Question on MT passenger truck boxes (attn Shipsure)

[randgust]

Tell me it ain't so, Joe.

OK, so I'll admit it's been a while since I bought some.

But when I did, I was surprised to see that the sliding box extension now has what appears to be a standard 1015 box on it.

Since time eternal, the MT passenger truck boxes have had the neatest, slickest, zero-clearance coupler box ever made.  If I had to put an MT coupler on something with simply NO ROOM, I'd buy a set of passenger trucks just to get that box, clip off the extension, and Goo the box on wherever it will fit.  It's on virtually every small critter I've ever made because it's a shorter box than the 1015, and a shorter box than the Z-scale, too.

There really isn't a substitute other than to scrounge around looking for old passenger car couplers.   

I'd suggested, and I'll suggest again, that that box - never mind the truck - has a whole lot more applications that what you give it credit for and should be offered as a separate part and promoted as a 'zero-clearance' universal box.  It's one of the handiest things ever made.

Here's what I mean.  There's no way you're getting a 1015 box on the end of the GE 25-tonner except to use that box.   1015 on the right, passenger box on the left tucked in behind the worm:



In a perfect world, this would be a Z-coupler alternative in a box this short......just sayin'.

[Lemosteam]

Totally agree.  I've done that a lot.  There are even some designs that were on the old steam pilot conversion kits that I wish I could get my hands on because they are so compact.

[peteski]

I'm not Joe, but I can chime in. 
Yes, the coupler design on passanger trucks has been changed to the standard type shank. The older (T-shank) couplers on a long extension were prone to vertical deflection and unscheduled uncouplings under stress (they would ride over and under each other and uncouple). The new design is much more stable.

MT does have a coupler conversion which is very short. I don't recall the number but it is the one used on Atlas Shays. Very similar to the one used on those old passenger trucks.

[randgust]

I'll partially agree with you.   That knuckle design was certainly prone to vertical separation.  But I'll also state that you could trim the 'fingers' just like any other pre-RDA knuckle and get them to lock/center into each other properly.

I have one of those passenger trucks on the FRONT of my spring-scale dynamometer car, so it's subjected to more stress than anything else I can think of right off the drawbar.   It popped all the time until I trimmed it.

[peteski]

I'll partially agree with you.   That knuckle design was certainly prone to vertical separation.  But I'll also state that you could trim the 'fingers' just like any other pre-RDA knuckle and get them to lock/center into each other properly.

I have one of those passenger trucks on the FRONT of my spring-scale dynamometer car, so it's subjected to more stress than anything else I can think of right off the drawbar.   It popped all the time until I trimmed it.

Yes, with the draft angle removed and under ideal condition (on a workbench), those couplers work quite well.  But in real life when the trucks in a multi-car train are traveling on non-perfect track, or start climbing a grade, then because they are mounted on a long extension from the center of the track, the couplers will get vertically misaligned.  That added to the fact that the coupler shank is offset will make them very prone to separating vertically.

IIRC, the reason they redesigned those trucks was due to customer's complaints about the couplers being unreliable.

[nkalanaga]

Could you use the short T-shank conversion coupler and make your own boxes?  For one pair, plastic or brass would work, or for mass production they could be 3D printed.

[randgust]

Not a bad idea.  So, what conversion(s) have the same coupler?    Is there a Z-scale short shank anything?  (back to the 'if we were really doing this right, dept)

EDIT:  OK, here's the coupler box disassembled.   If there is another conversion kit that uses a t-shank this short....can anybody ID it?   No sense thinking about a box if the coupler can't be found elsewhere either.

[nkalanaga]

They used to sell the T-shank couplers by themselves, in at least three lengths, to be put in truck-mounted Rapido boxes.  I suspect that's the MT-7/1128 coupler.  My very old package, that has both numbers on it(!), shows a length of 0.225 inches from the front edge of the T to the inside edge (pulling face) of the knuckle.

[randgust]

Found the 1128's.  May be what I'm looking for.  Now in the spirit of 'every problem looks like a nail if the only tool you have is a hammer', I'm looking at this like it wouldn't be that impossible to cast a new ultra low-clearance box out of resin instead of RP'ing one out of FUD or similar.   I'm not real happy with the brittleness of FUD, and unsure if I could get the tolerances out of something else.  Anyway, I can still scratchbuild a decent master for resin casting a whole lot faster than I can draw something up and wait out Shapeways.   

But this is a whole different direction from what I thought, so this has been a rather productive discussion.

Is there a T-shank Z coupler?  I'm still wishing I could put Z's on some of my critters and geared power rather than the big-knuckle N's.

[Lemosteam]

@randgust , have you made a bottoming tap yet for blind holes?  I have been successful at tapping into 0.3mm FUD and FXD wall and with the bottoming tap into shallow pocket holes, after cleaning the hole with the proper tab drill.

[randgust]

Since there's no screw hole in that box design, the MT method was a snap-on lid for a two-part box.  In Delrin, that works just fine.   If you imitated that in either FUD or similar you'd either snap off the edges of the lid or snap the top of the holes off.    I'm not sure about printing it in other materials if you'd be able to replicate those tolerances to gain durability.   I do know that resin would do it, also be very inexpensive to produce.

The footboards on the 25-tonner shell are a great example of that - they print just great but they are so incredibly fragile that they may as well not be there.    I also got a FUD-printed fork truck that was exquisitely printed but broke it into tiny pieces just trying to assemble it.   It's pretty tough stuff with enough thickness, but on tiny cross-sections it's next to impossible not to damage.

[peteski]

Is there a T-shank Z coupler?  I'm still wishing I could put Z's on some of my critters and geared power rather than the big-knuckle N's.

I don't believe so. They either come in a 1023 style (but smaller) or Marklin style (which is bulkier).

[bbussey]

Found the 1128's.  May be what I'm looking for.  Now in the spirit of 'every problem looks like a nail if the only tool you have is a hammer', I'm looking at this like it wouldn't be that impossible to cast a new ultra low-clearance box out of resin instead of RP'ing one out of FUD or similar.   I'm not real happy with the brittleness of FUD, and unsure if I could get the tolerances out of something else.  Anyway, I can still scratchbuild a decent master for resin casting a whole lot faster than I can draw something up and wait out Shapeways...

You also can render your master in FUD and cast the resin parts from that.

[peteski]

I'm thinking that even resin in this snap-lid design might be too brittle.  But there might resin out there which is more flexible than the stuff we usually use for molding shells and details.

[nkalanaga]

The Marklin-conversion knuckle couplers might be adaptable.  They fit a D-shaped post,with a spring behind them, and take about the same box space as the 1128.  If you can find a Marklin 2-axle freight car you could copy the design, which is really very simple.   Even without the car, designing a box that would work probably wouldn't be difficult, as all it really needs is the post, a keeper of some kind to hold the coupler on the post, and something to keep the spring in place.  The 902 conversion set comes with the spring.

They also made a longer version, 901 maybe?, but I don't have one of those.