Does anyone have a table with the curve radii for the curved slope pieces?

If not, does anyone have a good idea for measuring a third point on the curve?

Since I know the front and the back "coordinates" of the curve piece, I need a third point to get the radius. I was thinking about making some sort of jig, but I don't have any good ideas.

2 Answers 2


On reddit, user Pegajace used AutoCAD and LDraw models to produce the following results:

Combined album view From the album https://i.sstatic.net/LOAeL.jpg

Probably, the ones with 100.0 LDU and 170.00 LDU radii are correct, however the other ones that don't report an integral number of LDUs are probably slightly off.

I remember a presentation from a Lego Designer Michael 'Mike' Psiaki (who worked among others on the roller-coaster and Saturn V sets) at the LEGO Portugal fan weekend 2018 where the radii were presented in a table and only one curved slope had a non-integral radius. Unfortunately taking pictures of the presentation was discouraged.


These curves have been approximated by the contributors to the LDraw project. You can download free software to view and use the part files, from which you can approximate other points on the curve. For example, here is an LDraw part file shown in "wire-frame" mode:

enter image description here

LDraw parts are drawn in increments of the "LDraw Unit" (LDU) in which a standard 1x1 brick is 20 LDU wide by 24 LDU high (not including the top stud). By examining the part in an LDraw viewer, I was able to establish the coordinates of some of the points on the curve:

enter image description here

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