Re: 1:8 H Couplers

Tim L

Now that's just awesome!

It's been a very long time since I was involved with miniature rail (7 1/4" gauge but most stuff was 1:6 or 1:4.8" scale) and I don't know a lot about the inner workings of the couplers we used but a couple of things you could consider.

The knuckle couplers we used had what amounts to a bolt with a loop welded to the top which functioned as the lock and lift pin (top operated obviously). They also had a coil spring in them somehow that threw the knuckle open a bit when you lifted the lock enough to clear the knuckle "tang" (for want of a better word).

I'd look at the possibility of modifying the coupler drawing so that knuckle pivot hole goes all the way through so you can use a bolt like on the commercial couplers; it may be stronger than the short stubs on the Sergent design.

I'd definitely look at getting them cast in metal. You should easily be able to use the prints as the pattern for doing that, though you will have to take into account shrinkage etc.

- Tim

On 29/07/2020 17:57, Nathan Rich wrote:
Thought you guys might enjoy this, I upscaled the H coupler to 1:8 scale, for 7 1/2" gauge. I wanted to test the theory, because I wanted to use a correct H coupler on the front of a PA locomotive a friend is building.
I upscaled the files Mr. Sergent graciously provided us by 1087.5%, and printed then in PLA with 20% infill. I do not expect these to be actually used, I wanted to make sure they would mate with commercially available couplers (Shown here a Live Steam Products standard E coupler). This just proves how accurate the couplers Mr. Sergent made are. I'm certainly impressed.
For the ball, I used a 1/2" steel bearing, and the holes you can see are for using a Sergent pick to uncouple just like the HO version. With a little tweaking with a drill here and there, these things work great. They couple reliably every time!
For the one to go on the actual locomotive, I'll need to 3D print it at 100% infill or figure out a way to cast it in aluminum or brass, and possibly use a different mechanism for the knuckle. It needs to be able to be used in an unusual circumstance, but normally it should be on the front looking cool.
Nathan Rich

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