Finished Product

An animation of the final product.

Final Assembly Drawing

With the final CAD design finished I was able to then produce a 3rd Angle Orthographic Assembly drawing showing the dimensions of the crane design. The drawing also includes a bill of materials showing what type of material will be used for each part and also showing the part on the isometric view (top right). This drawing will then enable our finance officer to be able to draw up figures in ragards to the cost of the crane materials.

Final Design Assembly

This is the final design assembly for the crane. The structure is standing on four legs which are flexible and move independantly of each other, offering a stable support especially on uneven terrain. the main boom which will take the load is supported by a cable running from the two supporting Steel I-beams on either side. The eye bolts used with this cable can take maximum 750KG loads each and therfore they are more than suitable for our use. This will help in distributing the load across the 3 beams. the 4 pulley system will be hooked onto the eye bolt which is bolted onto the undersurface of the main boom. The eye bolt can take loads of up to 1.5 tonnes therefore it is more than suited for our 1 tonne max. The pulley system is then connected by means of winch (see previous posts) which has a 10 to 1 ratio.

As these beams will be made from steel, each of the parts on the strucure weighs a comfortable weight for two people to be carrying over short distances. Also this crane will be easy to assembly as it incoperates simple bolts and also benefits from some of the parts coming pre-machined. The legs will be kept secure at the required height by means of pins being threaded through the hole features found on the leg.

Not only do the straight I-beams have support but also the main boom has been modified to include a support system through the square steel tube. With the circular base connected to the underside by means of ball bearing, the structure is able to rotate indipendantly of the underside base.

Leg Design

This is the leg design we will be going with for our crane. In designing, it was important to make sure that we kept in mind the fact that the crane will be used mostly on rough terrain. Therefore the support for the whole crane structure needed to be flexible but still maintain structural strength. The led to the chosen design as shown above.

Each of the legs can be moved independantly from each other and then kept at that position by means of a steel bolt put through the corresponding hole. If position needs to be changed this can be done easyliy by repeating process with corresponding hole position.

Having constracted the supporting legs a way of connecting base to legs had to be designed.

The above illustrations show the fixings that will be used to connect the base to the crane legs. This will be done by a standard bolt bolted through the lower base and the legs at eacg of the four intersections as shown. The Upper base will not have any direct connections with the legs as this will allow for the rotation of the plate through the ball bearings between the Upper and Lower bases.

I Beam Support

Having chosen the ideal type and dimensions of I-beam I then went on to design the beam support which would be bolted on to the base so as to stop buckling when the beam was loaded. For this support, another industry standard was used, this time in the form of a SQ steel tube with dimensions 2x2x0.25. This is easily machined and would then be machine-cut at 45 degrees from each sized so as to fit perfectly onto the base and the standing I beam. The support itself only weighted a very small 3.592 KG and therefore is more would be very ideal if the structure passes the stress anaylsis.

Having done this it was now possible to carry out a stress analysis test on SolidWorks so as test if our chosen beam and support could take the max load that it will be subjected to.

Having carried out the test with the I beam in both set-ups as shown above, it was eveident that the beam was more structurally sound if the load was applied across the flange. The beam was under a lot more stress with a load applied along its width and therefore the flange was the best solution. When both the load and support where applied from the flange the stress anaylsis showed that the structure was not under any major stress. as shown I modelled the structure as fixtured on two surfaces (bottom of beam and support) which is where the structure would be bolted to the base. A load of 5070N (10140N halved between two beams) was applied at a point where the cable would pass through and the result shown was the van Mises stresses remaing in a comfortable zone.

The above screenashot is one showing the displacement that this load would have on the said beam. This was also a good results as the beam only showed displacement of maximum 9 tenths of a millimetre. As shown in read this displacement would occur at the point where the load was applied. This anaylsis showed that we could carry on with the beam size and support because they we able to take the load well.

Type Of Beams To be Used

Having established that we will use S type steel I beams for our two support beams and the the main boom, I was able to look up on the international I-beam standards so as to select one with the paremeters that we needed. As this is a mobile crane weight of individual beams/components is very important as we want to maintain weights that two people can comfortably carry to and fro the site. Considering the dimensions for our crane base the s5x10 beam standard was the ideal choice and coming in at a mere 13KG per metre, it is quite light. if this passes the stress analysis of being able to take load of upwards 500KG then we will go aheard with this choice. I was able to create this beam to exact industry standards thanks to the 'structural steel' tool on Solidworks and from here an accurate stress anaylsis can be carried out.