Set 8848 was released in 1981 as an "Expert Builder" set. It features rack and pinion steering, a front scoop which lift and locks via a lever in the cabin and can also be dumped, a rear differential with PTO, and a rear bed which dumps via a translating rack system. The great majority of the construction uses traditional studded building techniques, but the mechanical functions are rather unique among Technic.
This vehicle really doesn't have many peers among Technic. It is not really a dump truck although it does have a dumping bed. Neither is it really a loader even though it has a scoop. Its styling is very blocky, but its functions are fascinating.
Main model |
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Features |
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Steering |
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The front wheels can be steered using an overhead control. This model has the overhead "Hand of God" control, but it is hidden by the roof. This is the only Technic model which does this. The overhead control drives an axle connected to a pair of 14 tooth bevel gears. The second axle drives a rack via a pair of 8 tooth pinion gears. The steering mechanism itself uses the new control arms and toothed links as shown in the computer image. |
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Differential |
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The rear axle uses a differential gear. It incorporates a built in 28 tooth ring gear which can work either as a bevel or a spur, similar to the 24 tooth crown gear. It is made to house 3 of the new 14 tooth bevel gears. One is on each axle, and one planet gear in the middle allows the axles to turn at different rates. The differential drives a Power Take-Off (PTO) at both the front and rear of the vehicle. This PTO does not drive anything in the basic model, but various attachments could be added. |
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Scoop |
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The front bucket can be lifted from the cabin via a fascinating mechanism (see the computer image). A lever in the cabin pushes or pulls a link. This link is attached to the midpoint of a pivoting mechanism. When in the raised position, the mechanism is over center which tends to keep the bucket locked up. When the lever is moved, the mechanism pops back over center and turns a 24 tooth gear which is used as a crank (the axle does not pass through the center of the gear). This crank drives the upper link of a 4 bar linkage through a toothed connector which is locked to the rotation of the gear, allowing the entire bucket assembly to lower (see animation). Due to the equal length of the 4 bar links, the scoop remains parallel to the ground throughout its motion. The upper 4 bar link must be at a very specific angle with respect to the crank gear or the whole thing doesn't work. Interestingly, the angle shown in the instructions is not correct, and the mechanism will not go over center if this angle is used. The bucket can also be dumped manually via a pair of finger hinges. The linkage makes use of the new toothed elements, and the lift itself is primarily beams and plates. |
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Bed |
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The bed in the rear of the truck can be dumped via a connector on either side which is used as a crank. When this crank is rotated, a pair of 8 tooth pinion gears drive a pair of rack gears attached to push rods. These rack push rods are angled within the assembly and are trapped between the pinion gears and another axle. When pushed upwards, these rods cause the bed to rotate aft. One of the pinion gears also drives a 24 tooth spur gear which makes the second lever in the cabin follow along with the bed motion. The bed cannot be easily driven by this lever due to insufficient mechanical advantage. The bed is constructed of standard plates and finger hinges. |
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Wheels and Tires |
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This set contains 4 sets of wheels and tires of type:
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By Technicopedia