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I have lots of passenger cars, and hate the gap on nearly all of them. I’m sure it’s don’t to make them able to negotiate tight curves so I guess I understand.

i posted a want add for a premier Amtrak diesel and ended up buying a F40PH-2 from CentralFan1976. While negotiating I also bought from him a 5 car set of amfleet cars.

First off, great guy. Excellent communicator, excellent packing, and quick shipping. Everything showed up and is absolutely beautiful. Everything is great except for the large gap between the cars. In talking to him, he mentioned he had drawn in CAD closer couplers for them in hopes of bringing them closer together but had yet to have them made and fitted. I have a 3d printer so he sent me the file before the cars even shipped.

That evening I printed a pair of them and instantly realized they wouldn’t couple! Talked to him some more and he explained he had lost the original CAD file and only had the STL. I knew I wanted this to work but my ape brain can barely spell CAD let alone work with any of the fancy programs that are designed to show me how stupid I am.

I ended up spending the day in tinkercad and on YouTube watching tutorials. There’s no way I’m at the level that I could completely redesign it, but I could clearly see the issue. The inside of the coupler was too tight and there was no way to make them slip together. I ended up figuring out how to cut part of the drawing off and placed it out of the way. Then I just started adding boxes to the face I had removed the horn from and then sliding the horn back in place. Took all day but I’m getting close.

Here’s the original car gap and some of the printing progress. E68B21EA-ABBB-4328-BF32-1B07EF270FD17F3B1A81-1DBF-433A-8B9B-8840F0A51D0A


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Hours later and I’m finally learning to spell CAD and making progress.

No real measurements, just trial and error, but I finally got two couplers to mate and not bind. I printed with a brim which makes it a little bit of a pain post production. Might skip the brim in the future and see how it goes. Also had a lot of problems with supports as the part where the pin goes is the only part that touched the bed of the printer. Experimented a little and added to the bottom of the drawbar so it touches the bed as well. Not accurate, but also hard to see so I’ll take a cleaner part over absolute accuracy. FE6EBE4A-D7A2-4BD8-A7EE-32DBE38C8579F47B42B0-843F-4EED-9FEE-EEE0B8AFE40D


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Proof of concept…

Long way to go and lots of work to do, but I’m happy with the preliminary results. When “finished” I will print them in black.

The diaphragms fit together pretty snugly. Around 0-72 curves they slide and gap on the outside, but come right back together on the straights.

I’m pretty happy so far. Here’s a before and after shot. 763BBF42-9C5B-45C0-A1F2-16FD3A01C3936F9A1F88-DCC8-4AC4-8498-FD7E81390300


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I’m finally happy with the design. It’s taken 10x the work and time I originally anticipated but well worth it. I spent 2 days just trying to get the bottom portion to look right and in the end, it’s way too much post print work to be worth it. Cutting away supports just to have the ultimate detail is for the birds. The drawbar in particular is what I’m talking about. To have it elevated 1mm is a nightmare. I figure the only way you’ll ever really see it is if the cars crash off the rails and down to the ground, in which case I have bigger things to worry about.

The software fought me, the printer fought me, my fantastic eye condition (optic neuritis) fought me, the dogs wanting attention fought me, my ape brain fought me, but I won a small battle tonight. Funny how these things work, because I already have another betterer idea in mind after this is finalized.

Need to walk away from it for the moment, but will print them in black next and then fit them to my Amfleet cars. Had to use gray for testing as the print bed is black and I struggle enough as it is to see the details without having them blend in and fade away.

Again, thank you to CentralFan1976 for the original STL I used to make these work.



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Looking fantastic I think! Not sure if it’s just the different PLA or the way I modified my start and base layer sequence, but these are much smoother than all of my “test mules”. My biggest issue has been base layer adhesion but I think I have it figured out. Just got the printer for Christmas so overall I think I’m not doing too bad.



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Well, they finished printing and then a family emergency happened and we had to leave town for a free days. Got back home tonight and cut a few out.

Overall I’m pretty darn happy with them. They do exactly what I wanted and look plenty good. Here’s a finished pic along with a few comparing the coupler head to the stock lobster claw.



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Often, problems lead to solutions.

I said my next venture would be bringing them closer and only using one diaphragm per car. Well that came quicker than expected.

I got all 5 cars converted and the diaphragms between the cars fit pretty snugly. Still bothered me how much space was between the bodies though. Started running them and at nearly every single curve there was enough pressure to either lift the inside wheels slightly or make the car derail. The obvious answer was to slightly lengthen them and free up that pressure, but that is moving in the opposite direction of where I want to be, so I decided to pull a diaphragm from between each pair and go the direction I wanted, which is closer.

I also spent some time and experimented with the printer and some of its deeper settings. I can now print them without the adhesion brim which makes them useable right off the printer instead of cutting them (and my fingers) for an annoying amount of time.

Pics above are where I left off and below is todays progress. The first “cut” was arbitrary in size and just done by eye. The next 2 we’re done 1mm at a time. The final is as close to perfect as I dare to get. The diaphragm just slightly touches the other car in straights and in curves just slides on the end of the car. No binding, no pushing, no issues.



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Last edited by David K. Simpson

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