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