Katos that like to decouple and derail

Discussion in 'N / Z Scale Model Trains' started by Zug, Sep 26, 2003.

  1. Zug

    Zug Member

    I have two Katos, a SD90MAC and SD40-2, I run them with the SD90 in the lead. The like good at derailing stuff. they can't go to the inner loop of the two in the original part of my layout. each can go one at a time, but together the SD40-2 gets flipped off the track by the SD90 as it come off the switch (see my layout page on the line below) once I get them past, they derail the first car behind them. I have the MT long couplers on.

    I was just trying to drive them in to the switching yard and they decoupled the car just going through the switch, and it's not all that tight of a curver there.

    What is it about Katos that makes them like to derail stuff? I have Altas SD60 that I can drive full out through these same section ok.
  2. hemiadda2d

    hemiadda2d Member

    OK, you need to give us a bit more info...
    What's the radius of the curve they have trouble with?
    Are you using MT coupers, if so, are they the ones best for tight curves?
    Are you using the stock rapidos or Kato knuckle dummy couplers?
    Have you checked the guage *with an NMRA standards guage* of all the wheels on each loco? Have you checked the guage of the track in the problem area?
    Here's where I would start.
  3. Zug

    Zug Member

    The turn it 9 3/4" it the inner loop around the town, there picture on my layout page at http://train.kenttimm.com.

    I'm uin MT long couples, the onse listed for it on the MT converstion charts.

    Iv checked the wheel and track with my MT n-cale guage, everythin is the right spacing and the couplers the right eight.

    I'm thinking about change the sproblem section to use a wider radious curve if I can o it without detroying the town.
  4. hemiadda2d

    hemiadda2d Member

    Do you have a nasty kink in the problem area? My layout back in Minot, ND had that problem.
    The engines you have are compatable with the 9.75"r curves, but the makers didn't say they'd run well...
    At that tight radii, you need FLAWLESS trackwork, joints, and guage.
    Widening the curve will prolly alleviate your situation.
  5. hemiadda2d

    hemiadda2d Member

    Sorry to double, but I used an SD90MAC to track-test my layout. If it doesn't derail anywhere, the track work's good enough.
    The SD90MACs have such a wide wheelbase for each truck, that they become accident-prone.
  6. zeeglen

    zeeglen Member

    Are you using Atlas flex track in your 9.75" curves? From your pictures saw only sectional track, which is the best way to go. I've found that the Altlas flex track goes slightly out of gauge on tight curves just enough to give a 6 axle diesel trouble, the rails are just a little too close together and the Kato SD40-2 lead wheels climb over the rails. Haven't had any problem with Atlas sectional 9.75" track.

    The MT body mount couplers on my SD40-2 need to pull a boxcar with body mount couplers also, trying to match a truck mounted coupler on a boxcar with the SD40-2 body mount derails the boxcar every time on the sharp curves. But have no problem as long as the loco pulls a body mount boxcar.

    Also check rail joints, file a very slight bevel into the rails at the joints to help the flanges glide smoothly past them.

    For derailing on the turnout, is this when backing up? Truck mount couplers twist sideways in reverse and can derail the trucks far easier than with body mount, especially at the points if the very tip of the point is not bent slightly towards the stock rail. Also, if using the Peco #4 turnouts, their frogs are not great (try a NMRA track gauge through them to see what i mean); had to do a lot of frog rework to get mine to work proper (used a Dremel and thin sanding disc). The Peco #6 frogs are much better.
  7. n_gineer

    n_gineer New Member

    The early bird gets the worm, but look what happens to the early worm. I got detention ( an office call in those days) for that one. I was late for class and the teacher gave me the old Early bird thing and I said , yes but look what happened to the early worm.
  8. Zug

    Zug Member

    Thanks for all the replies guys. I'm going o try the body mouted boxcar coupler and se what happens. Everything else about the town loop checks out. All track is standard sections, no flex track.

    Maybe that'll help the switching yard entrance too. The raised hill on the expansion section has canged a bit since those photos. The courve i gone on the far left and goes to the main liht of th new expansion. I now have about 100' of main line:) Mostly fle track, soldered joins using a MT n-scale gauge as a solder spacer. The SD90 go go full on on the track!
  9. zeeglen

    zeeglen Member

    Here's something else to check. Looking at your website, the top right picture shows the inner loop and 2 more tracks against the wall. Is this the one that gives trouble? It looks like a nasty S curve at the inner loop turnout - when the locos come into the loop from the diverging track (moving left to right), as soon as they leave the turnout points they hit a sharp curve in the OPPOSITE direction to the curve formed by the turnout. This virtually guarantees exactly the problem you are having - a single loco has no problem with an S curve, but when coupled to anything, especially with the long overhang, the ends of the 2 locos are forced in opposite directions by the opposing curves and try to swing opposite to each other far more than the couplers were designed to handle.

    If this is your problem, try a left hand turnout here instead. Good luck with this.
  10. zeeglen

    zeeglen Member

    Sorry, ignore that. Looks like with the minimum radius inner loop there is no room for the left hand turnout. But you may have enough room to add a straight section at the points end of the turnout and extend the length of the loop at the expense of the scenery between the inner and outer loops. As long as the straight section is equal or greater than the length of the loco the S curve is eliminated.
  11. zeeglen

    zeeglen Member

    Looks like another pair of S curves (from both points and diverging track) in the far end turnout of the dual track in the expansion section (10th photo). Is that the troublesome switching yard entrance you mentioned? Here a left hand turnout would fit and solve the problem.
  12. storm

    storm Member

    ok i have had problem with sd90's on 9 3/4 curvs befro and all u hav eto do is add 1/4once of wate over the 2 trucks and it will track better. also cheack your trip pin higths as a low trip pin can make everything go wrong
  13. its easy kinda thelocos are geared prolly fare apart so on tight curves they will derail the SD40-2 is ment to run with the GE's and the SD45s and SD40s
  14. SD90

    SD90 Active Member

    I haven't changed the couplers on my SD90 's to MT yet, and I find they pull the first car off the track on my short switches. They don't pull an SD40-2 off though.

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