Strongest couplers?

[peteski]

I’m reviving this topic on “strongest couplers” having recently picked up a force gauge to scientifically prove what I’ve been observing in coupler testing. I’m looking for some community input on just how much force is reasonable to expect from a coupler before it fails.

If by "fail" you mean physical damage, then I believe that most couplers will uncouple (by sliding up or down over each other) long before a physical failure.  Not sure of this exercise is really useful.  That's because of factors like flexing shanks, vertical play in the coupler box, or even entire car lifting off the track.

[learmoia]

The only MT couplers I've ever broken resulted from dropping a car on the floor.  Yes, they will impact break.

Ok.. so formulate a drop test to determine at what height they brake when falling from the layout.. 

My vote for strongest coupler is the Precision Master/Red Caboose/Fox Valley/Scale Trains? Unimate..

[jagged ben]

A draw bar strength of 60 cars on a 2.5% grade should do it for me.  That said, I care a lot less about material strength than the following:

- knuckle design that pushes the knuckles closed when shoving
- knuckle design that doesn't separate with slack action (same, really)
- rough inside surface to reduce the vertical slippage others have mentioned
- designs with prototypicalish shelves

[robert3985]

A draw bar strength of 60 cars on a 2.5% grade should do it for me.  That said, I care a lot less about material strength than the following:

- knuckle design that pushes the knuckles closed when shoving
- knuckle design that doesn't separate with slack action (same, really)
- rough inside surface to reduce the vertical slippage others have mentioned
- designs with prototypicalish shelves

Hmmm...."prototypicalish"....I like that.  I'll have to use that word every now and then when appropriate! 

Cheerio!
Bob Gilmore

[Lemosteam]

A draw bar strength of 60 cars on a 2.5% grade should do it for me. 

This is as close a functional requirement as one can get.  Yes the grade and number of cars could be varied to determine the most commonly used scenario, but this is a good start.

At one point I was considering taking a 10' 1X4 and making an adjustable pivot track on a long wall and placing a fish scale with a stop at the upper end and a hook that is compatible with all couplers to do two things:

1: Create a ratio of car actual car weight vs. car weight on wheels on an inclined track, to determine an average baseline weight to assess the drawbar force per car at a specific incline.

2: Use the same scale fixture to hook to a pseudo car (pull pocket with a mounting attachment for the coupler box) on level track and pull to fail on various popular couplers

    -I have actually done a facsimile test 2 using an MT 2 bay hopper to fail.  Unfortunately, I did not record the measured force value nor do I remember the value.  I DO recall that surprisingly it was quite a bit of force that my hand used to break it.

This is my pull test gage in one of my traction tire pull test videos.  I would mount a similar stop on the incline track using the same device.  It is accurate to 0.1oz as can be seen:

[pedro]

I was always amazed at the 0-5-0 force required to move a 100-car hopper train (Atlas 3-bays) equipped with 100% MTL trucks/couplers on nTrak back in the day. Those were not particularly heavy cars, and the couplers pre-dated the advent of the MTL “reverse draft angle.” It seemed amazing to me (still does) that 5 Atlas/Kato geeps could move the train.  I don’t believe there was really any substitute for MT pizza-cutters with truck-mounted couplers in that scenario. Not to mention the heavier frames used on those engines… sometimes I think we’ve actually regressed with our featherweight DCC/sound-equipped engines and low-profile wheels. But I digress…

[Angus Shops]

By sheer volume of plastic, the “Rapido type” coupler is probably the strongest.

[ednadolski]

I don’t believe there was really any substitute for MT pizza-cutters with truck-mounted couplers in that scenario.

Pizza cutters will add drag,esp. on tighter curves.

Ed

[nkalanaga]

Angus Shops:  I suspect you're right.  I've broken cars with Rapido couplers by dropping them.  I don't remember ever breaking one of the couplers.  And, with no moving parts, they should be tough.

[robert3985]

By sheer volume of plastic, the “Rapido type” coupler is probably the strongest.

When my Ntrak club was running long trains, it wasn't the Rapido-style couplers that were failing, but it was their coupler "box" that was giving 'way with really long trains.  So, I guess since the "box" is part of the coupler design, it could be considered coupler failure....maybe. 

Cheerio!
Bob Gilmore

[nkalanaga]

That would depend on the box design.  The original Atlas/Minitrix design, with a solid box and a metal clip, wouldn't be likely to fail.  The Con-Cor design, where the coupler twists into place in an open, flexible box, doesn't look nearly as secure.

[turbowhiz]

It seems then that the ~60 car 2.4% grade /~250 car level track is probably a very reasonable benchmark. My rough estimate is those aren’t far off from each other. I’m estimating that represents ~2.2 newtons (.5 lbf/7.9 Oz) or so of force.  I want a reasonable number to consider a “full pull”; This is about offset reliability rather than failure strength; This is WAY below any failure strength I’ve measured. But above any number of pull apart values I’ve found with factory installed couplers.

Much of my strength testing previously has relied on using dead locomotives to create resistive forces simulating long trains. But as I began observing certain behaviors, I wanted to more reliably prove my casual observations in a more controlled and repeatable manner, enter the force gauge.

My coupler test setup isn’t super sophisticated, but I’m getting consistent and repeatable results. A pair of 1055 gauges, a bi directional force gauge shimmed to line up to the 1055 that measures .01 newton increments and which also holds a peak value, and some unitrack. Different couplers can be mounted up in the 1055 gauges too.



Any number and combination of cars can be setup between the 1055’s and then pulled or pushed. The unitrack section(s) can also be shimmed under cars to progressively mis-align couplers, or propped on joints to create humps, and force can be applied and measured.



Any bets as to which end pulls apart first ? (pre-production N-Possible (not TSC/derived TSC) scale couplers on the left, stock MTL on right, identical MTL models.

(For fun I’ve tested the brute strength of couplers by just connecting the 1055’s directly together and pulling (to destruction); It’s much more of an academic exercise rather than of any practical value but curiosity got the better of me)