Our Presentation.

Final Product

The following displays our final product, costs, materials and stress calculation results.

The Product:

The above image shows our crane. It is a gantry crane, the beam itself is 5m long, the legs are 1.5 metres long and the leg struts are 1m long.

Lifting Mechanism:
Clarke CNP 1250 Heavy Duty Power Puller

This winch was chosen because:
Lifting loads of up to 1250kg
Cable length of 3070mm
Cost = £21.14 including VAT
Limited parts so less can go wrong
Simple to use
No need for external power supply (fully manual)

Transport Mechanism:

This roller mechanism was chosen because:
Price = £46.98
Suitable for all winches and loads of up to 5440kg's
No need of external power supply

Chosen Beam Structure:

Hollow square cross section beam
Chosen because:
Can withstand vertical and horizontal shear and bending which would suit the purpose of this crane as load will be swinging so load not only in the vertical direction. Allows for worst case scenarios.

Stress calculation results:

Maximum deflection at worst case on the beam (center, 2.5m) is 4mm.
Buckling in the leg structs would occur at a load of 37730.61kN
The load at which the legs would start to plastically deform is 4000kN

All these results show that our crane can cope under the 1000kg load.

Material:

We have opted to use aluminium instead of steel for our crane as:
Aluminium is lighter
Although aluminium isnt as strong as steel, it is still strong enough for our purposes

Costs:

Aluminium structure = £333.91
Beam Supports = £100 approx
Joints = £55.74
Winch = £21.14
Roller system = £46.98

Total = £557.77 excluding labour costs

Final thoughts of Project

I personally have found this project challenging and interesting as it has increased my knowledge about materials and static mechanics in practical situations.

Throughout this project, the group have not been working well however. 3 out of the 5 of us did the minimum amount of work and i believe at without myself and Will the project would not have been finished on time. I have not enjoyed working with this group and i would not work with any of them except for Will in a group project again.

Stress analysis for hollow square cross section

Below is the stress analysis for the hollw square cross section beam.




As you can see, the steel beam was deflecting in the centre of the beam by approximately 115mm. This value is to large so a different material was tested to see if it would produce a smaller deflection.


Aluminium provided a great substitute for stell as it is lighter and thus gives a much larger structure for the same weight as a the steel beam. After much trial and error, the ideal structure dimensions were found and a maximum deflection of 4mm for found in the centre of the beam when the load was applied. This is a much more reasonable value and is within british standards for this structure.

Below is the buckling calculations for the legs and the connecting leg to beam strut.

Materials Research 2

MATERIALS

Our crane must be strong and durable. In order for us to succeed in choosing the best material, we have to look into many different properties of different materials.

We have chosen to decide out of steel and aluminium for the material of our crane. Below you can see some advantages of each material

Aluminium:

Aluminium has the following properties:

Density, 2.7 Kg/m^3.
Yield strength, 55 MPa
Tensile strength, 125 MPa
Young's modulus, 69 GPa

This would be an ideal material to use for the crane. It is low in weight, does not corrode easily and can be melted easily

Steel:

Steel has the following properties:

Yield strength, 250 MPa
Density, 7.85 Kg/m^3
Young's modulus, beteen 190 and 210 GPa
Tensile strength, 280 MPa

Steel would also be an ideal property, however it is very costly compared to aluminium.

Dimentions for cross section

From previous calculations, i worked out that the available cross sectional area to ensure that each 3m section of the beam only weighed 30kg was 1282.05mm2.

With this in hand, the dimentions for the cross section can be found.Where a is the outer square side length, b is the inner square side length and c is the wall thickness.

Now, i would think that a 80mm - 120mm size for a would be substantial enough to take a load of 1000kg therefore using a as 120mm,

a2 - b2 = 1282.05mm2
(120^2) - b2 = 1282.05
b2 = 13117.95mm2
b = 114.534mm

therefore the wall thickness c would equal (120 - 114.534)/2 = 2.733mm

I do not think that this wall thickness would be large enough so take a as 80mm

a2 - b2 = 1282.05mm2
(80^2) - b2 = 1282.05mm2
b2 = 5117.95mm2
b = 71.54mm

therefore the wall thickness c would equal (80 - 71.54)/2 = 4.23mm

this wall thickness is more substantial and might give us a strong structure for our purpose.

Cross sectional analysis

For a proposed hollow square cross section beam

Density of Mild Steel: 7800 kg/m3

If the maximum weight per section is to be 30kg, then the volume available for the beam is:

V = m / ρ = 30 / 7800 = 3.85e-3 m3

If the length of the beam is 9m, that gives an available cross sectional area of:

3.85e-3 / 9 = 4.27e-4 m2 ( = 427mm2)

This is equivalent to 20 x 20mm square. Clearly this is inadequate to support a 1000kg load.

If the beam is constructed of 3 sections each 3m long, then the cross-sectional area will be:

(30 / 7800) / 3 = 1282.05mm2

Which would give us a 35 x 35mm solid square cross section of mild steel. Once constructed as an hollow square, this may give us a second moment of area that can withstand a 1000kg load.

A hollow square cross section would be better suited to the job as it withstands vertical and horizontal forces whereas an I-beam would only withstand vertical forces. If the crane is to be used on uneven ground, which it is in this case, then the force will not be a direct vertical force as the beam would not be completely horizontal and as the load would probably be swinging as it is moved, the load will not be directly vertical.

Initial Concept ideas

Here are some things that i thought would be good:
1. Tripod leg base system for support
2. Motor or hand crank operated lifting system
3. Axiel rotation system to move load out the way.
4. Hollow circular cross section to decrease weight.

Ill load a drawing once i get my home computer running again
(its decided to pack up and die =/)

Adam

Job descriptions

ok guys, here is a list of everyones job title

Project Manager - Adam Speirs
Finance Officer - Rajan Judera
Chief Designer - William Stannard
Stress Analysis - Daniel Sy
Materials Specialist - Suraj Sohan

Post your initial ideas up here asap

the bog is up and running!