1977 - Technic sees light of day

Details: Category: Expert Builder Set; Hits: 19

1977

Set Year: 1977
Set Number: 98959
Set Parts: 40
Building Instruction: No
Currency: na

Read more: 870 - Power Pack

Details: Category: Expert Builder Set; Hits: 23

1977

Set Year: 1977
Set Number: 851
Set Parts: 340
Set Price: 56.25
Building Instruction: No
Currency: Guilders

In its year of introduction this set was priced 50.75 guilders.

Set 851 was released under the "Technical Set" series in 1977 in Europe. It made it to the US in 1978 with the number 952 as an "Expert Builder"set. This tractor features rack and pinion steering, a PTO (Power Take Off) which can power various implements including the thresher of the primary model, and a linkage to raise and lower the implements. Traditional studded construction is used almost exclusively, with the exception of the implement lift. This was the only set released by LEGO^® in the first year which used a four bar linkage. To this day, this is one of a very small number of sets which actually use the 40 tooth spur gear.

A number of tractors have been made over the years, but this one is the most elegant in many ways. I've seen old tractors which look very much like this one on many occasions while riding through the countryside in the Midwest of the USA (without the studs, of course). It is a very nostalgic design.

Steering

The front wheels can be steered using a wheel made from a 24 tooth gear at the driver's position. As can be seen in the computer generated image, the wheel drives an axle connected to a pair of 8 tooth pinion gears via a universal joint. The pinions drive a pair of racks. The steering mechanism itself uses 6 traditional 2x2 swivels with 2 pair allowing rotation of the wheels about the vertical axis and another pair acting as control arms attached to the rack gears. Simple axles allow the wheels to rotate freely.

Implements

The right rear wheel of the tractor drives a PTO (Power Take Off) via a bevel set using an 8 tooth pinion and a 24 tooth crown gear. This gives the PTO a gear ratio of 3:1. The left rear wheel is not connected to this mechanism.

The implement for the primary model is a thresher. The PTO drives a 40 tooth spur gear on the thresher which, in turn, drives an 8 tooth spur gear. This final set of gear reduction drives a trio of 40 tooth gears acting as cutting wheels. Yellow bricks are inserted into some of the stud holes in the gear to act as cutters.

The final gear reduction at the cutters is 9:1 with respect to the rear wheels, so these turn very quickly when engaged (see animation). They turn so quickly that this creates a lot of drag on the tire and tends to make it slip.

Lift

The thresher can be raised and lowered via a lever at the driver's position on the right side. The lever pivots about the frame and drives a push-pull link made from connectors. This link pushes a four bar linkage which raises the implement, keeping it (almost) parallel to the ground during motion. The reason it is not quite parallel is that the vertical distance between the upper and lower links is not equal at the front and the back, so the links are not quite parallel.

As long as the model is right side up, the push-pull linkage is always in compression so it tends to stay together. If the model is inverted, this is in tension and can pop apart.

If the thresher is lowered too far, the 40 tooth gear will fall under the PTO and jam. There are wheels on the thresher to make it level and prevent this from happening.

The original mechanism (pictured) had a weak spot at the aft end of the connector link. Only the friction on the studs kept this together, so it tended to come apart often. In 1978, LEGO^® changed the design to have a vertical 1x4 beam at this location to hold things together. This resulted in a slightly different parts list and count for this set.

Wheels and Tires

This set uses two rubber 17x43 tires and standard old gray wheels on the front. The rear uses a foam 24x43 tire and wheel, the biggest foam tire that LEGO^® made.

By Technicopedia

Details: Category: Expert Builder Set; Hits: 24

1977

Set Year: 1950
Set Number: 852
Set Parts: 364
Set Price: 0
Building Instruction: No
Currency: EURO

Set 852 was released under the "Technical Set"series in 1977 in Europe. It made it to the US in 1978 with the number 954 as an "Expert Builder"set. This helicopter features rotating main and tail rotors, and a collective pitch mechanism controlled at the pilot stations. Traditional studded construction is used throughout, with with a roughly equal amount of studless construction to accomplish the outer body shaping. This was the only Technic set released by LEGO^® in the first year which did not have wheels on the main model, and remains one of the very few such to this day.

Helicopters have been a very popular Technic subject over the years, and a large number of them have been made. This first helicopter is still the only one to feature collective pitch and flybars with paddles. It also has the most realistic rotation speed ratio between the main and tail rotors. In these respects, it has never been improved upon. Some of the newer helicopters have more elaborate bodies and exteriors, but the simplicity of exterior design of real helicopters is one of the things which make them ideal Technic subjects.

Rotor Crank

The rotors' rotation is driven by an input crank on the left side. This crank drives a set of 24 tooth gears. The gears on the level above (see computer image) are actually on two separate axles and rotate at different rates. The forward torque passes through a set of 8 and 24 tooth gears and then on to the main rotor, resulting in a 3:1 final gear ratio. The aft torque passes through a reversed set of 8 and 24 tooth gears which results in a gear ratio of 1:3 as the axle heads back to the tail. Two universal joints shift the plane of the axles, and finally the tail rotor passes though another set of 8 and 24 tooth gears which results in a final gear ratio at the tail of 1:1.

Rotors

Rotation of the twin blade main rotor is controlled by the input crank as described above. The main rotor is pitched down about 30 degrees at neutral. When the yellow drive block is translated upwards, the blue plate, acting somewhat like a swashplate, rises with it. A pair of links are connected to the blue plate and force the rotor blades to reverse pitch (see animation).

The main rotor head also features a pair of flybars and paddles, simulating a Bell-Hiller design. They are not functional. Ironically, it is these paddles which should really be driven by the collective, not the rotor blades themselves.

The tail rotor is a simple twin blade, fixed pitch design.

Both the main and tail rotors are constructed from standard plates.

Collective Pitch

The pilot controls move only forward and aft, and are bussed together at the floor. Under the floor, they attach to a pair of links which connect to a crank made of beams. When these beams rotate (see animation) it pushes another pair of links up. These links are attached to a translating block which controls the pitch of the main rotor blades, as described above.

There is no way to command the blades back to neutral. When the collective is moved back down, the yellow block moves away from the blue one, and the blue falls under its own weight. It sometimes sticks and will not return to neutral without some external force.

Skids

The landing skids are constructed from beams, axles, connectors, and pins. The geometry is such that all links are always in compression so the connectors do not tend to separate.

Details: Category: Expert Builder Set; Hits: 26

1977

Set Year: 1977
Set Number: 853
Set Parts: 602
Set Price: 97.00
Building Instruction: No
Currency: Guilders

How did Technic get started? We have been fortunate to talk to Jan Ryaa, one of the founding fathers of Technic back in the 1970s, where he worked with another designer, Erik Bach. At some point, these two stopped treating a brick as simply a brick, and they went to work with no more than their tool kit and some good ideas, and changed a few things.

Sets by Year

98959 - Motor

871 - Expert Builder/Gear Parts

870 - Power Pack

851 - Tractor

852 - Helicopter

853 - Auto Chassis

850 - Fork Lift

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