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Helix 2
An octotetrahedric double helix of pitch 10 around a cylinder made of 25 decagonal prisms. Both structures don't fit exactly one another; because of this, the cylinder undergoes an irregular deformation, ultimately responsible for its leaning:
 Helix 2A 2218 pieces: 508 balls, 1448 rods, 2 pentagons, 260 squares (11.65 kg) Helix 2A, detail
Both pentagons belong to a pair of pentagonal cupolas which close, and help to stabilize, the cylinder at both ends. In the following table, we give the piece quantities required for several numbers of helices and turns. We haven't counted the top ends of the helices which exceed the height of the cylinder, nor any special structure at their bases; we have counted two pentagonal cupolas, although it could be appropriate to use more for bigger sizes:
 helices turns balls rods pentagons squares 1 1 160 395 2 110 1 2 300 755 2 210 1 3 440 1115 2 310 1 4 580 1475 2 410 2 1 200 550 2 110 2 2 380 1070 2 210 2 3 560 1590 2 310 2 4 740 2110 2 410 ... ... ... ... ... ... m n (100+40m)n+20 (200+160m)n+40–5m 2 100n+10
In the previous construction, all modules in each helix are attached to the central support. However, the structure of these helices is strong enough to allow using much less support. In the following construction, for each of the turns of each of the three helices, just four of ten modules are attached to the central support, in this case a 1 × 3 × 21 parallelepiped:
 Helix 2B, view 1 2266 pieces: 524 balls, 1469 rods, 273 squares (11.91 kg) Helix 2B, view 2
Similarly to the previous table, in the following one we have counted just the helices and the central support structure:
 helices turns balls rods squares 1 1 148 367 143 1 2 280 713 273 1 3 412 1059 403 2 1 200 528 143 2 2 384 1040 273 2 3 568 1552 403 3 1 252 689 143 3 2 488 1367 273 3 3 724 2045 403 ... ... ... ... ... m n (80+52m)n+16 (180+166m)n+26–5m 130n+13
 Helix 2B, view 3
• Similar helices of pitch 15 at Helix 3
• Similar helices of pitch 18 at Helix 4