How is length of a car measured

On the prototype, it’s coupler face to coupler face, with the knuckles closed.

Thanks Rich.

The most useful length measurement of a railroad car is over “pulling faces”. That is the inside face of the coupler knuckle. That is the point that is in common with the adjacent cars. If the pulling face dimensions are added together you end up with the train length. The other dimension of importance on a freight car is the interior length. That tells the customer how much freight they can get in the car. When people talk about 40 foot or 50 foot boxcars, those are the interior lengths of the cars.

Thanks David, I really appreciate the education…..it is one of the reasons I asked the question

Is the above all true for models of railroad cars or only the real thing?

I do not know. I spent my career working with real trains, not models. I would guess that it is true for scale model, for 3 rail trains there may be variations.

I was trying to get my new Williams passenger cars to match the specs…measuring from coupler to coupler gave me the right length

Except you can’t measure most O gauge trains from coupler face to coupler face to get a proper scale match to the prototype. That’s because the couplers, which are grossly oversized already, have longer shafts and are designed to create greater spaces between cars.

When doing fine modeling, you need prototype dimensions of the body. That’s how the bodies are supposed to be scaled in O gauge.

Naturally, because of the couplers, O gauge cars and locomotives will always measure longer from coupler face to coupler face.

Thankyou Jim….one day I hope to attain the level of skill and knowledge many on this forum have, and the knowledge you share with me is greatly appreciated.  Being the simpleton that I am, I was trying to sixteen inches of length that the cars were supposed to be.  What I have found out is cool cause it’s just like life, the deeper you go into something, real accuracy counts.

I appreciate anybody who throws down their thoughts and/or opinions…..or shall I say , thanks for the education….today and in the future

Passenger cars "official" length for description and use as opposed to train length is measured differently than freight.    Generally the length described does not include the vestibule.    For example PRR had P70 and P54 coaches.    These were described 70 foot and 54 feet long respectively.    However, this dimension is inside the vestibules, so the cars are quite a bit longer overall.     To carry this on, the B70 baggage car was 70 feet inside similar to freight cars.

I think many RRs and car builders used this type of description for passenger cars.

I see that our models are different than reality….when I bought these Williams coaches, the description said 16 in…. I really appreciate seeing how the models and real trains differ…I have never even been on a train, except NYC subways when we visited my grandma…thanks for education, as a teacher I admire the knowledge on this forum…appreciate you prrjim

@Catdaddy posted:

I see that our models are different than reality….when I bought these Williams coaches, the description said 16 in…. I really appreciate seeing how the models and real trains differ…I have never even been on a train, except NYC subways when we visited my grandma…thanks for education, as a teacher I admire the knowledge on this forum…appreciate you prrjim

measure the body, not the couplers. that's the car length.   

When I did that , I was short of the 16….when I went coupler end to coupler end I got 16…..I wondered  if they happen to use a different source of couplers if the 16 in description is then accurate…I am going to go back and reread the description. Can car length and total length be different…I am going to get one of coaches and measure , and post a picture. I am a curios type, so this discussion is helping me understand . Dave, thanks for your response, I appreciate you.

@Catdaddy posted:

When I did that , I was short of the 16….when I went coupler end to coupler end I got 16…..I wondered  if they happen to use a different source of couplers if the 16 in description is then accurate…I am going to go back and reread the description. Can car length and total length be different…I am going to get one of coaches and measure , and post a picture. I am a curios type, so this discussion is helping me understand . Dave, thanks for your response, I appreciate you.

I see. The big problem , is that the 3rail Toy Train Manufacturer's make an abbreviated version a car, not a scale representation, as in a prototype. (they measure them wrong! )  An 80' car in O is 20" not 21".(as they advertise)  As far as getting you cars , its probably safe, to go with their description, enjoy them and have fun!

Yea, I think your right….and I am very pleased with my purchase….it is closest thing to scale that I have and sometimes I wish I was not so curios but I have fun learning about trains and playing as well….sending out good vibrations to all on the Sunday afternoon

Not all passenger or freight cars are undersized. But, yes, in 3-rail, you have to know what you’re buying. Manufacturers are not the most ardent scale modelers in our toy train hobby.

If you have a favorite railroad (mine is the long gone Pennsylvania RR), you can search for copies of their car (freight and passenger) and locomotive design diagrams.  On those diagrams, you will find all kinds of dimensions listed like coupler face-to-coupler face length, measurements of trucks (including diameters of wheels, distances between wheels, distances between truck centers, etc.), various height measurements and others.  These diagrams might be found online or in books, and they can be very useful tools if you are trying for model accuracy.

Unfortunately, there is no manufacturing standard for model measurement.  So a model listed as 16" might be measured from body end-to-body end or it might be measured from outside edge of coupler-to-outside edge of coupler or in some other unspecified method.  Regardless, with the prototype info described above, you can use a ruler or other measuring instrument to determine how "accurately" the model you are looking at was built.

Chuck

Like everything else in the 3R Hobby there is no standard.  I only own K-Line Cars and they are the length of the Body of the Car.  This is the conservative way to do it.

This means a Williams 16" car is about the same as a K-Line 15" car.