Modifying MTH passenger coaches to run on less than 22 inch curves

Model Railroader General Discussion (Model Railroader)
1

Hi,

I’ve just bought a SP coach set from MTH - very nice model - but discovered that the curves on my layout are slightly too tight - 21.5 inches - yes, I should have checked first… The coaches cant get around the curves without derailing.

Does anyone have any suggestions on how to modify the couplers to enable these coaches to run on tighter curves?

Thanks

2

Lots of things. First check the obvious, wheel gauge and weight. It’s not all that unusual for even a brand new car to be light, or have wheels out of gauge or both.

Then check that the trucks swivel freely enough. If the trucks are sticking on bits of underframe, they won’t swivel far enough. Fix this by removing the underframe obstructions. File or Dremel.

Then be aware that coupling a long car to a short engine can cause trouble. Two pieces of rolling stock the same length will swing their couplers off centerline the same amount. If you couple an 80 foot car to a long E-unit all is well. Coupling same car to a shorter F-unit can cause trouble. It may be that your car[s] need to be pulled only by long (passenger style) engines.

Couplers are trouble. Truck mount couplers work better on long rolling stock, since they swivel with the trucks, the coupler stays closer to the centerline and is less apt to pull the car off the track sidewise. If you have body mount couplers check that they move from side to side properly. You may find that installing longer couplers helps. In the old days scratch builders would fasten the coupler to a long shank pivoted from the truck bolster, and make a wire coupler keeper to hold the end up and permit the coupler to swing from one side of the car to the other.

3

Not sure if this will work for MTH cars but with Rapido they ask you to switch out your couplers,If you are going to use small radius curves.

All of the major coupler sets come with short, medium and long shank couplers.

Using the short coupler sets your coaches will require wide curves, by swapping out one of the short shank length couplers your car will not require such a wide curve, be using the long shank couplers your car will be able to take its tightest radius.

If you passenger car will still not take your curves then it is time to start to file (or dremel) items off of your truck and also items on the underside of your passenger cars that interfere with the movement of your passenger cars trucks.

4

Thanks very much for the comprehensive reply. Sounds like replacing the couplers is a good place to start.

I think the couplers are Kadee or similar, so a longer shank might do it.

Otherwise a simple hoop of wire to increase the distance between the coupler knuckles may also work.

Thanks again - your advice is much appreciated.

5

Trainman, I wouldn’t go and grind anything off those nice passenger cars just yet. Push the cars individually and very lightly around your 21.5" curves. If they do not derail or ride up the rails it’s not the truck movement. If the rubber diaphragms touch rather firmly when you have the cars coupled together, this may be causing the derailment! As suggested in an other reply I would check out couplers with a longer shank. I have these passenger cars too and they do have fairly short coupler shanks. Take one of the couplers off and see if KaDee have a whisker coupler with a longer shank.

Of course if you have derailing problems with the articulated cars then that’s another matter.

6

Kadee,#146,is a long shank whisker coupler…

Cheers,

Frank

7

I think that this is a pretty darn good summary and should be considered an Action Checklist.

Rich

8

Hello AustraliaJim,

Good suggestion - the cars run just fine. I removed one coupler - yes, shank is fairly short. Will try replacing with a longer shank coupler.

Thanks very much.

9

Hi Frank,

Thanks for the advice - I’ll try the #136.

Cheers

John

10

I have the same exact set. Actually I have 2 MTH passenger sets.

They have two options for the couplers. From the factory they have the close coupled screw hole. You can easily change this to the other screw hole, that provides more clearance for the couplers.

I just changed those stock couplers to the other holes, and that fixed my issues.

Try that first, you might not even need the long shank Kadees.

11

That’s a #146,for the long shank,whisker,John,should you need it…

Cheers,

Frank

12

Kadee doesn’t have a #136 coupler.

Rich

13

Make sure that the Kadee is the long-shank whisker coupler and not the long shank that comes with the older brass centering plate and spring. The MTH coupler pockets will not accept anything but the Kadee ‘whiskers’. I know, I replaced all the couplers on my own MTH Daylight set and only the whiskers will fit. The long shank should cure the problem just fine.

My problem is the opposite, trying to close-couple the cars to where they’ll run on 36" radius. Close-coupled, the cars only negotiate a 40" minimum, and as they come from the factory, they’re set for 22" minimum, which puts them too far apart to really look good.

But they’re gorgeous cars, anyway.

Tom

14

Hi Michael,

Thanks - the couplers came in the other screw hole you mention - this setting was still too tight for my layout. Long shank Kadees seem the best option.

If I get that to work I might just get another set - the NYC 20th Century looks good…

Thanks again,

John

15

Thanks for correcting me - just bought a set, will try out.

16

Tom,

Thanks - yes they are very nice cars - my main interest is British OO, but classic US trains like Morning Daylight are a growing interest - especially with such great models available.

Just bought some long shank whisker Kadees - will try that out.

Thanks again,

John

17

Hi Frank,

Thanks for the advice - the #146 long shank kadee worked perfectly. Easy to change the couplers supplied with the coaches.

With the #146 there is not much clearance between coach ends on my 21.5 inch curves - but still run just fine…probably wouldnt work on curves any tighter.

Can you recommend Kadee sets to change from NRMA horn n hook couplers?

Thanks again,

John

18

Kadee #146 worked just fine - thanks for your advice.

19

TRAINMAN DOWNUNDER,

Most people who change their Horn-Hook coupler’s,will use a standard shank Kadee #5,without draft gear,they have a copper looking flat spring,to keep the coupler centered,they should fit in the draft gear box,that you took the old coupler out of,if you like the whisker style coupler,like the #146,that you got for the passenger car,then you would get the #148 whisker,medium shank coupler,it is just like the #5,but it has the whiskers rather than the copper plate spring,Those two. styles will fit most rolling stock and some Engines…They are sold,in bulk,of 10 and 20pair…Then they have more coupler’s for specialty applications,If you can let us me or the other Forum Members can help…

Cheers,

Frank

20

Frank,

Thanks for the comprehensive advice.

I need to change one horn-hook on a passenger car to connect a train to a diesel with a kadee.

Maybe easier to change the kadee to a horn-hook?

The horn-hook on the passenger car is connected to the bogie - but I guess I could remove and attach a #148 to the underside of the coach at the end? Then test the kadee height above the rails?

Your advice is much appreciated - I’m returning to the world of model trains (30 yr later) - and expanding interests into US rail-roading (HO and On30) - so need to get familiar with models that differ from OO British outline.

This forum has been great.

Regards,

John