Body mount couplers, what's the big deal?

[GaryHinshaw]

While the timing is completely coincidental, I was testing some track on the layout this afternoon when I came across this situation:



The car on the left has body mounted Z scale (AZL) couplers with extended draft gear, the one on the right has truck mounted MT's.  The overhang on the body mount has forced the MT truck off the rails, and this is an 18" curve!

I suspect this would not be a problem if both cars had body mounted couplers, and it definitely is not a problem if both have truck mounted couplers; but it definitely is a problem with mixed stock.  I'm not looking for a solutions here, I just thought it was an interesting and timely (and annoying!) example.

-gfh

[wm3798]

I've got about 120 coal hoppers in my fleet.  I run them in blocks of about 25 to 30 when I'm running a solid coal train.

I have a fairly tight helix that climbs up to Elkins, the yard where coal gets marshalled.  I've body mounted the couplers on ALL of my Atlas 55 Ton fishbelly hoppers, because the grade up to one of my tipples was sufficiently steep, and pushing no more than 5 cars up the grade caused them to buckle all over the place.  This also occurred when pulling the loads down the grade (not a backing maneuver!)



The same problem occurs when truck mounted cars are pulled down the helix.  This would be a 10 car train descending a 13" radius 2.5 turn helix.  Body mounts however, are no problem.  It's okay to slip the occasional truck mount into a train from Elkins, but it needs to be toward the rear for best results.  Nothing like a few rolling stock restrictions to keep ops interesting!
Lee

[Brakie]

Gary,I know nothing of  Z scale so I will ask this(dumb ?) question.

Is there any side to side coupler play or is the Z coupler stiff? 

It just seems odd the Z coupler didn't swing with the truck mount coupler.

[Scottl]

Gary, that is a probably a key point in this- mixing body and truck mounts could be a difficult situation, especially with long cars with overhangs.  Not many people have 18" radius curves!

Spent time tonight trying to push the limits of this with my equipment.  I'm using Atlas code 55 track and I have some curves as tight as 12" radius.  No derailments, except at the points  of some finicky turnouts.   Of course, the derailments that are the most problematic are those that occur when you are not planning for them!

[GaryHinshaw]

Gary,I know nothing of  Z scale so I will ask this(dumb ?) question.

Is there any side to side coupler play or is the Z coupler stiff? 

It just seems odd the Z coupler didn't swing with the truck mount coupler.

The AZL couplers are very stiff, and definitely contribute to the problem.  I consider this one of my failed body-mount experiments.  I don't know for sure if a similarly-mounted MT coupler would work, but it might.  But as I said before, given the right combination of trucks and couplers, I think I could be perfectly happy with truck mounts.

-gfh

[bbussey]

Fair enough, but I think the argument that it looks more prototypical is overstated.   I started with the assumption that was the reason, but found few examples where the coupler mounting improved the look.  The truck, wheels and ride height definitely improve the look to my eye, but the body mount coupler seems almost incidental towards that effort.

Except that it is impossible to have a model with truck-mounted couplers ride at prototypical height without severely compromising the ends.  So it is more prototypical to have the coupler draft gear as part of the underframe, for more reasons than just the obvious.

Examples where the body-mounted coupler was designed as part of the model where the look of the ends is much improved over truck-mounted counterparts:

• Atlas NE6 caboose
• Atlas C&O caboose
• Athearn 40' Airslide
• Athearn C-50-7/8/9 caboose
• Athearn ACF 2970 covered hopper
• IMRC 60' flat
• IMRC steel milk reefer
• FVM B&O Wagontop boxcar
• TWX PS TOFC flat
• MTL C-30-1 caboose
• MTL PS2 4427 covered hopper
• MTL heavyweights
• BLMA PS2 CD4000 covered hopper
• BLMA ACF gondola
• BLMA F89J flat
• BLMA Trinity reefer
• ESM G26 gondola
• ESM XIH boxcar
• ESM X58 boxcar

[Bruce Bird]

Try being the helper crew on a 30 car coal train shoving up a 2% grade for a scale 2 1/2 miles.  Big difference there.

Honestly, blue-box Athearn HO cars have been body-mounted since the beginning of time so its about time the N manufacturers have brought their designs into the 1960s HO universe.  There's a reason that HO folks call N scale the 'toy trains'.

Bruce

[nkalanaga]

Gary:  Body mounted MT Z couplers work much better, and have at least as much side play as MT 1025s, which are used on the truck-mounted versions.  I have 55 ft passenger cars on my narrow gauge and they will go through 10 inch radius curves with no problems.  I have a few NG cars with truck mounted couplers, and they work reasonable well with the long body-mount cars.  There's quite a bit of side play, and the spring is considerably weaker than in the N couplers, which helps.  The biggest issue is backing a long train, regardless of mounting method, as the couplers tend to buckle under the stress.  On sharp curves this can cause the corners of the cars to touch if they're too close together, even if they clear in shorter trains.

I also have a train of Atlas ore cars with Z couplers, and they run fine with my SD9s, which have body-mounted MT N couplers.  Even with body mounts on both cars different car lengths may not work well together, and it gets worse as curves get sharper.  The BN restricted car combinations on many subdivisions due to sharp curves, such as "nothing shorter than 50 ft coupled to 80+ foot cars".

In my experience truck mounted MTs work fine pulling, even on only moderately good track, and with lo-pro wheels.  I had trouble backing 10 MT 2-bay hoppers with Precision Masters wheels through a handlaid #4 crossover.  While admitting that the track looks awful, the problem was solved after installing MT 1980s-version lo-pros.  While the PM wheels work fine everywhere else, they added just enough resistance that the trucks on the cars closest to the locomotive tended to skew, causing derailments.  The MT wheels rolled just enough better to solve the problem.  The same thing would have happened pushing more cars, as that would still increase the stress on the cars closest to the locomotive. 

So, I would say that, if you push long trains, or make a lot of reverse moves through less than ideal track, body mounts would certainly be an advantage.  If most of your moves are forward, as in "like to watch the trains run" rather than "like to do switching", it doesn't make much difference.  After all, Ntrack runs long trains with truck mounted couplers, and they don't seem to have trouble.  They also seldom back up!

[wmcbride]

Car weight, as mentioned above, is another variable.

Do you weight your cars to the NMRA standard or do you go a bit heavier?

[mmagliaro]

While the timing is completely coincidental, I was testing some track on the layout this afternoon when I came across this situation:



The car on the left has body mounted Z scale (AZL) couplers with extended draft gear, the one on the right has truck mounted MT's.  The overhang on the body mount has forced the MT truck off the rails, and this is an 18" curve!

I suspect this would not be a problem if both cars had body mounted couplers, and it definitely is not a problem if both have truck mounted couplers; but it definitely is a problem with mixed stock.  I'm not looking for a solutions here, I just thought it was an interesting and timely (and annoying!) example.

-gfh

I'd like to know, were you *pushing* this train, from left to right in the photo?  (I assume so).  And if so,
how many cars on the *right* are there?   I would expect this sort of thing to happen when there is
a long train being pushed on a curve like this.

Mixing body and truck mounts can be trouble, and your photo is a great example of why. 

I've got a wild mix of body and truck-mounted couplers and don't have this problem... probably because I don't push
30 car trains around curves or up hills.

[Brakie]

Try being the helper crew on a 30 car coal train shoving up a 2% grade for a scale 2 1/2 miles.  Big difference there.

Honestly, blue-box Athearn HO cars have been body-mounted since the beginning of time so its about time the N manufacturers have brought their designs into the 1960s HO universe.  There's a reason that HO folks call N scale the 'toy trains'.

Bruce

Bruce,I'll tell you this HO is not as "perfect" as many  HO guys like to boast..

Even with body mounted couplers try pushing a long train upgrade and around a curve.

As far as  calling  N Scale a "toy" that also applies to any scale,certain manufacturers HO models and according to some anything less then 110% correct engine or car is a "toy".

I model in both scales and prefer  N over HO even though 90% of my cars still have their truck mounted couplers.I started to convert my cars to body mounts but,after ruining a frame I decided it would be better to suspend the project.This is due to having limited use of my once dominate right hand and modeling with my left hand which is completely awkward.

[ednadolski]

If it ain't broke, why fix it?

For some use cases at least, it really is broke.

All other things equal, cars with truck-mounted couplers will always be more susceptible to derailments when being pushed then with body-mount couplers.  That's because pushing on a truck-mounted coupler always puts a torque on the truck that makes it want to spin.  It's just an inherent part of the geometry that you don't get with a body-mounted coupler.

If you're not pushing too hard, then the weight of the car is enough to avoid derailment.  That's why it can work OK for backing even long trains on level track.  But when you add in DPUs and uphill grades, all the pushing forces are increased, so it is easier to reach the point where derailments will occur.

Note that I said "all other things equal".  There are a lot of other things that affect the equation, including condition of the track, properly gauged wheels, properly weighted cars, car lengths, curvature, and such. The point is that even when you get all these correct, the truck-mounted coupler will always be at a disadvantage compared to a body-mounted coupler. Again, it come back to the basic geometry.   So if you want to run trains in cases where you will have higher pushing forces, then body-mount couplers are the way to go.

Ed

[altohorn25]

Here's what I do for what it's worth:

-body mount MT Z scale couplers
-use low profile FVM or BLMA wheels (the correct diameter for the given car of course)
-make sure the car is weighted per NMRA standards (a little extra weight is better than a little underweight)

I started doing this will all the rolling stock I've built in the last 2 years and I'm slowly going through my entire fleet of cars and changing them over as well.  I've found this to both be the most prototypical look as well as the best tracking performance.  I can pul trains of 75+ cars on both our modutrak layout as well as n-trak layouts (even with the less than ideal track joints between modules).  Backing performance is much improved as well as pulling - the weight of the train is on the car frame instead of on the trucks.

Nate

[wm3798]

Car weight was the deciding factor on my Atlas hopper fleet.  Since these cars are heavier than the average bear, the buckling on the up-hill pushing maneuver was amplified.  Lighter MDC and MT hoppers would track better, but were more likely to buckle due to track anomalies. 

Too light = bad
Too heavy = bad
Body mount = Good.

Lee

[GaryHinshaw]

I'd like to know, were you *pushing* this train, from left to right in the photo?

Max, this was a very simple setup of two box cars in isolation to test some new track.  Here is an overhead shot of the setup:



and a close-up of the couplers at the point of failure:



This is purely a case of the stiff AZL coupler finding it easier to push the lo-pro FVM wheels off the rails than to give a bit in the curve.  I was as shocked as anyone that this would happen here because the geometry is so mild: 18" curves with easements, and relatively short (62' and 53') box cars.

People who know me know that I'm trying to 'do everything right' with this pike: broad curves with easements obsessively shaped over CAD track templates, body-mounts couplers, lo-pro wheels, the whole 9 yards.  This is just an illustration that the best laid plans don't always work as one hopes.  I'll find another solution in this case, hopefully one that still employs body-mounts*, but not if it compromises reliability.

Cheers,
Gary

* Hopefully NZT's!  Definitely not AZL's.