The introduction of various larger radius corners has provided some interesting options for layout consideration. While it might be ideal to have all the same radius corners/junctions when putting together a layout, this may not always be an option.
It is possible to create a layout using mixed radius modules. In an ideal world, you have everything in pairs, and you can set them opposite (catty-corner) of each other in the layout.
The other option is to use some spacer track. With Kato track being 33mm spacing, each size corner (or junction) will have a multiple of 33mm for the difference. i.e. A standard corner has 315mm radius for the red-line, and a medium has 381mm radius, a difference of 66mm.
Radius Difference between corner/junction sizes
** we are assuming the "common" sizes as presented in the larger radius corners page.
| Size | Standard | Medium | Large | Extra-Large |
|---|---|---|---|---|
| Standard | 66mm | 165mm | 198mm | |
| Medium | 66mm | 99mm | 132mm | |
| Large | 165mm | 99mm | 33mm | |
| Extra-Large | 198mm | 132mm | 33mm |
Some Examples with just corners
In the first example, we have a matching pair of corners available, with no addition requirement for setup. So ideally we set those "catty-corner" from each other.
In the second example, the desired setup was to have the two large corners together (maybe they have concurrent scenery). We have 2 large, and 2 standard corners in this example. That creates a difference of 165mm x 2 - or 330mm. For this setup, we can use a single (308mm of track) and that only leaves a gap of 22mm. Ideally, you then use the Kato 29mm track piece to close that gap (a 7mm gap is easier to "fudge" then 22mm gap).
In the third example, we have 2 large corners, 1 standard corner, and 1 medium corner. When you look along the horizontal axis, we have 66mm difference due to the standard / medium match-up. Along the vertical axis, we have 2 different match-ups: large and standard along the top, and large & medium along the bottom. This gives ups a 165mm and 99mm difference respectively.
Filling the gaps: with the difference always being a multiple of 33, the obvious option is to use some number of 33mm pieces to fill the gap. But to minimize the number of pieces, one can use alternate, more 'standard' pieces. In most layouts, getting within a 10mm difference is completely doable. So for example, we can fill the 66mm difference with a 64mm piece (or even a 62mm mm piece). The 264mm gap (165+99) can be filled with 186mm + 45.5mm + 33mm (a total of 264.5mm). [Another option for the 264mm gap, is to use a standard single to fill it - 310mm. That creates a difference on the LEFT side of 46mm, which could be filled with the 45.5 mm piece]
Usage of Mixed Sized Junctions
When designing a layout, the junctions are really just "special" corners. They are effectively just two corner modules 'stuck' together. So we can equate them to "corners" when we think about the space they take up. The other "special" thing about them is the divide a layout into multiple loops. So where the yellow was once just a single loop, the yellow is now two separate loops (and the red line just follows along and encompasses the two yellow loops).
So the same processes noted above for mixed corners can be used when including junctions. Use "opposite" corner options when possible, but this time you are focused on the YELLOW loops, not the overall layout/loop. When you don't have the correct pairing to do "opposite corners", refer to the 'difference' chart to make up what ever space is needed.
Some Examples with junctions
In the first example below, we have a preferred example setup - we have matching pairs of modules, 2 large corners and 2 standard corners, and 1 large junction and 1 small junction. We can set these up using opposite corners idea, and we won't need any spacers.
Some might say, "But the two standard corners are not opposite each other". Remember, we only need to focus on the yellow loops for the design (red just follows along) So if you look at just the left side, the standard radius modules are opposite each other. And then look at the right side, and the standard radius modules are also opposite each other.
In the second example, we have very mixed setup. We now have 1 medium corner and 1 medium junction in the mix. If you look only at the left side, you will see that the standard/medium modules are "catty-corner", so that loop technically doesn't need any spacer. But on the right side we have a Large corner involved. We have the 2 standard sizes "catty-corner", with the Large/Medium mated up for the other corners. To make a medium radius cover the same distance as the large radius, we need to add 99mm to each leg. And since we are only looking at the "right loop" we only need to add the 99mm to the corresponding "right loop" sides of the junction (i.e the bottom and the right legs). When we add 99mm to the "bottom" leg of the junction, that also affects the left side of our layout, so we need to also provide a 99mm spacer there as well.
Filling the gaps: With 99mm space to fill, we could use a 64mm and a 33mm piece (97mm total) to fill in the gap. [a 62mm and 38mm piece would also work, and since there are double-track 62mm pieces, it might be a little easier to accomplish.]
One more "advanced" example
When looking at a layout with "4 corners, and 2 junctions" - this last example probably shows one of the more extreme examples. Hopefully this example, combined with the ideas above, can help you out in the process of figured out your own mixed radius layouts.
Here we have 4 "standard" radius modules, 1 "large" radius and 1 "medium" radius. We start with putting all the 'standard' radius modules in the same loop, so they are all on our left loop in the example. Now we add the 1 medium and 1 large corner to our right hand loop. When you look along the horizontal axis, we have added a 99mm gap (if both of these corners were the same, there would not have been any gap along the horizontal axis). So we add 99mm to the one side of the medium corner to make up that difference. Now along the vertical axis, we have 'ripped' our previous loop apart. The top half has pulled away 66mm (the difference between a 'standard' and a 'medium') and the bottom half has pulled away 165mm (the difference between a 'standard' and a 'large'). This is a total distance of 231mm.
Filling the gaps: We talked about filling a 99mm gap above (62mm + 38mm or 64mm + 33mm). To fill the 231mm gap, a 186mm + 45.5mm is (almost) a perfect fit.
- This information is pulled from the "Proposed T-TRAK Corner Recommended Practices" found on the Publications section of the N-Rail website