AAR Type E Coupler in N Scale from the Phrozen Sonic Mini 8k

[ednadolski]

Just to see what the PSM8k printer could do (but also to demonstrate that insanity knows no bounds) I decided to try printing an AAR Type E coupler in 1:160 scale.  I printed the body and knuckle as separate parts, but I think any attempt to actually assemble them (let alone trying to make it actually work anything like a prototype coupler, or even a Sergent HO coupler) would be an exercise in patience that could make anyone wish to be working in O scale.

All that aside, I do think that the printer did a pretty good job with the detailing, esp. considering how tiny these parts really are.  For reference, the styrene strip is 0.010" x 0.020".















Ed

Attribution Link:  https://cults3d.com/en/3d-model/art/aar-coupler-type-e

[SP-Wolf]

Wow - these are outstanding!!

Best regards,
Wolf

[Maletrain]

Those would certainly be great dummies for the fronts of locos and the backs of cabooses that will not see any switching ops.

And having a few around the engine and car shops would be another good use.  Maybe put a couple on the work train car that carries wheels.  Even a load of them in a gondola would look great.  Making the knuckles separate parts really adds to the potential for realism in some of those scenic uses.

[jagged ben]

Did you draw that or use a publicly available file?

[ednadolski]

Did you draw that or use a publicly available file?

It's a free public file:  https://cults3d.com/en/3d-model/art/aar-coupler-type-e  (I guess posting a link qualifies as an attribution).

I had to modify it somewhat, mostly to remove the internal hollowing that would have made it hard to print so small.


I did also find some online PDFs of prototype Type E and Type F couplers that could be used to develop a cad drawing:  https://web.archive.org/web/20121118021347/http://www.columbuscastings.com/railroad_undercarriage_components.html

Another option could be to try printing the Sergent design at a 54% reduction, but IDK how strong that would be in resin (or where to get some 0.5mm chrome steel ball bearings).


Ed

[timwatson]

I made some working n scale couplers in resin maybe a year and a half ago. It was based on a design @bbussey sent me. I had to change the geometry quite a bit to make it work in resin but it did work. I faked the AAR coupler vibe. If he’s cool with it I can post it and you can play with it too. The spring isn’t great because resin lacks “memory”.

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[Ed Kapuscinski]

@ednadolski , what is wrong with you? lol

This is really cool.

[garethashenden]

How do they compare to Micro-Trains True Scale Couplings?

[Sokramiketes]

@6axlepwr went down the road of N Scale Sargent style couplers a couple years ago.  He may have some notes to share from that experience. 

[ednadolski]

How do they compare to Micro-Trains True Scale Couplings?

They are pretty close in size.  The TSC has less detail so that it can be injection-molded, and requires the MT (1015?) sized box with the 00-90 mounting screw.  Operationally, the AAR has the pivot knuckle, which seems impractical to me for N scale, tho it could be modified to have an integral/rigid knuckle and split shank like the TSC.  IDK tho how strong that would be, perhaps it could be suitable for small applications; that said the TSC is probably much stronger, just considering the materials.  It is also not clear to me how well the printed resin would perform in a split-shank design, if the contact surfaces would operate smoothly enough against each other.   But yeah, for a dummy coupler, it could work well I think.

Ed

[6axlepwr]

Yes I did and they actually worked out pretty good some of the time. I had them 3D printed and then cast in brass. They were scale size and looked just like the Sergent couplers. Once you get the head of the coupler designed and working properly, the shank can be anything you want. I sourced the ball from some place in California that had micro miniature ball bearings. They were tiny. 

The fault was in the ball. Although the ball would fall back into the lock position some of the time, the ball was not heavy enough to fall reliably all the time. Meaning it would stick more times than not. It was just to light.

I think I still have pictures of them. I will see if I can dig them up tonight and post them. The concept DOES work. As mentioned, you could just take the Sergent design and resize it to N-Scale. The issue is the ball weight. Just need to find the right size ball that will drop freely when the knuckle is closed.

It would be best to have the couplers cast in brass or even white metal. Another possibility is to use an actual pin with a loop at the top. Then you have a pin vice with a small rod on it that lifts the pin. Have the pin cast in metal too.

Best metal to have something like this cast in is dental steel. It does not shrink. I used to have a son in law that was a dental caster and he would cast parts for me. I would just give him an original part and he would melt it out and pour the metal in. Exact same size fit.

I would say do not redesign something that does not have to be designed. Use the Sergent and fix the ball issue. Then just design an appropriate shank.

 

[ednadolski]

FWIW I measured the Sergent locking ball at 1mm diameter, tho that seems too large for N scale.  @6axlepwr do you remember what size ball you used?

Ed

[6axlepwr]

I think it was something like 0.025" or 0.030" diameter. Possibly even smaller like 0.020".

[peteski]

I think it was something like 0.025" or 0.030" diameter. Possibly even smaller like 0.020".

1mm is 0.039"

[6axlepwr]

Here are a couple shots of the ones I designed. Only two photos I took.






converted weirdly nested tags to inline images -gfh