I have heard the story of standard gauge having been derived from roman chariots, but what's the history behind couplers? How was the height of the coupler on trains established? This appears to be unchanged when the current knuckle coupler became common. Would we have been better off with a higher coupler height after rolling stock got taller? Or do I have it backwards?

The coupler needs to be inline with the center sill.

The size of the wheels pretty much determines
the height of the center sill.

-Hudson

You want to minimize the torque arm formed between the coupler and the bolster. You want train force to go through the car end to end, without inducing any moment on the car (tipping it like a skate board).

Most car wheels are pretty close to each other in size, relatively speaking, so the coupler height is stable.

If wheels had changed significantly in size since 100 years ago, then maybe coupler height would have been a discussion item.

My understanding is that the coupler height is set of a range of distance from rail to centerline by the AAR. This probably goes back to the MCB (Master Car Builders Association) that adopted the knuckle coupler as a standard.

Here's some material that may be of interest.

http://en.wikipedia.org/wiki/Railway_coupling

http://en.wikipedia.org/wiki/Janney_coupler

http://inventors.about.com/library/inve ... oupler.htm

http://en.wikipedia.org/wiki/Miller_Platform

http://trn.trains.com/en/Railroad%20Ref ... plers.aspx

http://discussion.cprr.net/2006/07/dang ... plers.html

http://cprr.org/Museum/Ephemera/Link-Pin_Couplers.html

http://harveycountyvoices.blogspot.com/ ... d-pin.html

It's a bit of overkill, but there's a good bit here; enjoy.

John White's History of the American Passenger Car has a discussion of many aspects of couplers (not entirely from a passenger perspective).

John White also has a book called The American Railroad Freight Car, which provides a lot of detail on coupler development. I used to believe that there were only link and pin couplers and knuckle couplers, and the first was abruptly switched to the latter in the late 1800s. White's book shows that there were many different styles and designs of both types, including hybrids of both types. Even the Janney automatic coupler, once adopted as standard, has changed since then.

But the link and pin coupler was in a constant state of development throughout its period of use. It was never standardized, nor even entirely compatible with other members of the group. The link and pin coupler is most widely known as being dangerous, but its problem of having loose hardware was also great. Much inventive talent was focused on both of those fundamental problems. It would be interesting to know how many hundreds of tons of links and pins are still buried on or near the routes of old railroad beds today.

The patent on the vertical matting face was released to the MCB in the mid-1880s, by the turn of the century the MCB had approved about 50 versions of the coupler. The differences being release and latch mechanisms, etc.

Over the years the size and mass of the couplers have changed; but the mating faces of the knuckle have always been compatible.

The American Railroad Freight Car book by John H. White is one of my favorite RR books and has several diagrams of interesting old style couplers. Coupler height must have been a problem with even the link & pin cars. Some of the old yard engine photo's you periodically see for use with link & pins will have a 2 or 3 position coupler pocket on the front of the engine wich undoubtably was for coupling to cars with different coupler heights.

Years ago when i first started digging up link & pins along abandoned RR's i found a few longer links that had stair stepped bends in the center. At first i thought they just got bent from years of use. Later on a friend of mine gave me a neat old book from Wilson Walker & Co Limited Iron Mills of Pittsburgh, Pa. 1885 that was full of advertisements for RR company's and car builders. On page 47 it showed those longer stair stepped coupling links for link and pin couplers wich obviously were for use on different coupler heights on RR cars.

I've since found a few more of those links and also some different coupling pins, one extremely long but with a bent handle wich i believe was used on the Barnes style hook coupler shown in the Whites book in the 2 lower diagrams on page 507.

Railroading at that time had to be something with all the new experimental stuff that was being introduced and also a nightmare for the brakemen coupling cars! At least with the coupling link it was pretty much universal with most drawheads or at least with the few i have in my collection. Coupling pins on the other hand came in all differnt sizes/types and they do not all fit in the same hole in the drawheads!

Imagine being on a train back in the 1850's or 60's when it would break in two due to a broken link or pin. Than goodness they were short trains and not these 1 1/2 - 2 mile long ones like today! Off you go for a walk carrying a link and probably 3-4 different pins. You have no idea if you'll need a fat round pin, a smaller round pin, and oblong pin, or a flat pin or if one of the cars had some kind of experimental coupler!

Then when you get back to the train seperation, if you can fix the problem you still have that unused exta iron to carry back to the head end if you feel like it. For most why bother, throw it over the embankment, throw it in the creek, river ect. That is why there is so much tonnage of discarded old iron along the old RR row's. Over the years i have filled many,many 5 gallon buckets with the stuff and even given alot away to friends. Some link & pins it's rather obvious why they were discarded due to the breaks or bends but others there is nothing wrong with them.

Ron and i both know there are tons of the stuff out there. For me just finding buckets worth along 50 miles or so along one RR line close to home is evidence that there are still hundreds of tons still burried out there across this country!

In Whites book on page 490 it says that at the 1875 Master Car Builders meeting it was reported that millions of pins were made each year but no one knew what became of them. And at the same time the Jeffersonville, Madison & indianapolis RR lost over 43 thousand link & pins each year.

Even the RR's marking their link & pins with the RR name did not keep them on the same RR or guarentee their return. A few years ago i found a nice marked N. C. & St. L. coupling pin in the river at Elmore, Ohio on a LS&MS Ry. line, i've even found a C&NW one at Ashtabula, Ohio. They were all used on trains going everywhere back then. Makes you wonder if by marking them if the RR's had some kind of yearly exchange program for their RR iron!

TAN: A Railroad Magazine article mentioned "robbing the iron", removing all links and pins from cars set on an interchange track. The same was done to the "Iron Box" on a tender before the locomotive went into a shop. Using a locomotive fresh out of the shop to pull cars off the interchange track wasn't the easiest job on the railroad for the brakemen.

And...



All this is true, but must not have been the major concern for the first seventy or so years of railroading, since the couplers were typically NOT on the center-line of the frame. It appears the car builders were more concerned with keeping the structural frame of the car uncompromised, and the couplers were installed between "draft sills" that were bolted and keyed to the underside of the actual center sills, which had the unintended consequence of supplying the bending moment mentioned above. Photos of old time cabooses damaged in switching accidents often show the platform broken or bent down to the ground because of this.

By the 1890's car builders were beginning to add a sub sill bolted to the bottom of the center sills between the bolsters that was better positioned to resist buffing forces, but draft forces had to wait a couple more decades until the advent of steel center sills before they were correctly accommodated, and then the builders had to work their way through the period when deep "fishbelly" sills were popular before a true straight line transmittal of forces through the car frame was achieved. Engineering progress came exceedingly slowly for the railroad industry.

Interestingly, the Colorado narrow gauge lines addressed this issue considerably earlier than the rest of the railroad industry; deciding that the end sill did not need to be continuous allowed them to do away with the draft sills and install the draft gear directly between the center sills.

Coupler height is more critical for the link a pin, than for the knuckle couplers. Some links will not interface at all with a little as 4"-5" of height difference. Long links and "Z" bent links are a remedy for that, but they too were a huge compromise.

Some of the fancy link & pin couplers allowed you to balance the link in one coupler, while you moved the other coupler together with the first. This required the couplers to be nearly at the same height. The required heights were only +- few inches or the link would then need to be held up, by a human hand, or a brakeman club, to get the pinned link started into the second coupler.

99% of US couplers now use an 11" (tall) knuckle. Back in the MCB coupler days, (mandated from 1903-1919) era the std knuckle height was 9" tall, but most of the locomotives used an 11" tall knuckle, that you can recognize in old photos by it appearing to be nearly as tall as the whole MCB coupler, unlike today.

Most MCB couplers had a 8" or 9" "head length".

MCB couplers ended development with the MCB 10, the one prior was the MCB 5, I believe. In 1913 (or so) the AAR had developed, released, and made the Type "D" coupler, it was made the standard for new equipment in 1919.

None of the AAR or MCB knuckles have the exact same knuckle contour interface, but like Brian said above, the couplers will all inter-couple from MCB 5 (pre 1900)- AAR 10A (in use today, found on the type "E" {plain/regular looking}) coupler.

In 1916 the type "D" had the then new -10 contour, that was std for the still new AAR, that took over where the MCB left off. The -10 was followed by the 10A contour a decade or so later.

The big improvement in the Type "D" was the massively increased height and thickness of the cross sections and of the individual components and its new -10 contour, which was developed by Mr. Janney himself while he was at ASF. Mr. Janney's said that the main advantage with the -10 contour was perpendicular "pushing" face, that is designed into the rear of the contour. That perpendicular face allows the couplers to stay inline when pushing against other -10 contour couplers. That saved huge sums of money on axle bearings and wheel flanges in all helper services that used them (some isolated roads never did). The older MCB contours did/do not like to stay inline when pushing.

The AAR -10 contour (which is so close to the 10A as to be the same contour except for a 1/32" in a couple of places and a large chamfer on the guard arm), was a revolution at the time, thats why it is about 100 years old and still in use.

What other part can claim (basically) a 100+ year std design, except for the use of the wooden cross tie and the rail (whose size and shape have changed dramatically) made from steel?

As long as we're on the topic of couplers, a related question:

Safety Chains

Did they work? Seems to me that if the couplers parted the shock on the chains being suddenly pulled taught would be likely to break them at least if the parting is near the front of a heavy consist.

Steve

I'm sure they worked well... except when they didn't. The chains I'm familiar with from the late steam era, illustrated here on C&IM 90 at Mid-Continent, had links nearly as large as link & pin coupler links.

http://www.midcontinent.org/collectn/stlpas/cim90c.jpg

One thing I've not been able to determine is when they were no longer required to be used. Some of the preserved Soo Line steel cars kept theirs to the end of Soo passenger service in 1967, but then again, some of the Soo coaches still had Sharon couplers that late. I've just never been able to determine if they were still connecting the chains.

Regarding Safety Chains. Orange Empire's Pullman CROYDON a 7 Comp-2 DRm car built in
1914 and in use until 1944 when sold to a movie studio still has safety chains.