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Old 09-18-2021, 07:03 PM
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Shark27
 
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Update: The second change I made was to the coupler, originally I used 3mm threaded rod (see earlier picture), to simulate the turnbuckle that is used to bring two rail cars closer together when coupled. I designed and printed the center piece with handle to represent the turnbuckle, if glued in place it would rotate the threaded rod and move the end pieces in the same direction, so not tightening the connection by bringing them together, their relationship would remain the same.

As I understand it, they would tighten the coupler to bring the buffers on both cars into contact which kept tension and minimized the jerking back and forth when starting and stopping the train, since the buffers worked like shock absorbers and these type of couplers have no compressibility, the buffers fulfilled that need.

You can imagine a train that was loosely coupled together would beat itself to death and likely derail from the shifting of inertia from all the cars in the train, whenever they would try to slow down or when traveling over a hill, the cars would stretch out going uphill and then once on the downhill slope the cars would catch up and would compress like an accordion pushing on the cars ahead.

To update the coupler I was able to locate on line some 3mm turnbuckles that are just like the real thing, right hand threads on one side left hand threads on the other.
These are used on RC cars to adjust the steering, this was just what I needed to make the coupler functional.

That did bring up two additional problems, the first problem was tapping left handed threads into the component parts.

The first one I did by just using brute force, luckily PLA plastic is pretty pliable and the part didn't split, the second one I did with a left handed thread tap, way easier and it works great.

The second problem was, I needed to drill a 1mm hole in the center of the turnbuckle in order to attach the handle used for rotating it.

Now the Bad News, these turnbuckles are made from Titanium, to make them light and virtually indestructible I guess.

If you have ever tried to drill into Titanium you know what I mean, if you ever have to do it be prepared otherwise avoid it if you can.


I went through about six drill bits getting the holes into the two turnbuckles I have.

Coupler in fully extended state ready to be coupled to second rail car.

Coupler in stowed position

Coupler in tightened position, some length adjustment to the shackle end piece may be necessary as it would not be able to tighten down this far with a coupler hook in place. It may not have to tighten anywhere near this amount as the distance will determined by the how soon the buffers contact the other rail car's buffers. Experimentation will tell.

The Germans at some point designed and used a double coupler, for lack of a better term it was for connecting cars with extra heavy loads, I think this application qualifies, so I may design and print this and update both couplers to this type.



Next up will be cutting the aluminum plate for the top of the bed and bonding it to the lower framework.
That's all for now!
Steve