Would 3D couplers be strong enough?

[timwatson]

You can also mix Siraya Tenacious with many more brittle resins to make them less brittle but it doesn’t necessarily improve their sheer strength. Also tenacious resin doesn’t have a memory as to its shape. It does kind of but not like silicone might.

[peteski]

Black?  If someone starts 3D printing couplers I sure hope they print them using rusty colored resin.  Even MTL now sells brown couplers for extra realism.

[ednadolski]

Even MTL now sells brown couplers for extra realism.

Nothing particularly realistic about the brown plastic.   If anything, it makes the oversized couplers all the more evident.   Not a totally bad thing, I guess, if you have to manually uncouple in dim light.  For realism a darkish sort of grey or some kind of umber would work better, just JMHO, of course

Ed

[peteski]

Nothing particularly realistic about the brown plastic.   If anything, it makes the oversized couplers all the more evident.   Not a totally bad thing, I guess, if you have to manually uncouple in dim light.  For realism a darkish sort of grey or some kind of umber would work better, just JMHO, of course

Ed

To me, oversize or not, rusty color plastic looks better than stark black.  But, as you mentioned, opinions differ.

[bbussey]

Yes it is Siraya Blu v2 but it is clear and has a yellow tint. That’s why I suggested the alcohol ink. There are darker resins but most are really brittle. They would not be able to check off your first criteria. I hope that helps to clarify.

Point taken.

[Chris333]

Saw this on Twitter. All I know is it is a 3D printed N scale coupler.

[timwatson]

They can be printed!! Woohoo!
Like I said previously, resin doesn’t have memory. So the springs don’t really “spring” so well. This resin is a nicely durable one without too much brittleness. Ironically it’s $14.99 for a small bottle. I have cured these small parts quite awhile and they are still flexible. Shown is a z-scale 905 coupler.
The coupler box is a 2004. The trip pin is from MT.

We need to devise some type of testing apparatus.

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[bbussey]

All the “springs” have to do is keep the coupler centered when it’s not coupled. And, return the coupler to center after passing over a magnet. If they do that, then we have a viable coupler option for Athearn rolling stock.

The test would be to install them on an Athearn product and pass it over a magnet to see what happens.

[timwatson]

All the “springs” have to do is keep the coupler centered when it’s not coupled. And, return the coupler to center after passing over a magnet. If they do that, then we have a viable coupler option for Athearn rolling stock.

The test would be to install them on an Athearn product and pass it over a magnet to see what happens.

As the design stands right now they don’t center and they don’t keep center. I have an idea on how to do that in resin. Working on a coupler box now.

[timwatson]

I was thinking something like this?


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[peteski]

That "spring" protrusion in the back of the shanks would still have to be capable of bending when the coupler swings, and return to the straight shape to center the coupler. Or maybe I'm not understanding the design?

[timwatson]

That "spring" protrusion in the back of the shanks would still have to be capable of bending when the coupler swings, and return to the straight shape to center the coupler. Or maybe I'm not understanding the design?

That’s right but it doesn’t require as much “springyness”. Right now the spring length hasn’t gotten much return. I thought tapering the new shape at the back might help. I need to test it to see if it’s printable.

[timwatson]

Orientation and how these were printed.


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Strength of the part in MeshMixer "Analyze". Red is weak.
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[Mark5]

Watching with interest. 

My gut feeling is the degree of "springiness" varies quite a bit among different types of "plastic".

[peteski]

That’s right but it doesn’t require as much “springyness”. Right now the spring length hasn’t gotten much return. I thought tapering the new shape at the back might help. I need to test it to see if it’s printable.

I would disagree.  The short straight "spring" will have to deflect to a greater degree than the long curved "springs".