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8443 Log Loader
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 Click the image to download the LDraw file of this model. Model by Eric Albrecht |
Features |
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Pneumatics
This model contains a double acting pneumatic system. The components of
this system are connected with rubber tubing routed through and around
the holes
in the beams as well as through some rigid tubes from the flex system.A single pump is located on the rear of the vehicle. Depression of the piston produces pressure. The pressure is split and fed to the inlets of two selector valves (switches) with two outputs each. Selection of the switches in either direction allows pressure to flow to either chamber of the actuators. Finally, there are two pneumatic actuators which have ports at the head and rod ends to accept input from the switches. Head end pressure extends the piston, while rod end pressure retracts it. This model has one large actuator and one small actuator. |
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Steering
The steering of this model is completely unique in the Technic line, and
that makes it very special. Virtually every Technic model with
more than 100 parts has steering, and virtually all of them are simple
rack and pinion using a 4 bar linkage. A few loaders use an
articulated chassis instead. But this 6 wheel model uses both.A "hand of god" control on the top turns a vertical axle with two 8 tooth pinion outputs. One output goes forward to a traditional rack and pinion system, but the other goes back and drives the ring gear of a turntable. The turntable is fixed to the aft chassis. The gear ratio is set such that the middle axle turns to a smaller angle than the turntable resulting is a nice flowing curvature of the 3 axles. Although the front axle technically doesn't turn, it still forms part of the curve. |
 Click for an animation of the steering in motion. |
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Suspension The rear axle features a pendular suspension with limited
travel, allowing it to traverse small obstacles and still keep all 6
tires on the ground. The red axle in the computer image is the
pivot point. Although you can see that the axles are mounted to
steering arms, they do not steer but are fixed to the aft chassis. |
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Luffing Boom
The boom can be lifted pneumatically. An actuator pushes to pivot
the boom up and retracts to pull it down. Because the actuator rod
end is not mounted to the boom itself but to a link attached to the
jib, a 2 stage motion results. As the actuator extends, the jib
first rotates outward because it requires less force. Once it
bottoms out, the entire boom lifts. This motion is repeated in
reverse on retraction. This system results in a system which
mimics the motion of a system with two independent actuation circuits,
but achieves it with a single actuator. Genius.make sure to watch the animation to understand the motion. |
 Click for an animation of the boom luffing. |
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Claw
The log grapple opens and closes with a small pneumatic actuator.
To prevent all the motion from happening on one side or the other, the
two halves of the claw are geared together with spur gears.
Despite being similar in appearance, this claw operates totally
differently (and much better) than that on 8868. |
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Wheels
This set uses six of the rubber 20x30 balloon tires and wheels.
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Other Views |
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Side View |
Top View |
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Front View
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Back View
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Computer Render |
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