Bending flexible track without a kink
Benjamin | TrackDrawer.com · published 11 November 2026
Bend flexible track along its whole length in one smooth movement, and only fix it once the shape is right. A kink nearly always forms in two places: at the end of the length, where you have no leverage left, and at the joint between two lengths. So let the length run past the end point and cut only after bending, and put a joint on a straight rather than in the middle of a curve.
Which systems have flexible track and when to choose it over sectional track is covered in sectional or flexible track. This article is about the bending itself.
Why flexible track kinks
Flexible track is a length of track whose sleepers can move relative to each other. When you bend it, the inner rail of the curve needs less length than the outer one. That is why one rail slides through the sleeper fixings: after bending it sticks out at one end.
The kink comes from uneven bending. In the middle of the length you have enough track on both sides to spread the force, and the curve becomes smooth by itself. Not at the end: the last few centimetres stay straight and the curve only starts a little further on, with an angle. The same happens at a joint. Two lengths bent separately meet with a straight end each, and the rail joiner holds them there at an angle.
A train feels a kink like that as a short, sharp curve. Long coaches and locos with a long wheelbase are the first to derail there, and the couplings pull askew at that point too.
Preparing
- Draw the centre line. On a full-size print or on the board itself. See laying track: from plan to baseboard.
- Lay the fixed pieces first. Turnouts and sectional pieces decide where the flexible track must start and finish.
- Choose a generous radius. The wider it is, the less chance of a kink and the more smoothly the train runs. Stay above the radius your stock can handle.
- Use a curve template if you lay many identical curves. A template of wood or card in the shape of the curve, or a row of pins along the centre line, keeps the radius constant.
Bending in practice
- Lay the length straight on the board, with the sliding rail on the side where you will cut it later.
- Bend with both hands at once, along the whole length, a little at a time. Do not bend from a single point.
- Keep the sleepers square to the track and evenly spaced. If they slide askew, push them back before you bend further.
- Hold the track temporarily with a few pins beside the sleepers, not through them, so you can still adjust.
- Sight along the track at eye level. A flat spot or a kink shows up straight away.
- Only when the shape is right do you cut off the protruding rail and fix the track properly.
If a curve must be longer than one length, join the two lengths straight first, solder the joint and then bend them together. The joint then bends like any other piece of rail.
How much curve do you get from one length?
How many degrees one length gives depends on its length and the radius. The table works this out for the smallest fixed curve of each system in our catalogue. The length of each flexible track is listed in sectional or flexible track.
| System | Flexible track | Smallest fixed curve | Curve from one length at that radius | Smallest bending radius in TrackDrawer |
|---|---|---|---|---|
| Roco Line | 42400, 42401 | R2, 358 mm | 147° | 322 mm |
| Piko A track | 55209 | R1, 360 mm | 150° | 324 mm |
| Märklin K track | 2205 | Industriekreis, 295.4 mm | 175° | 266 mm |
| Fleischmann Profi track | 6106 | R1, 356.5 mm | 129° | 321 mm |
| Tillig Elite | 85125 | R11, 366 mm | 139° | 329 mm |
| Tillig TT | 83125 | R01, 267 mm | 142° | 240 mm |
| Minitrix | 14901 | R1, 194.6 mm | 215° | 175 mm |
| Fleischmann piccolo | 9106 | R1, 192 mm | 232° | 173 mm |
| Kato Unitrack N | 21-000 | R216, 216 mm | 214° | 194 mm |
| Arnold N | HN8003 | R1, 192 mm | 199° | 173 mm |
| Märklin Z | 8594 | R1, 145 mm | 261° | 131 mm |
What this tells you: in H0 and TT you do not get a semicircle from one length at the smallest radius. A 180 degree turn then always has a joint in the curve, and that one you had better solder beforehand. In N and Z a semicircle from a single length does work. At a wider radius the same length gives fewer degrees: Roco Line at 600 mm gives about 88°.
Easing from straight into curve
A real railway does not go from straight to full curve in one step: the curvature builds up gradually over a transition curve. With flexible track you can copy that. Start the curve wider and only reach the final radius after a short distance. The train then rocks less as it enters the curve, and long coaches do not swing out suddenly.
If your flexible track joins a fixed curve of sectional track, let it carry on bending in the same direction rather than forming a straight stub just before the joint. If it joins a straight or a turnout, it starts straight and only curves afterwards. If you lay two opposite curves one after the other, leave a straight between them of at least one coach length, or you get a tight S-bend.
Cutting and the joint
- Cut after bending. Only then do you know how far each rail sticks out. Mark both rails at the same place, square to the track.
- Use fine tools. A fine metal saw or rail cutters. Support the rail right next to the cut so it does not bend.
- File off the burr. On the head and on the inside of the rail. A burr lets a wheel flange climb and does not fit in the rail joiner.
- Make room for the joiner. At the end, remove the fixings of the last sleeper, or slide that sleeper off, so the rail joiner fits over the rail foot. Then put a loose sleeper back under the joint so the track does not sag there. For Märklin K track, our catalogue lists joiners 7595 for the cut end of flexible track 2205.
How a joint lines up properly and why you do not solder every joint is covered in rail joiners and joints.
Bending flexible track in TrackDrawer
Select a flexible track in TrackDrawer and you get three buttons: Straight, Curve (with radius and angle) and To connection point. With the last one you tap a free connection point and the app finds a shape that joins exactly there, with the widest radius that fits within the length of your track. With Transition curves ticked, the curvature builds up gradually at the start and end of the curve. You always see how much of the length you are using, for example "Flex 760 / 920 mm". If the target is too far or too tight, the app says so, with the longest length and smallest radius it allows: no tighter than 0.9 times the smallest fixed curve of your system, or the smallest radius of your rolling stock if that is larger. If a gap remains after bending, the gap finder closes it from your collection. Enter your track and let the Auto-designer suggest a plan; then replace any run of fixed pieces with flexible track wherever you like.