Original Year	1991
# of pieces	300
Categories	Construction Equipment: Cranes Other: Universal Sets
Dimensions	various
Models	Forklift Crane Log Loader Grader

8074 Universal Building Set with Flex System

Set 8074 from 1991 is one of the better Universal Sets released. It used the new flex system to make 4 functional and interesting models. The forklift featured steering and lifting and tilting forks. The stationary crane featured a hoist, a luffing boom and jib, and full slewing via a turntable. The log loader, a rather unique model, featured steering, a rotable boom, a lift for the boom, and an opening loading claw. The last model, a road grader, is the only model of it's kind released by LEGO^®. It's long frame featured steering and a grading blade which could be raised and lowered. All of the models were quite large and assembled largely with pins.

This was the first set to use the flex system, which it does in every model. In all 4 of the models, they are used as push-pull cables. In the crane, they are also used as diagonal braces. In some models they are straight, and in others they are routed through sleeves which wind their way through the structure. If you are looking to get your hands on some flex system parts, this is the set to find the most of them. There are 20 end fittings , 10 cables, and 2 sleeves included. The lengths include 7, 9, 11, 13, & 19.

Although all of the models are excellent, I like the crane the best and chose to use it for my display.

1^st Model: Forklift
This forklift is an excellent model. The fork boom does not lift vertically, but pivots from the rear on a four bar linkage like a skid-steer loader, but in this case the model has rear wheel steering. It uses the flex system to control the tilt of the forks.	Click to download the LDraw file of this model. Model by Benjamin Wendl
Steering The front wheels can be steered using an overhead "hand of god" wheel. The wheel drives a pair of 24 tooth gears which drive a pinion. The pinion drives the steering rack. The steering mechanism itself uses steering arms and toothed links.	Click for an animation of the steering in motion.
Forks The forks are raised by a crank on the back via a 4 bar linkage. The crank turns a worm gear which mates with a 24 tooth crown. The crown gear drives an axle which rotates a pair of liftarms. These liftarms push up on a vertical beam which then lift the support arms. The support arms tilt down at about a 45 degree angle and are locked in position with a pair of liftarms. The angle cannot be changed. This means that the forks tend to change angle (tip back) as they are raised.	Click for an animation of the forks lifting.
Fork Tilting The forks can be tilted using a crank on the rear of the vehicle. The crank drives a worm which mates with a 16 tooth spur gear. This axle then rotates a pair of 2-blade rotors. The rotors are locked to the rotation of the axle at their center point. On either end of the rotors are attachments to flex cables. Because both arms of the rotor are the same length, the upper and lower cables move the same amount when rotated (see computer image). This type of system is often called pull-pull. Even though these cables can support some compression, there is no need for compression because either rotation direction can be carried in tension. Consequently, this would work even if just string was used. Look at the Curtiss Jenny for a great example! Through the cables, the rotation of the rotors is matched at the other end with another pair of rotors. These turn a liftarm which drives an axle as part of a 4 bar linkage. This could also have been accomplished with another pull-pull cable system. The last set of liftarms pivots the forks.	Click for an animation of the forks tilting.
2^nd Model: Crane
This is one of the few stationary crane models in the Technic line. It is quite functional and uses the flex system in great ways.	Click to download the LDraw file of this model. Model by Benjamin Wendl
Slew The upper superstructure can slew about the base truss using a geared turntable. A small crank on the side turns a pair of 14 tooth bevel gears. An 8 tooth gear then drives the turntable. Since the outer ring gear on the turntable has 56 teeth, the gear ratio is 7:1. Note that the cable for the hoist passes through the center of the turntable. This allows the top to rotate without pulling the cable.	Click for an animation of the crane slewing.
Luffing Boom The main boom can be raised and lowered using a crank on the back. The crank turns a worm gear which drives a 24 tooth spur gear. The spur gear rotates a pair of liftarms. An attached pair of flex cables attach to liftarms at the other end. These liftarms rotate another set of linked liftarms which raise the boom. Because of the offset weight of the boom, the flex cables are always in tension.	Click for an animation of the boom luffing.
Luffing Jib The jib can be raised and lowered using a crank on the back. The crank turns a worm gear which drives a 24 tooth spur gear. The spur gear rotates a pair of liftarms. An attached flex cable attaches to 2 blade rotors at the other end. The liftarms pivot at the bottom of the rotors, and the flex cable attaches to the middle. Another flex cable attaches to the opposite end which ends up amplifying the deflection. The second flex cable attaches to a final set of liftarms which are locked to the jib. Because of the offset weight of the jib, the flex cables are always in tension. These two flex cables are guided by sleeves which allow them to assue curved shapes without catching on anything.	Click for an animation of the jib luffing.
Hoist The simple cable hoist is driven by a crank which uses an axle as a cable drum. A 16 tooth spur gear is used as a ratchet to keep the cable from unwinding under load.	Click for an animation of the hoist in motion.
3^rd Model: Log Loader
There is only one other log loader in Technic history, and it wouldn't come until much later. For it's size, this model has a tremendous number of features, and it even looks pretty good!	Click to download the LDraw file of this model. Model by Benjamin Wendl
Steering The front wheels can be steered using an overhead "hand of god" wheel. The wheel drives a pair of 24 tooth gears which drive a pinion. The pinion drives the steering rack. The steering mechanism itself uses steering arms and toothed links.	Click for an animation of the steering in motion.
Slewing Boom The boom is supported by one of the new turntables. This is only the second set to contain one after 8094. A crank on the left side drives a set of 8 and 24 tooth gears. Torque then passes through a pair of 14 tooth bevel gears. Finally, an 8 tooth pinion drives the outer ring gear of the turntable which has 54 teeth. Final gear ratio is 21:1. If slightly raised, the boom can rotate 360 degrees without hitting anything.	Click for an animation of the boom slewing.
Luffing Boom The main boom can be raised using a pair of cranks on the turntable. Both cranks turn the same axle which drives a worm gear. The worm gear mates with a 24 tooth spur gear. The spur gear axle passes through a pair of liftarms which locks them to the axle. The other end of the liftarms is locked to the boom beams with axle pins, so the boom rotates at the same rate as the 24 tooth gear. Because of the 24:1 ratio, the crank can lift this large cantilevered mass easily. The system cannot be backdriven because the axial friction is higher than the backdriving torque due to the screw pitch angle.	Click for an animation of the boom luffing.
Claw The grasping claw on the end of the boom can be opened via a lever arm. The claw is spring loaded to the closed position with a pair of rubber bands near the lever. A flex cable attached to the lever runs up to a pair of liftarms which rotate to drive the claw. Keen eyed observers may note that the claw does not close completely. This is due to the fact that my set appears to have the wrong flex cable which is one unit longer than it should be.	Click for an animation of the claw in motion.
4^th Model: Grader
This is the only LEGO^® Technic road grader. This one is rather simple since it lacks the dual rear axles and pendular front axle of many real graders, but it is a fine model none the less.	Click to download the LDraw file of this model. Model by Benjamin Wendl
Steering The front wheels can be steered using an overhead "hand of god" wheel. The wheel drives a pulley used as a crank arm. On either side of the crank arm are long flex cables which run forward to a similar attachment on the front of the vehicle. A set of 8 and 24 tooth gears adjust the torque 90 degrees. The final axle drives an 8 tooth pinion. The pinion drives the steering rack. The steering mechanism itself uses steering arms and toothed links. In this case, the same length flex cable is used on either side. This type of system is often called pull-pull. Even though these cables can support some compression, there is no need for compression because either rotation direction can be carried in tension. Consequently, this would work even if just string was used.	Click for an animation of the steering in motion.
Grading Blade The blade can be raised and lowered via a 4 bar linkage. A crank is used to turn an axle which runs through a pair of 14 tooth bevel gears. The bevel gear turns a worm which drives a 24 tooth spur gear. This spur gear is attached to an axle which makes up one axis of a 4 bar linkage. Four liftarms keep the blade parallel which it lifts on a pair of 4L beams.	Click for an animation of the blade in motion.

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