Märklin C Track curved turnouts: a passing loop in the curve
Benjamin | TrackDrawer.com · published 10 November 2026
Märklin C Track has two pairs of curved turnouts: 24671 and 24672 split an R1 curve (360 mm) into an R1 and an R2 track (437.5 mm), and 24771 and 24772 do the same with R3 (515 mm) and R4 (579.3 mm). With two curved turnouts you can lay a passing loop entirely within the curve. On a 105 x 105 cm baseboard the Auto-designer laid a loop with two passing loops this way; without curved turnouts, the first loop with a passing loop only fits on 160 x 90 cm.
How a curved turnout works
A standard turnout has a straight road and a diverging road. On a curved turnout both roads bend the same way. The inner road is an ordinary curve: on the 24671 it is exactly a 30 degree R1 curve, the same as the 24130. The outer road runs out in a gentle S and ends after 30 degrees on the R2 circle, around the same centre.
As a result, both tracks simply continue beyond the turnout as an inner and an outer curve: inside with R1 curves 24130, outside with R2 curves 24230. The difference between the two radii is 437.5 - 360 = 77.5 mm. That is exactly the track spacing of C Track, the same spacing that a standard turnout 24611 with its compensating curve 24224 gives on a straight. A passing loop in the curve therefore joins up seamlessly with a passing loop or double track on the straight side.
Left and right are read from the points end, as with any turnout: the 24671 curves to the left, the 24672 to the right. More on that convention in left, right and symmetrical turnouts.
Two pairs in the catalogue
| Item | Inner road | Outer road ends on | Angle | Spacing between tracks |
|---|---|---|---|---|
| 24671 left, 24672 right | R1, 360 mm (like 24130) | R2, 437.5 mm (continue with 24230) | 30° | 77.5 mm |
| 24771 left, 24772 right | R3, 515 mm (like 24330) | R4, 579.3 mm (continue with 24430) | 30° | 64.3 mm |
| for comparison: 24611 left | straight, 188.3 mm | R2 road of 24.3° | 24.3° | 77.5 mm with curve 24224 |
The slim pair 24771 and 24772 belongs with the large radii. Its 64.3 mm spacing is the smaller track spacing that C Track also uses with the slim turnouts 24711 and 24712. For the curved turnouts 24671 and 24672 our catalogue lists the turnout motor 74491 and the built-in decoder 74461, the same as for the standard turnout.
You will find the full list of C Track pieces with their dimensions on the Märklin C Track system page.
Building a passing loop in the curve
Take a semicircle of R1: six 30 degree curves 24130. This is how you turn it into a passing loop:
- Replace the first curve with a curved turnout. Its inner road takes the place of the curve, its outer road ends on R2.
- Leave the 24130 curves on the inside. Lay the same number of 24230 curves on the outside.
- Replace the last curve with the second curved turnout, its points facing the other way. Seen from its own points, it curves the other way: a 24671 at the start goes with a 24672 at the end.
How long the passing loop becomes depends on the number of curves between the turnouts. The inner road of each curved turnout and each R1 curve measure 188.5 mm along the track; an R2 curve on the outside measures 229.1 mm.
| R1 curves between the turnouts | Share of the curve | Inner track, points to points | R2 curves outside |
|---|---|---|---|
| 0 (back to back) | 60° | 377 mm | 0 |
| 1 | 90° | 565 mm | 1 |
| 2 | 120° | 754 mm | 2 |
| 4 | 180° | 1131 mm | 4 |
Back to back, the passing loop is so short that it holds a locomotive or a single wagon at most: TrackDrawer works with a standard 250 mm wagon in H0. Over a full semicircle you get just over a metre of inner track, enough for a short train. Allow for the point where the two tracks still touch: the waiting train has to stand fully clear of it. How that works on an ordinary passing loop is explained in passing loop: how two trains pass each other.
How much baseboard it takes
The outer track sets the depth. A semicircle of R2 is 2 x 437.5 + 40 = 915 mm wide from outside edge to outside edge (40 mm is the width of the C Track roadbed). With a 50 mm margin on each side that becomes 1015 mm: a baseboard 105 cm deep. At 90 cm deep, R2 fits in only part of the curve.
We let the Auto-designer plan with an ordinary drawer of C Track, once with two 24671, two 24672, two 24771 and two 24772 added and once without curved turnouts, each time with a 50 mm margin. The goals were a continuous run and a plan with several trains and a station.
| Baseboard | With curved turnouts | Without curved turnouts |
|---|---|---|
| 105 x 105 cm | loop on R1 with 2 passing loops in the curves, 15 pieces, 2.92 m | loop on R1 without a passing loop, 18 pieces, 2.83 m |
| 120 x 105 cm | loop on R1 with 2 passing loops in the curves, 22 pieces, 3.82 m | double track R2/R1, 28 pieces, 5.70 m |
| 140 x 105 cm | rhombus on R1 with 2 passing loops in the curves, 22 pieces, 3.62 m | double track R2/R1 with a siding and a yard, 40 pieces, 7.60 m |
| 160 x 90 cm | rhombus on R1 with a passing loop in the curve and a yard, 31 pieces, 5.14 m | station with two platforms on R1, plus 2 sidings, 31 pieces, 5.32 m |
What this tells you:
- Curved turnouts gain the most on a square baseboard. On 105 x 105 cm they give a loop with two places to wait, where without them only a plain loop fits. That loop has three short straights and three 120 degree curves; the passing loops sit back to back in the curves and are therefore short.
- At 120 cm wide, double track fits too. From 120 x 105 cm the designer lays two full loops on R2 and R1. That gives more track than a passing loop in the curve, but each train then runs on its own loop.
- On a long, narrow baseboard the straight wins. On 160 x 90 cm an ordinary passing loop fits just as well. What C Track does on each board size is covered in how much space for Märklin C Track.
The slim curved turnouts 24771 and 24772 did not appear in these measurements. They need R3 curves, and a semicircle of R4 is 2 x 579.3 + 40 = 1199 mm wide: with the margin, a baseboard 130 cm deep.
Also for a siding
A curved turnout also makes a handy branch in the curve. The inner road stays part of the loop, the outer road becomes the start of a siding. On 105 x 105 cm the designer laid an R1 oval with two sidings this way, 19 pieces and 3.05 m of track. That saves a straight, which a small baseboard often lacks.
Curved turnouts in other Märklin systems
Trix C Track uses the same geometry under its own numbers (62671, 62672, 62771 and 62772), for two-rail DC. Märklin K Track (2268 and 2269) goes from Normalkreis I (360 mm) to Normalkreis II (424.6 mm), M Track (5141 and 5142) from 360 to 437.4 mm. In Z (8568 and 8569) the inner track runs at 195 mm and the outer track at 220 mm. The Auto-designer uses all of these curved turnouts when they are in your inventory.
Frequently asked questions
Can I combine a curved turnout with ordinary R1 and R2 curves?
Yes. The inner road is an ordinary 30 degree R1 curve and the outer road ends on the R2 circle. Beyond the turnout you simply lay 24130 on the inside and 24230 on the outside, or let one of the tracks continue straight with the same pieces you would use after an ordinary curve.
Do I need a compensating curve?
No. A standard turnout needs a compensating curve to cancel out the diverging angle; on a curved turnout both roads already run parallel around the curve, 77.5 mm apart.
Try it yourself
Browse the C Track plans in the Railfolio, or add the curved turnouts to your inventory and let the Auto-designer look for a passing loop in the curve on your baseboard.
