MT Heavyweight Pass. Car Derailments

[gkoproske]

I have a fleet of N scale heavyweight passenger cars as well as some new releases from Lowell Smith.  Every one of them has problems coming off the track on less-than-wide radius curves.  I tried installing regular profile wheels on the trucks but that didn’t help.  I’ve read discussions laying the fault on the body mounted couplers, that end up pushing other cars off the tracks due to the physics of how it is engineered and performs.  I have a lot invested in these cars and I just can’t run them.  Not only do they cause problems with Kato and Rivarossi passenger cars, they don’t behave with other MT cars either. 

[Lemosteam]

@gkoproske ,  Are the couplers swiveling a little?  If not they need to.  You might try replacing the press in pin with and MT screw that is not fully tightened to see if this helps.

How tight are the radii?

[nickelplate759]

Are the derailments  mostly where similar cars are coupled to each other (e.g. between MT heavyweight cars), or mostly where MT heavyweight cars are coupled to something else?   If the former, it suggest the couplers aren't able to pivot enough.

 If the latter, it suggests that mismatch in overhangs is an issue (a car/engine with truck-mounted coupler connected to body mounted coupler is pretty bad, but usually derails the car with the truck-mounted coupler first).

What helps MOST in either case is easement curves.  On my layout I have one bad spot - it's a 16" radius curve with no easement, and that's where passenger cars usually derail if they are going to.  Most of my curves have easements, and I have no problems there.

[gkoproske]

This is something I found on Trainboard when these cars hit the market.  In the discussion, some fellows returned them to their LHS for store credit.  The LHS guys were familiar with the problem with these cars.  Anyway:

"I can't explain it on paper, but when I slowly re-enacted the cars on the bend, it appears the body mounts laterally pull on each other, putting pressure on the already severely turning car and I saw no binding with any parts even the edges. It is just simple physics"

Another quote from the same thread:

"The derailments are because of the lack of swing of the 1015 couplers. They are fine in the middle of the corner, the problem is the transition from straight to corner. The couplers are pulling the cars off. ... I have noticed some of my cars had really loose couplers, as in they could spin side to side. If you have cars like this, then there is probably a little more leeway and the cars run better, but they are then a pain to couple because the couplers never center properly."

[Chris333]

I run mine on 13.5" super elevated curves using cars with the couplers sucked in to reduce the distance between them. Haven't derailed once.

[k27463]

Glenn,

Let me look at those next train show -- I had some issues with my 8 CB&Q cars and figured it out.  They're great runners now.

[thomasjmdavis]

Every one of them has problems coming off the track on less-than-wide radius curves.

Could you be a bit more specific on what "less than wide radius" is, in inches or millimeters?  My last layout had 14.5 minimum with easements, and I did not have any issues with MT cars.  I had issues with one turnout and a kink in the track, but those were resolved by replacing the turnout and fixing my own sloppy trackwork.  And MT cars had fewer problems than some of my other cars in those places.

More specifics generally might help us come up with some answers or things to try- radius, code, brand of track, and whether you have these issues with all MT cars or only certain ones, and do derailments happen anywhere on any curve of your layout, or only certain places?  What brand/type wheels did you use for replacements?

[gkoproske]

12" radius.  Layout has been in place for years, tearing it out is not an option.  Regardless, everything else I have runs.  These don't.

[randgust]

I've had issues with mine, mostly when I couple Rivarossi cars with the MT truck-mounted couplers to the MT's.  Well, that doesn't work at all.  The MT car always derails, but MT to MT doesn't.  I've also simply put Unimates (Red Caboose) in the Rivarossi Rapido coupler boxes, that doesn't work a bit better where an all-Rivarossi train ran fine.   I pretty much run my heavyweight consist as a unit train, so Unimates are fine with me other than the derailing issues.

I have easements and superelevation on all my curves; mainline minimum radius is 13" with some 11" on hidden track. 

What I've seen is that the MT cars basically have the normal 1015 coupler box with a short-shank on there.  An alternative is to mount a 1016 with a longer shank and move it back a bit.  That should work, lessen the torque factor a bit, and give some more side swing.

The Rivarossi to MT problem is a whole different animal.   I decided to bite the bullet and convert mine to body mounts, as the absence of steps makes them pretty awful looking in comparison, and only keep the truck mounts on the front end of the train.  I'm also adding GMM etched steps to them.  Initial tests on that concept proved that converting the Rivarossi cars to body mounts solved the problem, but filling in that cavern at the end of the cars to mount couplers on is a project in itself.

My heavyweight train is pretty much for special running anyway, but yeah, this is definitely a case where body mounts can cause no end of problems where anything else seems to work just fine.   I've got several body-mounted 89' piggybacks, and they don't have issues.   I did have one Atlas 89' with a short-shank coupler and it was a complete fail, constantly stringlined, and it was definitely leveraging itself on the distance between the short coupler and the truck bolster.  I ended up selling it.   So it's not exclusive to just MT's, it's a geometry and physics problem.

[nickelplate759]

...
The Rivarossi to MT problem is a whole different animal.   I decided to bite the bullet and convert mine to body mounts, as the absence of steps makes them pretty awful looking in comparison, and only keep the truck mounts on the front end of the train.  I'm also adding GMM etched steps to them.  Initial tests on that concept proved that converting the Rivarossi cars to body mounts solved the problem, but filling in that cavern at the end of the cars to mount couplers on is a project in itself.
...

John "Lemosteam"  of Keystone Details makes a nifty steps + coupler mount conversion for the Rivarossi heavyweights that make this a snap, and looks even better (to me) than the GMM steps.

http://www.keystonedetails.com/keystone-customs/2016/9/8/n-scale-4pk-steps-for-atlasconcorrivarossi-heavyweight-passenger-cars

[randgust]

Huh, apparently they are still made for the Lima cars but aren't shown for the Rivarossi anymore.....

[nickelplate759]

Hmm - here's a link to them on Shapeways:  https://www.shapeways.com/product/3BZ3TXX6C/n-scale-4pk-steps-for-atlas-concor-rivarossi-heavy?optionId=59977183

[Lemosteam]

Wep page for the Concor/Rivarossi steps page is corrected now @randgust.  These are slightly different from the Lima to compensate for a different ride height to put the couplers in the right spot.

Thanks for the plug @nickelplate759 !

Not sure how the link to Shapeways was removed- one of my earliest Keystone Customs listings...

[randgust]

Wow, so it's no secret that I have very little respect for Shapeways search engine, but I've never seen this one before.

Given that direct link, I can see them.   But go back to your Shapeways store, click on "N scale" tab, and they disappear.   Don't show up.   Go to the main search page, search for "N scale steps", and they show up.  Search your entire store across all scales, they show up.

I've got to do a count of how many cars I've got left, but yeah, that's a great design.

[Lemosteam]

Wow, so it's no secret that I have very little respect for Shapeways search engine, but I've never seen this one before.

Given that direct link, I can see them.   But go back to your Shapeways store, click on "N scale" tab, and they disappear.   Don't show up.   Go to the main search page, search for "N scale steps", and they show up.  Search your entire store across all scales, they show up.

I've got to do a count of how many cars I've got left, but yeah, that's a great design.

While not crystal clear on my shop, since these are not PRR specific items, they fall into Keystone Customs (my non-PRR brand).
https://www.shapeways.com/shops/keystone_details?section=Keystone+Customs&s=0

@chicken45 can shut up before he even writes.