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CAT | Cranes

Nov/09

14

Bailey tower crane

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This is a 1:20 scale model of a shipyard crane, working in the port of Vlissingen, The Netherlands.

It took me about 6 months to build it. The model weighs 16,6 kg (including some non Lego counterweight). The height is 2,25 m, the length of the jib (from tip to the end of the  yellow machinery room)  is 3 m. The wheel base is 0,5 m.

The model has following functionality added:

  • Crane traveling, 4 pcs. 9V motors;
  • Slewing, 2 pcs. medium PF motors;
  • Main hook traveling, 1 pc. medium PF motor;
  • Aux. hook traveling, 1 pc. medium PF motor;
  • Main hook hoisting, 1 pc. large PF motor;
  • Aux. hook hoisting, 1 pc. large PF motor;
  • The rigging of the crane is the same as in reality. Kite wire was used for this;
  • For the slewing bearing I used “hail fire droid wheels”. (See more in category Construction Solutions).

The scale 1:20 was forced upon me  by the use of the hail fire droid wheels for slewing. Fortunately the relation between the dimensions of the lattice construction of the tower and the jib, and the dimensions of the Lego parts used, proved to be within acceptable proportions, and quite pleasing to the eye. Moreover, a Technic figure could be added as a driver. This resulted in a rather slender construction of the jib, close to the strength limitations of the Technic bricks used.

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During building this once resulted in snapping of some 1 x 16 bricks. Building big models leads to big failures!

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This is the crane in reality.

The model was exhibited at the model building fair in Goes in February 2010:

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Following photo’s show some of the construction details:

IMG_1781 The crane has two slewing motors. As in reality the motors and gearboxes can move around their pinion shafts. This movement is limited with rubber buffers, which serve  to slow down the jib motion at the moment the motor brakes are applied.

Use of two Lego motors to drive 1 slewing ring proved to be a problem due to speed differences. This resulted in regularly wringing loose of one of the slewing gears during frequent demonstrations on the model fair.

IMG_1238 This shows some on the internal connections between the crane legs and the pedestal.

IMG_1777 The trolleys travel along the jib over the edges of 2 stud wide plates.

IMG_1797 The power cable reel.

IMG_1798 Here the connection between the crane legs and the wheel bogeys is shown. Note the 45 degr. angle between legs and bogeys. The crane load is distributed evenly onto 2 x 2 wheels at each corner. The reduction gear proved to be quite a challenge to get it into a very narrow space. Old high speed motors were used (I was out of PF motors) while the crane traveling speed had to be very slow.

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This is a functional model of a real 40 tons shipyard crane, working in the port of Vlissingen, The Netherlands.

The height of the model, when at minimum outreach, is approximately 1,9 m and it is built according to the general arrangement plans of the real crane, some photo’s and my own observation, as I’m working on the same ship repair yard.

The scale is more or less 1 : 30.

The model is functional for as far as the slewing and topping movement. The travelling, however motor driven is not very good. Hoisting with both winches works, but due to lack of ballast weight, the lifting capacity is very limited.

The force in each of the crane’s 4 legs is evenly distributed to 3 travelling wheels, which on the real crane, travel on rails with 15 m gauge. On each side of the crane an old 9V motor drives, via reductions, the travelling wheels. May be, if I had fitted the rubber tires on the wheels the crane would have moved over the floor covering.

The bogies are connected to legs with threaded axles and nuts.

The construction, having 3 wheels on each corner of the crane requires a bogie lay out with 2 wheels in 1 bogie and 1 wheel in the other. Even force distribution is achieved by applying the force from the leg on the forward bogie, but directly above the middle wheel, which is in the aft bogie.

Slewing gave me headache. I made a slewing table out of bricks on it’s sides which gave me a surface for wheels to travel on. In the middle of this table is a hole, in which a Technic turntable is anchored. The upper part of the turntable is connected with bricks through the center to the column of 2×4 bricks which is visible in the lower part of this photo. This column is supposed to bring the weight down to a thrustbearing in the center of the crane, where the horizontal cross members meet.
The slewing table is supported on the outer diameter by 8 rods which go up from each corner. The connection between these rods is shown here in it’s full misery.

The slewing gear is driven by a medium 9v power functions motor and was fun to built.

The topping, or luffing movement is what I like most of this type of crane.
In this case the jib is moved in and out by a crank-rod mechanism. When the jib moves out it pulls up a counterweight and so balances the movement of the jib.
The cranks are powered by a large power functions motor through a reduction, of course.

When the jib (also called the push arm) moves outward, the pull rod, which is connected to the tower, pulls the aft of the top jib (the part with the yellow tip) down. This, together with the outward motion results in a horizontally level movement of the tip of the top jib, and, consequently, in a horizontal movement of the crane’s two hooks.


This photo shows the main hoist (grey), driven by a large PF motor and the auxiliary hoist (yellow) driven by a small PF motor. For the hoisting wires I used kite wire.

The four motors are remote controlled with infra red. The battery pack is also hanging from the engineroom ceiling, as far as possible aft, to help provide counterweight.

Altough I hid some old small steel ball bearings in the floor of the engine room this was by far not enough counterweight. It was sufficient to compensate for the jib moving out, but the crane was not capable of any significant load.
In my next model I will have to add a lot of lead.

The crane in reality.DSC01134

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