G-N versus Consist Data for train construction


Mike Brock <brockm@...>
 

After several days of reading various views on the value of the G-N
hypothesis AS FAR AS PROVIDING A GUIDE FOR BUILDING A BOX CAR FLEET, I think the following applies...not unlike Charlie
Vlk's conclusion.

First, a small minority [ including myself ] of modelers on the STMFC have
access to actual frt train consists. There are those that cover the UP from
Laramie to Rawlins in 1938, 1947, 1949, 1951, and for Cheyenne to
Laramie...1956. Given the relatively small number of trains covered...34 during about a month in
the 1949 book...compared to the number operating [ the ratio is about
1/35 ], the consist information simply is too small to reach definitive
conclusions about the other 34 trains in a given day...let alone what
happened during the other 11 months. OTOH, the G-N hypothesis does give a
possible population over the long run if one makes certain assumptions...for
example, that "away" cars were more or less distributed randomly among other RR's. The actual
train consists appear to deviate considerably at times from the G-N
hypothesis [ the infamous SP cars for example but others as well ] but,
again, this is a short run view.

Those that have actual consists might like to model them even with
compression. Uh oh. For those few who don't know [ surely they care <G> ], I have video of a UP frt train pulling 36 SP box cars in a train of 96 cars. That is 37.5% SP box cars. OK...if I assume a max train length [ compression due to layout size ] of 35 cars, the train will need 13 SP box cars and, given that I compress to 8 frt trains down from 35 in a day, I'll probably need about 6 more SP box cars so that they are represented in the other 7 trains. That means that I will need 19 SP box cars in my fleet. However, SP box cars only represent 4% of the total national fleet. So, if I use the G-N hypothesis as a guide I'll need about
475 box cars in order for me to provide the SP cars. However, I
find that an EJ&E box car is in one of the trains in my
frt conductor book. EJ&E box cars represent only .002 of the national fleet. Hence, [ 0.95 cars ] I can have almost one car [ well, I'll leave off one of the cut levers ]. However, there is an FEC box car showing in a video near Hermosa Tunnel in 1953. FEC had 190 box cars...or 0.0002 of the national fleet. My 475 car population will provide me with 0.095 cars. That might get me 4 ribs on an end. Nooooo problem. I'll just increase my box car population to 4750. That will just about get me the car [ again, missing a cut lever ] and frequent visits to a therapist in Orlando.

The G-N theory is interesting and useful because it tells us
that box cars populated the various RR's in proportions somewhat similar to the national fleet over "long" periods of time. It doesn't appear to help much in modeling trains because trains often were "designed"
for specific tasks [ a lumber train, for instance ] and such a train might draw cars from a year's population at rates not similar to other trains. IOW, a model lumber train on the UP
originating from Cal might require 15 SP box cars while a model merchandise train from the northwest might require no SP box cars. Those of us with frt train consists are fortunate IF we are modelers modeling real trains...even those compressed...because we can simply acquire the cars we need [ or try ]. Fortunately for me I only have consists for about 70 trains in two different yrs. Those without such consists are left to use the G-N hypothesis to provide a frt car population. I don't know what one without consists would do to build individual trains...I suppose some manipulation of the G-N data. It can be done, of course, but the frt train consists I have access to seem to show trains of cars NOT in the mode of distribution that G-N proposes. For example, my frt conductor book shows a train of 40 MTY reefers...all but 3 PFE, 2 box cars in the middle of the reefers [ one loaded GM&O going to Butte, MT ], 2 tank cars and 26 box cars loaded with bauxite ore headed to the Northwest...not one UP box car [ or PA ] in the mix. There were 4 CN box cars, however, and 3 Frisco, 3 Q and, of course, the required NP. Not exactly your national fleet. I would also think that some sort of "small number" factor would need to be used with the G-N. How else to get that FEC car?

Mike Brock


Allen Rueter
 

It seems to me you might want four pools of cars. home road pool, favored/connecting interchange pool, National pool common cars , and national pool rare cars(<1%). you would want at least one standard deviation, if not two, extra cars in these pools to create
variety .


now you know why there is never enough staging space.
--
Allen Rueter
StLouis MO


Anthony Thompson <thompson@...>
 

Allen Rueter wrote:
It seems to me you might want four pools of cars . . . and you would want at least one standard deviation, if not two, extra cars in these pools to create variety .
Not a bad idea, Allen, but given the sort of data we have I would be entertained to see a calculation of the Standard deviation . . .
But I take your point, that we DO need rarities so that our trains will exhibit those rarities.

Tony Thompson Editor, Signature Press, Berkeley, CA
2906 Forest Ave., Berkeley, CA 94705 www.signaturepress.com
(510) 540-6538; fax, (510) 540-1937; e-mail, thompson@signaturepress.com
Publishers of books on railroad history


Mike Brock <brockm@...>
 

Allen Rueter writes:

", and national pool rare cars(<1%)."

And Tony Thompson follows with:

"But I take your point, that we DO need rarities so that our
trains will exhibit those rarities."

Yes...my "small number" factor in order to achieve the FEC car. Besides, when I was a kid I saw KO&G trains...they had 9 box cars. Let's see. If I conduct an op session once per day, the Cubs will win their second World Series before I can use it. Meantime...

Allen adds:

"now you know why there is never enough staging space."

Staging hell. Storage space for the 4750 box cars...seems like that many anyhow.

Mike Brock


al_brown03
 

I like someone's suggestion of reserving a small proportion of the fleet for rarities, which are rotated. Saves me the need for 974 X29s: I don't mind building a few, but hundreds of the same thing are a pleasure only for our distinguished SPF brethren (and maybe even only some of them!). :-)

Al Brown, Melbourne, Fla.

--- In STMFC@yahoogroups.com, "Mike Brock" <brockm@...> wrote:

Allen Rueter writes:

", and national pool rare cars(<1%)."

And Tony Thompson follows with:

"But I take your point, that we DO need rarities so that our
trains will exhibit those rarities."

Yes...my "small number" factor in order to achieve the FEC car. Besides,
when I was a kid I saw KO&G trains...they had 9 box cars. Let's see. If I
conduct an op session once per day, the Cubs will win their second World
Series before I can use it. Meantime...

Allen adds:

"now you know why there is never enough staging space."

Staging hell. Storage space for the 4750 box cars...seems like that many
anyhow.

Mike Brock


Tim O'Connor
 

I designed a track plan proposal for a club in 1500 sq ft that
included a hidden three level stage/elongated helix that would
have provided 700-1000 linear ft of level staging (18-24 long
trains) -- but the staging operator would have had a 36" duck
under. So they voted a plan with NO staging at all and a yard
that is about 70" high off the floor. Go figure. Anticipating
the sheer joy of operating such a layout, I quietly resigned.

Tim O'Connor

"now you know why there is never enough staging space."

Staging hell. Storage space for the 4750 box cars...seems like that many
anyhow.

Mike Brock