A journal following the history, design, construction and operation of Bernard Kempinski's O Scale model railroad depicting the U. S. Military Railroad (USMRR) Aquia-Falmouth line in 1863, and other model railroad projects.
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August 10, 2009

The dilema of links and pins

I am beginning to have second thoughts about using links and pins on my railroad. Although the prototype railroad used links and pins, they are tricky to use in model railroads. I haven't really given them a college try yet, as I only have 5 freight cars built and only three have couplers. But..... what little I have done has been problematic. They are very tricky to get coupled up and frequently the car you are coupling is derailed in the man-handling process!

There is a design implication of using links and pins too. The harbor end of the layout would benefit from a pier along the back wall. It is difficult to reach portions of that area. It would be impossible to couple a link and pin in that area. So if I stay with link and pins, then I'll have to omit that track.

But knuckle couplers aren't a perfect solution either, as there is no easy way to install a knuckle coupler to the front of an ACW locomotive without messing around with the cow catcher. The locos currently have an extended link like the prototype. Dave at SMR Trains says that this link wasn't designed to be used, it's mostly for show. However, I have tested it and it does work albeit with a lot of finicky fitting. I may have to make some links with slightly larger holes to allow easier insertion of the pin.

Another solution I am considering is to leave the extended link on the pilot and put a rule in the timetable forbidding the use of the link by road engines except in emergency circumstances. This means that road engines could only switch using the coupler on the tender. That will make things tricky operationally. I intend to build one engine that will be designated as the yard switcher. It will have the cow catcher removed and a conventional coupler installed on the pilot (either link and pin or knuckle). I also plan to have either a turntable or wye at both ends of the RR to facilitate turning the locos.


  1. What about magnetic link and pins? Use the couplers for show and alignment, but instead of relying on the "pin" use some rare earth magnets hidden in there somewhere to hold everything together.

    If Jaime could climb up some duct work with them, I'm sure they'll hold the ACW cars. You'll just have to find the right ones.

    But then again, modeling the PIA experience of these things is kinda prototypical, isn't it?

  2. On straight track magnets might work pretty well. When rounding the tight curves on my layout, the couplers swing pretty wide off center line. I doubt the magnets would hold. If they did, they'd probably cause a derail. Longer links solve that problem.

    You're right about the PIA, but prototype cars don't derail as you fiddle with the couplers. More weight helps, but not completely.

  3. Then what about using the magnets to handle the final alignment while you drop the pin in?

  4. Bernie, like this one... it's neat to see you going the extra mile to make this truly prototypical. One question: have you thought over "oversizing" the link & pin - while that's not the best solution, it would be prototypical and work with human fingers.

  5. I haven't given up on the link and pins yet. I think I'd rather do knuckles than go over-size L&Ps though.