Model Railroading > Atlas Commuter Car Derailment Issues?

Received my order of 7 Atlas Modern NJT Commuter Cars, along with a matching HO ALP-45DP locomotive.  Out of the box, here are my first observations on these cars:

Aesthetically, they are beautiful.  Very faithful to the prototypes, in dimensions and lettering.  The "tube" style diaphragms are rigid, and don't touch even in push mode.  Factory installed lighting is standard, but for some reason Atlas did not include a capacitor to prevent flickering of the lights if hitting a spot where the car doesn't pick up power.  I'll give them a pass on this one, as I believe these may be their first ready to run passenger cars.

Out of the box, the "Cab Car" has working headlights, ditch lights, and red markers.  On DCC (and I assume DC), all of the lights are on at all times.  There are provisions for installing a speaker and decoder for sound/customized lighting, and hopefully ESU (who did the sound for the ALP-45DP) will release a decoder for these cars.

Now ... the one caveat about these cars.  In order to allow operation on 22-inch radius curves, Atlas included a sprung, swinging coupler on each end.  The spring acts like the cushioned draft gear on prototype auto rack cars, where the couplers can move in and out slowly.  This allows the gaps between the model cars to spread on sharp curves if the buffer plates begin to touch.  While the intent of this design may have been good, in operation I'm not so sure it works as well as intended.  When I ran my 7-car set (which represents a peak-service NJT Raritan Valley trainset), the cars began derailing when being pulled.  This was on a club layout, with a minimum of at least 30" curves.  The derailment was not always the same car, and not always the same axle.  Tried running the cars in push mode, to see if they were any better.  They ran beautifully, with NO derailments with the same 7 car set over the entire layout.  Hmmmmm.  Okay, cut down to four cars.  No derailments, pulling or pushing.  Started adding cars one by one, and they ran well until adding the final car.  Sure enough the derailments started reappearing randomly throughout the train in pull mode, after the addition of the 7th car.

What the issue appears to be, is that all those springs reach a point where they start inducing a "whiplash" effect through the train.  You can see the gaps between the cars open up, and then close again as they navigate grades, and the power on the locomotive is adjusted.  The 'whiplash" effect seems to pull or push cars off the rails, much like slack on prototype freight trains can derail cars.  For most modelers, who will likely run a short set, it probably won't be an issue.  However, if you are going to run a full 10-car Northeast Corridor multi-level set, be prepared to possibly have some issues.  The longer the train, the more noticeable the effect becomes, and ... quite frankly ... the worse the appearance, as the cars in front will have huge gaps between them, while the rear cars are reasonably close.  As the locomotive's mechanism broke in more, and started to operate more smoothly, the derailments seemed to come less frequently.  However, any slight hesitation/stall of the locomotive followed by a sudden burst of power seemed to "crack the whip" and cause a derailment.

At this point, short of not running the full set, I'm considering possible "fixes" to the gaps/derailments.  Since they will be run on fairly broad radius curves, I'm considering replacing the springs with a stiffer version, that will only stretch if the cars actually touch.  Another option, may be to body mount some longer shank couplers, or use the Walthers swinging coupler kits.  While these cars are beautiful as-is, it is a bit unfortunate that the design begins to stumble a bit when operating a prototype length train.  Nothing that can't be overcome, but something that should have been considered in the design phase.

I have observed the same thing.  I was only running a 3 car train, but had derailments.  However, for me it was the same car and same truck on that car.  I have a minimum radius of 34 inches on the main, but I get down to 24 inches (with easements) on the branch where I would like to run them as well.  The one car did derail on 24 inch curve, but it also derailed on some of the broader radius curves as well.  I have only run them briefly and had not had time to check things out in detail.  I did loosen the truck that kept derailing (it didn't seem to turn freely), and it seemed to help a bit, but it still derailed at one point.  Once again, I have a lot more testing to do with them.

My first observation was the cars seemed very light.  I was looking for ways to add weight to them.

Great observation on the weight. Are they at NMRA spec? Neat looking trains, a little tune up in order.

Wonder if neoprene tubing could replace the diaphragms?

Do these passenger cars have talgo trucks (truck mounted couplers)? If so, you may want to consider body mounting the couplers.

SantaFeRuss

Posted from Android

I weighed one of the commuter cars and it was 7 ounces.  At nearly 12 inches long, this is about right.  It just felt light, but measurements don't lie.

SantaFeRuss Wrote:
-------------------------------------------------------
> Do these passenger cars have talgo trucks (truck
> mounted couplers)? If so, you may want to consider
> body mounting the couplers.
>
> SantaFeRuss
>
> Posted from Android

Not exactly. The couplers are separate from the trucks, but swing side to side similar to Walthers' longer cars.