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1984 - Pneumatics

1984

1984 featured the introduction of the first generation Technic pneumatic system.  There were four sets released this year:  two universal sets, a forklift, and an excavator.  3 of the 4 sets this year used pneumatics.  The pneumatics had serious limitations (discussed below), but were a welcome advance in real technical functionality.

The small universal set is an introduction to Technic, while the larger universal set is an introduction to pneumatics.  The forklift features a pneumatically lifting fork and rear steering.  The excavator has 3 pneumatic actuators to control the boom and a large number of tracks for the base.

This pneumatic system would only last 5 years and, in fact, only one more model would ever be released which used it.  Also new for this year were a threaded axle and a special bucket for the excavator.

Sets

8020 Universal Building Set
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8040 Pneumatic Universal Building Set
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8843 Forklift
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8851 Excavator
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Parts

Pneumatics
This first generation pneumatics, released this year, are exciting but were short lived.  The single acting system has some serious limitations which were corrected in the second generation of pneumatics.
  • Actuators: There are two different lengths of linear pneumatic actuators which differ only in stroke.  There is a single pressure port on the head end side of the cylinder.  Using this port, the actuator can generate both compression (via pressure), and tension (via suction).  The limitation on the compression force is that the piston head internal to the actuator will begin to leak after a certain pressure, acting as a pressure relief valve.  The limitation on tension force is that there is no such thing as suction!  Rod end pressure generated by the atmosphere actually pushes the piston the other way to produce tension, so there can never be more than atmospheric pressure generating tension.  This means that if you bring your excavator along with you when you summit Mt. Everest, it won't work very well.
  • Pumps:  The standard pump is identical to the actuator except that it has a spring on the rod.  There are two pumps which both use the short cylinder, but differ in using either the long or the short rod.  The one with the short rod has a short stroke because the spring bottoms out before the piston is fully compressed.  The other can achieve full stroke.  One of the limitations here is that suction is only generated by the force of the return spring unless you actually pull the rod up.
  • Distribution block:  This little gem is the magic behind the single acting system, and in fact the system would not work without it.  It is the size of a 2x4 brick but has 3 pneumatic ports.  The center port is for input from the pump.  Each outboard port contains a check valve so that flow can only occur in one direction.  Both are connected to center.  The left port is for suction, and the right for pressure.  Both of these ports are connected to the switch.
  • Switch:  The switch is really a pneumatic selector valve and is the size of two 1x2 bricks.  The outer ports are connected to the two ports of the distribution block.  The center port runs out to one or more actuators.  When the switch is at the center position, all ports are blocked.  When the switch is moved to one position or the other, one of the outer ports and the center port are connected to the distribution block and the other is vented to atmosphere.
  • T-fitting:  This splitter can be placed either between the distribution block and one or more switches, or downstream of a switch to allow multiple actuators on a circuit.
Compression Summary:  Depression of the pump produces pressure.  Pressure flows to center port of distribution block and out of right port.  Pressure flows to enabled switch and out center port to actuator, extending it.  Return of the pump draws in air through the switch via the left port of the distribution block.

Tension Summary:  Return of the pump produces suction.  Suction flows to center port of distribution block and out of left port.  Pressure flows to enabled switch and out center port to actuator, retracting it.  Depression of the pump blows out air through the switch via the right port of the distribution block.  (This is all backwards since suction is really atmospheric pressure, but it works for illustrative purposes.)

Bucket
A new single purpose bucket was introduced for the excavator which was only ever used in one other model.

Threaded Axle
A new threaded axle was introduced.  It has the same cruciform cross section as the regular axle but is also right-hand threaded.  With the addition of the new nut, this axle can now carry significant tension load instead of just compression and torque.  This allows it to be used to hold unstable structures together (like the superstructure of the excavator).  The nut fits between 4 studs to lock in position to a plate, and two nuts can be jammed together to lock them to the axle.

3L Axle
This is the first year that a 3L axle was available, the first odd length.  No other odd lengths would be available for a long time.

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