A short version of the previous long development video + new tests at the end.
The target is to generate the maximum possible pressing force with Lego. The progress is measured using a disassembled person scale (max 180 kg).
Enjoy!

The long unedited version: https://www.youtube.com/watch?v=vl6gLxoT1vs

p.s. Some of the gear ratios in the video are incorrect. Instead of 36:1 there should be 25:1. And 54:1 should be 45:1. Somehow I forgot that a middle sized bevel gear has 20 teeth, not 24.

List of parts for the strongest 70 kg build:
2x Power Functions M-Motor (8883)
2x Power Functions Battery Box (8881)
2x Power Functions Control Switch (8869)
2x Brick 8 x 8 (4201)
3x Brick 4 x 12 (4202)
28x Technic, Brick 1 x 16 with Holes (3703)
42x Technic, Brick 1 x 12 with Holes (6112)
4x Technic, Brick 1 x 8 with Holes (3702)
4x Technic, Brick 1 x 4 with Holes (3701)
16x Technic, Brick 1 x 2 with Hole (3700)
26x Tile 2 x 4 (87079)
8x Tile 1 x 8 (4162)
1x Plate 4 x 8 (3035)
6x Plate 4 x 6 (3032)
2x Plate 2 x 16 (4282)
4x Plate 2 x 12 (2445)
2x Plate 2 x 4 (3020)
1x Technic, Plate 2 x 4 with 3 Holes (3709b)
6x Plate 1 x 12 (60479)
20x Plate 1 x 10 (4477)
16x Plate 1 x 8 (3460)
16x Plate 1 x 6 (3666)
20x Plate 1 x 2 (3023)
4x Technic, Axle 16 (50451)
16x Technic, Axle 12 (3708)
4x Technic, Axle 8 (3707)
1x Technic, Axle 6 (3706)
8x Technic, Gear Rack 1 x 4 (3743)
24x Technic, Gear 24 Tooth (3648)
36x Technic, Gear 8 Tooth (3647)
20x Technic Bush (3713)
28x Technic, Pin 3L with Friction Ridges Lengthwise (6558)
12x Technic, Pin with Friction Ridges Lengthwise WITH Center Slots (2780)
paper :)