Small triangular double prismantiprismoid

The triangular double prismantiprismoid is a convex isogonal polychoron and the second member of the double prismantiprismoid family. It consists of 12 triangular antiprisms, 12 triangular prisms, 18 rectangular trapezoprisms, 72 isosceles trapezoidal pyramids, 18 tetragonal disphenoids, and 36 rhombic disphenoids. 1 triangular prism, 1 triangular antiprism, 3 wedges, 5 isosceles trapezoidal pyramids, and 2 tetragonal disphenoids join at each vertex. It can be obtained as the convex hull of two orthogonal triangular-hexagonal prismantiprismoids. However, it cannot be made scaliform.

A variant with regular octahedra and uniform triangular prisms can be vertex-inscribed into a small prismatotetracontoctachoron.

Using the ratio method, the lowest possible ratio between the longest and shortest edges is 1:a ≈ 1:1.37767, where a is the largest real root of 2a4-3a2-4a+4.