Z Scale Open/Closed Tri-Level Autorack

[Jesse6669]

Having no options for autoracks in Z scale currently-- the AZL ones are out of production and sold out everywhere--and wanting a slightly older version anyway, I decided to take a crack at one myself.  Little did I know the great variety of 89' autoracks out there.. but then again, research is part of the fun.  This will not be an easy print given the length of the car and somewhat delicate nature of the side bracing, but I figured I'd give it a try.

Looking over some pics I decided to base the model on this TTKX prototype.  The was an ex-NYC/TT car and they lasted into Conrail.  The initial model will be the "open" version, since I figure if I can pull that off, adding the sides shouldn't be too difficult in comparison.  I'll try printing the sides but the backup plan is some etched or possibly cut-to-fit corrugated siding of metal or plastic.
 
The biggest challenge I can foresee will be how to minimize distortion while curing--the long beds, but also parts like grab irons and bracing.

Here's the "first beta" design -- the "bones" are done but I need to add end ladders and some details.


I added some details and refined some components and this is the result:


Futile as it probably is/was, I tried a print of this early design;  Not unexpectedly it failed in multiple areas, notably under the decks as they were unsupported.  Note that this picture was also taken before it had completely dried, so some of the distortion would've gone away as they shrunk.  I normally let prints air-dry (no UV) for at least 12 hours before curing.  Also, the resin is Phrozen RPG gray.


The important thing about this print was it highlighted several design areas to be addressed:  Decks are now a separate print that will slide in from the ends (or from the top);  Some components were "beefed up" and supports added.  The next iteration is on the printer so we'll see how it comes out. 

[nkalanaga]

Separate decks will also make it MUCH easier to load, if one wants a loaded rack.

If the slide in from the end, it might even be possible to make them interchangeable.  Loads one way, empties the other, just by sliding the decks in and out.

[Cory Rothlisberger]

Next you have to print the cars to go with it... 

[Jesse6669]

Next you have to print the cars to go with it... 

Some of these..   

[Jesse6669]

Here's test print #2, which came out a bit better than expected.  I wanted to show how I did the supports for these.  As mentioned, the decks are separate, printed on edge to avoid the bulging/blistering that happens on the bottom of horizontal surfaces. 

The main car has fairly massive cantilevered supports coming in from each end, with small X braces going across the body connecting the posts.  The central support arms of this support are angled upward about 15-degrees.  Note, these were added in the design software, not in the slicing software. 

The parts of the car sides dried/shrunk and retained their shape much better, for example the ladders/grabs and unloading mechanism parts.  Sure, it's a bit "lacy" but honestly the resin is flexible enough that these are not too delicate to handle.  Side note, the underbody has big gaps in the frame to allow me to add tungsten putty for weight and a low center of gravity.





I'll do another update after I test the fit of the decks and trucks and give it a shot of primer.

[Sumner]

Nice work.  I can't quite wrap my head around designing in Z, N is hard enough.

I notice you are using different size supports.  I've started using the smallest for about everything I print.







I can usually break them with my thumb nail,  only using cutters for something really delicate (like what you are doing).  They might use more resin but I'm not mass producing parts and the easy of removing them is well worth it.

Sumner

[Jesse6669]

Sometimes "less is more".  The large cantilever support seemed to be imparting a defect on some of the posts for some reason.  So I left the cross-bracing and omitted the big honkin' supports on the end, and it turned out much better.  A couple more tweaks are needed--you can see the supports in the middle "let go", and the stirrups need a little bracing, but this version is nearly complete, and Version 4 is on the printer.  Adding sides will be an interesting project. 

Off the printing plate:


A close-up of the bracing:


Quick shot of primer and sitting on trucks:


@Sumner I tend to agree on the small supports; sometimes I need a larger tip diameter to "grip" better, usually around 0.30mm is the biggest, .20 or thereabout the smallest.

[Jesse6669]

Version 4 (with corrugated sides a la this prototype):

[cgw277]

Very nice work! Very informative how you have progressed with modifying you supports on each test print. I noticed your print is oriented parallel to the build plate, not angled at 45 degrees. I'm assuming since this is in Z scale you don't have any problem with the print getting pulled off the build plate?
Good luck with the next test print and hope to see the results.
Scot

[Jesse6669]

I noticed your print is oriented parallel to the build plate, not angled at 45 degrees. I'm assuming since this is in Z scale you don't have any problem with the print getting pulled off the build plate?

I very rarely orient at anything other than 0 degrees (no angle) and haven't ever had an issue with prints getting pulled off the build plate in Z or N scale--like the H22a hopper.  The N-20 caboose was angled around 15-degrees to get the roof to print without artifacts.   I do tend to use a lot of supports, usually at least 0.20mm diameter tips, but up to .30 or .35 sometimes.  IDK, it's just what has worked for me, and YMMV!

[cgw277]

Thanks for the update on how you orient your prints. I will try to vary my next test prints and see how they work out.
Scot

[Jesse6669]

The latest iteration after I fixed some details.  I made the lower placards/number plates separate since they were printing with noticeable layer lines.  There's a new one off the printer/drying with full placards on the "X" bracing.  The next test will be with sides added.. that's going to be interesting.  Quite happy with how this is turning out and will be working on decals for NYC, B&O, WP and ?

[Jesse6669]

I think I have the sides worked out. 

I first tried to print them in situ since the easiest design is fewer parts-- but despite some careful drying/curing, the sides wanted to warp and it ended up with this "basket weave" pattern. 



I've had success flattening parts by sandwiching between two pieces of clear styrene with rubber bands, and put in the sun to fully cure--but this is dependent on the part itself being designed flat--can't do that with a full car.  For example, the decks for this model have been straightened using this technique.



So, I tried doing the sides as separate parts to be applied over the open frame model.  This is actually a good option for two reasons: the "base model" is just the open autorack, and I won't have two full different models to print.  If you want it enclosed, just apply the sides to the open version.  I printed the sides flat (90-degrees to their orientation) with a lot of small supports of .20-.25 tip diameter.  Some of the delicate supports--like the small bits connecting the levels--were carefully cut after drying but before curing.  These parts remained quite flat so no ironing needed, I think.

 

Here's the test fit.  I think this'll work.






 

[Jesse6669]

Here's the "final" version of the open tri-level autorack.  The logo plates were done differently per prototype--some had 2, some had larger ones-- so I will adjust the design as I print them.
 


Here's the car with the sides installed.  They did shrink a bit, and there is some warping but they are acceptable I think.  One thing--in making a finished model I will want to paint the open rack before installing the sides as a final step.  The good news is I installed these tests with a bit of PVA so they should be removable.

[Ed Kapuscinski]

Have you considered making some of this stuff available through https://3dcentraltrains.com/ ?