Best Of Notes on body-mount couplers (work-in-progress)

[ednadolski]

• How do you like the folded box compared to the lid?

It's definitely faster, and I certainly don't miss the soldering.  I'm trying to come up with a way to allow it to stay fully folded.  Making the etch lines a couple of mils wider might do the trick by allowing some slight overbend, but I'm not sure if the etching process can can produce that level of precision consistently from sheet to sheet.

• It's fortunate that the shank length allows you to use the existing hole location for the pivot screw.   Do you know what kind of minimum radius is required when two Dash-9's are coupled with FT's?

I've got a few locos coupled together and running on my layout, and they seem OK on my sharpest curves which are ~ 16.5" radius.   These Z scale couplers actually do a better job of holding the consist together than the factory-installed long shank Kato couplers.  With the factory couplers I typically could run only a few circuits around the layout before one of them would let loose, but I haven't seen that at all with the Z couplers.

And of course, the enormous coupling distance of the long-shank factory couplers is ludicrous from an appearance perspective.

• Do you think a box like this would work as an insert in the new generation of body-mounted-MT-equipped rolling stock?

I can't say, I really don't have any idea of what the MT dimensions are.   I'd be concerned about the coupler height, and the diameter of the pivot post.

The Z couplers can fit in the ExactRail box with a 00-90 washer, if the post is trimmed away.   Might be able to do something similar with the MT box.   Aesthetically tho, that still leaves behind a fairly oversized plastic box.... 

P.S. The biggest challenge I have had with pusher ops so far is when a consisted rear unit, with long-shank Kato couplers, pushes against a truck-mounted couplers and torques the last freight car truck off the rails.  The combination of body-mounts on the freight cars, and the shorter shank FT couplers on the locos will solve that - and look way better to boot.   (The current incarnation of short-shank Kato couplers produce the wrong coupler height on the Dash-9's.   )

Longer trains on grades are a challenge with DPUs, because you can have one part of the train going upgrade while the rest of it is level or downgrade.  Even tho I've speed-matched all the engines, the speeds still show variations because the loading changes dynamically as different parts of the train move across the vertical inflection points.  So it is almost inevitable that the cars in front of the DPUs will be in compression at some point,  and that's where the body-mount couplers have the advantage.

I've also seen the case where truck mount couplers can derail in a long train descending a grade.  If the train is long enough, then the weight of all those cars can push against the head-end engines just as hard as if it were a DPU.  So you get the same situation where the compressive forces put enough torque on the truck-mounted cars that one of them derails -- typically the lightest one, or perhaps the two cars with the greatest mismatch in overhang.


Ed

[GaryHinshaw]

Thx Ed.  Good news on the min radius. The close coupling vastly improves appearance.

RE the MT body-mounts, I should have been more clear: I was thinking of the newer cars like the Exactrail boxcars, with their integral draft gear boxes, not the original MT boxes.  But it sounds like a box insert is not needed for the ER cars.

RE DPU's: I still prefer to control the rear units separately for best performance, but that requires a fair amount of (fun) attention.   

-gfh

[GaryHinshaw]

Here's a quick update on an installation that I've actually completed.  Another IM 2-bay cement hopper (need a bunch of these for my cement plant at Monolith).  Here's a before & after comparison:



On the right is a stock model with MT 70T trucks & couplers, on the left is one with BLMA 100T trucks and Bowser couplers.  The BLMA trucks improve the model a lot IMHO: the underslung bolster lowers the ride height and the longer wheelbase fills the space under the car much better.  (The ride height itself is not that much lower, but the hopper chutes are fractionally much closer to the rails than before; and since my cement plant site is at eye level, I notice this stuff.)  Here are a few closer shots showing the coupler and draft gear:







The best thing about these pockets is how small they are: about two-thirds the width and half the height of an MT box, so they're pretty easy to use in a variety of situations.  The downside of their size is that everything else looks kind of chunky now: the handrails and even the wheel tread width...  Oh well - they look really good in person, especially now that they're painted. 

I have half a dozen other cars also done now; I'll post a few more pics when I finish weathering them.  (Still need to add some cement residue to this hopper too.)

-gfh

[wazzou]

Beautiful Gary!

[ednadolski]

Hey Gary that's looking real good!  The reduced height is always an improvement.  (The BLMA trucks are great,  I just wish there was a way to get bulk pricing on them.)

I guess you've installed these with one hole drilled for the mounting screw, and another for the styrene rod?   One thing I noticed on some cars, the metal around the rod can 'dimple' upwards a bit if you drill/enlarge the hole from the inside of the box.  In some cases that can be enough to keep the top side of the box from fitting completely flat against the floor of the car, causing the whole pocket/coupler to have a slight downwards tip or droop.  So I will either drill a slightly larger counterbore to the rod hole, or file the whole rod/dimple flush with the top of the pocket (in cases where I would not be using the rod to prevent rotations).  The filing doesn't seem to affect how well the rod remains secured in the pocket holes.

Re: the chunky look, the Athearn 2-bay hoppers have finer/wire handgrabs.   They also have an integral plastic box sized for the McHenry couplers....  I haven't gotten around to trying the Z couplers in those, but that is on my short list.   I'm hoping to use the trucks that comes with the Athearn hopper, tho I've upgraded mine to the FVM metal wheels.

Ed

[GaryHinshaw]

Ed, I agree that keeping the top flat is important for level mounting. After I tap the top hole for the pivot post, I file off any raised portion to make sure the top is flat.  Then, when I screw the plastic pivot post in, I trim the top end flush with the box top to keep it flat (I have abandoned the idea of using it to prevent rotation - see below).  Even with the post trimmed flush, it is held securely by the threads in the lid.  I then mount the box to the car with a screw through the rear slot of the box.  To keep the box from rotating I use some Pliobond on the joint to complement the screw.  The combination is rock solid even on some of the extended draft gear I have now mounted (photos coming soon).

I'm really glad to have gotten 100% of the way through a few samples now.  The results look great and the system performs as well as it looks.  This approach is a keeper in my book.

BTW, now that I have a few painted samples, one detail that really pops is the angle cock valve, which stands out nicely against the black air hose.  Very nice job you did on these!

-gfh

P.S. The Athearn 2-bays are really nice, and I have a few of them in the queue.  But what the N scale world really needs is a Trinity 2-bay, not yet another ACF 2-bay...  I did pick up a few undec Trinity 5161's to see if I could chop them down to 2-bays without making a hash of it.  We'll see...

[basementcalling]

-gfh

They look damn fine on that ballasted track with painted rail clips. 

[ednadolski]

But what the N scale world really needs is a Trinity 2-bay, not yet another ACF 2-bay...  I did pick up a few undec Trinity 5161's to see if I could chop them down to 2-bays without making a hash of it.  We'll see...

Just to indulge in a little thought tangent.....  I wonder how hard it would be to make these out of an etched metal kit?  Doesn't look like there would be a need for too many cast parts, except maybe the air reservoir & valve.   Anyone have any blueprints?   

Ed

[GaryHinshaw]

Some time ago, the TrinityRail site had pdf pages with basic dimensions of most of their cars.  Sadly those pages seem to be no longer posted (though they do have a Request Info contact page).  Here is the link to the 2-bay 3281 cuft hopper page.

FWIW, I think this would be a tricky project for etching (mainly getting the curves right) and I think bashing this from the 5161 is not that difficult, if you're willing to overlook a few seam placement issues (I am).  I think the hardest part will be cutting down the roof walk in a way that doesn't look butchered.

But please feel free to give it a shot!
-gfh

P.S. How about a 3230 cuft PD hopper while you're at it?   

[GaryHinshaw]

Cars continue to trickle* out of the shops.  I'm a sucker for the most generic cars in the modern fleet: plain black tank cars, plain grey hoppers, etc.  Here is an Atlas 4-bay hopper with new trucks, couplers & cross walks, and some very light weathering (mostly these proto cars just seem to fade/chalk and accumulate some grime around the seams):




I have tried to be very careful about standardizing coupler height, so I was a bit miffed when I got everything re-assembled on a pair of hoppers and found this:



Both couplers individually pass my height tests , but one must be epsilon high, and the other epsilon low.  I'm sure they'll be fine in normal duty, but I haven't stress tested this pair yet.  So far I think I'm achieving a tolerance of about ±.01",  which is probably about what is needed.

-gfh

*Trickle is the operative word here.  Between lowering ride height, changing trucks & couplers, adding a few details, applying conspicuity stripes and/or graffiti, and weathering, I'm spending a few hours per car.  I think I need TK's stop watch! 

[ednadolski]

So far I think I'm achieving a tolerance of about ±.01",  which is probably about what is needed.

I've been using the MT height gauge.  I try to line up on the nominal centerline height (0.216"), and my limits are that the upper edge of the Z coupler can be no higher than the upper edge of the gauge coupler, and the lower edge of the Z likewise can be no lower than the lower edge of the gauge.  At some point I'll convert the gauges to the Z coupler too (might be easier now that I have the loco boxes to play with).

I'm spending a few hours per car.

That somehow reminds me of this:

[GaryHinshaw]

For some reason, the center of the N coupler in my MT gauge is higher than 0.216" (more like .225" IIRC), so I have been using my calipers as a gauge and sighting the center parting line on the knuckle.  I also have one Bowser-equipped car I set aside as a standard to compare to.  I think these will be fine, and this is the worst pair I've had to date - it was just annoying.  On top of that, one of the bolster holes in this hopper developed a split, so it wouldn't retain the bolster pin reliably.  These cars would benefit from a beefier bolster than the little cast-in tube they have.

[DKS]

Both couplers individually pass my height tests , but one must be epsilon high, and the other epsilon low.

In looking at that photo carefully, I notice the one on the left appears to "droop" just a little more, for lack of a better word. And I wonder if this drooping varies with individual couplers depending on where it happens to sit at any given time. I imagine there is a bit of vertical play within the coupler box, and so after being moved the coupler itself may come to rest within a range of positions. Just wild speculation, mind...

[ednadolski]

In looking at that photo carefully, I notice the one on the left appears to "droop" just a little more, for lack of a better word. And I wonder if this drooping varies with individual couplers depending on where it happens to sit at any given time. I imagine there is a bit of vertical play within the coupler box, and so after being moved the coupler itself may come to rest within a range of positions. Just wild speculation, mind...

Perhaps a very thin shim inside the box (say 0.002" or so) is worth a try to see if it helps.   Another thought, perhaps this could be a case like I mentioned previously where the box ends up getting installed with a slight tip.  I had one case like this, and I corrected for it by installing a thin shim between the pocket and carbody (on the bolster side of the screw only).   A bit inelegant, but it seemed to work.

Ed

[babbo_enzo]

Hi all
I know it's maybe a dumb question, but ... I've very few cars with a body-mount coupler, so I've not so much direct experience.
One friend here ask about "minumum track radius" as he have some tight curves up to 22-23 cm ( more or less 9") and expresses concern that this modification can take to some trouble.
Can somebody tell us about his experience or give a "dumb rule"? Relation with car length, etc ....
Thanks in adv
Cheers