Engineering Design A2

In the Engineering design part A.1 we have defined the following:

1. The problem:

The problem was defined, as deficiency in current design and what is expected as follows

The current shelves for storing aircraft parts during maintenance are fixed structures in the hangar and the height of three different sections is not been designed to store heavy parts such as gearboxes. The middle shelve is used most of the time. The top shelve is too high to be used and the bottom shelve is too low and as a result there is always a chance of back injury while using the bottom shelve. Also when working away from the hangar, there is no way of transporting these shelves. There are alternative benches provided when working away from the hangar but most of the time they are not fit for purpose and very hard to move around as they are very heavy items.

The task: To design a product which can be used more efficiently and can be transported with ease with the help of forklifts and can be loaded and unloaded on to a truck for transportation. Also the product should be cost effective to produce.

1. Design comparison:

BSI EN 1090 is a harmonized standard that covers structural/construction steel and aluminium products that are installed in a permanent manner. Since our product will be made from structural steel, it must comply with EN 1090-1. All the material for the design will be within regulations of BSI EN 1090-1(Euro code 3). Any material bought will be checked for CE markings by the BSI. These regulations are covered by Scope of EN 1090 document provided by BSI. I have provided a link for the document in reference section of this assignment.BSI has another provision for new products such as ours which can be certified after their rigorous checks for quality and safety. An application form will be sent once the product is tested for use; it can be checked by one of the BSI representatives and certified according to the requested class.

1. Design limitation: The initial load bearing and design specifications have been taken from previous design used for shelves. In the current design, the safe load bearing calculations have been done according to BSI 1090-1. This still doesn’t certify the design, so the application will be sent to BSI product certification department once the project is complete and tested.
2. Design specifications: The final product will be a section of 2.5 metre long storage racks with forklift lifting points on each unit. The height of the top shelf will be 680mm and the height of the bottom shelf will be 340mm from the floor which will make it easy to lift heavy parts from the bottom shelf easier. These measurements are in line with BSI safe load lifting height. Also the gap between shelves will provide enough room for bigger parts for storage.

These 2.5 metre long racks can be placed next to each other as a two or 3 according to the type of aircraft and the maintenance to be carried out. There will be forklift lifting points to move the racksand also make them easy to load on a truck for transportation.

Diagram proposed in part A1 was :

With Manufacturing and safety requirements:

 The product will be manufactured from stainless steel and cast iron due to the load carrying during their service life. It can be assembled on site and once assembled, will be easy to use than the previous storage facilities. There is a designated fabrication bay on site with certified EN ISO 14731fabricators, capable of fabricating all the required parts for the new products. They will do the weight limit tests before it is installed for safety.

Maintenance requirements : The product will be designed to last for a very long period of time with paint protection and minimal inspections required. The painted surface will prevent any contamination from aircraft fluids. These inspections will be very basic and can be done by the user. So no professional maintenance or inspections are required.

Safety requirements: The product will be designed to bear loads for 1000 kg per shelve which are more than enough than the previous design with 600kg weight limit. Since the finished product will be heavy and not suitable for manual movement, it can only be moved by forklifts.

Environmental hazards and recycling requirements : Old racks can be fully recycled as they have been manufactured from the same materials. There is a possibility to reuse some of the parts from the old racks and modify them for the new ones. Water based paints will be used and use of packaging will be minimised to reduce environmental impact.

Life cycle requirements: The finished product intends to have a 25 years’ service life.

Patents requirements : N/A

Intended market: The product will be designed for in house company use only.

1. d) Project planning techniques presented was : 1) Critical path analysis and 2 )ii) Gantt Chart:
2. i) Critical path analysis:For huge, complex projects that have an enormous number of exercises that could be acted in equal and where conditions exist between those activities, a ‘Critical Path Analysis’ is a compelling strategy. It assists with recognizing whether tasks can be run in parallel, the necessary sequence of the activities and their general need inside the task.

Advantages:

1. Activities thatcan run parallel to each other are determined easily.
2.  It helps the project manager identifythe most importantelements of the project.
3. It providesa practical and disciplined foundation bywhich to determine how goals will be achieved.

Disadvantages:

1. Personnel scheduling is not handled by this method. 
2. It is difficult to estimate the completion time of an action. 
3. The critical path could become complicated when time limits are not met.
4. ii) Gantt Chart:Gantt chart is one of the most useful tools when planning projects. They are used to plan and monitor tasks, report costs and expenses at each stage of the project, report progress and create reports. In a simple flow chart, they represent activities and costs over time in an easy-to-understand form. A Gantt chart can also be created as a set of software tools or spreadsheets.

Advantages:

1. Ganttcharts allow you to createa project plan and visualize all the work in one bar chart over time. 
2. Ganttcharts allow you to document and understand work dependencies.
3. The Gantt chart requires thetask assigned to theowner. As a result, you can see who is working on which task.

Disadvantages:

1.  Software such as Microsoft Project, Smart sheets takes time and effort to set up, especially if you try to incorporate task links from the traditional project management software.
2. Gantt chart can become confusing and complicated for large projects.
3. Too much project detail can make them hard to understand.

I have used Gantt chart for my project due to its various advantages for small project. First of all, the data used for the project is simple and in small quantity, so it is easy to understand and configure in a spreadsheet.  As shown in part (e) of this assignment, the data has been entered step by step and critical path clearly shows the undertaking of different stages to complete the project.

Gantt Chart diagram :

Monthly plan:

In the screenshots from the spreadsheets above(Fig.1), the Gantt chart critical analysis clearly shows how each step has been numbered with time constraints. This is where it shows the time frame that each step will be completed and keeps the project on track. Critical Path formally identifies tasks which must be completed on time for the whole project to be completed on time.

In figure 1 above, the task goes through:

All the above phases have time limits in which they have to be completed. This is where critical analysis help in a project to manage and understand time limits for each task.

Now is part A2 we focus on some alternate designs and see their advantages

Alternate 1:

To increase the load bearing capacity, and achieving this objective with lesser dimension sections so that design cost and handling gets improved.

Let us propose adding diagonal elements starting from power joint from one end and joining at elevated end.

Since total frame has two sides to take the vertical load a) the front frame and b) the rear frame. We can take one frame to bear the full parts weight, that we will get a factor of safety 2.

We need to design the self for 1000Kg of material handling at each level, and we have two levels, so bottom section must bear total load of 1000 Kg/2 = 500 Kg parts and (Assumed) self-weight of 500 Kg.

Here we are adding two diagonal frames named as Dia_F1 and Dia_F2

Now the top and bottom of the middle section gets additional support, and most heavily loaded center element can be considered to have rigidity of rotation also.

Let us do the column bucking analysis and chose a section what can bear a compressive loading of 1000Kg*10 m/s² load , and do not fail for design length requirement of 340mm = 0.34m

A box section can be chosen with wall thickness 2mm and outer dimension 25 mm.

The moment of inertia of such section = 2*(2*25*12*12)mm⁴ = 14.4*10³ mm⁴ = 14.4*10^-9 m⁴

The buckling bucking formula given by Eulerassuming elastic column is

Max Compressing bearable load = 4* π²EI/(le²),

Since here we have Fixed/fixed joint 4

Let us use Steel as material since we need out design to last long without corrosion and take care of oil leaks from parts placed, and maintain strength.

E for steel is 210 G Pa , Let us now calculate bearable load

 = *)/(0.34*0.34) = 1.03*10⁶ N

With free_free joint we get least load bearing capacity = 0.064*10⁶ N

Maxing loading is 1000*10 N = 0.010 *10⁶ N

Thus the chosen section will be able to bear the load with factor of safety of >6

Now let us check if mass of the design is within chosen 500 Kg

Mass per unit length = 200mm² * 7800/(1000²)=1.56 Kg

Total length = 4*(1.05+1.05)+ 4*()+ 10*(0.34) = 16.2 m

Total mass = 16.2*1.56=  25.3 Kg

So our assumed frame mass was very high, and hence no further iterations are required, but factor of safety becomes more.

Next critical element of the frame are 1.05 m length horizontal connection at middle elevated level.

Since the diagonal element will be under tension, the horizontal part will be under compression.

Next Design iteration

For symmetry we can add 4 more diagonal elements

Which will increase total length requirement

= 4*(1.05+1.05)+8*()+ 10*(0.34) = 25 m, and mass to 40 Kg.

Iteration 3

The members in tension and compression are marked with T and C for load L

To optimise we can reduce the section in tension elements to 1 mm from 2mm used for compression elements.

Thus the mass will get reduced by 25 % to 30 Kg

Free Body diagram at load application point which is L

Compression C1 = L

Tension T1 * Sin( Angle between T1 and C2) = C1= L

C2 = T1* Cos(Angle between T1 and C2)

So

C2 = L* Cot(Angle between T1 and C2)

C2= 1000N *1050/340 = 3.09 k N = 0.003* 10⁶ N

bearable load

 = *)/(1.05*1.05) = 0.007*10⁶ N

We have factor of safety 2 even with free_free  assumption..

Bill of material

The sections required are :

1. 10mm*10mm wall thick ness 2 mm, lengths required with numbers are as per table number 1.

We may add 6 more elements of 0.34 m thus the horizontal element will have more bucking strength. So astrong frame can be made within 20 m length= 60 feet

As 6 feel length comes so we can fabricate each unit using 10 lengths.

Total mass = 20 m *(0.025*0.025- 0.021*0.021)*7800 Kg of steel = 30 Kg

Total mass with then be 1.56*20 = 31 Kg ( Still quite light structure)

The cost of material is $5/kg, so cost of material will be $140

Cutting and welding may be done within $160 so each rake will get fabricated in $300.

Reference 3 gives material availability.

References:

1https://mechanicalc.com/reference/column-buckling2. Smartsheet. (n.d.). Sheet. [online] Available

2 https://eurocodeapplied.com/design/en1993/steel-design-properties

3: https://www.indiamart.com/proddetail/square-tube-8513204412.html