Design Project Final

8/3/2019 Design Project Final

1/15

1

Yeovil College

Design Assignment

Unit 6

Ken Hurren


2/15

2

Contents

Introduction 3

Assignment 1 4

Assignment 2 Design Report 8

Assignment 3 CAD material 13


3/15

3

Introduction

In this assignment we shall investigate what happens when the company wishes to

improve on the design of an already existing product. Therefore as I have done theproject on the Mk8 Oxygen Walkround Set I want to base this assignment on thematerial that the actual cylinder is manufactured from.

As the cylinder is made from cast steel I want to investigate what would happen if theRAF as the customer wishes to have the unit made from composite material. Therewould be no difference in actual dimension just an alternate material.

The majority of this assignment will be based around Computer-aided design (CAD)and its place in the modern engineering world.

Please also be aware that all costing figures and drawing dimensions will all beapproximations.

NOTE:Due to specific authorisations I am limited to disclose any actual costingsheets or drawings and designs.


4/15

4

Assignment 1

Establish Customer Requirements

As the customer the RAF have had the Mk8 Oxy Walkround Set for quite some

years and want to improve on its weight issues. The unit itself weighs approx. 1.8kgs

this includes the head unit, therefore to be able to carry more units per aircraft the

weight has to be considerably reduced. The company Kidde Graviner (Kidde) have

been approached to source a new material for the cylinder and have come up with

the only solution which is to use Carbon Fibre. This was decided based on its

properties of being very light weight and very strong, so all that was left to do was

design and manufacture the item.

As this was going to be based on the Tristar fleet the figures will be worked out forthose aircraft only. At present the Tristar carries approx. 80 units per airframe and

with 9 aircraft in operation that is a total of 720 units to be re-engineered.

Number of Aircraft Number of Units/Aircraft Total Units

9 80 720

Total Units @ 2.5kgs/Unit Total Weight

720x2.5kgs 1800kgs

Weighing in at just over 1.5 tonnes, the overall weight seems to be quite substantial

for such a small unit. This is because they are made from cast steel, now, because it

has been laid down that the Tristar fleet want to expand the number of units by a

further 10 per aircraft the weight issues are of greater importance.

The new contract has states that the newly manufactured units must be of the same

dimensions, i.e. length and width; this will reduce costing because no modifications

will be required on the aircraft where the units are stationed.

On the following page Fig 1. is a photo of the component needing re-work and table

showing new weight figures per unit and total weight per airframe.


5/15

5

Fig 1.

As the new unit will weigh considerably less, a figure of 1.2kg per unit has been

agreed upon therefore looking at the table below we can see the following results:

Total Units @ 1.0kgs/Unit Total Weight

720x1.2kgs 864kgs

All units includingExtra 10 per aircraft

Total Weight

810x1.2kgs 972kgs

A weight saving of 828kgs will be gained in the overall fleet weight, and per aircraft

will be 108kgs, so quite a difference in the weight results.


6/15

6

So the contract was drawn up to re-work the component and Kidde began to draw

plans for the new unit.

Determine the major design parameters

As mentioned in the previous section the material for the new unit was agreed upon

and also the size. As the Tristar already has dedicated stations for these units to be

fitted, again mentioned previously no modification will be required for the airframe.

Therefore the only parameters that need to be discussed and resulted upon were the

final material thickness on the cylinder wall and maximum pressure that the cylinder

will be able to retain without rupture.

As a metal cylinder is tested to 1 & a half times its maximum pressure this should

also be the same for the composite item. The Mk8 can hold an operating pressure of

1800 psi, therefore its maximum pressure is 2700 psi.

After a lot of testing Kiddes final material spec was to have an aluminium one piece

liner wrapped in carbon fibre. With the use of a metal liner we were worried about the

weight but Kidde have assured us that the change in the weight figures will be

minimal.

Below, Fig 2 shows what the cylinders construction could look like.

Fig 2.


7/15

7

Obtain design information from appropriate sources & prepare a design report

Kidde were approached for this project as they were the original designer and

manufacturer of the product. Later in the Mk8s life it would be reconditioned by a

company called Meggitts who were also approached for this modification but did not

have the facility to undertake such a project.

So Kidde Graviner were asked to take up the challenge and happily accepted. The

drawings for the original cylinder were released from archive and used as a

reference guide for the new unit again keeping costs down.

A design report was drafted and agreed upon soon after the initial contact and can

viewed in the following section.


8/15

8

Assignment 2

Design Report Dated 15 September 2010

Summary

This report presents the re-design of the Mk8 Oxygen Walkround Set for the Tristar

aircraft fleet at RAF Brize Norton. The design makes use of composite materials to

replace the original steel used in the manufacture of the cylinder assembly. By

changing the material specification the unit will be stronger and lighter than the

original. This design has many potential applications, including be used in the armed

forces medical world and for parachute jumping.

Introduction

This report is dedicated to the remanufacture of the Mk8 Oxygen Walkround Set as

used by the RAF on the Tristar aircraft.

As shown in Fig 1 the unit itself is seen manufactured from a cast metal, what Kidde

have been approached to do is to remanufacture it using composite materials.

The two main aims for this idea were to keep its dimensions and retain strength

integrity. Also included in this task was the fusion of a metal alloy liner to the

composite outer shell in which the gas would be contained.

The work would be shared between a team of 6 engineers, 3 on the design side and

3 on manufacturing.

Therefore this report has been written to assess the design of the new cylinder and

its testing.

Fig1.


9/15

9

Design Procedures

Prepare an analysis of possible design solutions

Initially the design was to be configured differently, but after many meetings and

phone conversations it was agreed that the original design would be kept. This was

decided because the Tristar airframe would have to be modified, so to keep costs

down we wanted the original pattern of the unit kept.

As a sample component was needed for research material the personnel in the

Oxygen Support Section at RAF Brize Norton made sure that we had one sent back

for reconditioning so therefore removed from their supply system and replaced with a

serviceable item to fill the gap.

As we at Kidde basically knew what the RAF were looking for in this component,

most of the hard work had already been done i.e. size and materials required. The

next stage was to design a metal liner for the cylinder.

The material chosen for this was Aluminium Alloy because it was light and easily

extruded when heated and machined. So an example piece was drawn up to present

to the customer and get their approval.

The RAF Engineering Board was delighted with the result and gave us the go ahead

to proceed with the alterations to the unit.

The only real issue was to get the AP Maintenance Procedure altered to accept the

new component. As it was an urgent requirement this was done without any problem

at all.

Produce and evaluate conceptual designs

Our engineers got to work on a prototype design and looking at the pictures below

came up with a final element. The colour of the cylinder will not be finalised until the

unit has had all relevant tests carried out. As this was a fairly straight forward project

our designers used a program called Abaqus, which is a Structural Analysis Programin the design of the cylinder.

The testing procedure will be very straight forward, but we must discuss material

specifications. The aluminium alloy liner will have a thickness of 6.00mm and the

composite surround will be 5.00mm thick. This we found would be more than

adequate for the operating pressures supplied for us by the RAF.

All relevant technical information that was on the previous cylinder will be placed

onto the new model in exactly the same place, near the neck where the head will be

fitted.


10/15

10

Use computer-aided design software to prepare a design drawing or scheme

Fig 1

Fig 2

Select the optimum design solution

As with the previous version the design was the most optimum for space saving

ability so that is why the original design was kept. Trying to optimise another design


11/15

11

for the component would cost a lot more money. After comparison against the

original design the new model looked identical in size, then they were both measured

using a variety of techniques and the results were extremely close to within a couple

of millimetres. As you can see from the results the post mod design has improved by

300 psi giving the component slightly more of an upper tolerance.

Carry out a compliance check

After being stress checked the cylinder had to be pressure checked, so it was

inflated to explosion in a controlled environment. The engineers at Kidde

manufactured a test piece and the results can be viewed on the next page.

NOTE: We must bear in mind that the cylinders are pressure tested to 1.5 x max

pressure.

As you can see from the results in the above table, the upper max tolerance has

increased by 300 psi. Therefore the design was finalised and all details sent to the

RAF Engineering Board. After very little deliberation the board were more than

happy with the results.

Conclusion

The new design will be more than capable of handling the pressures it has to use

and not only that it will be stronger and lighter.

Min PressurePSI

Max PressurePSI

Result

Pre-mod design 450 2700 Pass

Post mod design 450 3000 Pass


12/15

12

Prepare a final report

Ensure that the design specification meets requirements

After seeing the test results, we were keen to receive the new units and put them to

test both on the aircraft and on parachutists. Luckily for us we were due to providebreathing apparatus for some 12 trainee jumpers the week after receiving the newly

designed components. All set up techniques were exactly the same as there was no

change in design, but the weight difference was quite dramatic. The new sets were

so much light than the previous ones.


13/15

13

Assignment 3

Use Computer-Based Technology in the Design Process

Abaqus

Abaqus is used in the automotive, aerospace, and industrial products industries. Theproduct is popular with academic and research institutions due to the wide materialmodeling capability, and the program's ability to be customized. Abaqus alsoprovides a good collection of mult-iphysics capabilities, such as coupled acoustic-structural, piezoelectric, and structural-pore capabilities, making it attractive forproduction-level simulations where multiple fields need to be coupled.

Abaqus was initially designed to address non-linear physical behavior; as a result,the package has an extensive range of material models such as elastomeric

(rubberlike) material capabilities.

Evaluate software that can assist the design process

Abaqus/CAE is capable of pre-processing, post-processing, and monitoring the

processing stage of the solver; however, the first stage can also be done by other

compatible CAD software, or even a text editor. Abaqus/Standard, Abaqus/Explicit or

Abaqus/CFD are capable of accomplishing the processing stage. Dassault Systemes

also produces Abaqus for CATIA for adding advanced processing and post

processing stages to a pre-processor like CATIA.


14/15

14

Identify the key features of a computer-aided design system

Computer-aided design(CAD), also known as computer-aided design anddrafting(CADD), is the use of computer technology for the process of design anddesign-documentation. Computer Aided Drafting describes the process of drafting

with a computer. CADD software, or environments, provides the user with input-toolsfor the purpose of streamlining design processes; drafting, documentation, andmanufacturing processes. CADD output is often in the form of electronic files for printor machining operations. The development of CADD-based software is in directcorrelation with the processes it seeks to economize; industry-based software(construction, manufacturing, etc.) typically uses vector-based (linear) environmentswhereas graphic-based software utilizes raster-based (pixelated) environments.

CADD environments often involve more than just shapes. As in the manual draftingof technical and engineering drawings, the output of CAD must convey information,such as materials, processes, dimensions, and tolerances, according to application-specific conventions.

CAD may be used to design curves and figures in two-dimensional (2D) space; orcurves, surfaces, and solids in three-dimensional (3D) objects.

CAD is an important industrial art extensively used in many applications, includingautomotive, shipbuilding, and aerospace industries, industrial and architecturaldesign, prosthetics, and many more. CAD is also widely used to produce computeranimation for special effects in movies, advertising and technical manuals. Themodern ubiquity and power of computers means that even perfume bottles and

shampoo dispensers are designed using techniques unheard of by engineers of the1960s. Because of its enormous economic importance, CAD has been a majordriving force for research in computational geometry, computer graphics (bothhardware and software), and discrete differential geometry.

The design of geometric models for object shapes, in particular, is occasionallycalled computer-aided geometric design(CAGD).

Finally

This report has helped me greatly in the learning process of remanufacturing a

component to make it more suitable for todays modern needs, and also respectingup to date costing systems. As the economy fluctuates it becomes more difficult to

empower outside companies to assist in the design and build of such items. I wish to

thank all those parties involved for their help and experiences.


15/15

15

Aknowledgements

Wikipedia -http://en.wikipedia.org/wiki/Computer-aided_design

RAF Engineering Board

KIDDE GRAVINER
http://en.wikipedia.org/wiki/Computer-aided_designhttp://en.wikipedia.org/wiki/Computer-aided_designhttp://en.wikipedia.org/wiki/Computer-aided_designhttp://en.wikipedia.org/wiki/Computer-aided_design

Documents

Design Project Final