Impact on couplers in a rear ending

[MK]

I've always wondered about this as I've see it so many times at train shows and even experienced it myself a few times.  And it's a perfect  question for the audience here.   

Let's say we have a unit train pulling a dozen+ of, say, the Atlas shorty beer tank cars though I think it could have been 90 ton hoppers for that matter as I don't think it will make a difference in this scenario.  Trucks are a mix of Accumates and MT.  Pulling this consist is a Kato 6 axle unit.  The train is stopped on the main line due to traiffic ahead.

Coming in the rear is another train pulled by another 6 axle unit.  It's pulling 6 or so mixed rolling stock though I think this is irrelevant.  Engineer wasn't paying attention and it's barreling down at, say 80 SMPH.

Boom!  Rear ending at full speed.  The beer tank cars were all derailed and scattered.  Any potential damage to the couplers?

They all seem to work fine though at one point in the layout, after the incident, there was a one time uncoupling for no reason.  Before the collision the unit train was going round and round happily.  Visually they look fine though one car, nearest to the loco, had both coupleres that were a little high though I don't know what is was before and it could have been that way.  It didn't look like it was bent or anything.

So for these types of scenarios, what are your thoughts?  I know the locos have some weight and inertia but the rolling stock are compartively light so when hit, they would just "get out of the way" by derailing to the side.  If the rolling stock stood its ground there would probably be damage.

Where are they phsyicists and  s????   

[learmoia]

Probably not... forces wouldn't be strong enough to damage anything.. (well maybe the accumates would explode cause a feather can cause that..) But its fixible.

If you have a ham fisted 5 finger wreck crew cleaning things up, that is more likely to bend / break parts than the derailment itself.

If any of the derailed cars head to the hardll floor, then you could get some broke parts.

You would need repeated stress over a period of time to fatigue the plastic to the point of breakage in normal operation.. or sudden impact for an immediate breakage. 

Now.. I'm assuming truck mounted trucks and couplers, where the derailment forces would be mitigated by the coupler box pivoting freely with the truck..

However I wonder of body mounted couplers would be more prone to damage since the forces are transferred differently on a jackknife or tip over.

~Ian

[MK]

Probably not... forces wouldn't be strong enough to damage anything.. (well maybe the accumates would explode cause a feather can cause that..) But its fixible.

If you have a ham fisted 5 finger wreck crew cleaning things up, that is more likely to bend / break parts than the derailment itself.

If any of the derailed cars head to the hardll floor, then you could get some broke parts.  None headed to the floor.

You would need repeated stress over a period of time to fatigue the plastic to the point of breakage in normal operation.. or sudden impact for an immediate breakage.  Well, I'm not concerned too much with breakage since it will be obvious visually what broke.  But more concerned about bending of the coupler parts past permanent deformation, just a tad enough to give you trouble from that point forward.

Now.. I'm assuming truck mounted trucks and couplers, where the derailment forces would be mitigated by the coupler box pivoting freely with the truck..  Yes, truck mounted.

However I wonder of body mounted couplers would be more prone to damage since the forces are transferred differently on a jackknife or tip over.  I would assume so too since forces can't be mitigaged by rotational movement.

~Ian

Replies in red above.

[robert3985]

I doubt any coupler problems will happen because of a rear-ender.  However, broken couplers are easy to spot.  What isn't easy to spot is if the "Magnematic" dongles on a few cars have somehow been bent or have slipped downward in their mounting holes.  I had many more problems with those than coupler breakage until I started snipping them off years ago, and a low dongle can cause big problems at turnouts, diamonds and grade crossings. 

If my train has been rear-ended, I'd just put it back on the track and see if there are any problems now that there weren't previously.  Run it a bit and if everything runs okay, then that's the end of it.

Cheerio!
Bob Gilmore

[thomasjmdavis]

In this era of $40 cabooses and observation cars with another $20-50 invested in DCC controlled lights and drumheads and such, and nowaday a freight train of any length can cost $1000, couplers are pretty far down my list of things to worry about.  But if the in-my-head calculation is correct, 80 scale mph works out to something like 8 or 9 inches per second, and without doing the rest of the math, I am going to postulate that such a collision between a locomotive and the caboose of a stopped train certainly could damage a coupler.  Less if the train in front is long- the slinky effect will be in your favor and some of the force will be absorbed in the springs of all of the other cars in the train.  But if the train in front is running light, and the train in the rear is a big one with a lot of weight, I could certainly see the possibility of coupler damage. and ladders, brakewheels, lights, etc.

But if it were to happen to me, the probability would be it would only happen if the last car on the train were brass or something rare with a lot of delicate parts, and the probability of it not diving for the floor would be virtually nil.

Suddenly, I see an arduino based train detection system in my future....

[Maletrain]

[ Guests cannot view attachments ]

[MK]

Suddenly, I see an arduino based train detection system in my future....

N-scale PTC! 

[MK]

(Attachment Link)

That's what happens when the caboose stood it's ground and not allowed to "move" so to speak and took the brunt of the forces.  But in our case, the cars have easily swiveling trucks and because they are so light, are allowed to be pushed off the track thereby not absorbing the full impact.

[Ed Kapuscinski]

N-scale PTC! 

N-scale ERA!



(I know, I know, that's not actually ERA, but it was the best gif I could find)

[JMaurer1]

Did the engineer of the second train pee in a cup for the mandatory drug testing?

[MK]

Did the engineer of the second train pee in a cup for the mandatory drug testing?

That's what I told him! 

Funny related story:

At a recent train show this year, I was at one end of a good size T-Trak layout when on the other end there was a collision mishap.  Minor but nevertheless, derailment, etc.  I was across the layout and yelling "Drug Test!  Drug Test!  Pee in a cup!".  The adults had a chuckle.  It was the afternoon so there were a big crowd watching.  And in this crowd was a girl about 7-8 years old.  She heard what I said and went walking around the layout yelling loudly "Drug Test!  Drug Test!".   

I'm glad she didn't chose the latter part of my sentence!   

[ChristianJDavis1]

(Attachment Link)

But are the couplers okay?

[Doug G.]

A coupler on the rear of one of my cabooses did break when rear ended years ago. It was a brown MT and I replaced it with a black one. Years later, when I decided to replace the black one with a brown one to match the other one, the brown color was different.

Doug

[Maletrain]

But are the couplers okay?

I think the couplers are shot.  Too bad Microtrains/Kadee doesn't make couplers in 1:1 scale.

[randgust]

I've had accumates blow apart on hard impacts and derailments, and damage to about 3 MT couplers in 40+ years of this.

That's not the worst part though.   Truck kingpins working loose as a result of a hard collision (or even a hard stop on a long train) is.   Drop a truck kingpin in a moving train and you get more than a silent derailment dragging the truck around if it is front truck that fell.   When you do find it, then the next challenge is finding the dropped pin.  I couldn't.   It was on hidden track at the back of the layout, firmly stuck between two ties making a 'ramp' derail on a 2% downgrade and the train behind it dived off the layout; 3 locomotives and 14 piggyback flats hit the floor with the momentum generated.    By far the most spectacular and damaging derailment I've ever had as a result of something so seemingly innocent and completely unrelated to track.

Those of you with 100% bodymounts are allowed to chuckle here, but you've got your own devils if the cars can't rotate the couplers on a rear-ender, something has to give.