superelevation, banking or cant question

[NittenDormer]

Hopefully simple question : when track is super elevated going round a bend, is it always the case that the outer rail goes higher, or does the inner rail ever get lowered?

I am going to be using a cork underlay, cut lengthways along the centre of the track, wondering if using two different thicknesses of cork (to support the inside / outside of the track) would be a suitable approach.

Thanks

[96701]

What gauge and scale?

[F-UnitMad]

A bit of advice from experience: start the cant on the straight track, not once the curve has started. Asking a model loco to twist and turn at the same time is asking for trouble.

[Miss Prism]

In the absence of twisting the track base, which will give the most natural and gradual transition into a section of superelevated track, your best bet is likely to be some layers of paper, glued with PVA and sanded when dry, and then put the cork on top. Cork layers can be sanded, but is more effort. If you use different thicknesses of cork layer (thicker on the outside of the curve, thinner on the inside), there is a danger you track will not be fully supported underneath the transverse length of each timber. Depends a bit on what your track is and how you intend to lay it of course.

 

 

 

[alibuchan]

of for very easy use, you can just buy this.....http://www.kernowmodelrailcentre.com/p/49568/86613-Tillig-HO-Styrostone-curve-super-elevation-sheet-950mm

 

which gives the correct angle for the cant and is £2 for nearly 1m.

 

they are expecting it back in soon or you can try other places.

 

Alistair

Edited February 9, 2018 by alibuchan

[NittenDormer]

of for very easy use, you can just buy this.....http://www.kernowmodelrailcentre.com/p/49568/86613-Tillig-HO-Styrostone-curve-super-elevation-sheet-950mm

 

which gives the correct angle for the cant and is £2 for nearly 1m.

 

they are expecting it back in soon or you can try other places.

 

Alistair

that looks far too simple and straightforward.

[Miss Prism]

The Tillig wedge gives a fixed superelevation. What you need is gradual transition, particularly if you are using fixed chassis.

Edited February 9, 2018 by Miss Prism

[DCB]

The superelevation needs to start gently as does the transition from straight to curve so probably best to start both together otherwise the trains will lurch horribly if the cant starts on the straight. It always looks to me as if the inner rail drops by as much as the outer rises.   I wouldn't attempt superelevation below about 2ft radius in 00 as rigid chassis locos with fine flanges can't cope with that much twist in the trackbed.  It is important with double track that the tracks are canted separately rather than the whole double track bed canted over.    Most model curves need check rails rather than superelevation.

[AndyID]

Hopefully simple question : when track is super elevated going round a bend, is it always the case that the outer rail goes higher, or does the inner rail ever get lowered?

I am going to be using a cork underlay, cut lengthways along the centre of the track, wondering if using two different thicknesses of cork (to support the inside / outside of the track) would be a suitable approach.

Thanks

 

I believe some people deliberately reverse the camber (low on the outside) on very tight curves like those in hidden reversing loops as it reduces the tendency for long trains to de-rail. I've never tried it myself but it sounds like it might work.

[34theletterbetweenB&D]

... It always looks to me as if the inner rail drops by as much as the outer rises...

 From observation I believe that to be correct, perhaps a track specialist can advise? Mechanically it is what I would expect as the mean height of the vehicles thereby does not change (much), reducing the resultant forces to only thse from the necessary accelerations in transition from tangent/curve and vertical/cant.

[ISW]

 From observation I believe that to be correct, perhaps a track specialist can advise? Mechanically it is what I would expect as the mean height of the vehicles thereby does not change (much), reducing the resultant forces to only thse from the necessary accelerations in transition from tangent/curve and vertical/cant.

From my 30 odd years working on railways, the superelevation is always applied by raising the outside rail. The one exception I had was Singapore Metro North-East Line & Changi Lines (built concurrently) where the superelevation of the tunnel tracks was applied by rotating the whole trackform about the centroid of the vehicle (~1m above the plane of the rails). Causes all manner of headaches, and I believe this was not repeated.

 

Ian

[Pete the Elaner]

I tried superelevation on a club layout over 25 years ago.

 

The trains which handled it looked great. Some of the rolling stock did not allow the bogies to 'twist' (IIRC, they were Lima Mk1's with Westward Commonwealth bogies). These had a tendency to go straight on once the superelevation ceased.

I went to University before seeing this experiment through & I believe the track was flattened soon afterwards. If I had continued with the layout, I think I would have probably flattened it myself.

I never tried it again because I have not since built a layout with curves on the scenic section.

Would I try it again? - Probably not.

 

I have since read that this needs to be introduced & removed VERY gradually in order to work properly, like 2-3' between flat & fully elevated for 00 scale.

 

It was also earlier asked in this thread what gauge & scale? This is important because most RTR has rigid wheelbases & will be much happier on flat track so stock with suspension or compensated chassis will be more likely to cope with it; chassis compensation being more common in P4/S7 than in 00 or N.

 

If you are still keen to try it, then good luck. It won't be easy to get right but should look great if you can do it.

[Gwiwer]

I used canted track around appropriate curves on Penhayle Bay.

 

For OO it is only necessary - at the most - to shim a sliver of Plasticard beneath the outer ends of sleepers on the side to be superelevated.  If you start shaving cork you could run into all manner of frustrating and avoidable problems not least of which is the potential to over-cant.  The outer rail is elevated; I know of nowhere where the inner rail is lowered.  And remember that each track of a double track railway is separately treated rather than having the track on the outside of the curve with both its rails higher than those on the inside.

 

It is quite easy to ballast accordingly once the superelevation is in place and the line tested to ensure it doesn't cause problems.  To the naked eye the difference should be barely visible - almost begging the question "Is it there?"  You are, after all, replicating in scale a very small amount of superelevation in real life.

 

It is possible to create transitions into and out of superelevation though the difference is hard to see; the difference in performance however might equate to that where transition curves are used instead of trains lurching from straight to fixed-radius curve and back.  Using flexi-track this really isn't hard at all.  The trick is "less is more" and not to overdo it.

 

Here is a still image of one curve which has superelevation though in this case the effect is slightly exaggerated by the model which has a realistic (if over-scale) tilting action.  

 

 

And a video which I am told breaks a few of the rules.  A station on an S-bend with the track canted around both curves.   That imparts a just-visible twist as the cant reverses at the precise moment the direction of curve also reverses.  Experienced modellers have suggested to me that this was a recipe for disaster.  I never ever experienced a problem here other than coupler over-ride which was caused by the downhill gradient rather than the curvature or the cant.  The superelevation (or cant - those terms are interchangeable but banking means something altogether different on the railway) is visible but only just.   

[Chuffer Davies]

We (the Shipley MRS EM group) have used superelevation on two layouts these being Hungerford and Clayton. The following picture illustrates the superelevation as applied on Clayton, our newest layout which is still under construction.

The approach we take is to lay separate lengths of 3mm cork underlay for each track. This is then roughly worked by using a Stanley knife blade edge on as a scraper. The blade leaves a rough surface but shifts material quickly. Once the elevation is roughly as wanted we then use glass paper wrapped around a cork sanding block to smooth down the underlay to restore the surface. Running the flat of your fingers over the surface is a good way of sensing any lumps and bumps.

 

I would agree that you don’t want to make the angle too severe as it will look wrong. We start the transition at the start of the curve and take around 300mm to reach the full elevation. We have not experienced any derailments using this approach and have both compensated and rigid frame locomotives on our layouts.

 

Regards,

Frank

[njee20]

I just chucked some 1mm card strips under the outside rail on my (n gauge) layout. Nothing's ever derailed. I let it sort itself out on the straights. It's quite subtle, but that's what I was after, I think it's one of those things that can be overdone, but I'm pleased with it. Weirdly I also have a Voyager demonstrating it, one missing the coupler it appears!

 

Edited February 10, 2018 by njee20

[NittenDormer]

Thanks all for the suggestions, from carefully thought out to 'just chucked some card'. I'm an OOer.

 

Gwiwer - lovely video. Reminds me of the classic comedy situation where 10 people come out of a mini, then 10 more, then 10 more...

 

Thoughts of fiddling with cork abandoned, I am off to eat some more cereal. Bits of card testing commemces tomorrow.

[royaloak]

The maximum cant allowed is 6 inches so only 2mm in OO gauge remembering that the rails are much closer together than they should be.

 

Models also have rigid wheelbases/bogies whereas real trains have suspension allowing axles to move individually so you will have to gently cant the track on the straight so the locos arrive at the curve already canted.

 

A whole lot of trouble that still wont look right because your trains will be canted on straight track or, if you try and cant the track prototypically derail a lot due to the lack of suspension on the stock.

[Dagworth]

The maximum cant allowed is 6 inches so only 2mm in OO gauge remembering that the rails are much closer together than they should be.

 

Models also have rigid wheelbases/bogies whereas real trains have suspension allowing axles to move individually so you will have to gently cant the track on the straight so the locos arrive at the curve already canted.

 

A whole lot of trouble that still wont look right because your trains will be canted on straight track or, if you try and cant the track prototypically derail a lot due to the lack of suspension on the stock.

The answer there is transition curves, the curve starts gradually and gets tighter, the cant goes with it. 

 

Dagworth had cant on the curves, around a millimetre was plenty. I've not bothered on Ravensclyffe though, the curves are much gentler.

 

Andi

[Bomag]

Going back to the original question, when I was in P/W design the long section profile for elevation was always on the low rail (datum was always the 6 foot rail on anything other than single line) so unless any down gradient was more than the rate of increase in cant then the outside rail will always be raised rather than the inside rail lowered.

 

Having played round with adding cant in both OO and N an equivalent of 200mm in OO and 300mm in N looks quite good (150mm is prototypical max) but only if there are transitions of about the same length of two of the longest coaches.

[JZ]

 It is important with double track that the tracks are canted separately rather than the whole double track bed canted over.   

 

Not always the case. At Freshford, it goes from the whole trackbed canted, to each separately canted, on the reverse curves through the station. I do have the advantage of being able to see it from the cab window.

 

As for the Tillig superelevation foam strip. I have used it successfully on Gurney Slade. It was used under the 3mm Depron foam underlay. Start on the straight and sand it away to nothing. Using under also helps with the transition. I have a phot which shows it to good effect, but can't find the damn thing at the moment.