TheRailwire
General Discussion => 3D Printing => Topic started by: ednadolski on February 07, 2023, 01:14:50 AM
-
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".
(https://i.imgur.com/9jVJtir.jpg)
(https://i.imgur.com/GJ5ifPs.jpg)
(https://i.imgur.com/ptldyIX.jpg)
(https://i.imgur.com/IH591va.jpg)
(https://i.imgur.com/P691u8J.jpg)
(https://i.imgur.com/uUguM48.jpg)
Ed
Attribution Link: https://cults3d.com/en/3d-model/art/aar-coupler-type-e
-
Wow - these are outstanding!!
Best regards,
Wolf
-
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.
-
Did you draw that or use a publicly available file?
-
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
-
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”.
[attachimg=1]
[attachimg=2]
-
@ednadolski , what is wrong with you? lol
This is really cool.
-
How do they compare to Micro-Trains True Scale Couplings?
-
@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.
-
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
-
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.
-
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
-
I think it was something like 0.025" or 0.030" diameter. Possibly even smaller like 0.020".
-
I think it was something like 0.025" or 0.030" diameter. Possibly even smaller like 0.020".
1mm is 0.039"
-
Here are a couple shots of the ones I designed. Only two photos I took.
(https://live.staticflickr.com/65535/52676076289_b261969f8f_k.jpg)
(https://live.staticflickr.com/65535/52676076319_b30551d87f_k.jpg)
converted weirdly nested tags to inline images -gfh
-
When I talked to Frank about getting his permission to use his design, but in N-Scale, he was concerned about the ball being to light.
-
I thought I lost my 3D drawings, but I found them and they included the ball. The ball is 0.024" diameter.
-
Thanks @6axlepwr for sharing the pics & info. WRT the ball being too light, yep, that's that thing where physics doesn't scale. Seems there are a couple of options, tho I don't know offhand which might work any better:
- Increase the internal clearances around the ball, if that is possible to do without compromising the functionality.
- Some kind of heavier ball, which either means larger (if that could be made to fit) or denser (if such a material exists and still has the needed magnetic properties -- not too sure about that one).
- Some combination of a larger (overscale - maybe 20% would still look ok?) coupler and larger ball, if such a combo could be found that would work reliably.
Not sure what other possibilites there are, otherwise perhaps there are other alternatives to a locking ball.
Ed
-
There would be an alternative, but it would require a bit more interaction with your operations. Use an actual pin. A pin that is cast in brass or even white metal. The pin would have a loop or a hook at the top. The pin is designed to be installed before the couplers are assembled and would have a keeper at the bottom so it could not be accidentally pulled out when lifting.
The "more interaction" would be that the operator would have to actually pull the pin to uncouple the cars. The pin WOULD be heavy enough to freely fall back down to lock because it would be much larger than a ball and probably more mass and weight than even the HO scale ball.
-
Brian when you say 'pin' I am picturing essentially a cylinder with a hemispherical bottom end, so that it would engage with the (unmodified) tab on the knuckle in the same manner as the ball, so that the closing/locking operation would still function as designed.
Perhaps if the pin had a small bit of steel at the top for the loop/hook then it could still be operated with the magnetic wand. Operating a loop/hook with a pick or tool would need a very light touch to avoid pushing the couplers out of line when lifting the pin.
Ed
-
LOL! You guys are *WAY* out there! 8) It would be interesting to see how this works in practice. :scared:
-
But just look how cool that image is with the open knuckle. That's the stuff dreams are made of.
-
Yes Ed, that is exactly what I am referring to. An actual pin. Your idea there is really good. and easy. Hell, the pin could be cast in brass with a cup at the top. CA the steel ball to the cup and you are as good as gold with the magnet.
I really like this idea and all this discussion is stimulating my brain. It would have to wait till later this year though when I would have the funds to have new molds made. I would want to redesign the shank also. Probably to work inside a Micro-Trains box so it could be a direct retro fit. It would be way easy to duplicate the Micro-Trains shank.
-
Having done a whole lot of development work on operating scale couplers (in N scale), I would think an operating knuckle might be a little impractical, but a cool concept nevertheless.
If you need to compromise the prototypical look of the coupler by say having a steel ball visible on the top of the coupler to pull the pin, it might rather defeat the purpose. Or making it overscale...
If it’s truly modelled in scale, it would be interoperable with split shank designs like the upcoming N-Possible scale coupler as well as the MTL TSC.
-
Having done a whole lot of development work on operating scale couplers (in N scale), I would think an operating knuckle might be a little impractical, but a cool concept nevertheless.
If you need to compromise the prototypical look of the coupler by say having a steel ball visible on the top of the coupler to pull the pin, it might rather defeat the purpose. Or making it overscale...
If it’s truly modelled in scale, it would be interoperable with split shank designs like the upcoming N-Possible scale coupler as well as the MTL TSC.
@turbowhiz speaking of the N-Possible scale couple, any news on that front?
-
Having done a whole lot of development work on operating scale couplers (in N scale), I would think an operating knuckle might be a little impractical, but a cool concept nevertheless.
If you need to compromise the prototypical look of the coupler by say having a steel ball visible on the top of the coupler to pull the pin, it might rather defeat the purpose. Or making it overscale...
If it%u2019s truly modelled in scale, it would be interoperable with split shank designs like the upcoming N-Possible scale coupler as well as the MTL TSC.
Never heard of either of those. That would save a lot of time and effort. I want to focus more on the layout and building models. Not really on designing anything. Except for my models of course.
OK, so I just watched the YouTube video on the N-Possible couplers. What I saw I liked a lot. I just looked up the MTL TSC coupler and it looks very nice too!
Brian
-
@6axlepwr there is a thread and some videos that you might want to check out:
https://www.therailwire.net/forum/index.php?topic=54237.msg743458#msg743458
Ed
-
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”.
(Attachment Link)
(Attachment Link)
Where did you source the trip pins? I've been considering a 3D printed HOn3 coupler but finding a source for trip pins is a bit tough
-
Never heard of either of those. That would save a lot of time and effort. I want to focus more on the layout and building models. Not really on designing anything. Except for my models of course.
OK, so I just watched the YouTube video on the N-Possible couplers. What I saw I liked a lot. I just looked up the MTL TSC coupler and it looks very nice too!
Brian
N-possible only came about because of my progressively more sophisticated efforts to make the TSC a functional coupler (it really isn’t in its stock form). I never had commercial ambitions at all, but the end result was something so effective and elegant that I just couldn’t ignore the market potential. It was a slippery slope, and I’ve fallen down hard for better or worse… My own modeling ambitions have suffered greatly!
-
N-possible only came about because of my progressively more sophisticated efforts to make the TSC a functional coupler (it really isn’t in its stock form). I never had commercial ambitions at all, but the end result was something so effective and elegant that I just couldn’t ignore the market potential. It was a slippery slope, and I’ve fallen down hard for better or worse… My own modeling ambitions have suffered greatly!
Your earlier post stated "...split shank designs like the upcoming N-Possible scale coupler..." and here you state "...I’ve fallen down hard for better or worse…". So which is it? Is the project dead or still alive?
-
@turbowhiz speaking of the N-Possible scale couple, any news on that front?
Well, in terms of an update, expect more formal announcements shortly. But as a teaser, I’m confident that I have a truly commercially viable product design after a recent breakthrough. I finally cracked the true drop in compatibility problem, so a wide range of factory body mount models (and truck mounts too, because I can) are truly drop in. And the ones that aren’t truly drop in are easily modified to work in almost all cases. Supplier sourcing has begun in earnest. The prototypes I demonstrated in Nashville (and the YouTube content, including Ed’s) were great, but they are proof-of-concept prototypes rather than a production ready product. Although my spring design works wonderfully for magnetic uncoupling applications as well, scale couplers will definitely be first to market.
-
Your earlier post stated "...split shank designs like the upcoming N-Possible scale coupler..." and here you state "...I’ve fallen down hard for better or worse…". So which is it? Is the project dead or still alive?
"Fallen down hard" referring to the fact I'm finding myself in the MRR business, even though it was never my intent to turn my hobby into a business.
N-Possible is very much alive, despite the fact that I've been very quiet on the public front.
-
"Fallen down hard" referring to the fact I'm finding myself in the MRR business, even though it was never my intent to turn my hobby into a business.
N-Possible is very much alive, despite the fact that I've been very quiet on the public front.
Well that is great new for those of us who have been anxiously awaiting any news.
-
Where did you source the trip pins? I've been considering a 3D printed HOn3 coupler but finding a source for trip pins is a bit tough
I used some that I had lying around. That is a more difficult part to source.
-
I used some that I had lying around. That is a more difficult part to source.
Not really. If you contact MTL (call them and ask), they do sell coupler parts (like trip pins). They are not very expensive. I bought some for the GOEMON couplers, but unfortunately few years ago MTL apparently shrunk down their trip pins, so they are too loose in GOEMONs. The current pins are thinner than the ones from a decade ago. But if you use them in 3D pritned couplers that makes no difference.