Offroad Lifting Crane

Cyrus Tabrizi, 7/10/12

      This was my entry to the "Lifting Crane" category of the 2010 August Technic Challenge. It is an 8-wheeled crane truck that has a variety of manually-controlled functions.

Offroad Lifting Crane (53)

     It was not built to mimic any real crane, but rather to achieve a balanced mix of authenticity, function, and design instead. It should be noted that despite the presence of two battery boxes in the rear of the truck and in the counterweight of the crane, this model does not sport any motors, lights or other electronics-each function is controlled manually via knobs or pneumatics.


     The red, yellow, and black color scheme is a favorite of mine as it fits my parts palette perfectly- thus, I tend to use this style repeatedly across many of my MOC's. The cabin is red as I have sufficient parts to make it interesting and unique and the crane is yellow to make use of my many yellow beams and to mimic the typical color associated with various construction machines and cranes. The rest is mostly gray or black and an effort was made to conceal the gray parts within the truck's belly or behind other black parts. This also matches the black and gray found in the eight wheels. The black wheelguards give the truck a sleek, sturdy, and sporty look while maintaining its offroad appearance. This look is supplemented by the styling of the balloon tires from the 8297 Offroader and the Telehandler. This combination of large and small tires is done both because of my limited part supply and because of the uniqueness factor it provides to the truck.


     In terms of function, this truck is both diverse and a minor feat of engineering. As usual, this crane has a fake engine, a V10 to be specific, and is powered by differentials in the rear two axles. The front two axles have stepped steering that is controlled via a knob on the side of the truck. This means that the wheels on the first axle will turn more than the ones on the second axle to allow for a smoother drive. The cabin in the front of the truck is divided into two compartments each with two seats. In between the seats of the lower cabin lies a winch with a quick release mechanism. The lock is released through a lever on the side of the cabin. When it is pushed, the winch is free to spin in either direction. When it is released, the winch will only be able to reel the hook back towards the cabin. The top cabin can move forwards and backwards depending on whether the truck is stationary and the crane is in use or if the crane is lowered and the truck is in motion. To keep the crane steady and secure when the truck is moving, the cabin is moved forward via the gray knob on the side and a gear rack built into the cabin. When the cabin moves forward, it lifts a support brace for the crane arm to rest on. It also reveals the fake V10 engine. When it is moved back, the supports are lowered into the truck's body.


     Next there is the actual crane arm. A knob on the side opposite the steering knob controls the turntable that provides full rotation to the crane. The up and down movement of the crane is done by only one linear actuator and is controlled by a knob in the rear of the truck. This knob transmits its power through the turntable to the linear actuator. The crane has a dual-stage boom and can extend an additional 10.5" inches via the rotation of yet another knob. The winch is also controlled by a knob at the end of the crane arm. It has a limited slip lock that utilizes a rubber piece to hold the winch in place. There is also a small cabin for the crane operator on the end of the main crane arm. This provides the operator with the best view possible at all times. To balance all this weight and place the crane's center of mass within the circumference of the turntable, an adjustable counterweight with a quick-release was built. It used a battery box to offset the weight of the crane arm and could lower or raise to balance any of the crane's load.


     Perhaps the most amazing feature would be the pneumatic lift that is built into the body of the truck. It sports four pneumatic cylinders-two on either side of the truck between the second and third axles, and two mounted at an angle in the back of the truck. Together, these four cylinders are able to lift the entire truck, supporting all of its weight and stabilizing it while the crane arm is in use. They are controlled via two switches: one for the rear, and one for the middle. Each switch, in turn, is supplied with air from its own hand pump mounted at the rear of the truck between the two cylinders. This allows the height of each pair of cylinders to be adjusted individually. When the truck is lowered, it has anywhere between 1 and 2 inches of clearance, depending on where this distance is measured. The truck measures 2' 1" or 63.5 cm in length and weighs approximately 2.5 pounds.


     When it was completed, it was, by far, the biggest Lego I had ever designed by size, by weight, and simply by the number of functions it had. In this regard, I was impressed, even though it lacked the usual PF integration, and I think it is a decent MOC given the time constraints of the competition -I was impressed to know I could build something of this magnitude in the time provided. It's certainly not as complicated as some of my other builds and its construction is not particularly unique in terms of the techniques that were employed in various parts of it, but I enjoyed taking a break from the motors and wires that are a part of the PF system -not to say that I don't enjoy the PF system enormously -it's simply that it entails a different style of building, one that is, in some cases, more flexible and less strict. Looking back on it, I realize that it lacks any advanced transmission or geartrain design, and it doesn't even have suspension! This would have been understandable 5 years ago when I had a smaller and more limited collection of parts, but is hardly inline with my recent MOCs. Additionally, it has its set of design flaws -the main crane arm is practically impossible to lift with the flawed geometry in the linear actuator's mounting and the gearing and my use of knob gears in the undercarriage is hardly adequate for powering the actuator through the turntable. Another flaw in its design was the "quick-release" I used for the counterweight -I should have made it so that it could be lifted without the need to unlock and only be lowered when the lock was undone. My favorite part was, by far, the sliding cabin. Although such a feature is not exactly common -or even existent- in real life, it is fun to play with and useful when considering the support arm that is lifted for the crane to rest on. For some reason, I almost feel like this model laid some sort of groundwork for my enormous Tow Truck that I built afterwards -even though the two models share nothing in common except for their color scheme and for having a crane and eight wheels.

More pictures can be found on Flickr.


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