As a 'placeholder' for what will likely be Ed's better drawing of the various AAR plates 'together' to show the differences at a glance, there is this:
https://gritton.org/greg/rail/docs/clearance/AAR_plates_with_UIC.gif
For anyone interested in a detail procedure to do clearance design, this is an older reference (consider the software reference!) but the principles are still sound:
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.648.7570&rep=rep1&type=pdf
LazersHi NHTX & Chris, thanks for your replies. As I half-guessed, it is a Width over Height ratio - sort of thing.
Not a "ratio"... as Dave says it's the whole shape (outline) of the clearance profile. It's height, width, but also the overall shape especially the extreme corners.
Chris van der Heide
My Algoma Central Railway Modeling Blog
One has to look at the entire shape of the plate to see the differences. For example, before I retired there was a committee working on a "plate L" for locomotives. The big bone of contention was not at the top, but at the bottom. The lower foot above the top of the rail. The western roads were pushing to lower the bottom of the steps, to make it easier to get on and off the engine, but the eastern roads were pushing back because the lower steps wouldn't clear many of the passenger platforms in the commuter districts, other roads were concerned about clearing the lower braces on through plate girder bridges.
The UP spent millions grinding out the "corners" of tunnels to clear double stacks.
The clearance diagrams are more than just the height.
Dave H. Painted side goes up. My website : wnbranch.com
Hi NHTX & Chris, thanks for your replies. As I half-guessed, it is a Width over Height ratio - sort of thing.
I always try to research before posting a Q and it was just that out of all the Diagram Outline Comparison drawings I found on-line, Plate D didn't even get a mention, let alone a look-in.
I've been watching (again) 'Pat's Train Videos' - "Manifest compilation" (Indiana) I find the variety of stock, particularly Hi-Cubes and older style Boxcars from former R/R's (now merged) or existing Class 3 lines - fascinating. Tonight I saw & researched MDW, Sultran, SGLR & TOE.
I still regularly see Southern Pacific, Conrail and GTW + some Short-line specials. UK Railways are nothing like this. Nationalisation destroyed our Railway system.
Regards, Paul
"It's the South Shore Line, Jim - but not as we know it".
Plate diagrams aren't just a max. height restriction, but a full cross-section profile. Plate E also has a taller allowance for the upper corners of the car.
Paul, wise move erring on the side of caution, some of their stuff has prototypes, that exist only in fertile minds.
Plate D does exist. It can be found in the Official Railway Equipment Register. On page 1662 of the January 1988 issue is a chart containg a graph for the "Method for obtaining maximum allowable width of car, other than at centerline of car, for unrestricted (Plate B-1) & limited (plate C-1) interchange service. Adopted 1966. Association of American Railroads, Mechanical Division".
It contains some mathematical formulas that make my eyes bleed. Fortunately we modelers don't really worry about such minutia as determining maximum widths at centerlines and at different points between truck centers any more that we worry about gross rail weights.
I've noticed a couple of recent occasions (ebay UK) where because a Boxcar looked like a Hi-cube, it was listed as one, when in fact the decals clearly read Plate C, not Plate F as should be. Being Roundhouse & older Bachmann models, I erred on the side of caution.
This got me to checking Jeff Wilson's book 'Modern Freight Cars'. From T.O. Rail, Plate C = 15'-6", Plate E = 15'-9" and then Plate F (Hi-cube) jumps up to 17'-0". I wondered what happened to Plate D? Is this for Gon's, Tankers or some purpose-built car? I'd be interested to learn, if only out of curiosity. I have done a bit of research but Trains mag 01/05/2006 although useful, was all I found.
The small difference between C & E is puzzling too. Is this due to a height/width ratio of the Car? Thanks, Paul