Technic sets were first introduced in Europe in September 1977 under the name Technical Sets. Advertising, such as in catalogs, called the new theme "Technical Sets" although the boxes didn't have any name on them. The term Technic would not be coined until later. These new sets still used much of the traditional studded construction of other LEGO® sets, but now introduced a small number of new parts which could be used to reproduce realistic technical functions. There were gears and axles, and new special beams and plates with holes in them to allow installation of the axles. There was even a piston element which could be used to accurately reproduce the lower part of a reciprocating engine.
These sets, intended for older children, expanded the Lego range into much more complex mechanical models, or -as early advertising stated- models "as technical as the real thing". The original series consisted of 4 models, including a 590 piece Auto Chassis, and 2 supplementary sets. In Europe they were given 850 and 870 series set numbers.
Several of these new elements, such as the cross axle and universal joint were holdovers from the earlier Gear wheel sets and were changed very little. Several other elements were new, more refined versions of the Gear Wheel elements, such as the technic beam that replaced the 2 x 4 brick with holes. Still other elements were entirely new, such as gears, the connector peg and piston rod. The 2 original supplementary sets included examples of all of the new elements.
The crown gear:
The original crown gear is a good example of how the new Technic elements replaced earlier elements. The Samsonite and Lego gear wheels could act as either a pinion or crown gear due to the relatively large size of their teeth. However, the smaller Technic gears required a new design. The crown gear featured a tooth similar in profile to a claw, (or a "bird's head" according to the 1976 UK patent application). Acting as a pinion it could mesh with the bottom of the tooth or as a crown gear with the top of the tooth.
UK patent 1,543,128
The piston rod:
These new elements were intended not only to provide alternatives to the traditional stud and tube coupling but to provide realistic technical functions. A good example of the purpose of these new elements is given in the 1976 patent application for the piston rod and brick. 2 piston rods on either end of a cross axle could act as a eccentric connection to a gear and a 2 x 2 brick with a bearing replacing the tube underneath the brick. This arrangement could translate the reciprocal movement of the piston into the rotational movement of a gear or wheel and served as the basis for the technic engine until 1990.
US patent 4,124,949
853 Auto Chassis: 
The large auto chassis models have always been among the largest and technically complex sets and serve as a good indicator of Technic state-of-the-art. Although relatively unsophisticated by todays standards, the 853 Auto Chassis was by far the most technically complicated Lego set in 1977. It had a 4-cylinder in-line engine, 2-speed transmission, front wheel rack and pinion steering and adjustable seats. The new elements offered interesting new possibilities but the 853 as well as other first generation models utilized a large percentage of typical Lego bricks and plates and used rather traditional construction techniques. The use of the Technic beam as a true beam would be several years away. Because there were still so few specialized elements, technical functions tended to be rather bulky and limited. The rack and pinion steering, for example, was built from 2x2 turntables and 2x1 beams and the seats were built entirely from standard bricks.
All the Technic parts were new in 1977! The basic set of parts is shown to the right. This comprises all of the new parts which were included in the sets, but does not include the motor or battery box which were available as an accessory pack.
Beams & Plates
The "standard" Technic parts, which have now become ubiquitous, are the plate and the beam. Beams are just like 1x bricks, but have perpendicular holes at points midway between the studs. Technic plates are just like regular 2x plates, but have parallel holes at points midway between the studs. These holes are sized to accept either pins or axles. Beams originally came only in even lengths: 2, 4, 8, and 16. Plates came only in 2x4 and 2x8. Many more sizes would later be available. Studded beams are still in use though they have mostly been replaced by links.
Gears
Most technical functions were and still are accomplished with gears. In 1977, there were three sizes of spur gears (gears which transmit torque on parallel axes): 8 tooth, 24 tooth, and 40 tooth. The two larger gears also have axle holes and stud holes off the center which allow them to be used for other purposes (such as a crankshaft). There was also a 24 tooth crown gear which could be used as either a spur gear or a bevel gear (gears which transmit torque on perpendicular axes), and a rack gear. The 8 tooth gear is still in use, but the others have been replaced with improved versions. The 40 tooth gear still exists but has been used in very few sets.
Axles
Axles are the basic unit of torque transmittal in Technic. LEGO chose to use a cruciform cross section. This has the advantage of never slipping, being easy to assemble, and centering well in a hole. Axles are the same size as a stud in diameter, and originally came in only even lengths: 2, 4, 6, 8, 10, and 12, and they were always black. These are all still in use although the 2 axle has been modified and odd lengths are now available, as are other colors.
Connectors and Special Parts
The bushing was used as either a spacer or a retainer and fit onto an axle. The pin was frictionless and was used to joint two beams or as a pivot. The connector fit onto the end of an axle and included a perpendicular hole which would accept a pin. It could also be used as a connecting rod for the piston. The universal joint connected two axles and allowed rotation around axes angled apart as much as 45 degrees. The pulley was used only as a crank in 1977, but would later also be used with belts. These parts could all be used in multiple applications, but only the piston had a single use. The 2x2 square piston was used for engines, and had to be used with a connector element. At this time, these parts were available only in light gray.
Wheels and Tires
LEGO® already had lots of wheels and tires, but they were not big enough for some of the new sets. A new 24x43 wheel was introduced with a dense foam tire. This tire was later available in other sizes, and would eventually be replaced by all rubber tires.
1977 sets:
- 850 Fork Lift Truck
- 851 Tractor
- 852 Helicopter
- 853 Car Chassis
- 870 Motor with battery Box
- 871 Supplementary Set
Based on Isodomus and Technicopedia