ME312 - Mechanical Design 3A

Group 2

Striving for EggcelenceEgg Lifting Device – Design Report

Jonathan Smith, Campbell Simpson, Jack Lucas, Andrew McKenna, Ahmad Sheikh, Max Brown12/15/2014

IntroductionThe following report shows the progression of our group’s design from receiving the original brief to the details of the finalised design. First, the initial brief was read with all constraints taken into account then a PDS (Product Design Specification), which highlights the crucial specifications for the design, was created. This list of ten important areas relating to the product allowed a list of specific requirements to be produced. The Statement of Requirements and the PDS were then used as a tool to generate creative and effective designs solutions which fit in with the guidelines.

After long discussion it was realised that any ideas the group came up with could be separated into four categories of design. Using comparison tables and a Pugh Matrix, we quickly decided on the most favourable being a self-contained driving and lifting mechanism.

Each member of our group was then assigned the task of creating their own concepts so that we had a wide range to choose from. Various different options were picked as suggestions for each part of the design i.e. a suction-cup, claw, pincer and net, to be used as the mechanism to pick up the egg. Then each of these options was put into another Pugh Matrix to assess the strengths and weaknesses of each concept on a rating scale. Whichever option achieved the highest score was then used to help the process of creating the final design to take further. This was done for all parts of the design, the egg collection mechanism, the lifting mechanism and the driving mechanism.

Each group member then came up with and presented a design (using the components decided on from above) which they felt would most effectively accomplish the task in hand. These concepts were discussed in detail and were then combined to finalise our design.

This final concept was then sketched by hand and then drawn in detail, using both pencil and CAD (Computer Aided Design) software. Material properties and control systems were researched and various suggestions were produced for both. Again using comparison tables, we were able to choose the best materials and motors for the job, while sticking to our £300 budget.

Finally, with all of the components decided on, and their function described in detail, a conclusion was written, summarising the project.

Initial Brief“To design a device that is capable of lifting a raw egg from one location and depositing it safely in another location. The entire device must be located at least 1m from the egg initially. After the device has initially lifted the egg it must then deposit the egg safely to a position located 1m to its side and 1m above the initial location. Finally, the device must withdraw at least 1m horizontally from the location in which the egg has been deposited.”

Project PlanOur group was briefed on their design specification-to design an egg lifter- on week 2 in the first semester of third year mechanical engineering. Work was split up between the 6 group members; with each task being assigned to the members according to their specific strengths and weaknesses e.g. the most artistic team member was to produce our drawings. We created our own deadlines for work to be completed by the group so that we did not fall behind and have to rush our work on the final day-creating a sub-standard design. The first two weeks were spent brainstorming on the most effective and creative way to lift the egg. Week 4 was used to create a statement of requirements and week 5 to generate a PDS (Product design Specification) to fuel our creativity and help us arrive at our final goal of an innovative design. By week 6 we had put all of our ideas on paper with each group member coming up with their own specific design, producing an annotated drawing of their concepts. By week 7, a Pugh Matrix was used as a tool to select the best design and work began on perfecting this design while creating better, more detailed drawings. Material properties were researched before we finally chose the correct materials for each component while staying within our £300 budget. We then collected all of the information and put together a report before the final presentation in week 12. We aimed to have completed all of our tasks by the start of week 11, to leave time to reassess our work and perform any necessary tweaking.

Task Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9Week 10

Week 11

Week 12

Brainstorming IdeasStatement of RequirementsPDSConcept Generation TablesFinal Component SelectionDesign GenerationSelection of Final DesignDetailed Design DrawingsCalculationsMaterial SelectionComprising reportCostingsCreate final Presentation

Statement of Requirements

We must design a device that will lift a raw egg from an initial location and deposit it in another location that is 1m above and to the side. The device must be capable of starting 1m from the egg. The device must be capable of lifting the egg safely and in a controlled motion, and be structurally stable throughout all motion. The working environment of the device is not known and so the device must be capable of operating on multiple surfaces and areas. Our budget is £300 for the whole project.

Product Design Specification

Performance 1.1 The device must be able to lift a raw egg from one location and

deposit it safely in another without breaking it.1.2 The device must be able to collect the egg from a starting point

1m away horizontally.1.3 The device must be able to lift the egg 1m vertically to a new

position and deposit the egg1.4 The device must be able to move 1m away from the final position

of the egg1.5 The device must be able to operate at every stage without

physical human interaction with the egg1.6 The device must be structurally stable and secure at all times1.7 The device must move at a safe controlled speed1.8 At no point in the process should excess forces be applied to the

egg

Environment2.1 device must operate indoors at room temperature2.2 The device must be able to operate on various common indoor

surfaces (wood, carpet, linoleum etc)

Life in Service3.1 The device should last a minimum of 12 weeks and stand up to

multiple rounds of testing including multiple demonstrations3.2 No components should have excess stress on them, risking

damage over time

Maintenance4.1 The devices components must be easily accessible for

replacement, repair or modification4.2 The device must be easily cleaned and maintained (cleaned of

any egg waste)

Ergonomics5.1 The device must easily controllable5.2 The device must have a control system able to be operated by

only one group member5.3 The device must be light weight enough to be moved to the

demonstration area easily5.4 The device must be easily dismantled and reconstructed if

necessary to reach demonstration area

Quality6.1 The device must be created using solid materials that will neither

deteriorate nor fail with repeated use6.2 The device must be well finished with no loose fittings or defects6.3 The device must be constructed in a way where it will not fail,

structurally or mechanically6.4 Motors and electrical components must be chosen that will

reliably power the actions of the device6.5 No parts of the machine should be under excessive load so no

components deteriorate between first construction and final testing

6.6 The device’s performance should not diminish over time

Materials7.1 The materials must be cheap enough to stay under budget7.2 The materials must be durable and strong enough to complete

the task at hand7.3 Where possible, the device must be made of readily available

materials to cut costs7.4 No load bearing materials should be of low quality 7.5 Where possible, components should be bought domestically, or if

possible, picked up locally in order to cut emissions in transportation and costs in delivery

7.6 All materials should be checked for defects so to avoid failure

Target Cost8.1 The device must cost under £300 to manufacture

8.2 Wherever possible, components and materials should be taken from readily available sources which the team members already have access to, to cut costs

8.3 Manufacture should be done by team members or lab technicians within the university in order to keep costs down

8.4 For any specialised parts, the best price should be found with extensive research into that area

Safety9.1 The device must have no sharp edges that could cause harm to

the person moving it9.2 The device must be electrically safe (human interaction must be

low voltage)9.3 The device must not produce harmful emissions (as it is operating

indoors)9.4 The device must move at a safe, controlled speed to avoid

crashing into anything and causing any damage9.5 The device must be structurally stable at all times as to avoid

falling and harming anyone or anything9.6 Any automated components should be powered by electrically

safe, tested components to avoid fire or electrocution risks

Weight & Dimensions10.1 The device must be lightweight enough to be moved to

the demonstration area easily10.2 The device must be able to reach the demonstration area,

therefore be small enough to fit through doors

10.3 If the device is required to be assembled on site, all separate components must be small enough to fit through doors and make it to the demonstration area

10.4 The device must be small enough to operate indoors, in a small room

10.5 The device must be light enough to be powered by the chosen motors

Comparison Tables

The following pages demonstrate the concept generation stage of our design. It was clear from our initial conversation and preliminary ideas that deciding on our type of design was of paramount importance. Each category is shown below then following this, a weighting and rating table concludes our ideal category.The rest of this section follows the same layout but for solutions to each of the necessary components in our design. There is a comparison table, describing each option then a waiting and rating table to decide on our ideal component.

Categories of DesignCategory Advantages DisadvantagesFlying(reaching the egg by air, picking it up, reaching the desired altitude by air and depositing the egg)

Device is in one assembly; all functions are achieved by the same machine

The machine is extremely manoeuvrable and adaptable to changes in the test environment compared with the environment that has been planned for

Design is ambitious and original; it may be scored more highly by markers

Device will be difficult to program Device will be difficult to make, several motors will be

needed and very specific components will be required Entire device will have to be kept very lightweight. The

grabbing part for example must be kept as light as possible

The weight of the egg itself may severely alter the control of the device

One mistake in control (a crash) will be devastating

Stationary(stationary base, arm extending horizontally, picking up egg & lifting to desired height)

Easy to construct, most components will be large and easy to tinker with by hand

There will be no size or weight restrictions Control will be relatively simple, with only a selection of

forwards / backwards motors required

Balance will have to be considered, in order to reach out the full distance the device may become unstable

Moments on the device may be large and counter weights may be required

The device will have to stand very tall The device may be unstable during certain parts of the

process The device may be very heavy and difficult to transport

Driving & Self Contained Lifting(reaching the egg by driving over land, picking up the egg then raising it up and depositing it, all as part of the same, portable assembly)

Entire device will be one assembly Device will be able to adapt to changes in environment

such as position of egg Device will be very manoeuvrable The Device should be reasonably stable as it is not

required to reach out Required components will be easy to come by

Control may be complex, with programming required for several parts of the process all contained within the same machine.

The device will need to be kept lightweight in order to complete the full task, moving and elevating

Power will be required to operate the driving of the machine on the flat as well as elevating the egg

The device may be top heavy, driving around with tall components required for the elevation process

Driving & Separate Lifting(reaching the egg

Simple control as the separate parts of the job will be split up between machines

No weight constraints will be required

Design may struggle to be within constraints of the design brief as it may not be able to withdraw a metre from the egg

Comparison Table of Design Categories: Each column has a multiplier in order to weight that comparison category according to its importance. Each value is given independently of sum of that column, so each design category receives the correct score. (1 being very poor, ranging to 4 being excellent)Category Power

Method and Source [2]

Build Complexity [2]

Ease of Operation [2]

Aesthetics [1] Egg Safety [3] Stability [2] Dexterity [2] Adaptability [1]

Total

Flying 1 1 1 4 1 1 4 3 26Stationary 4 3 4 1 3 2 1 1 39Driving & Self Contained Lifting

3 4 3 3 2 4 4 4 49

Driving & Separate Lifting

2 2 2 2 2 3 2 2 32

Component Concepts – Egg GrabberConcept Advantages DisadvantagesSuction Cup No hard surfaces in contact

with egg shell Idea is more original and

unusual than some others

Requires a high power source to maintain vacuum

Egg may drop if a tight seal is not created

Closing Net No hard surfaces are in contact with the egg

There are no concentrated forces acting on the egg at any point

Idea is original

The net will require an innovative system in order to close up the open end once the egg is inside

The net may be difficult to place accurately over the egg

The net may be difficult to re-open once the egg in in position

Claw Control will be relatively easy Components will be simple to

make

There will be a small number of hard points of contact with the egg

It may be very easy to crush the egg by accident

Cage Egg will be secure Picking up and depositing of

the egg will be easy Idea is original Concept should look good

Component will be difficult to manufacture

Egg may rattle around inside cage and be damaged

Components may be specialised and difficult to acquire

Comparison table of egg grabber concepts: Each category is given a respective weighting depending on its significance to a successful operation. Each concept is rated from 1-5. 1 being very poor and 5 being very good. 3-ok. 4-good. 2-bad.Concept Power

requirements(2)Build Complexity(2) Ease of

operation(2)

Aesthetics(1)

Egg Safety(3) Originality(1) Total

Suction cup 1 2 3 3 2 4 25Closing net 3 1 2 3 3 3 27Claw 4 4 4 4 3 1 38Cage 2 2 1 3 5 1 29Scoop 4 5 3 2 3 1 36Pincer 3 3 5 4 4 2 40Spoons 4 4 3 1 2 1 30Forks 4 4 4 1 4 1 38

Component Concepts – DrivingAdvantages Disadvantages

Wheels: front wheel drive, front wheel steering

Stable Cheap Easily powered

More complex than separate steering and drive systems

Will require a specific steering system

Drive and steering system will need to be applied at same wheel

Wheels: rear wheel drive, front wheel steering

Relatively simple control Stable Cheap Easily Powered

Specific steering system will be required

Possibility of bad traction Large turning circle

Wheels: 4 wheel drive, front wheel steering

Extremely stable Can deal with different terrain More power can be delivered

Susceptible to breakages and failure Difficult to construct Very reliant on good differentials All motors will need to be

synchronised Drive and steering system will need

to be applied at same wheel

Wheels: powered (Forwards and Reverse) wheel on either side with

Easily controlled and Powered Easy to make

May be difficult to ensure the castors are aligned and the assembly is not

free to rotate caster wheels for support

Cheap Very good turning circle

wobbly May struggle with different terrain

(carpet or uneven floor) Motors will need to be synchronised

with one another

Caterpillar Tracks: independently driven (forwards and reverse motors) left and right

Extremely stable Very simple control Very good turning circle Durable Good on different terrain (lots of traction) Controlled motion Heavy tracks may provide low centre of gravity and stable

base

Slow (though this is a small negative) Slip may occur between tracks and

driving wheels Difficult to turn while on the move,

stationary turning may be the only option

Heavy and cumbersome design May require more power to drive

heavier construction Tracks may be difficult to construct

Wheels and Pulley: unpowered wheels and powered external pulley

Simple to control Easy to power Cheap components

Only one direction is available without human interaction

Pulley must be heavy in order to drag entire assembly along

May not fit design criteria (not starting a full metre away)

Comparison Table of Driving Methods: Each column has a multiplier in order to weight that comparison category according to its importance. Each value is given independently of sum of that column, so each design category receives the correct score. (1 being very poor, ranging to 5 being excellent)

Category Available Driving Power[1]

Steering Complexity [2]

Build Complexity [2]

Accuracy [2] Aesthetics [1] Egg Safety (Smoothness of Travel) [3]

Stability [2] Total

Wheels: front wheel drive, front wheel steering

2 2 2 3 2 3 3 33

Wheels: rear wheel drive, front wheel steering

2 3 3 3 2 3 2 35

Wheels: 4 wheel drive, front wheel steering

3 1 1 4 2 3 2 30

Wheels: powered (Forwards and Reverse) wheel on either side with free to rotate, caster wheels for support

2 4 4 5 2 3 3 45

Caterpillar Tracks

4 4 2 4 3 2 4 41

Wheels and Pulley

5 3 4 1 1 2 1 30

Component Concepts – Lifting MethodConcept Advantages DisadvantagesPneumatics Simple

Easy to control (on vs off) Easy to generate a lot of lifting power Legs do not need to be at full extension while

driving

Difficult to compress air May require inbuilt compressor Extra weight will be added with canister and

pump Regulator will be required to ensure the correct

amount of pressure is used All legs must be connected to ensure equal

pressure on each support

Hydraulics Very powerful lifting method Easy to control Simple

Could make a big mess if a leakage occurs Difficult to actuate Will be very heavy to drive around Possibly very expensive

Screw Cheap Stable Easy to operate Simple to control Easy to have a controlled, slow lift

Complex as you may have to coordinate several screws to lift the machine in unison

Difficult to create components which will allow free screw rotation without conflicting with other components around it

Design may have to include heavy feet to ensure stability throughout the demonstration

Legs will have to be at full height even when driving around and not in use

Rack and Pinion Simple to construct Simple to control Reasonably lightweight

Not as creative a solution Could be flimsy when reaching such a high height Legs will have to be at full height even when

driving around with the legs not in use. The Feet will have to be extremely heavy to

ensure stability throughout the demonstration.

Pulley Simple to make Lightweight

Legs will have to be at full height even when driving around with the legs not in use.

Comparison Table of Lifting Methods: Each column has a multiplier in order to weight that comparison category according to its importance. Each value is given independently of sum of that column, so each design category receives the correct score. (1 being very poor, ranging to 5 being excellent)Category Available

Lifting Power[2]

Power Source Complexity [2]

Leg Build Complexity [2]

Ease of Operation [2]

Aesthetics [1] Egg Safety (Smoothness of Lift) [3]

Stability [2] Total

Pneumatics 5 2 2 4 5 3 3 46Hydraulics 5 1 1 3 4 3 4 41Screw & Motor 3 4 3 5 3 4 3 51Rack and Pinion & Motor

3 5 5 5 2 4 4 58

Pulley & Motor 2 4 4 5 1 5 2 50Spring 5 4 1 3 4 1 1 35

Final Components

From the comparison tables, we can conclude that the ideal design for the task will be a self-contained, driving and lifting machine with a pincer mechanism for picking up the egg, a Rack and Pinion for achieving the desired altitude and two powered wheels at either side with freely rotating caster wheels around for support.

Suggested Designs

All group members were now free to go away and come up with a final design as they saw it, utilising the components decided upon in the comparison tables. This resulted in the concepts as shown below.

Concept 1 -

• This concept has 2 driven wheels and 2 free wheels

• The base has a slice taken out to allow the claw to reach the floor and pick up the egg.

• The lifting mechanism has 2 gears on ether side of the pole to allow for stability when lifting

• The claw closes by use of a small motor

• This design is controlled by using a wired control devise which is lead away from the base and to the operator’s hand

• There will be switches to control each motor (turn on, off and reverse

• The 2 wheels will be individually controlled to allow for turning

Concept 2 –

This concept is self-contained, and the lifting mechanism sits on top of the body in the centre.

The lifting uses a rack and pinion method, with the motor attached to the large gear at the back of the pincer arm.

The pincer is a 4 arm design, with 2 lower arms to support weight and 2 moving upper arms to stabilise the egg.

The wheel setup has 2 driven wheels at the front using 2 independent motors, and 2 fully rotational wheels at the rear. The device can be turned by altering the movement of the 2 front motors.

The base is a solid square plate to create a low centre of gravity for balance and stability.

The function of the design is to drive up to the egg and pick up the egg onto the pincer, and then drive to the new location and stop all wheel motion. The pincer and egg will then be lifted using the rack and pinion to the required height.

Concept 3 –

This concept is really in two halves, the driving part of the design is all contained within the box at the bottom, where the majority of the weight will be. The other half is the claw and extendable arm, attached to a frame that sits on top of the driving box. This means the frame and egg grabber assembly can move up the 4 legs alone, leaving the majority of the weight on the ground as part of the driving box.

This concept has 4 legs, all with teeth up them and 4 motors, synchronised in order to lift the frame and grabber assembly up smoothly and stably.

The pincer is extendable as shown in the detailed view of the rack and pinion, contained within the centre of the frame. This pincer extends along the upper, horizontal part of its arm, as shown by the arrows in the drawing.

This extendable idea is to allow greater control when picking up and depositing the egg, so not to solely rely on driving the entire machine into the exactly correct position.

The extendable arm angles down so the pincer may pick up the egg from ground level. The suggested closing mechanism for the pincer is shown in another detailed view, using a tiny motor and a screw.

When the egg is collected, the four lifting motors (powered by a battery pack held in the centre of the frame) start driving the frame and grabber assembly upwards, to reach the desired altitude.

The two driving wheels are positioned on either side of the driving box with four caster wheels, one at each corner for support. All batteries and motors for driving are contained within the assembly at the bottom.

Concept 4 –

There are two parts to this design; the driving part is a simple four wheeled vehicle with front wheel drive where the pincer will be there to pick up the egg. The second part of the design is 3 extendable arms which are arranged in a triangle formation which will lift the entire unit more than 1 metre off the ground.

The three extendable arms which all have a rough bottom on them for grip, is controlled by 3 individual motors which will supply the necessary power to lift the unit from the ground.

The pincer is extendable and contains two individual pincers. One which grips the egg at its top and one that grips the eggs at the bottom providing the egg are in the upright position.

The main advantage of having an extendable arm is that it when the egg is lifted a distance of one metre vertically the arm can extend out from the contained design to safely deposit its load of an egg.

There will be two separate small motors which will be used to close and open these individual pincers with the help of two screws.

The whole design will be powered by a battery pack stored within the base of the driving unit. This shall be located in the centre of the design as to try and make the structure as stable as possible when airborne

Concept 5 – This concept has a rectangular base and most of its weight will be

concentrated at the front of the device It has 4 wheels. The base sits on top of the wheels. The front two

wheels are connected to independent motors located underneath the body. The two rear wheels are free to move in any direction.

The device has two racks located near the front of the base that stand vertically.

Connected between the two racks is the lifting device, from the centre of which the claw extends forwards past the base of the device.

The side of the racks containing the bites faces inwards so both racks are facing one another. Connected to each rack is a worm gear. These gears are powered by the motor located on the lifting device which causes it to rise vertically.

The arm connected to the pincer is not extendable. The pincer has two arms that are curved in a way that allows

them to grab the egg from underneath applying pressure to the underside as well as the sides of the egg and hold it securely.

The inside of the arms contain a soft, shock-absorbing material to aid in safely managing the egg.

The closing mechanism of the pincer head has one motor. It is connected to a gear that turns one arm of the pincer. This gear also causes the opposite arm to close through the turning of an additional gear. Both arms will close at the same speed.

Concept 6 –

This concept is fully self-contained There are four wheels, and the front two wheels have

independent drive motors to allow forward and reverse motion for both wheels

The pincer is 2 arms attached to a central cog driven by a small motor, and this is attached to an arm which features a lowered front section so that the pincers can pick up from ground height. There is also a rack along the length of the arm to allow extension of the arm towards the pickup location

The rear of the base is fairly large to encompass possible radio technology, and to allow for additional weight to balance the moments caused when the pincer is at maximum height

The front of the base is a beam structure to minimise weight The lifting of the pincers is through a pulley system up a 1-

metre pole, powered by a motor at the rear of the vehicle The insides of the pincers contains a soft material to act as a

shock-absorber

Final Design

To create the final design, the six concepts were discussed to consider the advantages of each part of each concept, and these advantageous parts were taken out from the concept. We combined these to create a design that we felt contained the best of every concept.

It was decided that a single rack and pinion, such as from concept 2, was all that was necessary to provide the lifting for the accumulative weight of the pincer and egg. This would minimise complexity that would be caused from combined lifting, as it would not be required to synchronise lifting with multiple motors acting upon multiple rack and pinions. It also reduces risk of failure due to less components. Stability could still be ensured by taking appropriate dimensions of the central rack. The gear chosen to move up the rack was a worm gear as shown in concept 5, as this would provide higher torque and be less likely to slip than a standard cog gear.

The pincer design is to be deep, cup shaped pincers that are curved in a way to allow the weight of the egg to be supported from underneath to reduce the pressure required on the sides of the egg to lift it, taken from concept 5. This helps reduce the force required to act upon the egg for stable lifting to prevent damage being caused to the egg.

The pincer arm was taken from concepts 1 and 3, which would be for the arm design to lower to ground level at minimum height. This was chosen to ensure that the egg can be taken from all heights, to improve the flexibility of the design. It is also to be extendable as shown in concept 3. This allows the pincers to be moved out towards the egg at a slow and stable speed to prevent the egg being damaged or moved if impacted by the pincer arm at a high speed.

The wheel design was chosen to be similar to concept 3, involving 2 independantly driven wheels at either side of the midpoint of the base to provide a forward and reverese force to both sides of the base. This allows the device to turn completely on the spot and move in any direction. Extra fully rotational wheels are to be placed at the front and rear of the base to provide stability.

The base was chosen to be of octagonal shape. A circular shape was initially considered as from concept 1 but this was simplified to an octagon due to the manufacturing complications of a circle. An octagon is also more asthetically unique.

Final Design – Revision

After some consideration regarding materials and control in the sections to come, we decided to revise our final design. When looking further into manufacture we decided to go ahead and solve some problems before we came to them. Firstly, we have mounted the lifting motor above the worm so to allow the arm to go as low as possible, without having to cut a hole for the motor to sit in.

Secondly we have simplified the angled section of the arm by achieving the drop in elevation with two overlapping beams, bolted together.

In this area, it is also noticeable that we have done away with the arm extension mechanism. This is because with further research into control and motors (covered in the following two sections), we have come to the realisation that we will be able to drive the machine accurately enough to collect the egg safely without an arm extension mechanism. This decision will make the entire assembly far simpler and make the arm far lighter to lift.

Our final design revision is of the pincer. Here, the size of the proposed motor has been more accurately considered and the cog diameters have been calculated to allow a slow closing motion around the egg. In order to reduce bending moments on the pincers, an additional support has been added at the bottom and the curved sections have been revised in shape to allow easier manufacture.

This drawing shows the pincer mechanism with all main parts dimensioned. This drawing was done at a scale of 1:1.

This drawing shows the entire arm assembly with all appropriate dimensions. This drawing was done at a scale of 1:3.

The drawing on the left shows the base assembly, including wheels, motors and battery pack. (Scale 1:5)

The drawing on the right shows the pillar and rack assembly, along with a plate for connection with the base assembly. (Scale 1:10)

Material selectionIn this section is shown how the needs of certain components were identified and suitable materials were analysed in order to choose the ideal material for each component. All materials were judged on things such as price and availability while different materials were judged on more specific criteria such as strength, density, friction co-efficient and malleability.

*Modulus of rupture is an accepted criterion of strength though it is not a true stress.

Recommended materialWhite Pine wood seems to be ideal for the base of the device. Due to its good strength to weight ratio it should be able to support the lifting device and power source with minimal weight added to the structure as a whole. Additionally, the fact it is easy to work and machine, glues and finishes well and is cheaper than the stronger white oak means it would be best suited to the task.

Base Requirements: Strong, Light as possible, load bearingPossible materials

White Pine wood

Structural Steel Aluminium White Oak wood

characteristics Strong and cheap. Easy to machine and shape. Very good strength to weight ratio. Moderately durable- needs to be treated with preservatives.

Durable, resilient and strong. Denser than wood and more costly.

Low density, high strength, malleable and easy to machine.

Workable by hand and machine. Rot resistant, used for boat building.

Numerical Values:

Density:400Elastic Modulus: 8.55GPaUltimate Tensile Strength: 40MPaModulus of rupture*: 59MPa

Density:8000Elastic modulus:200 GPaUltimate Tensile strength: 400MPa

Density: 2700Elastic modulus:69 GPaUltimate Tensile Strength:110MPa

Density:600-900Elastic modulus:12.15GPaModulus of rupture*: 105MPa

Worm Gear Requirements: Strong, stiff, low frictionmaterial Nylon 6 Structural Steel Polyoxymethylene(POM)Characteristics Very Strong and

abrasion resistant. Low friction co-efficient. Excellent wear resistance, good toughness, hardness and low density.

Very strong and stiff. Higher density and higher friction coefficient when dry.

A thermoplastic with high stiffness, low friction and a high strength that is injected moulded.

Numerical Values

Density: 1150Elastic modulus:2-

Density: 8000Elastic modulus: 200GPa

Density:1410-1420Elastic modulus: 2.9-3.5GPa

4GPafrictional coefficient v steel: 0.35Ultimate tensile Strength: 45-90MPaYield Strength:45MPa

Kinetic frictional coefficient(Steel on Steel): 0.6Yield Strength: 250MPa

Kinetic frictional coefficient on steel: 0.21Compressive strength: 31MPa

Recommended materialNylon worm gears are often used in small electrical appliances since they are cheaper than metal gears and require no lubrication. Furthermore, the low density and abrasion resistance of nylon make it an ideal material for this purpose. Steel, although stronger and stiffer than Nylon, is also heavier, more expensive and would require lubrication to reduce the co-efficient of friction between the gear and the rack. POM is slightly denser and has around the same stiffness as Nylon. It may however, not be as available to acquire. Therefore, we intend for this component to be made from nylon.

Rack Requirements: low friction coefficient, glues and joins wellMaterial Stainless

steelNylon POM Aluminiu

m alloyBrass

characteristics Strong and stiff, Higher friction coefficient than nylon and pom. Could require lubrication. Denser than nylon and pom.

Strong and stiff but not as strong as steel. Has a lower density and lower friction co-efficient

Strong and stiff also. Not as strong as steel.

Stronger and stiffer than Nylon and POM but less so than steel.

Alloy made from copper and zinc. Low friction coefficient and malleable.

Recommended materialRacks can come in the form of solid racks or flexible racks. If a flexible rack is used it would need to be attached to the side of the central pillar. It would offer no structural support and possibly require a thicker pillar or a stronger material. It would however be cheaper. It also appears that it would be difficult to get racks of the right size. To acquire a steel rack at a length over a metre in length would be costly and take up a large part of the budget. However, a steel rack is what we intend to use as it is strong and has a low friction coefficient with nylon.

Pillar Requirements: Strong, low density, glues and joins wellmaterial Steel Aluminium

alloywood

characteristics Strong and stiff. More dense than Aluminium.

Not as strong as steel but less dense.

Less dense than both steel and aluminium while offering good strength to weight ratio.

Recommended materialSince the purpose of the pillar is to support the rack this means the material used depends heavily on what material is chosen for the rack. Since the rack is to be made from solid steel, this lends itself to wood being used since less support would be required and the weight of the

structure will be minimised. Steel and Aluminium would be more expensive also.

Recommended materialSince the pincer arms are to be a more complicated shape than other components, this will need to be taken into account when choosing the material. Additionally, the density of the material is important as heavy arms would cause a larger moment and put a larger strain on the structure. Initially different woods, metals and plastics were considered until the idea of using rigid foam that is easy to carve came to the fore. As this material was readily available to us and its low weight offered a great advantage, modelling foam became the chosen material for this component.

Recommended materialStyrofoam and other rigid, close-celled foams don’t provide the `cushion’ that we desire from this component. As we are using rigid foam to form the pincer arms, it is possible that no additional `cushioning’ material

Inner pincer arms Requirements: shock absorbing, glue well.material Styrofoam Low density

foamBubble wrap

Characteristics Lightweight, buoyant used for insulation. Rigid and close celled.

Low density and soft. Shapes to things it comes in contact with.

Trapped pockets of air. Sock absorbing material used to protect fragile objects.

Pincer Arms Requirements: workable, easy to shape, good tensile strengthmaterial Mild steel Aluminium wood Plastic Modelling(close

celled) foamCharacteristics Ductile

and malleable. Strong and dense.

Very malleable and very ductile. Less dense than steel and less strong.

Can be carved or cut into shape. Good strength v weight ratio.

Malleable, low cost and easy to manufacture.

Rigid foam structure that has very little weight. Very cheap and readily available.

would be required. If, however, it is required then bubble wrap would be our chosen material for its shock absorbing properties, versatility and availability at a low price.

Lifting arm Requirements: strong, low density, workablematerial Steel aluminium wood PlasticCharacteristics Strong but

dense. Workable.

Strong and less dense than steel. Malleable and ductile.

Good strength to weight ratio though not as strong as steel or aluminium. Easy to shape and cut.

Less strong than steel or aluminium but stronger than wood. Less dense than metal alloys.

Recommended materialAlthough this component has to be strong, a large part of the load applied to this component is its own weight. This gives wood and plastic an advantage. Aluminium would be better than steel for its malleable

qualities and because steel is more dense. Due to possible budget constraints, a type of wood with a low density such as pine or basswood that is easy to shape and readily available would be more ideal than a plastic composite.

Summary of recommended materials

The base should be made of wood. We have planned for using white pine wood. The rack will be made from steel and the worm gear nylon. Wood has been chosen for the pillar so a minimal amount of weight will be added to the structure by the component. The pincer arms should be made from rigid, close celled foam with bubble wrap attached to the inside of the arms if required. The lifting arms itself will also be made from wood because of its excellent strength to weight qualities. A low density softwood like basswood would perform well for this component.

Construction Methods

The base we will construct by cutting out the corners from a wooden block using a circular sawing tool. The front part of the base will be cut out using a jig saw tool. The worm gear and rack should be ordered in the correct sizes so no additional work will be required. The motors will be screwed to the underside of the base and are connected to the wheels through the drive shafts. The wheels will be rubber coated and made from plastic. The battery pack is also screwed to the underside of the base towards the back end of the device. Using the jig saw, a rectangular hole will be cut out from the centre of the base. The rack and pillar will be glued to a metal rectangle that will be screwed into the underside of the base. The rack and pillar will be glued together using an adhesive. The lifting arm is broken into two parts to make it easier to construct. Starting with two wooden beams, sections will be cut out using a jig saw to create the desired shape. The circular shapes will be cut out using a hole saw. The two parts of the arm will be bolted together at two points. The

pincers will be shaped with a high precision knife and connected to the gears at the end of the lifting mechanism using small aluminium bars. The bubble wrap will be attached to the close celled foam using an adhesive. The lifting motor will be attached to the back of the lifting arm at the same side as the counter weight. It will be screwed in place using metal plates and supports. The lifting motor will be connected to the worm gear and keep it in place.

Control Selection:

One of the first thing decided for the design was how it should be

controlled. A few control methods discussed where manual control

(crank/lever etc.), wired semi-automatic, wireless semi-automatic, fully

automatic (sensors and self-correcting feedback loop i.e. completes task

without user input) and combinations of the four options. Manual control

did not show our competency and was underwhelming so was not an

option. Fully automatic control was too complicated and would need

heavy programing, some sort of egg recogniser device and would

probably be difficult considering the cost and construction time

constraint. It was decided that this option would show extreme

competency, however, would not likely be the best option. It seemed that

the device should be controlled either through wired or wireless

communication. After doing some research it seemed possible to do

either one. It came down to the benefits and disadvantages of each type.

Wireless:

Advantages:

Showed competency

Would be really impressive

Would not be confined by wires running to the user

User would not have to be moved and could control the egg lifter

from a phone/wireless controller

Electronics can be confined to device and hidden to improve

aesthetics

Disadvantages:

Group would need to learn programing to control the device

More potential problems/complications

Likely to be more expensive than a simple wired solution

More complicated that a wired solution

Multiple power sources or voltage steppers will be needed to

supply multiple devices e.g. microcontroller, motors, wireless

communicator etc.

Wired control:

Disadvantages:

Not as impressive as wireless

Not as aesthetically pleasing as wireless as will be shown and

strung to the user

Needs manual input e.g. switching switches

May need multiple power supplies depending on motor selection,

however this can be solved by using motors of same voltage

Controller will need to move along with the egg lifter

Advantages:

Simpler wiring and control drawings than wireless

Can be sourced by one supply

Easier to control

Can me modified easily via hardware changes instead of

programming

Less expensive

Less possibility of things going wrong and reliable

Physical tactile feedback

Components readily available

It was decided that the egg lifter would be controlled by wired switches

and physical input by the controller someway away from the device due

to simplicity and cost.

Power Source selection:There were three main ways to power the device. Through solar, fixed

power supply e.g. wall supply and through a portable battery fixed to the

lifter. Solar would not provide enough electricity and a fixed supply would

mean that the device was tethered in another place other than the user

and the components would have to be A.C. compatible. The best option

was to use a battery placed on the device to supply power as batteries are

widely available and came readily in different configurations. This meant

that the device could move around freely and still have sufficient power

to run. The battery pack would have to be as small as possible so would

only provide enough current for the motors to operate and no more.

Motor Selection:In order to generate movement in our chosen designs at least 4 motors

are required: two for the wheels, one for the arm lifting and one for the

claw mechanism. The driving motors as well as the lifting motor would

have to produce a high torque in order to move around the full weight of

the entire design. The driving motors would need variable speed control

so that the lifter can reach the egg with precision and not knock it away.

The claw motor would have to be small, slow and light weight in order to

ensure egg safety and add as small a moment as possible acting on the

arm. Possible motors include DC brushed/brushless motors, DC geared

motors, server motors and stepper motors. Normal dc motors have too

high an rpm and not enough torque so where excluded. Stepper motors

where somewhat bulky and could not reach the desired speeds and

would require multiple power sources for components. Servos would also

need multiple power supplies (for the microcontroller and the servo),

would only be suitable for the claw (due to only tuning a certain number

of degrees and back) and would also need to be programed so these were

also excluded. Geared motors could be used in every part of the device

and could also be run from a single power supply. Almost any speed could

be achieved and they could run without being programmed (through

switches). They can also be reversed and have high torque.

Therefore geared DC motors where chosen to run the egg lifter.

After some research it was evident that most geared motors run

efficiently at 12v so only 12v geared motors where selected so that they

can be run of a single 12v battery pack without having to be adjusted.

Motor Requirements:Claw:

This motor is to close the pincer extremely slowly so we can visually judge

when the egg is securely held but not yet being crushed. We estimate

that for 10 seconds between fully open and meeting the surface of the

egg we need this motor to rotate at 2-4rpm (assuming that a fraction of

one rotation would close the pincers). There are no specific torque

requirements for this motor apart from it should be able to support and

close the pincers (which at 2rpm would not be a problem for any geared

motor). The motor must be small enough to fit onto the backend of the

claw and light weight. It should also have an

offset output shaft so that it allows room and is

not in the way of claw operation, as can be seen

in the final concept drawings (right).

Lifting motor:

This motor must produce large amounts of torque in order to elevate the

entire arm including the cradled egg to the desired height. It must also

rotate quickly enough to reach the correct

elevation in a reasonable amount of time. We

estimate for 20-30 seconds to the 1m height we

would need a motor rotating at 2000 – 3000 rpm

due to using a worm gear. Each rotation of the

gear leads to a 1mm increase in height of the

arm. This motor does not have a size requirement

as long as it fits the design and a worm gear can

be sourced of large enough size to expand over the motor edge. It would

probably be necessary to include a small spur gear (and lower the worm

diameter) to lower the effect of friction between the worm gear and the

rack (left top and bottom image). The speed would not be affected in this

case as long as the spur gears pitch remains at 1mm.

Driving motor:

The driving motors must produce a high torque, in order to move around

the full weight of our entire design (max 10kg). The motors must also

have variable speeds in both forwards and reverse directions in order to

accurately navigate to complete the task in hand. They would be

operated using pulse width modulation (rapid on and off switching of the

motor) which would allow for variable speeds with constant torque. So to

travel 1m a 10cm diameter wheel will have to turn just over 3 times. If

this took about 10 seconds then the wheels should turn at 18rpm. The

motor speed should however be approximately 50rpm (un-geared) for a

2.5-50rpm range (assuming 5-100% p.w.m. range). This would allow for

slow, precise movement while manoeuvring and faster movement when

driving straight. This motor could also be attached directly to the wheel

given enough torque.

Final motor selection list:The motors where chosen to meet their requirements at minimal cost

and their specifications are as follows:

Claw Motor:

Rated Voltage: DC12V Gearbox

Diameter 40mmRated Current: 0.06A DC Motor

Diameter: 32mm

Output Speed: 2RPM

Overall Size(Approx.):

54 x 52mm Max. Width*Height)

Output Shaft Diameter: 5mm Weight: 90g

Price: £7.78Source: http://ebay.eu/1z9J6B6

Lifting Motor:

Rated Voltage: DC12V Diameter: 35mm

Rated Current:0.52A(2.85 at max efficiency)

Overall Size: 47 x 96mm Max. Width*Height)

Output Shaft Diameter:

6mmWeight: 234g

Price: £20

Max torque: 0.88Nm(stall) Rated torque: 0.294Nm

Rated RPM:

2633rpm at max efficiency, 12V

Efficiency: 64.9%

Sorce: http://www.maplin.co.uk/p/61-mfa-large-single-ratio-motor-gearbox-n98bn

Driving Motors:

Rated Voltage: DC 12VRated Torque 1.289Nm

Rated Speed: 50 RPMShaft Size: 15 x 6mm

L*DMotor Body Length: 62mmThread Diameter: 2.5mmTotal Length(Included Pins): 85mm

Rated Current: 0.5652Amps

Weight: 200gMotor Body Diameter 37mm

Price: £11.19Source: http://ebay.eu/1yPGRE4

All motors may change according to next semesters design requirements/changes as well as according to availability and shipping time but at the moment they are all suitable for the egg lifter. Any other motors will be as close to these as possible.

Circuit Diagrams:Circuits one, two and three show how the motors might be wired. Circuit

one shows a voltage divider with a fixed motor speed as well as a stepped

down voltage. This was not needed since all the motors where the same

voltage so could be run off one supply. Circuit two shows a variable

voltage divider with a variable speed motor. Again this design was initially

thought to be used but since the only variable speed motors in the

system where the drive motors (using pwm) this was not needed. Circuit

3 shows how the driver motors could be wired using pwm. The pwm

component is to a standalone device that sends a variable pwm pulse

through its outputs varies via a turn knob. This component can be bought

for around £5 and means that no programing is needed. In this solution,

as the motor speed decrease so does the torque. All motors are reversible

via the double pole double throw switches which can be wired as shown

in the

physical

representation. The switches put the motor in forward, off, and reverse

states, controlled by the three switch positions. The full circuit diagram

shows how all the motors will be wired to a single power supply. All

switches will be wired away from the egg lifter to a control board in the

user’s hand. The diodes prevent back e.m.f from the motor reversal. It

was estimated that the battery should provide at least 3amps at all times

when needed and only 1 or 2 motors would be on at any given time. The

supply would provide power to the pwm component as well. A battery

pack of at least 2.5amp hour battery is needed to provide a constant

maximum current of 3Amps to any device that may draw from it. The

motors will not draw more than 3 amps. The battery pack could be a Ni-

MH battery pack as these are easily rechargeable, small, and relatively

light but would cost around £20. Alternatively 10AA alkaline batteries

could be wired up in series which would be equivalent but not be

rechargeable. This set up would cost £10. Since the egg lifter is designed

only to be used once including testing (30mins-1hr) buying batteries and

wiring them up would be suitable.

Motor Placement & Wiring

These diagrams show our design for the layout of the electronics in the machine.

On the left (from top to bottom), the first drawing (at 1:3) shows the arm assembly, showing the placement of the wire running along the arm, the lifting motor above the worm gear and the pincer closing motor at the free end of the arm.

The second drawing shows the base at 1:5 and the pillar / rack assembly at 1:10. The plan view at the bottom of this drawing shows where the wire will come through the base and coil, while the view from underneath (positioned above the plan view) shows the placement of the driving motors, the battery pack and the wiring.

The third drawing shows the pincer assembly at 1:1 and where the motor will be placed in it along with where the wire will have to reach in order to reach the supply pins.

On the right, you can see the full assembly of the machine with the same colour coding applied.

This drawing highlights a possible issue for the design, the prospect of having a wire coiled on top of the base. When manufacturing the machine, a system may need to be put in place in order to allow the wire to smoothly coil and uncoil as the arm climbs and descents the rack.

Blue – Motors

Red – Wires

Green – Battery Pack

1 2 3 4

5 7

8

6

Semester 2 – Project Plan

Task Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9Week 10

Week 11

Week 12

Finalise Design and DrawingsPlanningOrderingDesign ModificationsCraft BaseCircuit Board AssemblyCreate individual partsPart AssemblyTesting

1. Finalise Design and Drawings2. Planning3. Ordering4. Design Modifications5. Create Individual Parts6. Circuit Board Assembly7. Part Assembly8. Testing

Final Considerations

Lift LockingThere may be an issue with the lift arm after having reached its

destination height where the worm gear may begin to slip and start to fall back down. Obviously it would be preferable for the gripper arm to lock in place and not slip once the motor that rotates the worm gear stops rotating. We could implement a locking system such as a solenoid with a rubber stopper mounted underneath the lift arm to activate and extend its arm onto the centre pole to lock the arm in place once it reaches the desired height. However it may be the case that the worm gear provides enough of a friction force to stop the arm from falling back down once it reaches the desired height, however we would not know this until we complete testing (due in semester 2) on the lift design and may need to implement a locking system at that time. It would be preferable however if we could save on weight and not have to add extra components to the lift arm.

Braking SystemAn issue may arise with the driving system as currently there are

no brakes designed to bring the vehicle to a halt, hence the driving and handling of the system is not likely to be very precise. The system may continue to roll once put in place which is clearly not ideal as there needs to be a degree of accuracy to the placement of the egg. To eliminate this there may need to be a braking system implemented to increase the accuracy of the driving. One example of how this could be done would be to have two solenoids which are mounted on the underside of the chassis next to the two main drive wheels. The solenoid would extend and stop

the wheels from moving (through friction). This would allow us to stop the vehicle when it is in a particular spot and keep the brakes held on to stop it from rolling (this would be especially useful for when the lifting procedure takes place). It could also be the case however that the weight of the vehicle itself may cause a friction force high enough that this issue could be disregarded, however this is again something e cannot fully understand until the testing stages.

Gripper IssuesIt needs to be taken into consideration that the pincer grip will

need to be manufactured as well as possible because the consequences of the pincer being faulty would be catastrophic. Not having enough grip without breaking the egg etc. We have chosen to go with a double pincer grip hence there will be two moving components that need to be controlled. In the lifting, we will need to be aware of their weight so to avoid large moments on the arm. We will also need to be aware of how the gripper will actually operate (as both of these arms will need to close at the exact same speed and have a very slow rpm) also both of these arms need to come together which required some precision.

Runner on Gripper ArmThe surface of the lift arm that will contact the flat side of the

rack may generate a very high amount of friction. This may cause an issue when the worm gear is trying to rotate and lift the arm that it may not provide enough torque to overcome the friction created by the two surfaces rubbing against one another (technically the friction will be caused by the weight of the gripper causing a small rotation in the gripper arm by creating a moment around it). One easy way to get around this

1. Finalise Design and Drawings2. Planning3. Ordering4. Design Modifications5. Create Individual Parts6. Circuit Board Assembly7. Part Assembly8. Testing

would be to add in a runner wheel to contact the centre pole. This will be free to rotate hence decreasing the friction when the arm is ascending. This would easily eliminate the issue of friction and is most likely to be implemented into our design as it would also be very cheap and effective to introduce.

Do we need an extension (Decided)?Originally we have designed the system to have a small extension

arm to allow it to easily extend and allow for a longer reaching distance. However we discussed whether or not this was particularly necessary and whether or not it could be omitted. If it were to be omitted then we would decrease the number of motors we would require and save weight on the lift arm (the most crucial piece of the device that requires a low weight). We eventually decided that we would omit the extension, but we would put more effort into our driving mechanisms to maintain accuracy (as the arm would have extended slowly and it may be more difficult to do this while driving). Therefore it is very important for the speed of the motors to be very variable between inching forward towards the egg, to driving the 1m distance required without taking too long.

Rack & Worm Size and FrictionA potential issue may arise with trying to obtain the correct size

of rack (needs to be just over 1m in length) with a worm gear whose pitch will match that of the rack. Another consideration will be how quickly the lifting process will be carried out; as for a worm gear, 1 rotation = moving vertically 1 tooth. If we assume that each tooth is 1mm in length and we want the lift to take no longer than 30 seconds to reach the desired height then the motor must rotate at 2000 rpm. That speed of rotation however (approx 33revs or 33 mm per second) is relatively fast but

generally faster rotation tend to mean lower torque which could give rise to more problems. The rack and worm system should work well if all parts are properly sourced and pieced together however, but if we struggle in manufacturing and the rack does not live up to current expectations and what we have researched then we do have other potential backup ideas for lifting (e.g. a pulley system).

It seems difficult to purchase a combination rack and worm gear to fit our needs so it is likely that we will buy independent components and combine them. The main problem with this is likely to be a friction factor far too high for our motor. While this may entirely eradicate the need for the lift locking mechanism, the static friction may actually be too high to be overcome by the lifting motor. Or if this is possible, it may burn the motor out with a slowed motion due to excessive kinetic friction. A possible solution to this may be to insert an intermediate spur gear to connect the worm gear to the rack. However if the worm gear and rack are compatible and the arm can climb then this will not need to be addressed.

ConclusionGroup 2 thoroughly researched every option that they felt was available to come up with an effective design within the £300 budget. Pugh’s design methodology was used through the process in order to find the

best performing pieces on each part of the design. Concept generation tables were used extensively during this process with the assigned weighting system concluding upon the best results. Detailed drawings were done by hand along with using CAD programmes in order to properly show what the prospective design will look like. Materials were extensively researched for properties and to make sure that we kept within the £300 budget.

The group had a weekly meeting during the timetabled Monday slot, where each member was assigned their own individual task in accordance with their skill set which had to be completed before the next week e.g. create CAD drawings. We set our own deadlines to ensure that work was

completed on time and we met outside tutorials and used social media to

Appendices

Appendix 1 – Mass Calculations

Parts ListComponent Suggested Source Estimated Cost (£)

Pincer Independently 0Pincer Connectors eBay – Aluminium Flat

Bar2

Cogs RS POM Gear 12.32Pincer Motor eBay – Geared Motor 7.78Pins eBay – Steel M8 6Pincer Motor Casing eBay – Al T Profile 2Arm Beatson’s /

Independently2.04 / 0

Arm Bolts Ross Castors 0.5Worm Gear RS Worm Gear 8.68Lifting Motor Maplin 19.99Base Independently 0Caster Wheels Cyber Market 21.82Driven Wheels Ross Castors GV 6.6 + DBattery Pack We Sell Electrical 6Wires The Tool Box Shop 2.32Driving Motors eBay 22.38Speed Regulator (p.w.m.) RS 3.89DPDT Switches Maplin 11.16Rack Belting online 61.32Pillar Beatson’s /

Independently4.24 / 0

Connector Plate Beatsons’s / Independently

6.08

Screws Screwfix 4.49Total (Estimated) Cost £211.61

Appendix 2 – Parts List with possible suppliers

Component Suggested SourcePincer Independently

Pincer Connectors http://www.ebay.co.uk/itm/ALUMINIUM-FLAT-BAR-15mm-x-2mm-600mm-LONG-NEW-/390506219000?pt=UK_BOI_Metalworking_Milling_Welding_Metalworking_Supplies_ET&hash=item5aebfc05f8

Cogs http://uk.rs-online.com/web/p/spur-gears/5217506/

Pincer Motor http://www.ebay.co.uk/itm/5mm-Dia-Shaft-DC-12V-0-06A-2RPM-High-Speed-Gear-Motor-/121477015813?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c48982905

Pins http://www.ebay.co.uk/itm/like/261204298955?limghlpsr=true&hlpv=2&ops=true&viphx=1&hlpht=true&lpid=108&chn=ps&device=c&adtype=pla&crdt=0&ff3=1&ff11=ICEP3.0.0-L&ff12=67&ff13=80&ff14=108

Pincer Motor Casing http://www.ebay.co.uk/itm/ALUMINIUM-T-PROFILE-20mm-x-20mm-x-2mm-x-300mm-LONG-/251194596531?pt=UK_BOI_Metalworking_Milling_Welding_Metalworking_Supplies_ET&hash=item3a7c5d5cb3

Arm http://www.beatsons.co.uk/timber-sheet-materials-c1586/red-pine-dressed-c143/dressed-planed-c152/beatsons-red-pine-dressed-45mm-price-per-m-p14011

Arm Bolts http://www.rosscastors.co.uk/index.php/catalog/product/view/id/100/s/m8-x-30-stainless-steel-threaded-bolt/?gclid=CPq3vIjYxcICFeLItAod2BMAAg

Worm Gear http://uk.rs-online.com/web/p/worm-gears/5216890/

Lifting Motor http://www.maplin.co.uk/p/61-mfa-large-single-ratio-motor-gearbox-n98bn

Base Independently

Caster Wheels http://www.cybermarket.co.uk/shop/music-disco/flight-case-accessories/castors-different-versions-in-986649.html?utm_source=google&utm_medium=base&utm_campaign=H7Media&gclid=CNmku4TkxcICFSnkwgod2AUAqQ

Driven Wheels http://www.rosscastors.co.uk/wheels/grey-rubber-wheels.html

Battery Pack http://www.wesellelectrical.co.uk/duracell-procell-aa-battery-box-of-10?gclid=CMnT6p7kxcICFRHHtAodWGYAhQ

Wires http://www.thetoolboxshop.com/0-952-51-1-100m2-red-black-875a-flat-beacon-and-lighting-electric-cable-sold-per-metre-8244.html?gclid=CICZ66rkxcICFeHHtAodaEcA5Q

Driving Motors http://www.ebay.co.uk/itm/DC-12V-50RPM-6mmx15mm-Shaft-37mm-Body-Dia-Magnetic-Gearbox-Motor/121153766387?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D28111%26meid%3D0f8d65e0d0cd440683dfd40649155352%26pid%3D100005%26prg%3D11472%26rk%3D1%26rkt%3D6%26sd%3D190838364360&rt=nc&tfrom=190838364360&tpos=unknow&ttype=price&talgo=origal

Speed Regulator (p.w.m.) http://www.ebay.co.uk/itm/12V-24V-3A-DC-Motor-Speed-Regulator-Controller-Switch-Control-PWM-HHO-RC-UK-/351155646086

DPDT Switches http://www.maplin.co.uk/p/sub-miniature-toggle-switch-f-on-off-on-dpdt-fh05f?gclid=CPnEv6zjxcICFWjItAodDQUAFw

Rack http://www.beltingonline.com/1-0-mod-x-2-0-metres-sr10-10h-2a-steel-rack-6791

Pillar http://www.beatsons.co.uk/timber-sheet-materials-c1586/red-pine-dressed-c143/dressed-planed-c152/beatsons-red-pine-dressed-45mm-price-per-m-p14011 / Independently

Connector Plate http://www.beatsons.co.uk/timber-sheet-materials-c1586/red-pine-dressed-c143/dressed-planed-c152/beatsons-red-pine-dressed-45mm-price-per-m-p14011 / Independently

Screws http://www.screwfix.com/p/timbadeck-countersunk-carbon-steel-decking-screws-4-5-x-75mm-pack-of-100/74706?kpid=74706&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&kpid=74706&cm_mmc=Google-_-Shopping%20-%20Screws-_-Shopping%20-%20Screws&gclid=COnpwunkxcICFczMtAodUSsAkw

Appendix 3 - Motor Calculations:The required toque for the driving motor and the lifting motor where calculated as shown:

No calculation is required for the claw motor as any geared motor under a few hundred rpm should be able to close the claw.

Appendix 4 – Egg Impact Calculations