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Car length - how measured?

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PED
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Car length - how measured?
Posted by PED on Wednesday, December 05, 2018 8:43 PM

Been looking at some info recently on car lengths (full size) and trying to compared them to N scale models. I do not expect the models to match full size exactly but it made me curious about how full size car lengths are measure and if there is any common practice. 

For a boxcar, is it from the outside of one end wall to the outside of the other end (excluding couplers) or does it include any protrubances such as roof walks, ladders or enything else that extends beyone the end wall?  How about tank cars which may have a lot of railing or other stuff that extends beyond the main tank?

Although I am curious, my question aso has a practical purpose for me. I am using JMRI and the length of a car becomes a factor in calculating how much track length a car uses as well as other parameters in JMRI.

 

Paul

Washita and Santa Fe Railroad
Circa late 1970's in south central Oklahoma

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Posted by gmpullman on Wednesday, December 05, 2018 8:53 PM

Actually, it depends on who's interested.

A shipper wants to know the inside length, width and height.

The mechanical department looks at length "over pulling faces" i.e. coupler knuckle to coupler knuckle.

The operating department wants to know the clearance profile, i.e. overall height, width and length. Cars designated as "plate C" or excess height may not be able to operate over some routes.

http://www.icrr.net/plates.htm

Bulk cars have a weight capacity and a cubic foot data as well (the house cars do as well, of course).

New ULMER data can provide operating crews with actual train lengths so that by setting a counter the engineer knows exactly when the rear of the train clears a siding switch or end of a speed restriction.

https://www.railinc.com/rportal/umler-system

 

Regards, Ed

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Posted by 7j43k on Wednesday, December 05, 2018 9:02 PM

Boxcar lengths are frequently measured on the INSIDE.  Thus, a 40' boxcar will have in internal length of 40'.  Or so.

For all freight cars, there are external lengths.  Measuring over the end sills is common.  Projecting walks and ladders usually don't count.  I think sometimes there is a measurement over the coupler pulling faces, which would appear to be more useful for your JMRI concern.

The ORER lists internal and external lengths, but I can't find a definition in the book for the latter.  Perhaps they just let the railroad submit any number they choose

For widths and heights, projections frequently DO count, because of clearances.

 

Ed

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Posted by dehusman on Wednesday, December 05, 2018 9:34 PM

Common lengths are the inside length.  A 40 ft boxcar is 40 ft inside length, a 52-6 gon is 52' 6" inside length.  Outside or extreme height and width are over the doors, grab irons, handbrakes, etc.  Outside length is either over the 'strikers' (the area over the couplers) or to the pulling face of the couplers.  

Dave H. Painted side goes up.

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Posted by johnnyrails on Thursday, December 06, 2018 5:53 AM

I think that JMRI takes into account the space requirements for the couplers, & adds 2' on each side of the car, ie a 40' car is assigned 44' on a track...I think?

PED
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Posted by PED on Thursday, December 06, 2018 9:03 AM

JMRI needs "face to face" numbers so it takes whatever length you plug in and adds 2' per coupler thus 4' overall. A 40' boxcar becomes 44' in JMRI for purposes of calculating track length.

My question was driven by the variances I saw in the length of a N scale car vs the stated length of the prototype. I think my best approach is to ignore the prototype length and then input the actual scale length (minus couplers) and then let JMRI do its math to calculate track used by the car. That is what is important for JMRI operations.

Paul

Washita and Santa Fe Railroad
Circa late 1970's in south central Oklahoma

  • Member since
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Posted by kasskaboose on Thursday, December 06, 2018 10:15 AM

Measuring lenght on the inside makes sense.  Measuring the outside is probably too subjective.  Avoiding subjectivity saves money.

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Posted by dehusman on Thursday, December 06, 2018 9:28 PM

I have seen timetables where siding capacity was stated in car lengths and a car was set at 45 ft.

Different people want different lengths.  Customers want inside length, dipsatchers and yardmasters want length over the pulling faces.

Dave H. Painted side goes up.

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