Laying flextrack - to cut or not to cut (long curving section)

[AndrueC]

I'm laying track and I have a flowing layout. I'm about to lay a third section of flexitrack which goes round two 90 degree curves (both at least 3rd radius, if not more) with a short straight section between them then onto a some gentler curves. I've soldered the first two sections together because the joint is in the middle of a curve. This next joint will also be in the middle of the second curve. As luck would have it the next joint is on a straight so won't need soldering. So the result will be three lengths of n-scale flexitrack soldered together to form a 180 degree turn in total.

 

So my question: How many lengths of flexitrack is it reasonable to solder together? The layout is in my spare bedroom which is north facing so temperature variations are probably 16c to 30c.

 

It doesn't seem sensible to cut a length of flexitrack just so that I can have an unsoldered joint with an expansion gap but is there a point at which it becomes essential?

Edited April 13, 2022 by AndrueC

[Dr.Glum]

I used to have a 00 loft layout, about 24ft x 8ft and it suffered a large annual temperature range e.g. 0degC to 30-33degC, i.e. twice what you are suggesting. I soldered all joints (AFAIK) so there were some continuous runs of at least 20ft between points. I had read about expansion problems and worried about it, but then over 10 years I never had any evidence of a problem. Mind you, that was 00. Will that make a difference? I don't know.

Points are good because the insulating rail joiners automatically make a break, and I used to be generous with the gap on some to get a clickety-clack. Good luck.

[SM42]

In theory ( IIRC) as long as the track is firmly and evenly fixed down when the temperature is somewhere in the mid range of the extremities ( 22C say) and the basic structure of the track holds together then any expansion will take place at the ends of the rails and not force things out of alignment. 

 

However, theory and practice don't always mix, so I would not create longer runs than are absolutely necessary without some form of expansion joint and use the natural track breaks on the straights  rather than  cut one 

Personally I think you have reached a good point at 3 lengths to leave a gap.

 

 

Andy

 

[melmerby]

12 hours ago, AndrueC said:

I'm laying track and I have a flowing layout. I'm about to lay a third section of flexitrack which goes round two 90 degree curves (both at least 3rd radius, if not more) with a short straight section between them then onto a some gentler curves. I've soldered the first two sections together because the joint is in the middle of a curve. This next joint will also be in the middle of the second curve. As luck would have it the next joint is on a straight so won't need soldering. So the result will be three lengths of n-scale flexitrack soldered together to form a 180 degree turn in total.

 

So my question: How many lengths of flexitrack is it reasonable to solder together? The layout is in my spare bedroom which is north facing so temperature variations are probably 16c to 30c.

 

It doesn't seem sensible to cut a length of flexitrack just so that I can have an unsoldered joint with an expansion gap but is there a point at which it becomes essential?

Why are you soldering?

I don't solder mine at all, unless I need a short length (maybe 10cm) to finish a run.

All joints use Peco joiners for alignment. As long as the track is well fixed down there is no problem.

BTW my railway room has been below freezing and up to 35C or more. It stands in the garden with south facing windows!

[Matt]

On one of my old layouts in a spare room facing east I suffered a piece of track that buckled so badly it popped its chairs over a significant length. I’ve no idea what temp variation might have been to cause but after that I kept blinds in room down when I wasn’t there. I guess the track might have been in compression before the temperature effect. Never had a problem since but designed my train room in this house to have north facing roof lights to minimise risk of temperature fluctuation and sun damage

[AndrueC]

9 hours ago, melmerby said:

Why are you soldering?

I don't solder mine at all, unless I need a short length (maybe 10cm) to finish a run.

All joints use Peco joiners for alignment. As long as the track is well fixed down there is no problem.

BTW my railway room has been below freezing and up to 35C or more. It stands in the garden with south facing windows!

I'm only soldering joints that are in the middle of a curve to minimise the risk of getting a dogleg. My track is glued to foam underlay which is glued to the baseboard and there is a bit of give to it. At the radii I'm using (should be at least third radius if I follow my plan) there doesn't seem much pressure from the track but soldering joints that might be under particular pressure seems prudent.

[Bernard Lamb]

10 hours ago, AndrueC said:

I'm only soldering joints that are in the middle of a curve to minimise the risk of getting a dogleg. My track is glued to foam underlay which is glued to the baseboard and there is a bit of give to it. At the radii I'm using (should be at least third radius if I follow my plan) there doesn't seem much pressure from the track but soldering joints that might be under particular pressure seems prudent.

There should be no need to solder if you curve the track to a slightly smaller radius and then ease it back to the radius that you need as you lay it.

Don't tell the experts but you can even put a very slight dog leg in the rail close to the end to ensure that there is no pressure on the rail joiner.

Bernard

[Mick38]

Good luck with your 180 degree curve! My track popped up when expansion won over the restraint of being glued in place. I would certainly recommend no longer than two meters soldered up, and allow for the inevitable expansion at the rail joiners. Nice to hear the clickerty-clack anyway.

[Michael Hodgson]

I have known track to buckle because of heat in a former loft layout and I've always found flexible track difficult to lay on curves because of dog-legs at joints, even by staggering them.  However I have sometimes found a strategically placed pin outside the outer rail at the joiner helped to avoid/reduce dog-legs. 

 

I've always just relied on the unrealistic fishplates to join them both mechanically and electrically, and soldering the rails together had never even occurred to me, but it does sound like a good idea.  I only soldered the track feeds and that worked OK with conventional DC, though I did sometimes have trouble with the joiners losing continuity which I have always blamed, perhaps wrongly, on their quality.  Sometimes such failures could be fixed by nipping the joiner with a pair of pliers, but a better repair was by soldering not the joiner itself but by bridging with a short length of bare wire as an electrical bond, similar to the electrical bonding carried out for prototype track circuits.  I have taken on board DCC advice to use a dropper on each separate length of rail but assumed that advice was also because of the poor electrical quality of the joiners.

 

With hindsight, I think I need to revise my approach to flexi-track and joiners and the way I have used them.

 

 

[RobinofLoxley]

Come to this a bit late judging by the latest photos from the layout....

 

I dont think the temperature range is wide enough to be an issue. So its about the best way to lay a half loop in flexitrack. Ive never done it, and neither have most people. Someone who has laid a helix using flexi would be good to ask, I should think thats the highest level of xpertise available. Where are they when you want them?

 

I laid all my long tight curves in setrack to avoid this problem, but had I been doing it from flexi I am sure I would have soldered two sections at least together. If you think expansion could be a problem, imagine you had fixed reference points at each end of the planned curve, that had compensation for expansion in the approaches, for example by gaps at the joints. So if the curved section expands, it does so by trying to bulge. If its all glued down it cant do that but even so if there are exapnsion gaps at each end of the bulge, based on the small T differential, Im sure that would work. It seems preferable to the risk of a kink developing at a fishplate join in the bulge. I have never glues any track down but I imagine creeping on the joint as it dries could be an issue requiring very careful pinning.

 

As a rule I have soldered short sections onto longer ones to reduce dropper making. Original fishplates which i have a lot of where I have pulled them off setrack items, are good quality but replacement ones corrode quite quickly, so if I have to use those I solder as a rule. Plenty of places where Im using clear insulating fishplates to create some gaps. Very little solder, on the outside of the rail only, makes a good and unobtrusive joint.

[Michael Hodgson]

1 hour ago, RobinofLoxley said:

Come to this a bit late judging by the latest photos from the layout....

 

I dont think the temperature range is wide enough to be an issue. So its about the best way to lay a half loop in flexitrack. Ive never done it, and neither have most people. Someone who has laid a helix using flexi would be good to ask, I should think thats the highest level of xpertise available. Where are they when you want them?

 

 

Room ambient temperature range varies depending on the type of premises, and no doubt from country to country.  Lofts can be worse than sheds which are usually worse than indoor rooms in the house.  Insulation and ventilation can help, but may not be enough.  Outdoor layouts can suffer badly from the sun directly heating the rails like the full size railway - the metal quickly gets too hot to touch although there may be a pleasant breeze in the air above.

 

Threads on building a hellix tend to suggest it's easier using set track.

[DCB]

16 hours ago, RobinofLoxley said:

Come to this a bit late judging by the latest photos from the layout....

 

I laid all my long tight curves in setrack to avoid this problem, but had I been doing it from flexi I am sure I would have soldered two sections at least together. If you think expansion could be a problem, imagine you had fixed reference points at each end of the planned curve, that had compensation for expansion in the approaches, for example by gaps at the joints. So if the curved section expands, it does so by trying to bulge. If its all glued down it cant do that but even so if there are exapnsion gaps at each end of the bulge, based on the small T differential, Im sure that would work. It seems preferable to the risk of a kink developing at a fishplate join in the bulge. I have never glues any track down but I imagine creeping on the joint as it dries could be an issue requiring very careful pinning.

 Talking 00 code 100 here I also use set track  for sharp curves, anything less than 2ft radius as it does not kink like flexi.  I have a 40" section across a lifting flap which suffers from expansion, as it is by a window, with a blind.  the tracks sometimes foul at the ends  and or rails break out of their soldered fixings.  That is despite generous rail gaps and two per 40" length.   My garden railway has it's track set in concrete and is laid on hot days with small rail gaps which open out far more than the theorists predict, I get gauge narrowing on curves.  Re laying during winter leads to broken chairs and badly distorted track eve if ridiculous expansion gaps are left.    Father in Laws outside branch suffers with broken chairs where the track expands and the track bed is fixed, this movement also snaps the droppers, but quite often we don't notice/ bother to  re solder them.  I have tried soldering rails together, it doesn't work for me, the fishplate stays attached to one rail the other soon comes loose. Then again my success rate soldering droppers is pretty dire so I now usually solder wires to fishplates to avoid ruining too many sleepers

[Reorte]

Laying on foam was mentioned - is that flexible enough to accommodate some of the expansion?

 

I guess laying the track when the temperature's in the middle of the expected range might minimise issues.

[AndrueC]

5 hours ago, Reorte said:

Laying on foam was mentioned - is that flexible enough to accommodate some of the expansion?

 

I guess laying the track when the temperature's in the middle of the expected range might minimise issues.

I've not noticed any issues so far but then temperatures haven't varied by much. Might be 3c higher than when I laid the track. None of my curves are tighter than 3rd radius as I set AnyRail up to warn me if any part exceeded that. The curves under discussion are greater than 3rd by a bit.

Edited May 31, 2022 by AndrueC

[Il Grifone]

I always make sure that the ends of curved rails are curved to the required radius to avoid any tendency to straighten out and cause dog-legs. in my experience, even proprietary track sections tend to be straight at the ends.

Staggering the joints will help too.

[Philou]

I am pleased to find this topic as later this year I shall (hopefully) start laying track in a barn that will be insulated but not to the max due to sloping ceilings and low headroom, thus I expect there will be some variation in temperature. The wisdom that I have recently received is to solder the joiners to one section of flexi track, pin to the desired curve with the joiners towards mid-curve keeping them parallel and then solder the next length of track into the joiners and work the curve into place pinning as you go along. Snip off the excess as desired both ends (easy now with a track cutter).

 

When I did my first big layout in the late 60s, I hadn't heard of soldering joiners and I did try pre-bending the track but even on a 3ft radius, it wasn't satisfactory due to malformed curves or dog-legs. Cutting excess rail in those days was with a junior hacksaw and that wasn't too clever due to the form of the frame of the saw below the blade - used to dig into the fibreboard.

 

Yay for the clacketty-clack! I shall be re-cutting the top surface of my flexi once laid into panel-length sections to maximise the clacketty-clack and clicketty-click!

 

Cheers,

 

Philip

[Harlequin]

I wonder if there’s a correlation between kinks in curves and pinned track? And maybe pinning into a soft substrate?

 

I have most recently glued my track onto cork, on a ply base and while obviously I had to ensure the joins in the curves were smooth while the glue set, I haven’t had any problems with kinks in the curves since then. I didn't pre-curve the track in any way and I never felt the need to solder any rail joints but I did employ a trick that someone recommended, which was to stagger the rail joins in curves by a couple of sleepers.

 

(Code 75 Streamline HO/OO, 2ft radius, BTW.)

 

Edited June 1, 2022 by Harlequin

[Il Grifone]

Sometimes I have found it necessary to slide the rail out of the plastic sleeper base to curve it smoothly. It's a bit of a pain to remove (and even more so to put it back!). Doing this care must be taken to not twist the rail

Edited June 2, 2022 by Il Grifone
An 'e' went walkabout!

[cypherman]

I used to have a loft layout which had similar temperature ranges over the year. We soldered the joints to make a good electrical contact. It was 20ftx16ft in size. It was a terrible mistake as when it became really hot the track buckled and warped. Had to unsolder the joints. The same happened to friends 16 mm narrow gauge garden layout. Expansion points had been put in place and there was no soldering done as it is a live steam/radio-controlled railway, But they were not wide enough causing the track to buckle. So in some cases it appears you are damned if you do and damned if you do not. In the end for my own layout I used wire droppers to link the rails.

[Philou]

@Harlequin I have heard of staggering joints but never seen it done. Did you have any trouble sliding your Code75 rails in the sleepers? I remember when adjusting my ancient Peco Code100, it wasn't a straight forward slide-on, just as @Il Grifone mentioned above.

 

Cheers,

 

Philip

[simonmcp]

I read somewhere that it's a good idea to file a slight taper on the end of the rail to help sliding it into the chairs.

[Il Grifone]

On 03/06/2022 at 19:42, simonmcp said:

I read somewhere that it's a good idea to file a slight taper on the end of the rail to help sliding it into the chairs.

 

Yes and there is often a burr on the rail end which needs filing smooth.