New Crossbar Design

The new crossbar has a triangular face with a base of 125mm and a height of 90mm

nb. it should be 5mm thick

New Leg Design

During the stress analysis we didn't realise how thin the walls were in the crane legs at just 1mm so a new design was made. The walls are now 10mm thick so during the new stress analysis a larger second moment of area was calculated.

I = 1.0479e-6 m^4
P(critical) = 55,862N
mass = 7.53kg

Crossbar Calculations

The crossbar was designed to be hollow instead of solid so the same equations were used in the stress analysis but a different second moment of area was used.

Crossbar ( initial )

The crossbar which was initially designed was similar to andy's , however, andy's design was picked as we developed it to suite the needs of the rest of the crane. Even so, the stress analysis which was initially done for the crossbar is given below.

Basic sketch for the crane design .

After all the stress analysis was done, a basic sketch was done of the design to see what it would look like after the open top legs and the 1.7m legs were decided. The CAD which will be done will show the dimensions to a greater degree of accuracy, however, this basic sketch allows the CAD to be formulated. Below is the sketch.

Calulations for the crossbars

The original idea which was posted up by romi was constructive , however, a sample of calculations for the crossbar have been given below . It was important to make sure the stresses were correct on the crossbar as it has a lot of loading. Below are a sample of calculations.

Calculations for the sidebars

The sidebars took quite some time to do as they were an important part of the structure , hence everything had to be moulded around the dimensions for the sidebars. Below are examples of the sidebars being calculated with a second image showing a more realistic result when doing

the calculations .

The bar was concluded as being 300 mm in depth and 50 mm wide.

initial calculations for the legs

When working out the level at which the legs will buckle at in accordance with the amount of stress induced, a force of 250 g is applied from top . Basic stress analysis was required for the legs. Eulers equations were used to determine buckling. A sample of calculations can be seen below.

Calulations for End bars

The end bars are the two bars at the back of the crane whilst the side sidebars are the bars running along the side of the beam Calculations needed to be made for the end bars so that they could fit inside the top part of the legs, and appropriate dimensions were calculated obtaining a suitable weight . The end bars were circular rather than rectangular like the rest of the bars. The calculations are shown below.



The calculations were fairly straight forward and simple , however, the only hardship was to get the right dimensions in accordance to the other bars in the crane.

Tender Proposal: Leg & endbar calculations

Leg

• Aluminium
• E = 70 E9 N/m ^2
• Stress = 40,000,000 N/m^2
• Stress (crane ) = P= ((Pie ^2) *E*I) / 4L ^2 = 8659 N ( Max load = 2453N)
• b = 15 mm
• d= 52 mm
• I = 1.4489e-7m^4
• 5 mm thick
• Volume = 9.69 e-4 m ^3 ( minus the cut away = 5.94e-4 m^3)
• Density = 2690 kg / m^3
• Mass = 2.61 kg

Endbar

• Aluminium
• E = 70 e 9 N / m^2
• stress = 40,000,000 N/ m^2
• Stress ( crane) = 6,688,013 N/m^2
• diameter = 50 mm
• I = 2.6704 e-7 m^4
• 10 mm thick
• Density = 2690 kg / m ^ 3
• Mass = 20 .282 kg
• Volume = 7.5398 e-3 m ^3

Tender Proposal - crossbar calculations

Crossbar

• mild steel
• E = 200x10^9 N/m^2
• σ yield = 220 MN/m^2
• σ = 71,038,835 N/m^2
• b = 40 mm
• d = 120 mm
• I = 2.4325x10^-6 m^4
• 5mm thick
• volume = 0.0018750 m^3
• density = 7825 kg/m^3
• mass = 14.672 kg

Sidebar

• aluminium
• E = 70x10^9 N/m^2
• σ yield = 40 MN/m^2
• σ = 10,006,703 N/m^2
• b = 50 mm
• d = 500 mm
• I = 1.2867x10^-4 m^4
• 5 mm thick
• volume 0.0054 m^3
• density = 2690 kg/m^3
• mass = 14.526 kg