Body mount couplers, what's the big deal?

[Brakie]

Gary,I've seen the same thing before in HO-the overhang of long cars with body mounts pulls the following car of the track.

I notice the slight overhang and coupler location in your first photo.

This is where the side to side coupler swing comes into play.If the coupler on the longer car had free movement it would follow the truck mounted coupler-like the body mounted coupler on a long locomotive does.

[BN1970]

I had a similar situation except it was a Kato SD40-2 where the trucks are back from that long porch.  The SD40-2 was pulling the truck (of a truck mounted coupler) over the points on a curved turnout with 100% of the train (34 cars) on a trailing grade.  Shorter wheel base diesel locos (F-Units, SD45 & U30Cs) had no problems.  When I converted to body mounted couplers the problem was totally fixed.

In my experience if your running truck mounted couplers with the older Micro Trains pizza cutter wheel sets your most likely to have few derailments.  But as flange size gets smaller, your train length (weight) goes up, you like to switch (go backward) with longer cuts of cars, then body mounted couplers are essential for reliable operation. --Brian

[Scottl]

Thanks all, very interesting range of opinions and perspectives.  Most of the concerns centre around pushing performance, one person seems to have derailments in either direction going up, down etc. ( ) and a few point out the improved look and protypical fidelity of body mounts.

I have a few more days to play around with this before I pack everything away for my time away, but I have to admit, I can't reproduce the concerns raised on my own layout (code 55, 2% grades, 12" limiting radius, 18 car trains, no long cars, mix of wheels and truck mounted couplers).  I do like the idea of body mounts, maybe if NZT has a viable product in the years ahead...

[GaryHinshaw]

Just a quick follow-up regarding the mix of body and truck-mounted couplers.  I replaced the 62' box car that had the AZL couplers with a BLMA reefer which has body-mounted MT's with a similar (actually slightly larger) wheel to coupler overhang. Here's a shot that shows them coupled on the same curve as before:



The body-mount MT coupler has swung over to accommodate the truck-mounted one, and the pair coasted down through the Loop with no problems.  Yea!  NZT take note. 

-Gary

[BN1970]

I went on a multi month testing spree a few years ago.  When you look at what truck mounted couplers will do or will not do - they behave very differently (skewing or not skewing) when you have two cars verses 30 or more cars.  Especially at the front near the locos.  Throw in grades, curves, as your train size goes up and those truck mounted couplers will skew the car trucks into derailments. 

Your cars wheel set flange size will also play a part in this along with the layouts track geometry, an example.  I have two, 2 scale mile long helix's with 21 inch radius curves and a 2.1% grade.  My freight train size is 34 car freight cars + caboose (using low flange wheel sets).  I found that at some point going down into one helix, the rear of the train would run in the slack onto the trains front.  Unlike a real trains I could not set the brakes.  As it turned out under the front of the train's leading cars was a turnout.  All of a sudden the weight of my train was onto the 1st few cars as the slack ran in.  It was much like backing up - except I was going forward.  The truck mounted couplers how were being pushed from behind skewing the trucks causing derailments (at times). Body mounted couplers the fixed the problem.

The other fix could have been to go back to using pizza cutter wheel sets, run a smaller train or move the turnout.  But I like to switch long cuts of cars with out having to stop and re-rail my cars.  So I chose to body mount everything which I completed about 2 years ago.  I don't regret doing so. --Brian

[Brakie]

Body mounted couplers the fixed the problem.
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Brian,Actually it doesn't..I seen derailments at the HO club from the run in of slack going down a 2% grade.

While body mounted couplers will help they're far from the cure all derailments.



I figured out years ago that side to side play was a important part of long cars coupled to short cars negotiating curves together yet,I never seen it mention by magazine operation "experts" or on forums.

As far as backing a long train upgrade and around curves..That would depend on several factors.

[BN1970]

Brakie, I agree you will still have derailments with body mounted couplers, I do.  Just less of them, thats what my testing showed on my layout. 

The other really interesting thing that I have noticed with body mounted couplers is that when derailments occur the cars act differently, especially when going down grade (my helix).

With truck mounted couplers the trucks tend to be steered to the side, the resulting derailment is often a jack knife affair.  Body mounted coupler cars on derailing tend to keep going forward in the direction of travel.

Your also correct that car length is a factor plus I'll add car weight.  Properly weighted cars in my experience derail less than those that are to light for their length and yes you can over weigh a car.  Each layout will have a different mix of parameters.  So its hard to state a hard and fast rule that will fix everything. --Brian

[Scottl]

Your cars wheel set flange size will also play a part in this along with the layouts track geometry, an example.  I have two, 2 scale mile long helix's with 21 inch radius curves and a 2.1% grade.  My freight train size is 34 car freight cars + caboose (using low flange wheel sets).  I found that at some point going down into one helix, the rear of the train would run in the slack onto the trains front.  Unlike a real trains I could not set the brakes.  As it turned out under the front of the train's leading cars was a turnout.  All of a sudden the weight of my train was onto the 1st few cars as the slack ran in.  It was much like backing up - except I was going forward.  The truck mounted couplers how were being pushed from behind skewing the trucks causing derailments (at times). Body mounted couplers the fixed the problem.

Late last night, I was able to force this type of derailment on a 2% down grade with truck mounted couplers.   It occurred when stopped the train abruptly to see what the forces might do.  I was not consistent, perhaps only 2 or 3 times out of 10 attempts.  While some of my cars are underweighted, the visible evidence for the truck skewing was unmistakable. 

Still can't make a car derail pushing long strings (up to 18 cars), even through turnouts.   My trackwork is not stellar, so I'm having difficulty seeing how couplers make much difference in this regard.  Obviously, experiences may vary.

[hpwrick]

Looks to be I maybe the wet blanket on truck mounted couplers.

   Scary that some of you still like, play and want them.    

I have nothing but trouble with them as they will turn and jack knife the train cars, as I give them a reverse shove.     Plenty of negative stuff going on ... on my layout.

My body mounted train cars, in a reverse move, operate the best.    Without a doubt.   Yes, like most of you my fleet is made up of truck mounted couplers.    Give me time...I will get them switched over.

As far as I'm concerned "Body mounted is best mount" along with "Wide curves are the best curves" and "Close coupling is the best coupling".   That is (uh oh am I about to make an exception...nope) "All train cars need to be properly weighted".   See NMRA standards.   Are you seeing a trend here?

I do agree with Brakie, and want to note:   Your track work has everything to do with the overall performance of any type of coupling.   May I add any and all operations of your trains.   "Everything"

"It's your layout, you make the rules and the most important one is to have fun" Jim157 UP.   

All I can say is try it for yourself.     Why, would you need some scientific study, to tell you what old railroad model heads have been telling us... for more years then I've been around?    That's 62 years and I started my first model railroad at the age of 12.  Read my first Model Railroader at 11 and it had an article talking about body mounted couplers.    How long ago was that?   

Words of an old grey beard.   Have fun.

RickH aka BarstowRick

[BN1970]

Scott, I regularly switch 30 car cuts of cars.  I can easily do 60 cars with out derailments, repeatedly.  Plus it doesn't matter that longer cars are next to shorter cars.  I doubt that would be the case with truck mounted couplers.

When I did my testing I did that 50 times with different combinations of wheel sets in truck mounted couplers.  The total was 200 reverse moves using 34 forty foot boxcars through 18 turnouts, a three of curves, no grades.  Later I did the same test (backing up 50 times, same 34 boxcars, route) with in my opinion were the worst wheels sets, but with 100% body mounted couplers.  The result was no derailments.  Granted truck mounted couplers with pizza cutter wheel sets had the same 100% no derailment rate.  But I wanted to move to a smaller flange as my layouts standard.  So I made the effort to body mount everything.

Again each of us will have to decide whats best on our respective layouts. --Brian

[Brakie]

So its hard to state a hard and fast rule that will fix everything. --Brian
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Absolutely! I wish I could find a absolute cure all woes rule.

But,as you noted every layout has its own woes.

Talk about  a derailment try 17 out of 35 cars..That's exactly what happen to me at the HO club going down a 2.3% grade around a curve in a tunnel a tad to fast-another member was watching the trains and cranked up the speed..

Another lesson learned from that calamity-check coupler pocket screws.

[Brakie]

RickH :Why, would you need some scientific study, to tell you what old railroad model heads have been telling us...
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That my old forum friend is a very scary thought! 

I been in this hobby for as long as I care to remember and have found things a lot different then those "old railroad model heads" preach most has complicated the simplicity of the hobby while stating their modeling style as the gospel.

Best to try different methods and find what works best for you.

[BN1970]

What started me in all my testing was to see if a given brand of wheel set was less prone to crud build up.  The less wheel crud the better.

But when going down that particular helix, clean wheels actually meant the slack ran in a lot faster, upping the chance for derailing.  The trains weight pushed down on the first few cars.  Having some wheel crud at the rear of the train would act like set brakes and in this case be better.  Go figure? Its something you learn the hard way. --Brian

[Scottl]

Ha, ha, the whole point of this thread in the beginning was to get people to lay out the arguments for body mount couplers.  Based on my read of forums, I was not aware of a discussion of the pros and cons, just the almost axiomatic statement that they were better.  The scientist in me likes a systematic demonstration, and clearly, like most issues, the devil is in the details and general statements are just that.

My emerging conclusion, based on my limited experience, is that derailments with truck mount couplers operating with modest train lengths (<20 cars) of "average" (50' length or so) cars with mixed metal and plastic low profile wheels are the result of unprotypical operations, like instantaneous emergency stops at the bottom of grades.  If I am careful, I can avoid it with smooth operations, but if I jam on the brakes, I can force a derailment. 

As I said, experience must clearly vary, given the comments here.

[bbussey]

I like metal wheels, which slows down the crud build-up.  I also like a pair of MTL springs axle in the caboose, which mutes the coupler oscillation.  I go back and forth on putting an axle spring on every car.  Currently, I'm against it.