Tight Curves certain wagons derail - not all

[Chrisjh]

We have just finished converting a very old layout to DCC however one of the curves is rather tight not sure what radius it is, but one or two of my wagons (not all) derail and or decouple. Unfortunately the track cannot be relaid as it has been previously super glued into position (it would appear) as we have tried to relay the track but it wont budge. So just wondering if anyone knows some one who manuafctures something like a template that would fit inside the track so the wheels adhere to the track. We made a tempoary template which we inserted inside the track using cardboard and this did indeed work and the wagons stopped derailing / decoupling, as the wheels were forced to follow the curvature of the track. Appreciate any thoughts, many thanks.

 

Best Wishes,

Chris

[ikcdab]

You mean a checkrail then? Take a length of rail from another piece of track and use that. 

[The Johnster]

Checkrail, they are used on the big railway as well, on the inside rail of the problem curve laid (superglued) direct to the sleepers, but it's a little more complex than just taking a peice of rail and using that, it has to be curved to an exact radius to provide the same gap between it and the running rail over what might be a considerable length.  I have had success with this by laying the bottom of the checkrail to the outside edge of the moulded chairs, but if your curve is very tight you made need a bit more gap.  It is going to be a trial-and-error thing, as too tight a gap will drag on your flanges, and too loose will fail to prevent derailments.  You may have problems with long wheelbase locos and wagons because of the sharper angle at which the flange is held to the rail.  The exact size of the gap will be determined by the wheel profile of the locos and stock, the radius of the curve, and the wheelbase of the longest fixed-wheelbase vehicle to be using the curve.  The shorter the checkrail the easier it will be to install it without those problems.

[Dunalastair]

Worth a look at previous discussions, perhaps? Though generally approached from a cosmetic rather than practical angle.

e.g. https://www.rmweb.co.uk/forums/topic/142307-check-rails-on-curves/

I would have thought that bending / tapering the checkrail at the ends (as on points) might help. 

[tom s]

if you fit some weights to the wagons like some coins, does the problem persist?

[tom s]

Example check rail

[Michael Hodgson]

A checkrail has to be laid fairly accurately to be of any use - the gap must not be too tight for the flanges of any of the vehicles, nor must it be too wide, or it won't stop derailments.

 

But if most of the stock is OK but certain wagons derail, I would suspect the fault lies with them, not with the track.  First check the back to backs.  If they are bogie vehicles, do they have enough swing for the curve - or are they perhaps catching on the body when they do swing?

Another possibility is forces acting through the couplings.  The tension can cause wagons to lift off if the couplings don't pivot relative to one another, or as Tom S suggests above, if the stock is too light.  You don't want to add too much weight or you'll have trouble on inclines.  I aim for most of my 4-wheel wagons to weigh about the same, likewise but heavier with bogie stock.  I try to avoid putting heavy stock behind lightweight stock because that seems to cause trouble on tighter curves.

 

[Chrisjh]

Many thanks Gents much appreciated yes I think a check rail is the answer. I have checked the couplings using standard NEM couplings, Kaydee Couplings and megnetic couplings and the problem persists. Tried experimeneting with adding weights and lossening the bogies, so I think the answer is suggested is to use a check rail.

 

Many thanks and Best Wishes,

Chris 

[F-UnitMad]

34 minutes ago, Chrisjh said:

Many thanks Gents much appreciated yes I think a check rail is the answer. I have checked the couplings using standard NEM couplings, Kaydee Couplings and megnetic couplings and the problem persists. Tried experimeneting with adding weights and lossening the bogies, so I think the answer is suggested is to use a check rail.

 

Many thanks and Best Wishes,

Chris 

I'm assuming from this that it's OO gauge stock? (No one has asked what scale!!)

You also mention 'loosening bogies', so can we also assume it is long stock that is derailing, not short 4-wheelers?

Do these pieces of stock derail when tried on their own round the curve, or when coupled up? Have you checked close up that buffers aren't contacting neighbouring vehicles and puting the couplers under strain? Or check the bogies aren't turning so much that they (or the wheels) are contacting part of the underframe, so they can't turn more as the vehicle goes around the curve. Either of those situations can cause derailments, & a check rail won't help.

How flat and level is the track? If the curve is 'warped' in any way that can cause trouble with long stock.

I ask all these questions because bogie stock is usually more forgiving than fixed axle stock - that's why pretty much everything on American railroads ride on bogies, or 'trucks' in their terms, so I'm intrigued why it seems to be bogie stock giving you trouble.

[Dunalastair]

For 6.5mm gauge, trains of 'shorty' bogie stock will happily go around 45mm radius curves without checkrails, but four wheel stock of a prototype outline will bind...

 

 

 

The equivalent for 16.5mm gauge would be about 115mm or 4.5" so tight radii are possible with the right rolling stock.

[Michael Hodgson]

OK if you build your layout on a dinner plate

[Dunalastair]

1 hour ago, Michael Hodgson said:

OK if you build your layout on a dinner plate

 

Yes, this is the day for over-loaded dinner plates, even if the circle is usually around the Christmas Tree,  but the small radius Rokuhan 180 degree curves did allow me to build a trial N6.5 layout on a mantlepiece (the return track loops under the hillside) ...

 

 

... and later to build a fantasy layout with a serpentine track layout running through a subterranean cavern (Walking on Glass). 

 

 

I agree that super-small radius curves are not for every layout, but that they work shows that reduced radius need not be an insuperabale issue, especially with appropriate bogie stock.

 

After all, if it is good enough for the prototype ...

 

 

https://en.wikipedia.org/wiki/Minimum_railway_curve_radius

Edited December 25, 2023 by Dunalastair

[DCB]

6 hours ago, tom s said:

Example check rail

 

For a working rather than cosmetic check rail you need a lot more clearance than that, I used a couple on some awkward curves and generally taper the gap from wide at the start to actually pull the outer wheel flange away from the rail.   Mine are higher than the running rail (as per modern full size practice  which has seen flangeless wheels banned from NetworkFail or what ever this weeks title is.)    Fixing them is a challenge, ideally use set track rail which retains its shape when flexed, mine are soldered to screw heads but you could use cut down sleepers inserted between existing sleepers or solder to brass pins through sleepers.

13 hours ago, Chrisjh said:

We have just finished converting a very old layout to DCC however one of the curves is rather tight not sure what radius it is, but one or two of my wagons (not all) derail and or decouple. 

 

Best Wishes,

Chris

Have you cleaned the track.   Not the top, the sides of the rail head the "Gauge Corner"  My outdoor battery powered 00 line needed the gauge corner cleaned to prevent derailments on occasion.    There does not seem to be any commercially available track cleaner capable of cleaning the inside edges apart from an abrasive rubber.   I have a knurled wheel Triang Dock shunter with different gear ratios for each axle planned as a rail grinder rather than cleaner.

[Chrisjh]

Many thanks Gents very interesting, sorry its a 00 Gauge layout. Good point I will check the distance between the buffers I hadn't thought of that exellent point. The track is cleaned and appears to be fairly clean. 

 

Many thanks and Best Wishes,

Chris