The Flex System
1991 EU Technic catalog
6 new sets, including the 8838 Shock Cycle and 8856 Whirlwind Rescue, as well as a new Idea Book were released. Lego also included an extra instruction book with the 8024, 8815 and 8820 to build a meta set from these parts. Although this had been done in other themes before, it was the first in the Technic theme.
There were several new parts released, including new motorcycle wheels and large shock absorbers as well as an entirely new system of flexible cables and cardan joints.
US patent 5,733,168
The Flex System:
The new Flex System consisted of thin, flexible rod-shaped cables with coupling heads, larger flexible sheaths and connectors that could be attached with axles or ball joints. When used together with the flex tubing the flex cable allowed for the transmission of force much like a Bowden cable. The small size and flexibility allowed it to be used where traditional gears and cross axles would be too bulky or impractical.
The original patent application also made a claim for using the flex cables as a means of stiffening static constructions, however this was never fully realized in any Technic models. The use as a Bowden cable, however, was utilized in a number of models, most notably as a helicopter or airplane control mechanism. The system remains one of the more elegant Technic construction methods and has always been underutilized by Lego.
US patent 5,360,364
The Cardan Joint:
The cardan joint consisted of a spherical ball with axial grooves, a loose-fitting ring with ball attachments as well as a guide ring with carrier pins. The pins of the guide ring meshed with the grooves of the cardan ball, allowing the transmission of torque but also allowing the guide ring to pivot about the sphere. The loose fit of the ball attachments allowed them to remain static as the rest of the assembly spun and be controlled by a flex cable. Not only did this allow for 3-axis control of a helicopter rotor but also formed the basis of a constant-velocity joint. Another example of the increasingly sophisticated specialized elements Lego was now developing.
8838 Shock Cycle:
The Shock Cycle featured both front and rear wheel suspension, accurate steering and a 2-cylinder chain drive, The new shock absorbers and hollow rubber tires, along with the new engine elements resulted in a quite realistic model. As Lego continued to release new, highly specialized elements the designers were beginning to create very realistic models, both in terms of function and form. The Shock Cycle would serve as the basis of a number of motorcycle models over the next decade.
8074 Universal Set w/ Flex System
8810 Cafe Racer
8815 Speedway Bandit
8820 Mountain Rambler
8838 Shock Cycle
8856 Whirlwind Rescue
8891 Designers Idea Book
meta Racer (8024+8815+8820)