Western Railroad Discussion > Locomotive coupler question

On some freight roads, sometimes I see locomotives equipped with tightlock couplers. Why? Sometimes they're carrying regular freight without business trains... They still have them. Why is it not a standard to have all locomotives built with tightlocks since the 70's?

Tightlock lugs aren't just for passenger equipment. Many tank cars have them in addition to the required top and bottom shelves. Rotary Dump cars have them to keep the couplers properly aligned to each other both in the dumping process and in transit.

Pardon my ignorance, but what is a "tight lock" coupler and how does it differ from other couplers?

TIA,

Fritz in HSV, AL

Most you see today are "interlocking". "Tightlock" was for passenger use, with a spring loaded horn & knuckle face. It also had some rubber parts, and eliminated the noisey jiggle & slack in the coupler itself. Interlocking couplers look similar, with the horn and pocket, but they are not the same. The coupler body is a one piece casting, and so is the knuckle. They are for freight use, but you will see them on passenger equipment sometimes now that true tightlocks are mostly gone. With both, if a drawbar is pulled from one car, they stay connected and cannot fall down under the train. They keep vertical movement to a minimum, and on rough track couplers cannot "pass", or move up and down vertically so much that they go above or below one another on the move.

And many loco motives now have extra knuckles on a bracket on the end of the unit, usually the rear end, on either side of the coupler. They usually have one type "E" and one type "F". They type "E" is the conventional, the type "F" is the tight lock coupler.

I've noticed that most of BNSF's new grain hoppers have the tight locks

E- knuckles are gingerly used on locomotives

Gary Wamhoff
Laramie, WY

josie Wrote:
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> E- knuckles are gingerly used on locomotives

This is because of the forces between units in a consist?

The spare knuckles are carried more for use on a trailing car than on the loco itself.

NZ

ddg Wrote:
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> Most you see today are "interlocking". "Tightlock"
> was for passenger use, with a spring loaded horn &
> knuckle face.

Thanks for this clear definition!

~ Bob Z

ddg Wrote:
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> Most you see today are "interlocking". "Tightlock"
> was for passenger use, with a spring loaded horn &
> knuckle face. It also had some rubber parts, and
> eliminated the noisey jiggle & slack in the
> coupler itself.

What you are talking about are type CS (Control Slack) couplers, and they are obsolete. The current standard for Tightlock couplers, which has been in use since the 40's, is the type H, and it is still in production. They have a pocket and a guard arm that inserts into the pocket of the mating coupler. This prevents uncoupling by sliding vertically, which is possible with standard freight couplers.

Locomotives generally have type F couplers, which come in a form that mimics the type H, as well as ones that have upper or lower 'shelves'. In all cases the aim is the same--keep cars coupled in the event of a derailment.. They are not Tightlock, however.

The tolerances in a true tightlock coupler are such that there is very little slack between two couplers, and they couple easily at very low speeds, which of course is important when adding a car with passengers aboard.

>"Tightlock" was for passenger use, with a spring loaded horn & knuckle face.

There are E, F, H, and controlled slack couplers (which is the one with the spring plates). Es, Fs, and Hs were/are used on freight cars, with the Fs and Hs being termed "tightlock". Es, Hs, and the controlled slack version were/are used on passenger. Fs can be considered a short-shanked, freight version of a tightlock. Contrary to their names, tightlocks don't lock tightly but prevent vertical movement between the two couplers (this includes the controlled slack version).

>E- knuckles are gingerly used on locomotives

E knuckles are used in type E couplers, and locomotives generally have a high strength version (no core hole). There is a code on each knuckle around the core hole which describes its design and manufacture. There is a separate code on the top of "thumb" side which describes the manufacture of the coupler.

Are there coupler specs available anywhere to read without being a member of the AAR?

Amtrak currently uses H tight lock on their equipment.

So with all the different type couplers available for use, are all the coupler pockets built to an "industry recognized standard" as well as the coupler shanks to go into them?