Round Base Plate with Train Tracks

Lego bricks does not lend themselves to circular objects very well. So trying to build round things out of Lego is always interesting. Today I’m going to tackle this problem from the bottom, literately. Curved train tracks are some of the few pieces with studs not placed on a rectangular grid (even the perfectly circular plates have studs on a square grid). Therefore they are best suited for our goal. There are two types of curved tracks, the smaller 8-wide 45° and the larger 10-wide 22.5°. It takes 8 of the smaller ones to complete a circle, and 16 of the larger. The circle formed by the smaller tracks is 54 studs in diameter, and 88 studs for the larger one.

Download the LDD file of the larger version

Round Base Plate (100.2 KiB)


The Build Details

Now that we’ve decided on the basic strategy, let’s get down to some of the details of building the round base plate. First of all, the train tracks alone is very flimsy. We’ll need to reinforce it underneath with something flat. Tiled base plate is the easiest option. To better connect the train tracks to the base plate, 9 turn tables are place on 4 diagonal corners and the center as shown. We also need to connect the two circles with plates.

round plate1


Next we will fill in the pie-shaped gaps with studs to form our base plate. That is arguably the hardest part of all. We’ll start from the edge and work towards the center. To minimize gaps, we can either use wedge plates or various half-plate offset techniques. Let’s first look at the half-plate offset below. Jumpers and hinges are used to achieve the half-plate offset. Two different shapes are alternated to minimize the gaps even more.

round plate2


Next let’s look at how to fill the gap with wedge plates.

round plate6 round plate7


In my example, I used half-plate offset for the first half of the pie and wedge plate for the second half. But it’s not the only way. The ends of the 16 plates from 16 directions are tied together with hinge pieces, and the center is completed with round plates.

round plate8


The final result has a few holes and gaps without stud on them. But once you add the surface structures, they will be covered. For example, the following two mocs are done with this techniques. The sci-fi city is done with the larger circle, and the Mina Tirith is done with the smaller circle.

Metro Infinity (development)

Minas Tirith

Questions and comments are welcome!

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