that hoppers owned by New England roads did not stray far from their home road. Instead they were loaded at New England seaports with coal brought there by coastal steamers. This coal was being delivered to on line customers and, thus, interchange of such cars was very rare. Coal was also transfered from foreign road cars to home road cars to keep car costs down. The Rutland did much of this at their Alburg, VT yard. This tells me that one needs almost as many home road hoppers as they do foreign road cars for coal. Then, too, the make up of a local freight was usually very different from that of a through freight. In this case the mix of car types was usually higher, depending on the variety and number of customers each local freight might serve.
Look at the commodidties that we received in New England in house cars. Anything that was bagged instead of shipped in a covered hopper as many things are today, even bulk grain for feed mixing plants, came in box cars in those years. Cement was about the only product carried in the region in any quantity in covered hoppers so we don't need many of them in that era. Tank cars should be more important than covered hoppers for that time frame. Our food products came in meat reefers, again 36 ft. cars, and regular 40 ft. reefers. The latter could and did go out with loads of New England products as well, especially potatoes from Maine. And many of the large numbers of boxcars that arrived loaded headed toward home as empties. This was a chronic issue with New England roads as the higher value goods produced from the raw materials that arrived in many of these boxcars took up far less space to be shipped out in. The big exception to this was paper, an important and large commodity originating on all roads in northern New England except the litte Rutland. These are just some of the factors those modeling New England roads need to consider when determining their freight car fleet needs.
Don Valentine