Released in , set has the first and only motorized pneumatic find on any LEGO® model, and in fact this is the only set with a motorized compressor. Find great deals for LEGO Technic Air Tech Claw Rig (). Shop with confidence on eBay!. Shop LEGO Technic Air Tech Claw Rig. Free delivery and returns on eligible orders of £20 or more.
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Click the image to download the LDraw file of this model. Model by Eric Albrecht. Click for a high resolution rendered animation of the pneumatic connections. Click for an animation of the differentials in motion.
LEGO Technic Air Tech Claw Rig (8868)
Steering, V-6 engine, dual differentials, pneumatic compressor, slewing cab, luffing boom and jib, grasping claw. With a compressor, 4 switch valves, 4 large actuators, one small actuator, and four rigid tubes, there are a total of 23 flexible pneumatic hoses legi route through this behemoth. Many of these hoses then pass aft through another beam and up through the center of the turntable for the loader.
The color coded computer images can be used to decipher the routing of the hoses in this system, which can then be used to derive the logic of this mechanical computer. A single compressor is integrated into the body. The pressure is split and fed to the inlets of four selector valves switches with two outputs each.
Selection of the switches in either direction allows pressure to flow to either chamber of the actuators. There are five 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. The actuators are designed to work in compression during their power stroke.
A real hydraulic actuator has significantly less output force in tension than in compression due to the fact that the annular area of the rod end of the cylinder is less than the full bore area of the head end. Because there is continuous supply of pressure, this model operates very smoothly and multiple functions can even be run concurrently. One or two of the pneumatic air tanks which came out years later make great replacements for the fuel tanks and really bump the functionality up to the elgo level with lrgo virtually limitless source of pneumatic power.
I’m sure no one leto have any trouble finding a place to route even more pneumatic hoses! Incidentally, if you are wondering how long it took me to model all of those pneumatic hoses on the computer, leho amount of time is too long to comprehend. Motorized Compressor Feast your eyes on the only Technic pneumatic compressor.
Why they never used this again is one of the great mysteries and tragedies of our time. For the first time, a 9V battery box was actually integrated into the body of a model instead of being remote. This serves legoo make this model pretty heavy. There’s a 9V motor mounted under the battery box which drives a large pulley through a belt.
Reciprocation on this crank gives the compressor cylinder a stroke of 1 stud. Due to the small gear ratio, it operates very fast.
The compressor cylinder itself looks like a small actuator but has a port only at the head end. When driven to retract, it forces air out through the port. When extending, it draws in air from the atmosphere. There is an integral relief valve which prevents the pressure from building above a safe level, although the torque required to drive the compressor to relief pressure slows the motor considerably.
Click for an animation of the compressor in motion. Pneumatic Slew By this time, there had been quite a few cranes which featured a slewing turntable, but this is the first time it was controlled pneumatically and it only happened one more time many years later. The color coded computer image shows the way the dual pneumatic cylinders are cross connected. The head end of one actuator is connected to the retract port of the other.
This way, pressure causes one legoo extend and one to retract simultaneously. A pair of rack gears are connected to the actuators and are used to turn a 16 tooth spur elgo. Since the bottom half of legp turntable needs to 8868 fixed, a unique driving method was required.
A vertical axle which connects to the 16 tooth gear drives a horizontal axle which passes through the holes in the upper turntable. It is important to get the two actuators even and centered when rigging the system to make sure ,ego it can rotate 90 degrees in either direction.
Because all of the other pneumatic hoses have to pass through the center of the turntable along with the driving axle, the crane can only turn so far before the hoses snag. Extra length is required when at the centered position. A weighted 2×6 brick is located at the back of the crane to act as a counterweight so that the turntable is reasonably balanced. Click for an animation of the loader slewing. Pneumatic Boom The 888 boom can be luffed via a single pneumatic cylinder working in compression.
The actuator attaches almost half way along the length of the boom. This gives it excellent mechanical advantage to lift the weight, but also means that the total boom rotation is small; in this case about 45 degrees. Technic “triangles” are used as lugs to attach to the rod end of the actuator.
LEGO Technic Air Tech Claw Rig () | eBay
The compressor has plenty of pneumatic pressure to lift the boom, even at full extend. Click for an animation of the boom in motion. Pneumatic Jib The jib has two sections, a fixed section and a movable section.
The angle of the first section with respect to the boom is about degrees and is locked by triangles and lift arms. The second section is movable and is lifted by a single pneumatic actuator driving another pair of triangles. Compared with the boom actuator, this one has fairly poor mechanical advantage, but less is required due to the decreased moment arm of the lifted load.
The smaller arm allows a greater range of motion; in this case almost 90 degrees. Click for an animation of the jib in motion. Pneumatic Claw A grasping claw on the end of the jib is driven by one of the new miniature pneumatic actuators. Because of the very small area, this actuator has a small output force and the grip of the claw is not very strong, but it does the job.
Unlike the other actuators, this one has to work in both tension and compression, and in fact the lower tension force is what is used to close the claw. The actuator attaches to the middle hinge point of the claw which allows it to drive both sides at once. The outer angle of the claws is fixed at 90 degrees. The claws are supported by 3 arms which are free to pivot at the ends.
This allows the claw to remain perpendicular to the ground no matter what the jib angle is. A look at this computer image and those in the above sections will demonstrate that the hose’s path to this actuator is pretty circuitous.
Flex system rigid sleeves are used as pneumatic tubes to span the sections between the pneumatic hoses. This allows them to be clipped to hooks which makes certain that the hoses move with the boom and jib and do not become tangled. The claw can be lowered to grasp the rear bumper to help keep the crane stable when the truck is in transit. Click for an animation of the claw in motion. Steering The front wheels can be steered using an overhead “Hand of God” control.
The overhead control drives an axle connected to a pair of 14 tooth bevel gears. The second axle drives a pair of 16 tooth spur gears and then the steering rack via an 8 tooth pinion gear. The steering mechanism itself uses steering arms and toothed links as shown in the computer image.
The steering arms may seem small for a model of this size, especially since the weight of the model is cantilevered out the wheels via only a single hole as a support couple.
But it seems to work fine. Click for an animation of the steering in motion. Engine The rear wheels are used to drive a V-6 engine. Torque from the differentials passes through a long drive shaft to a point under the front of the engine. A combination of an 8, 24, and another 8 tooth gear pass the torque up without changing the gear ratio or direction.
A belt then actually drives the crankshaft of the engine via a pair of pulleys which increase the rotation about 3 times. This makes the engine turn fast. The front of the crankshaft uses a 3 blade rotor as a fan. The engine is made from cylindrical engine elements. The two cylinder banks have a standard V angle of 90 degrees.
Each pair of pistons shares a common crank pin. Because the crank pins are each offset degrees, the forward and back cylinders are synchronized. This can be seen clearly in the animation. A big diesel truck like this would indeed probably have a large displacement 6 cylinder engine although probably inlineso this engine fits very well. Click for an animation of the engine in motion.
Differentials The dual rear axles are both “live” and use a pair of differential gears which incorporate a built in 28 tooth ring gear which can work either as a bevel or a spur, similar to the 24 tooth crown gear. The differential ring gears are linked via an axle with 14 tooth bevel gears at either end.
While this allows them to rotate at the same rate, it could make one differential rotate backwards.
Instructions For LEGO 8868 Air Tech Claw Rig
To solve this, the ring gear of the second differential is located on the opposite side. The differentials leog made to house 3 of the 14 tooth bevel gears. One is on each axle, and one planet gear in the middle allows the axles to turn at different rates. Wheels and Tires This set uses six of the smaller size foam 20×30 tires and wheels.
While tandem rear wheels would have been nice, there is no way they would have fit into the width of this model.