How to "narrow the gap" on MTL Heavyweights

[InterurbanModels]

To explain why I do what I do, voilà the "gravity law" that applies to me: A modular layout on the dining room table, build up for 2-3 days every two weeks (supervised with a smile by the lady), to the left the pile of MTL 5-car-packs, not counting the dozens of individual cars. Not showing the Kato packs, the Intermountain, RailSmith and other cars with factory truck mounted couplers. I want to run them all, and all mixed, as they did in those motley consists of the 40/50ies.



(If some one shows up unexpected for dinner, this has to go in 30 minutes ...  )

[bbussey]

Bryan, certainly you know that not everyone has the space or resources to build layouts to the same standard as you or others who attempt to do so with a high fidelity to prototype track dimensions.
I commend someone who has sought solutions to improve the appearance of model trains running on tight radius smaller layouts.
To suggest that because they have limitations with space, track radius and resources, they should only operate 44T locomotives pulling 40’ boxcars isn’t a good look.

There are many models available that operate on tighter radii. Atlas makes 60’ heavyweights that can handle it. The MTL RPO can handle it. The longer cars simply don’t operate well on tight radii no matter what modifications are made.

[thomasjmdavis]

It strikes me that perhaps what some modelers want are MTL (or other) cars with 1018 trucks- which have an adjustable coupler shank that allows you to get a pretty close couple, or can be lengthened, if needed, to allow for tighter radii and clearances.  MTL still sells them.  Many of my elderly Rivarossi cars are equipped with them.  To apply to the current MTL cars would require drilling a new offset hole in the truck, or moving the bolster.  And futzing with the truck detail, if you want scale 36" wheels.

The other option would be to use an original Rivarossi truck with the coupler replaced with ac(in current parlance) Fox Valley 51000 short shank static coupler.

Look, I am not a purist- all my Kato cars have the same truck mounts as they day they put them in the cases in Japan.  And if another car runs frequently with my Kato stock, I usually put Kato trucks on it- because they work so well.

But, PLEASE, it took us 30 years of begging to get a manufacturer to make passenger cars with body mounted couplers.  Blame it on me if you want to- I had discussions with several manufacturers over just this.  MTL made the first mass produced heavyweights with STEPS.  And reasonably accurate underbody detail, where everything before left the steps (and details) off just to clear the truck mounted coupler.

Those wishing to modify these (or any) cars to negotiate tight radii, more power to you.  But the body mounted coupler is a feature, not a bug.   

[wazzou]

There are many models available that operate on tighter radii. Atlas makes 60’ heavyweights that can handle it. The MTL RPO can handle it. The longer cars simply don’t operate well on tight radii no matter what modifications are made.

I think you’re still on the periphery of the point.
Who are we to say what they should want to purchase or therefore run in what space they have?
Here is someone that is offering a possible solution to allow them to do that.
They should be applauded.

[thomasjmdavis]

Before I posted on this subject earlier, I went to the MTL website and tried to find their recommended minimum radius for their various passenger cars, and was unsuccessful.  Also can't find anything on the label. Is there an 'official' manufacturer's recommended minimum radius? 

[randgust]

Part of the problem with the MTL heavyweights is the decision to put a 1015 shank and box on them instead of moving the box back and putting a slightly longer 1016 shank on them.  It's amazing how much difference that can make.  And you can adjust the coupling distances that way too.

I've personally found the havoc that can result from mixing truck-mount Rivarossi cars (simply with Unimates, converted) with the MT cars.  I converted all my Rivarossi cars to body mount and added steps, but discovered that 1016 trick by accident simply because I had a surplus of 1016's.

But the bigger surprise was on the MT baggage; the combination of bolster centers just a hair further back, and the 1015's actually caused some stringlining on a heavy train just with 11" curves.  Same solution, longer shank, further back toward the bolster, solution.   That short shank was also the fatal flaw with the Atlas piggyback flats but the was no fix for that.  The physics geometry between car length, bolster center, and centerline of coupler pull on a curve can turn on you and roll a car over if the train is long enough.

The older MT six-wheel trucks and the newer ones are not interchangeable; the older ones put the bolster and pin right under the center axle, the new ones put the bolster between the first and center.  Presumably that was to help the curve performance.  But at least on the old ones you could adjust the length of the coupler box.

[InterurbanModels]

The older MT six-wheel trucks and the newer ones are not interchangeable; the older ones put the bolster and pin right under the center axle, the new ones put the bolster between the first and center

The center hole is clearly a missing feature, and MTL surely knows it: When I bought the new Louisville & Nashville 5 pack - a beautiful paint job of course! - I discovered some "cheated" engineering: Those L&N 12 wheel coaches were conjured out of the MTL single window 8 wheelers, just put on 6 wheel trucks. The excentric 6 wheelers then are grossly out of range, sitting too much inwards.

It was a quick fix, for this L&N set, I redesigned my "copycat" truck with center holes (an extra flat hat plug also, under the center wheel set).

PS: There is no need to remove or carve doorsteps for a truck mounted coupler, as long as it is designed with a narrow shank

Original MTL version left, modified right

[thomasjmdavis]

Not to be argumentative, but has MTL changed the truck on their single window coach since I bought mine?  While the ones I have are 'wrong' in the same way, it is not as bad.  On the ones I have, the trucks are modified from the trucks on their other heavyweights, and the bolster hole is closer to center  than the one shown in the photo, moving the trucks closer to the ends. (Note the bulge around the bolster pin, the trucks modified for the single window coach do not have this, and the hole is closer to center).  The single window trucks are still not close enough, but closer.

Those L&N 12 wheel coaches were conjured out of the MTL single window 8 wheelers,

In MTL's defense, the prototype for these cars are NYC cars, some lots were built with 4 wheel trucks, and some with 6 wheel trucks- but with identical bolster centers of 54 feet- so, the prototype 12 wheelers were "conjured" out of prototype 8 wheelers.  The bolster centers on the MTL underbody are very close to correct (my own measurement  came out to 53' 10", but it might just be that I need new bifocals).  So with the 4 wheel trucks, it is correct. I can only assume that the offset bolster pin on the 6 wheel truck is so important to either production or to operation that they kept the offset (although reduced) on the 6 wheel trucks for the single window coach and decided to live with the gap between the truck and steps. My understanding is that the offset serves 2 purposes- to make it easier to negotiate small radii (I am not clear on the physics of this, but I will accept it) and to make it easier to produce- the truck can be assembled, and then attached without removing the center axle- and likewise, if the modeler wants to remove it, it can be removed without pulling the axle out.   

[nkalanaga]

The old ones can be removed without removing the axle - just pull the truck off.

Getting it back on without removing the axle is a little harder, but can be done, by pushing the pin in with a small screwdriver or wooden dowel.

[crrcoal]

That is a neat little layout. Love it!

To explain why I do what I do, voilà the "gravity law" that applies to me: A modular layout on the dining room table, build up for 2-3 days every two weeks (supervised with a smile by the lady), to the left the pile of MTL 5-car-packs, not counting the dozens of individual cars. Not showing the Kato packs, the Intermountain, RailSmith and other cars with factory truck mounted couplers. I want to run them all, and all mixed, as they did in those motley consists of the 40/50ies.



(If some one shows up unexpected for dinner, this has to go in 30 minutes ...  )

[wm3798]

A similar approach could be used to close the gap between Intermountain F units.

Lee

[turbowhiz]

This thread inspired me to pick up another MTL heavyweight to do some quick testing…Both cars are of the longest variety.

For reference:
Stock under draft:

Stock under buff:


The cars are so far apart stock it's hard to notice just how extreme the draft/buff distance difference is, but its very substantial.

Below are my short shank couplers, installed in a setback hole drilled immediately behind the stock MTL mounting pin.

< 1 mm between the diaphragms. I’ve not 100% established if the coupled distance is perfectly scale, but if its not, its within a scale inch or two. Cars still automatically couple perfectly, and the coupled distance here is constant under draft or buff. MTL Z scale couplers have literally 2 scale feet of motion in a coupled joint between draft and buff. You can probably get them a hair tighter, but freehand drilling the setback hole this was as good as I got. Even on the slightest offset view the diaphragms look tight although they technically aren’t.

This joint will work on broader curves, I tested it to down 18” and Atlas C55 #7’s and it was totally fine. It will not do 13 ¾ unitrack however.

Offset View:



Top View



Straight On View



What if you have tighter corners?

By replacing both couplers with medium shanks in the same setback configuration the coupled distance is definitely not prototypically correct, but it is dramatically better then stock:

When so configured, these work equivalently to the stock MTL arrangement. They even work down to unitrack 9 ¾ corners without easements, but don’t combine S bends with those tight radiuses. They do go through Kato #4’s in this fashion too. No, it’s not pretty but it works.



Tight Radius Straight on side View:



Tight Radius Configuration Top View:


In time I will develop some more bespoke designs for specific applications, but I wanted a quick "day 1" attempt at how this would work out.

As an aside, I'm thinking these MTL heavyweights are riding a bit high stock it seems? Anyone attempted correcting that?

[chessie system fan]

They aren't high, I believe. They just look high because they are missing the under frame above the trucks for clearance reasons.

The couplers look great!

[NorsemanJack]

What does "under buff" mean?

[turbowhiz]

What does "under buff" mean?

Under buff is "slack in"... Cars are being pushed together. 

Buff:
This refers to the compressive force, or pushing force, that occurs when cars are pushed together, such as downgrade movements or when a locomotive pushes a train (reverse movements).

Draft:
This refers to the tensile force, or pulling force, that occurs when cars are pulled apart, i.e. when a locomotive pulls a train.