Athearn LPG tank car MTL coupler conversion

[GaryHinshaw]

LEZ = "Lee English Z" scale coupler, a.k.a the Bowser Buckler.  LEZ was coined by Ed N back when we were dabbling in those as an alternative to other N scale couplers.  Nowadays I'm pretty sure that I'll be taking the plunge with the N-Possible's when they're out.  It looks like an awesome product.

Back on topic, it's too bad Athearn chose not to include the coupler pocket dimples that would have allowed a simple MTL coupler swap.

[peteski]

Back on topic, it's too bad Athearn chose not to include the coupler pocket dimples that would have allowed a simple MTL coupler swap.

And again off-topic  but related, Scale Trains seems to be doing this too.  The Big Blow turbines had coupler boxes with those dimples which directly accepted the MTL coupler innards, but their Standard Turbine models do not.  Well, there is an an indentation in just in the bottom cover, but it is molded on the wrong  side! And it cannto be just flipped as it is not reversible. And even if it was, the other part of the coupler box is not compatible either.

[turbowhiz]

BTW, we had an earlier discussion (in another thread) about the MTL coupler design and what keeps them closed, but I was told that I didn't understand how they worked, so this time around I didn't not mention that those nubs are responsible for keeping the coupler closed while it swings to the side.  And now you mentioned that.  Go figure.

I think maybe this is a nuance of language, and we’re actually saying the same thing ?
 
The nubs do not technically "keep the coupler closed when it is pulled to the side". Either the knuckle or thumb operates independently from each other, and the nubs do not contribute in any way to keep the coupler closed in any position other then the center. Just gently pull on either on either the knuckle or thumb in its respective direction, and you can observe this behavior. You can move either the knuckle, or the thumb apart from each other independently of each other. It doesn't stay closed. If the coupler does stay closed, its doing so with no real force and only by random influence of the spring position in the slot, and not by the nubs. A "nub free" MTL coupler will sorta kinda but not really close or stay closed in exactly the same fashion. That is why I precisely said "they won't reliably close" without nubs.

What I would say is that the nubs function in conjunction with the spring to center the knuckle or thumb against each other, and therefore close the coupler in the centered position.

Or... To quote from US3469713A, the original Edwards brothers patent for this design:

"The coupler is characterized by a knuckle and an opposed lip, unitary, respectively, with separate, superposed, slotted shanks. A longitudinally extending compression spring is located within the shank slots and exerts an inward, lengthwise thrust on each of the shanks. Fixed abutment means at opposite sides of the shanks stand in opposed relation to abutment means on the respective shanks, so that, in response to the spring thrust, the knuckle and lip are yieldingly rocked, scissors fashion, toward one another, being arrested by direct interaction of the balanced shanks, to stand in potentially automatic coupling relation, or in coupled relation."

Much clearer. 

I guess they called the "thumb" a "lip". I like to call it a "retainer". Seems knuckle is clear... But the naming the other half of a split shank coupler is very much open to interpretation!

(oh it seems they aren't called nubs. They are "fixed abutment means")

[peteski]

I think maybe this is a nuance of language, and we’re actually saying the same thing ?

I believe you are correct.
I will be first to admit that the richness of my English vocabulary (especially when engineering terms are involved) is nowhere as full as native English speakers'.
Thanks for digging up that technical explanation.