Acronym	tatriddip
Name	truncated triangular duoprism
Circumradius	sqrt[(2y2+5y+5)/3]
Face vector	36, 72, 51, 15
Confer	extremal cases: triddip   retdip
External links

Truncation would result in 3 different edge sizes in the outcome polychoron. That one here is scaled such so that the shorter specified one becomes unity. Then the larger specified edge will have size q=sqrt(2). The third one would be the arbitrary expansion size y (corresponding to the arbitrary truncation depth). In fact, for y=0 this results again in the retdip, while y → ∞ results again in the pre-image triddip (rescaled back down accordingly).

Incidence matrix according to Dynkin symbol

((xo3yb by3ox))&#zq   → height = 0
                        y > 0 (arbitrary expansion size)
                        b = y+2 (pseudo)
(q-laced tegum sum of 2 alternate (x,y,b)-thiddips)

  o.3o. o.3o.       & | 36 |  1  1  2 | 1  3 2 | 3 1
----------------------+----+----------+--------+----
  x. .. .. ..       & |  2 | 18  *  * | 1  2 0 | 2 1
  .. y. .. ..       & |  2 |  * 18  * | 1  0 2 | 3 0
  oo3oo oo3oo  &#q    |  2 |  *  * 36 | 0  2 1 | 2 1
----------------------+----+----------+--------+----
  x.3y. .. ..       & |  6 |  3  3  0 | 6  * * | 2 0
  xo .. .. ..  &#q  & |  3 |  1  0  2 | * 36 * | 1 1
((.. yb by ..))&#zq   |  8 |  0  4  4 | *  * 9 | 2 0
----------------------+----+----------+--------+----
((xo3yb by ..))&#zq & | 18 |  6  9 12 | 2  6 3 | 6 *  titrip
  xo .. .. ox  &#q    |  4 |  2  0  4 | 0  4 0 | * 9  disphenoid