Bruce Hansen writes: This model is an SPLR (Self Propelled Lunar Researcher) built from a 1969/70 Master Engineer type III set. The set came out right after Apollo 11 had landed on the moon. Not coincidentally, a large number of the models illustrated in the manual were moon/space vehicles. The action in this model is a Powermatic motor/hoist powered crane with hook and boom control. Also, a pair of antennas rotates and the whole model moves forward/back via walking “legs”.
The Master Engineer set included two Powermatic motors and a 4.5V transformer. Both motors were not under power at the same time. A SPDT switch alternated power to the appropriate motor. Here’s a shot of the model’s back side showing the selector switch, hoist, motor for the crane functions and the antenna. The antennas were driven via a pair of P48 mitre gears and P7 pulleys/string. Type II enthusiasts will be familiar with the mitre gears which were included in type II sets size #6 1/2 on up for around 30 years. This happened to be the last set to include the mitre gears.
The drive “legs” are powered by a second Powermatic motor which is geared down to 1/4 its slowest speed with a pair of 14/28 tooth sprocket/ladder chain reductions. The output shaft has a BT pierced disc on either side with a “leg” made from a square angle girder assembly.
The model actually works quite well. The crane hoist is a typical type III setup which always worked well. The walking action was very smooth after I extended the “box” that the leg travels up/down and pivots on by 1/4”. In fact, it walked about twice as fast as the type II walking giant/robots I’ve built in the past (about 5 ft. per minute). The manual shows the antennas reversed from my model. I found the string/pulleys couldn’t drive the larger antenna so I flipped them so the heavy one was directly driven by the motor.