Stiff couplers derailing trains, how to fix?

[Baronjutter]

Hi guys, I've got a slight, well major problem.  I have a nicely eased curve after a turnout that some of my locos are derailing the car behind them every single time.  When I laid the track I tested everything with my biggest longest loco, an sd90mac.  I figured if it could do it, anyone else could.

I also have a kato sd40 and kato dash-9, both are shorter but they derail what ever is behind them at the exact same point every time.  The point is the end of the turnout which is where the the butt of the locomotive is at it's maximum swing vs the car behind still being on a straight.  The track its self is fine, all my other locos handle it fine and don't pull their cars off.  It's just this sd40 and dash-9.

After trouble-shooting I realized the other difference between my 3 6-axle locos is the coupler.  the sd90 has a very very loose coupler that can swing in a huge arc.  The Dash-9 had it's stock kato coupler replaced by something else (MT?) and is stiffer and doesn't swing as much.  The sd40 still has its stock kato coupler but it's of a slightly different design and much stiffer/springier than the sd90.

So my question is, how do I fix this?  I can't really change the track geometry.  I could try, but any extra easement I add after the turnout will have to be "paid for" in a tighter radius on the other side.  And I've never done a coupler conversion or replacement let alone trying to modify.

Any fixes?  Carve the little boxes the couplers sit in out?  Some how make them looser?  Replace with another brand/type? Long shank?

The sd90 and dash-9


the sd40


All 3

[davefoxx]

Those long Kato locomotives are known for derailing the first car behind them on sharper curves.  This is compounded, if you are running a truck-mounted coupler on the first freight car.  Try running something with a body-mounted coupler and see if it's better.  Otherwise, I have no suggestion for modifications to the locomotive.  I'd do everything in my power to add the easement, even if that requires a slightly sharper curve, because it's that transition into the curve that's getting you.

DFF

[JoeD]

Part of the proto push to have everything body mounted resulted in the problem you are having.  Wider and wider radius turns are necessary to compensate for that additional swing going through a switch or an S.  My suggestion, if these are body mounts is to try the 1016 which is our longer coupler...that might be enough to get you through the switch.   If this doesn't work, then have a boxcar with a truck mounted coupler behind the loco to compensate for the swing.  Like our Heavyweight Passenger cars and ESM's Mill gon, examples off the top of my head, do not like radius' under 10" without some coupler gymnastics.  What Number switches are you using?

Joe

[bbussey]

Those long Kato locomotives are known for derailing the first car behind them on sharper curves.  This is compounded, if you are running a truck-mounted coupler on the first freight car.  Try running something with a body-mounted coupler and see if it's better.  Otherwise, I have no suggestion for modifications to the locomotive.  I'd do everything in my power to add the easement, even if that requires a slightly sharper curve, because it's that transition into the curve that's getting you.

Agreed.  It's not the "stiffness" of the coupler, it's the length of the wheelbase and the longer distance between the coupler pocket and the truck that swings the entire end porch (and coupler pocket) far outside the outer rail.  The units aren't designed for under 10" or 11" radius and pull rolling stock with truck-mounted couplers.

Having the first trailing car equipped with body-mounted couplers will help.  But if you're running over 9¾" radius, even with easement it may not help.

At the very least, there should be easement on all curves.

[Baronjutter]

Thanks for the info on the 1016, but maybe it's my lack of coupler knowledge, but the 1016 looks exactly like what's installed on the dash-9 already, the shank doesn't look any longer.  Can you tell what's already installed on it from the photo?

The easement is about 15" and the tightest section of the curve is about 12".

[bbussey]

The MTL coupler on the BC Rail unit appears to be a #1015.
 

[bbussey]

Part of the proto push to have everything body mounted resulted in the problem you are having.  Wider and wider radius turns are necessary to compensate for that additional swing going through a switch or an S ...

It's only an issue with long cars and motive power with long wheelbases.  The majority of equipment from the Steam and Transition eras will work without incident.  You need wider radii for modern equipment.

[Ed Kapuscinski]

Or... keep in mind, it looks like there's some painting and weathering in play. I've often had issues where paint fouls the free swing of couplers. You might want to make sure they're as free swinging as you think.

[Baronjutter]

If I order 2 of those medium-shank couplers think hat will solve the problem or should I try re-doing my track first?

[bbussey]

If the MTL coupler configuration is working on the BC Rail unit to your satisfaction, I recommend changing the couplers on the other two units to match the configuration of the BC Rail unit.  The truck/coupler distance is similar on all three units, and it's far easier to try that rather than rearranging your track.

[Bob Horn]

I think the 40-2 is the old Kato push in style with the wings for springs. New style Kato will fix that or 2004 MTL. Bob

[ednadolski]

If I order 2 of those medium-shank couplers think hat will solve the problem or should I try re-doing my track first?

I'd suggest fixing the track if at all possible.   Otherwise you will have to fix every loco and rolling stock that you will want to use on that track.

Ed

[Baronjutter]

The SD40 is indeed the "wing" style and it's quite a bit stiffer than the sd90's copper-plate system which offers barely any resistance. 

I think I'm going to try to re-jigger my track a bit.  Now that I have my backdrop up I can probably spare an extra inch or so since there's a void between the wall and the table now.  I just don't want to re-do the track to fix the problem at the turnout only to find in order to do so I created a 9" curve or something on the other end.

Lucky for me it's all ME flex so I can play with curves and run trains on them without needing pins or glue.  I used to be very anti-ME flex but since I was forced into giving it a try I've learned to like it. 

[Baronjutter]

Fixed it by doing this.  What an easy fix!!

[Scottl]

That is holding the curve without any adhesive?