Super Elevation and Couplers

[Sir TophamHatt]

Now I've super elevated some corners, I've found some couplings are catching on the slightly higher sleeper.

 

I plan to upgrade most trains to Kadee couplings which I think may solve this but is it simple because I've banked the track too much?

[34theletterbetweenB&D]

Which coupler type is it that is catching?

Does the catching happen solely at locations where the transitions from plane to canted occur? If so make the transition in and out of cant longer.

How much cant is applied? Steam era scale cant in OO maxes at the high rail being 2mm above the lower rail. (It may be more on our modern go faster railway.)

Is the cant achieved with the mean track height remaining constant? (Lower rail falls, higher rail rises.)

 

If the couplers don't catch on flat track, they shouldn't catch on canted. The axles should remain parallel to the sleepers, so the vehicle and thus coupler height should be constant above the sleepers.

[The Johnster]

You probably haven't banked the track too much as much as you've done it too suddenly; superelevation needs a transition curve at each end.  In theory, you could bank it vertical so long as the transition was gentle enough and the speed was high enough!  Same goes for changes in gradient and, ideally, for ordinary curves as well but train set geometry does not for this.

 

The best way to avoid the problem is to lay your curves as large a radius as possible, and superelevate gently, but I appreciate you may not have the room for this.  Set track curvature, even no.4, is much sharper than any prototype curve on a running line scales to, and even most 'finescale' layouts incorporate curves that would have very severe speed restrictions on them in reality.  You will realise this if you attempt to use 'scale' couplings; your buffers will lock even when you are hauling the stock, and force the wagons off the road.

[HLT 0109]

I agree with everything that others have said but I appear to have accidentally achieved super elevation on my layout on a third radius curve - see attached photos  It is evidevt from the second photo that the approach is level but the cant in the first photo is genuine - I promise you!  I am sure if I tried to replicate it I would have difficulty but even 1mm elevation at the centre of the curve will be visible.  The cant appeared after I modified the track to insert a curved point crossover and the ballast has fixed the track in place.  As I think you can see, I do use Kadee couplings.

 

Harold.

[Il Grifone]

The coupling droppers should clear the rail surface by 1/32", so there should be no question of them catching in the sleepers. The transition to canted track should be gradual as should the transition to curved track. (Pedantic as it's not always possible on a model.)

[Sir TophamHatt]

So, the plot thickens.

 

 

Video: https://drive.google.com/open?id=1r9t_G-4nbbaVdkOSsnVp68ZAMXSxF3WF

 

It's the Dapol Class 68 that does it when running light loco.

I've noticed the coupler does dip down somewhat.

 

The curve is the 2nd largest of Hornby (sorry don't know what radius this is).

 

It seems the coupling jumps over the rail as the loco is heading round the bend and catches on the outside sleeper sections.

 

I don't plan on using it light loco much, if at all, but didn't want this to affect other trains.

 

Ran a Class 170 in the same spot and it doesn't happen. Tried a couple of steam locos and they're fine too - although the may have been carrying a coach.

Edited September 10, 2018 by Sir TophamHatt

[34theletterbetweenB&D]

Drooping appears to be the trouble. Maybe the whole front end piece of the loco abomination drooping, or the coupler mount set too low, or the coupling fitting to slack and thus allowing the coupler to droop, or some combination of these factors. I have some recollection of other owners finding the tension lock coupler was set too low. A scan of the Dapol 68 thread might shed some light.

[HLT 0109]

How come the coupler is outside the rail?  I know you said it seems to jump it but I have never seen that before, with a loco that is still on the rails.  If it remained between the rails, it would probably not catch the sleepers.  I think the second largest of Hornby's curves would 3rd radius.

[The Johnster]

This one's drooping rather than set too low.  I'd check that it is sitting correctly in it's NEM dovetail; if it isn't, you should be able to push it back into place, and a spot of superglue will secure it there; take care not to get any on the waggly bit that gives the coupling it's flexibility. 

 

I've had a few of these dovetails that are looser than others for no obvious reason, and one on a Hornby 42xx fell town off, but the fix is easy and effective.  If it is another problem, please ignore my ravings and let us know the details.

[tractor_37260]

How come the coupler is outside the rail?  I know you said it seems to jump it but I have never seen that before, with a loco that is still on the rails.  If it remained between the rails, it would probably not catch the sleepers.  I think the second largest of Hornby's curves would 3rd radius.

 

Assuming the 68 has a CC cam ?  it would appear that the coupling assembly has not returned to it's central position, or perhaps it's catching on some of the BB detail ? or the CC mechanism is sticking - a common problem.  As mentioned above, it's also looks a bit low/droopy ? 

Edited September 11, 2018 by tractor_37260

[Sir TophamHatt]

How come the coupler is outside the rail?  I know you said it seems to jump it but I have never seen that before, with a loco that is still on the rails.

Sorry, I can't take another video to investigate now as I changed it to a Kadee yesterday and put the other coupling away in the box.

 

If it does it with another loco, I'll update here.

[ejstubbs]

I think the second largest of Hornby's curves would 3rd radius.

 

Correct (unless you count the 852mm radius "special" curves for use with the Y turnout).  3rd radius is 505mm.

Edited September 12, 2018 by ejstubbs