Truncated enneagonal duoprism

The truncated enneagonal duoprism or tredip is a convex isogonal polychoron that consists of 18 truncated enneagonal prisms and 81 tetragonal disphenoids. 1 tetragonal disphenoid and 3 truncated enneagonal prisms join at each vetex. It can be formed by truncating the enneagonal duoprism.

It can also be obtained as the convex hull of 2 semi-uniform enneagonal-octadecagonal duoprisms chosen such that the octadecagonal and enneagonal prisms have the same circumradius. if the octadecagons of this duoprism have edge length 1, the enneagons have edge length $$1+\frac{1}{\cos\frac\pi9} ≈ 2.06418$$.

Using the ratio method, the lowest possible ratio between the longest and shortest edges is 1:$$\frac{2\cos\frac\pi9}{\sqrt2}$$ ≈ 1:1.32893.