Knuckle couplers are driving me crazy

Discussion in 'HO Scale Model Trains' started by, Mar 20, 2008.


    I've always loved the looks of knuckle couplers so when I built my little 4 x 8 layout. Pics at The Train Guy I decided to remove all horn hook couplers and make the switch. Everything looks great and runs fairly well, but there's a 4% grade and at the top of the grade, the height difference between the car that's at the higher level, and the car coming up the grade causes one coupler to raise above the other and decouple the cars. Then the entire train comes back down the mountain. Any ideas on how to solve this? Shims in the couplers, etc.? The layout runs great with my old equipment and horn hook couplers but every proto2000 piece I put on it comes disconnected.:curse:
  2. tetters

    tetters Rail Spiking Fool!

    I got rid of all the my plastic P2K couplers and replaced them with Kadee # 5's. I found the P2K couplers too fragile and too easy to break.

    That said, it almost sounds as if the transition in your grade is too sharp, allowing the coupler to rise over the other one as it comes over the grade. I am pretty sure that some other members will also suggest you check your transitions and if possible try to smooth them out and make them as subtle as possible.

    Just my 2 cents.

    Yeah I thought about smoothing out the transitions, the problem is that when I tested everything prior to gluing down the track/ballasting etc., everything was perfect, and now it's sort of immobile. I'm worried that trying to fix this at the track level will cause a lot of damage.
  4. HoosierDaddy

    HoosierDaddy Member

    It sounds like a grade transition problem to me too. If it goes from 4% grade to 0% grade too abruptly, the coupler on the trailing car will drop out of the bottom of the leading cars coupler. If you can ease the transition, making it less angular and more curvatious. If you need, I can draw it better than I can explain it.

  5. Russ Bellinis

    Russ Bellinis Active Member

    Hoosier Daddy nailed your problem. If you used plywood to make your grade and began it at the bottom of the grade and ended it right at the top of the grade, you are guaranteed to get a vertical curve that will cause the problem you are experiencing. What you need to do is cut a piece of plywood longer than your grade. Fasten it flat at the bottom of the grade, and then bend it up into the grade. At the top of the grade, bend the plywood over into the flat. The plywood will make a correct transition curve that will eliminate the problem at both ends of the grade. If the grade is too long for one piece of plywood, you can butt splice two or more pieces together part way up the grade. Just make sure the grade doesn't change over the splice, and put a "bridge" piece under the splice overlapping both ends to keep the ends in proper alignment.
  6. lester perry

    lester perry Active Member

    it is not the couplers. without seeing it I can tell you it is the hump at th top of the grade. as for my 2 cents, bight the bullet and fix the track. you will find that a hump on level track can cause the same problem. Guess what, the real RR has the same problem, I have seen it. you will probably like the appearance of the smooth transfer better also.
  7. lester perry

    lester perry Active Member

    oh yeah I agree with tetters about p2k couplers and any others other than Kadee I am a believer in kadee I have tried many other brands but they all have an unacceptable failure rate.
  8. Kanawha

    Kanawha Member

    I would test your coupler heights on a level section of track. If any are off height, a grade will make it very apparent, but if they are all at the same height on level track, then its definitely not a coupler issue. Good luck!

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