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

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