Summary

Project Summary

As a group we feel the project has been successful. If we were to carry out the same task again, we all agree that we would do nothing different. The crane itself was designed and tested very well. The group had a very wide variety of skills, the design engineers were very confident with CAD, and the mechanical engineers were very confident with the stress analysis. As a group we worked very well together from the beginning stages to the very end of the project. We set deadlines and met them almost perfectly every week, and with sometimes up to three meetings a week we were getting through the work at a very good rate. We as a group feel we could not have had a better group to work with.

During the duration of the project we faced some challenges. The hardest were probably the choice of material and the stress analysis. We had to change material a few times after stress analysis so the crane itself would not fail under stress. The choice of the design was also a difficult phase, we had a lot of different designs and different crane styles to choose from. Choosing the right one was a vital stage in the development of our crane, a bad choice would ultimately have led to a bad project.

Our final design was a very good design and we felt it was the best it could be, it was engineered to a safety factor of 1.5 and very different to most the other designs we saw. We felt a lot of the designs we saw had many more flaws than our own.

To summarise, the group was very happy with the whole project and the final design. We all feel that given the chance again we would not change anything and would carry out the task in the same way.

Presentation

Calculations For Buckling

Shown below are the calculations carried out to find out if the crane stucture would buckle and fail. The calculations were carried out on the members which would be likely to buckle under a compressive load.

The calculations prove that the members under compressive load would not buckle at 1.5 times the recommended lifting capacity.

new calculation for the crane

Material Decision

After a group meeting, the final decision between Aluminium 6061, Aluminium 6063, Cast Carbon Steel, and Carbon Steel 1023 was discussed. The group as a whole agreed that using any form of Steel would be too heavy of a material. This left the choice between the two grades of Aluminium. After some final research, we found that the cost of Aluminium 6063 is slightly more than 6061 but their properties are almost identical, however Aluminium 6063 is slightly heavier also. Both materials were had good joining properties, both could be welded through TIG (Tungsten Inert Gas) and MIG (Metal Inert Gas) welding.

This ultimately led to the decision that Aluminium 6061 should be used.

Aluminum 6061 can be found in a very wide range of products. A very common product would be a bicycle with a tubular frame. Here is an example of a bike using aluminium 6061.
The picture shows the front of the frame where three seperate parts of the bike meet together and are welded together. This is just above the front fork of the suspension. There would be a considerable amount of load going through this section of the bike. The weld is also very neat which suggests the parts are easily welded together.

For the crane, a hollow tubular frame would be welded together to form the Truss' that will join together to create the crane.

Here is an example of a tubular frame used on a race car. The frame is designed to be strong but lightweight which makes it good for its application.

http://www.gtbicycles.com/GTFiles/ProductImages//2000_1300_G10AVA1D_255.jpg
http://www.galmerinc.com/images/dsr_frame.png

Material Analysis II

Materials Analysis II

After a group meeting where the material of the crane was discussed, we decided that cost was going to be a major issue as well as availability. Using the Materials Analysis it was decided that both Aluminium and Steel would be options for the material of the crane. The following data is the analysis of the different types of Aluminium and Steel available.

Aluminium
First to be analysed was the different types of Aluminium available. There is a wide variety of Aluminium available with varying grades of aluminium mixed with other materials. The beginning number, ranging from 1-8 of the 4 digit number represents the strength of the material. 1 being the weakest form, and 8 being the strongest.
The material will now be analysed. As alot of the numbers are the same, they have been given equal values for the analysis phase. Each section is worth 9 points and a maximum of 54 can be attained.
As alot of the data is similar or the same, the results are ranged quite close together. Out of the 9 materials available only 3 would suffice for the application. Aluminium 6061, Aluminium 6063, and Aluminium 7050. The reason for this is their strength is greater than the latter grades of Aluminium, the stronger the material the more resistant it will be to deformation under loads. The material must also be easily worked with, and due to grades above 7000 having poor weldability and corrosion resistant qualities, Aluminium 7050 must be ruled out. This leaves a choice between Aluminium 6061 and Aluminium 6063.

Steel
The material will now be analysed. As alot of the numbers are the same, they have been given equal values for the analysis phase. Each section is worth 9 points and a maximum of 54 can be attained.
From the table above we can see that there are some quite mixed results. This is due to the different types and grades of steel available. There are alloy steels which are mixed with other materials, and there are varying qualities of steel depending on its purity. Although the materials are very similar in regards to their properties, the two that would be considered for the crane would have to be the Carbon Steel 1023, and Cast Carbon Steel. This is because Carbon Steel has high strength characteristics as well as a low cost factor. In the crane industry alot of cranes are made out of a carbon steel as mentioned in the materials research. However, this is usually for very large cranes which will carry a much heavier load than compared to the crane we are designing. With this in mind we must consider the weight factor of steel compared to Aluminium. The weight of Aluminium is a considerable amount less than the weight of Steel. This can be seen from the Density of both materials. The more Dense the material the more it weights. For a crane that will need to be carried over rough terrain by people, the lighter and easier it is to transport, the better.

The data will be presented to the group in the next meeting, we will discuss further the choice between Aluminium 6061, Aluminium 6063, Cast Carbon Steel, and Carbon Steel 1023.

Forces/Stress Calculation (i)

To find the counter balancing weight required for the crane beam to lift 1500kg and the total force going through to the boom, we use moments -

Equate the clockwise and anticlockwise moments:

(About C clockwise) - Xg x 1 = 55.2g x (1.5 - 1) + 1000g x 2

Xg = 27.6g + 2000g = 2027.6Kg mass required for balance

2027.6 x 9.8 = 19870.48N force required for balance

Equating the forces in a vertical direction:

R = Xg + 55.2g + 1000g = 2027.6g + 55.2g + 1000g = 3082.8Kg Mass

4582.8 x 9.8 = 30211.44N Force - Both of which is the total amount acting through to the boom.

Forces/Stress Calculation (ii)

This means that the total pressure acting downwards on the first box support is –

Finding the area of the circular support –

Π x [(140-120)/2]² = 314mm² = 0.314m²

Therefore the stress acting on the surface area of the circular support is (Using s = F/A)

s = 30211.44/0.314 = 96214.78Nm^-2

As there are four supporting strut ‘legs’, the total force would be equally distributed along them as such:

30211.44/4 = 7552.86N per ‘leg’

Through the individual rods attached to the ‘legs’ -

a = 7552.86 x cos30 = 6540.96N

b = 7552.86 x cos60 = 3776.43N

c = 7552.86 x cos60 = 3776.43N

The second boom/box support has the combined forces of the previous boom/box supports weight as well as the total weight of the boom with maximum load and counterweight.

Using previously done calculations of structure weight –

Therefore, the approximate mass of the boom support can be assumed to be ~ 27.6kg = 270.48N

So the total force acting down on the second boom support is 270.48 + 30211.44 = 30481.92N

Overall force acting downwards on the structure is – 52.5 + 27.6 + 27.6 + (13.4x4) = 161.3kg

Which is 1580.74N of force, as well as the force of the weight and counterweights which gives

9800 + 19870.48 + 1580.74N = 31251.22N