Bucyrus 495HF Mining Shovel

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Bucyrus 495HF, picture 1


Six electrically controlled functions:

  • Left crawler forward - stop - backwards
  • Right crawler forward - stop - backwards
  • Swing drive
  • Hoist motion
  • Crowd motion
  • Bucket door mechanism using adder-subtractor geartrain

Introduction - Lower Carriage - Upper Carriage - Crowd Mechanism - Bucket - Details - Remote Control - Video
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Bucyrus 495HF, picture 2

Bucyrus' 495 High Performance series of mining shovels consists currently of two machines. Both share the same upper works while there are differences on the lower carriage. The HR version is designed for hard rock applications while the HF shovel features a lower carriage designed for applications where low ground bearing pressure is required. This is the case when mining oil sands as it takes place in Canadas Fort McMurray region in the province of Alberta.
My model represents the HF version and is designed in the colors of Albian Sands, one of the three big companies involved in the oil sands business. The model bears the number 01 thus representing the first Bucyrus 495HF shovel shipped to Albian Sands.
Inspiration for the model came after I built a Liebherr T 282 mining truck in scale 1 / 50 which is roughly minifig scale. I decided that there has to be an adequate loading tool for the truck. As the latter one belongs to the biggest machines currently available, the shovel had to be at the top of the range as well. Scale is 1 / 48 which resulted in an even number of studs for the width of the upper carriage.

Bucyrus 495HF, picture 3Bucyrus 495HF, picture 4Bucyrus 495HF, picture 5

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Lower Carriage

Bucyrus 495HF, picture 6

As mentioned above, the HF version of Bucyrus' 495 series shovels is designed for low ground bearing pressure applications. This means that there have to be wide crawlers to distribute the massive weight of 1450 tonnes to an area as big as possible. On the real shovel the track shoes measure 3.5 meters which resulted in eight studs on my model.
I used two rows of the wide Technic chain links side by side of which every second link carries a 1' x 8' plate. This time I didn't use 16 tooth gears for the track rollers but small tires like they are used on the LEGO City airplane wheels. They fit perfectly in the groove of the chain links and make for a much smoother ride than the gears. There are eight pairs of these rollers per track frame. The drive sprocket and the front idlers make use of 40 tooth gears.
Two old style 9V motors drive the left and right crawlers independently. They are housed in the center part of the lower carriage where the gear train is located as well. The last stages of the two drivetrains consist of a chain each using one stud wide Technic chain links. They are located on the inner sides of the track frames and drive each a 24 tooth gear sitting on the same axle as the drive sprocket. The chains are hidden by the track shoes and the drive motor mockups.
On the real shovel, a single power cord enters the lower carriage at its rear end delivering the electricity for the different propel and digging motions. My model features six cables - one for every powered function. To prevent the cables from getting in contact with the crawlers during repositioning of the shovel, they are held away from the lower carriage by a truss construction. Colored in red for better visibility, this component can be found on the model as well.

Bucyrus 495HF, picture 7

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Upper Carriage

Bucyrus 495HF, picture 8

The upper carriage is connected to the lower works by a standard Technic turntable mounted with the studs up side down. Thus the 56 tooth gear ring is fixed relative to the lower carriage allowing the swing drive to be on the revolving frame. The latter one consists of an old style 9V motor, driving two sets of drive pinions with eight teeth, located on the left and right side of the upper carriage.
Because there is not enough room for a proper roller bearing, the revolving frame is supported by two sets of rollers, consisting of two 12 tooth bevel gears each, revolving around the turntable on a circle of tiles. One set is located on the front side of the upper carriage, the other one is opposed by 180 degrees.
The revolving frame carries the main components of the shovel. First of all there is the gantry, an A-shaped construction that supports the boom by a set of four tension cables. Then there is the hoist winch, consisting of two cable drums each made of a wheel of the size 20 x 30. They sit on the same axle and are driven by two old style 9V motors of which one is located on the left and one on the right side of the hoist drum. Finally there is the crowd mechanism as a main component of the upper carriage.
The rear end of the revolving frame houses a counterweight compartment filled with tin. It is used to balance the weight of the boom, stick and bucket.

Bucyrus 495HF, picture 9Bucyrus 495HF, picture 10Bucyrus 495HF, picture 11

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Crowd Mechanism

Bucyrus 495HF, picture 12

The most complex part of the whole model is the crowd mechanism. On Bucyrus shovels the stick carrying the bucket is hinged between the two main chords of the boom at about half of its length. To be able to vary the digging radius and to position the bucket at the right place over the dump body of the mining truck the stick can glide forward and backwards in its saddle block. This motion is achieved by a set of ropes. Thus and because of the fact that the stick is tubular allows it to revolve around its center line to compensate for forces that are applied on the digging lip off the center of the bucket during the digging cycle.
On the real shovel the crowd mechanism consists of a double rope drum each carrying two ropes - one to extend the stick, one to retract it. This mechanism can be found on my model as well. But because there is a rope operated bucket door, another rope drum has to be installed which has to unwind the rope when the stick is moved forwards and to roll it up when the stick is retracted.
On real machines the bucket door rope drum is independently driven and always keeps the rope under a predetermined tension. This was not possible to implement on my model. Therefore I opted for an adder / subtractor drive allowing the bucket door drum to revolve when the crowd drum revolves too and to be controlled by an own motor that can add or subtract a revolution of the bucket door drum when the rope should be unwound or reeled in relative to the crowd motion.
The construction of these mechanisms can be seen on the pictures below. The drum with four studs diameter carries the two ropes for the crowd motion - the red one to extend the stick, the blue one to retract it. It is driven by an old style 9V motor. This same motor also drives the cage of a differential gear with two output shafts one of which carries a two stud diameter drum for the bucket door rope. The other shaft is connected to a 9V micromotor which usually stands still and is only powered when the bucket door should be opened or closed.
Because the second shaft stands still the one carrying the drum revolves at twice the speed of the differential cage. Therefore the small drum unwinds the same amount of rope in the same time as the four stud diameter crowd drum. When the bucket door should be opened while there is no crowd motion, the rope drum is only driven by the micromotor. This mechanism works fine. All you have to ensure is that there is only one layer of rope on the drums as more than one layer can result in different rope speeds forcing the bucket door to open even if not desired.

Bucyrus 495HF, picture 13Bucyrus 495HF, picture 14Bucyrus 495HF, picture 15

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Bucyrus 495HF, picture 16

The real 495HF carries a 44.8 cubic meter bucket which equals 0.4 litres on my model. Both the original and the model are therefore able to load a 360 tonne mining truck in four passes.
The design with slanted rear corners results in high fill factors and the dipper lip with six teeth allows easy bank penetration. These characteristics I tried to copy with my bucket design resulting in a quite complex but sturdy construction incorporating several SNOT techniques.
To position the bucket over the trucks dump body, there are two red cones hanging from the dipper stick indicating the shovel operator the correct dumping position. This is important because it is vital for transport safety that the truck load is equally distributed to prevent rolling over during tight turns or on side slopes. Furthermore the correct positioning of the bucket extends dump body life as the bucket door can swing open freely without touching the truck.
The bucket door is held closed by a bolt attached to the bucket door rope whose mechanism is described in the crowd mechanism section. By pulling the bucket door rope the bolt realeases the door which opens driven by gravity. To close the door again, the bucket has to be lowered which is the case when positioning for a new digging cycle. The rope then can be released and the bolt moves back in its original position thus locking the door.

Bucyrus 495HF, picture 17Bucyrus 495HF, picture 18Bucyrus 495HF, picture 19

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Bucyrus 495HF, picture 20

The shovels scale of 1 / 48 makes it suitable to be operated by a minifig. Therefore a lot of details are needed to make for a comfortable working day. First of all there is Bucyrus' spacious SuperCab with excellent visibility. Two air conditioning modules are mounted at the back side of the cab. Access to the shovel is ensured by a retractable ladder on the left side of the machinery house and a swing out stairway on the right side.
Thirteen flood lights are mounted all around the machinery house and additional lighting makes operator acces safe 24 hours a day. Railings and an overhead crane rail on the front left corner of the machinery house are more of the details that can be found on the model.
Further details include air intake pipes for machinery house ventilation, GPS sensors and a pair of flags with the manufactuer and the operator logos. Finally there are self made stickers with the model designation and machine number as well as a big Bucyrus logo on the counterweight assembly at the back end of the revolving frame.

Bucyrus 495HF, picture 21Bucyrus 495HF, picture 22Bucyrus 495HF, picture 23

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Remote Control

Bucyrus 495HF, picture 24

The six electrical functions of the shovel can be controlled by a hand held remote control unit. It houses a power source and several control levers.
The model either can be powered by a 9V battery box containing six AA batteries or it can be connected to a LEGO train speed regulator that plugs to the mains. A big compartment usually covered by a lid houses the battery box and a connecting cable. If running on batteries, the cable is stored in the compartment. When using the train speed regulator the cable can be taken out of the compartment. A hole in the cover allows it to be closed nevertheless.
There are four control levers for six functions which means that two of them are used to control two functions each. The left and right levers are configured as two axis joysticks, using two pole reverser switches. The center levers are each directly connected to a pole reverser switch. They are used to independently control the left and right crawler tracks. The left joystick is connected to the swing motion (left - right) and the crowd motion (forward - backwards). The right joystick controls the bucket door (left - right) and the hoist drive (forward - backwards).
Thus all the main digging functions can be controlled with the index fingers and the thumbs while holding the remote control which is easy due to its low weight. Nevertheless operation of the shovel is not an easy task when reasonable cycle times should be maintained.

Bucyrus 495HF, picture 25Bucyrus 495HF, picture 26

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For the first time I am able to provide a video which shows my model in full action. I recorded a complete digging cycle including loading of the mining truck. Of course I haven't dug real dirt as the model is not designed for heavy duty outdoor operations and 0.4 litres of dirt would result in some serious weight on the hoist rope. Finally it is to mention that the movements of the model are a bit slower than when powering it with the train speed regulator. But at the spot where I took pictures and recorded the video no power socket was available. Therefore the shovel run on (weak) batteries.
Feel free to download the video and enjoy real time action in 640 x 480 resolution!

Bucyrus 495HF video

MPEG-1 video (10.8 MB)

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