chapter01 worksheet

7/26/2019 Chapter01 Worksheet

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Mechanical Design. PRN Childs, University of Sussex. Chapter 1 - WORKSHEET SOLUTIONS

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Chapter 1: Design

Worksheet Solutions

Most of the questions in this worksheet do not have unique answers. The solutions outlinedhere represent an attempt at the task identified in the questions. Alternatives to these are

possible and a number of the solutions are not complete.

1.1) Any of the following and more.What size nails are to be used in the machine?What force is required for the nailing action?How rapidly should the nails be applied?How heavy can the machine be?What manufacturing facilities are available?What power source should be used?What access to the job is necessary?How are the nails to loaded?

What length of set up time is acceptable?What kind of triggering is desired?

1.2) No unique solution.

The brief identifies the requirement for a snow sports activity vehicle. The briefhowever does not set definite bounds on the design requirements. These need to bedeveloped so that design can proceed. This activity needs to occur as a dialoguebetween the design team and interested parties which would include the managingdirector and potential customers. The ideas developed here represent the beginningsof a possible product design specification.

The spider chart given in Figure 1.10 can be used as starting point for the developmentof the specification. This acts as an aid for identifying aspects for consideration. Thespecification is developed here using a standard pro-forma. Only a few items are listedhere. The specification should however be developed further with consideration of thebulk of the items identified in Figure 1.10. In addition further detailing will be necessaryfor most of the aspects.

Note each aspect, objective, criteria and test condition specified requires consultationand agreement from the brief owner, e.g. the management board.

ASPECT OBJECTIVE CRITERIA TEST CONDITIONSPerformance Operation atlowtemperatures

Assume arctic conditions. Operation attemperatures between 40

oC and 25

oC.

Test components atextreme temperatures.

High speed 60 mph maximum. Rolling road test ordynamometer test.

Highacceleration

Limit to the ability of an average person tohold on to and control vehicle.

Test existing productsand identify maximumacceleration suitable.Test prototype onrolling road or


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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSdynamometer.

Highmanoeuvrability

Less than 5 m turning circle. Test model.

Easy steering Steering must be responsive to driver intentand provide adequate feedback of drivingconditions.

Use a focus group toevaluate steering on aprototype model.

Easy starting Push button start. Expose CAD model toa focus group forassessment. Expose aprototype model ofstarting to a focusgroup.

High range 2 hours operation or 120 miles. Dynamometer orrolling road test.

Good braking Must be capable of braking from 30 kph in 30m on fresh snow.

Rolling road test.

Accommodation

2 people Driver plus one passenger. Test accommodationof two people in theproduct using digital

manikins in the CADmodel. Use a focusgroup to evaluate thelayout andaccommodation usinga prototype mock-up ofthe design.

Cost Acceptable costfor marketsector

The works cost price must not exceed 3000. Obtain quotations forconstituentcomponents fromOEMs and estimatesfor in-housemanufacturedcomponents andassembly costs.

Size Small Must be able to transport device on a smalltrailer.

Determine size ofconcept from CADmodel. Test concepton a CAD trailermodel.

Noise Low Noise levels must not exceed nationalstandard limits.

Test to nationalstandards.

Materials Appropriate todesign

Compatible with low temperatures and fuel(fire retardant, see standards).


Weight Low One person must be able to move the device.Two people must be able to lift the device.Mass not to exceed 120 kg.

Determine weightduring design fromCAD model. Weighprototype components.

Safety High Power plant must cut out when driver losescontrol.

Bench test.

Materials must be fire retardant to nationalstandards.

Bench test.

Fuel Readilyavailable

Any readily available fuel such as petrol,diesel, kerosene or electricity.

Propulsion Availabletechnology

Any available technology power plant

Aesthetics Attractive Current trend/modern sports style. Expose concept


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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSstyling. design ideas to focus

groups for appraisal.Expose prototypes tofocus groups forappraisal.

1.3) No unique solution. The solution developed here represents some ideas.

Ideas that spring to mind concerning this brief include conventional lawnmowers,strimmers, grazing animals and use of artificial grass to negate the need for cutting.However the question asks for the development of the specification. The spider chartgiven in Figure 1.10 can be used as starting point for the development of thespecification. This acts as an aid for identifying aspects for consideration. Thespecification is developed here using a standard pro-forma. Only a few items are listedhere. The specification should however be developed further with consideration of thebulk of the items identified in Figure 1.10. In addition further detailing will be necessaryfor various of the aspects.


ASPECT OBJECTIVE CRITERIA TEST CONDITIONSPerformance Low wear of

moving partsSwitch will operate 10000 times without fault.Electric motor will operate for 250 hourswithout fault.Cutting blade will cut effectively for 1000hours without attention.

Test to BritishStandards.

Continuous runlaboratory test.

Low probabilityof damage

Body of lawnmower can withstand a sideimpact without cracking as a result of being

dropped from a height of 1 m.

Practical test.

Low level ofvibration

Static out of balance of cutting blades not toexceed 2 grams.

To British Standards.

Long run time Device to run for at least one hour without theneed for re-fuelling or recharging.

Bench test primemover.

Cost Medium cost Works cost price not to exceed 75 Euros. Obtain quotations forconstituentcomponents fromOEMs and estimatesfor in-housemanufacturedcomponents andassembly costs.

Weight Low Total weight of machine not to exceed 15 kg. Determine weightduring design fromCAD model. Weighprototype components.

Safety The devicemust be safe

As a minimum the design must comply tonational safety standards.


Packaging Robust The packaging for the product must be robustso that the product can be displayed to itsadvantage in stores.

Test packaging underdistressed conditionsto simulate transportand expected handlingin storage and display.


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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSShelf life Long The device must be able to be stored and

suitable for sale for up to 2 years withoutidentifiable degradation in visual appeal orfunction.

Test packaging andproduct underdistressed conditionsto simulate rapidaging.

Aesthetics Highly attractive The design must be highly visually attractive

with greater appeal than competitive products.

Expose concept

design ideas to focusgroups for appraisal.Expose prototypes tofocus groups forappraisal.

Patents No royaltypayments tocompetitivecompanies.

The design must not expose the company topayment of royalty or licence fees for use ofIPR to competitive companies.

Patent search. ProtectIPR developed byseeking new patents.

Disposal Environmentallyacceptable.

The constituent components for the producthave to be recyclable. Compliance to EU andother national standards for recycling andsustainability.

Test disassemblyprocess on prototype.

etc.


A water sports activity vehicle is required. Information required to undertake designincludes:1) How big?2) How fast? What performance?3) How many passengers?4) Weight?5) What power plant?

6) What fuel?7) What cost?8) What kind of styling/aesthetics?9) Is safety an issue?10) Should it float?11) Starting?12) Materials?13) Control?14) Noise?

A product design specification for this product is developed here. This represents a

start to the task of developing the PDS. The spider chart given in Figure 1.10 can beused as starting point for the development of the specification. This acts as an aid foridentifying aspects for consideration. The specification is developed here using astandard pro-forma. Only a few items are listed here. The specification should howeverbe developed further with consideration of the bulk of the items identified in Figure1.10. In addition further detailing will be necessary for most of the aspects.



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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSSize Small Must fit on a small trailer.

One person must be able to pull it onto landfrom water.

Performance High speed 40 mph maximum speed. See national legal

regulations to identify any requirements forspeed limiter.

Acceleration limit to the ability of an average person to holdon to and control vehicle

Accommodation

Driver + one passenger

Highmanoeuvrability

Turning circle of less than 5 m diameter.

Noise Low Minimise noise compatible with use of productwithin a public environment

See nationalstandards/legalrestraints.

Weight Low 100 kg maximum Determine weightduring design from

CAD model. Weighprototype components.

Fuel Readilyavailable

Any compatible with marine use

Cost Low 2500 maximum works cost price Obtain quotations forconstituentcomponents fromOEMs and estimatesfor in-housemanufacturedcomponents andassembly costs.

Aesthetics Attractive Current/modern styling. Expose design to

focus groups.Safety High Power plant cut out if driver falls off or loses

grip of controlTest prototype.

Device must float when un-powered. Estimate buoyancyfrom CAD model. Testprototype.

Components must be fire resistant to Nationalsafety standards

Test components tonational standards.

Reliability High Easy to start. Must start with 99.5% reliability. Test product underdistressed conditionsto simulate repeatedstart conditions.

Life Long The product should have a minimum

expected life of five years.

Test product under

distressed conditionsto simulate extendedlife.

1.5) No solution provided.




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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSSize Small Must not obstruct rider accommodation.

Maximum diameter of clutch must be lessthan 120 mm.

Measure diameter onCAD model.

Weight Low Total weight of clutch plates, mechanism andhousing must not exceed 5 kg.

Estimate mass fromCAD model. Weigh

constituentcomponents.

Life Long The clutch must operate reliably for aminimum of 1000 starts. The clutch mustoperate reliably for a minimum of 12000 milesuse and 30000 operations.

Test individual clutchcomponents underdistressed conditionson dynamometer. Testprototype clutch underdistressed conditionson dynamometer.

Aesthetics Attractive The clutch housing must be visually attractiveto motorcycle owners.

Expose design tofocus groups.

Performance Full power Must transmit design power of 90 PS at 8000rpm

Test individual clutchcomponents under

distressed conditionson dynamometer. Testprototype clutch underdistressed conditionson dynamometer.

Partial loads Must transmit torque at off peak loadconditions.

Test individual clutchcomponents underdistressed conditionson dynamometer. Testprototype clutch underdistressed conditionson dynamometer.

Speed The clutch must function at speeds up to

10000 rpm to accommodate over revving ofthe engine.

Test individual clutch

components underdistressed conditionson dynamometer. Testprototype clutch underdistressed conditionson dynamometer.

Materials Readilyavailable.

The materials and out-sourced componentsmust be readily available. Use existingdeveloped materials.

Source examplecomponents andmaterials at outset ofdesign activity.

Safety Maximise There must be no exposed sharp or rotatingcomponents. Lubricants must be containedwithin the casing.

Test prototype to anyrelevant nationalstandards.

Patents No royaltypayments tocompetitivecompanies.




The constituent components for the producthave to be recyclable. Compliance to EU andother national standards for recycling andsustainability.


Environment Compatibility The clutch must operate at temperatures from-15

oC to 50

oC.

Test individual clutchcomponents attemperature extremes.


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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSTest prototype clutchat temperatureextremes.

etc.



ASPECT OBJECTIVE CRITERIA TEST CONDITIONSSize Small Must be readily accommodated in wheel arch.

Must be as small, or smaller than currentcompetition.

Measure dimensionson CAD model.

Weight Low Total weight of all brake system componentsmust not exceed 16 kg.

Estimate mass fromCAD model. Weighconstituentcomponents.

Life Long The braking system must operate reliably fora minimum of 15000 miles use and 30000steady stopping cycles from 30 mph to 0 overa 50 m distance and be capable of 20emergency stops without noticeabledegradation in performance.

Test individual brakecomponents underdistressed conditionson dynamometer. Testprototype brakingsystem underdistressed conditionson dynamometer.

Aesthetics Attractive The visible brake components must bevisually attractive to vehicle owners.

Expose design tofocus groups.

Performance High brakingtorque

The braking system must develop therequired braking torque, set at 100 N m perbrake, with four brakes in the system.

Test individual brakingcomponents underdistressed conditions

on dynamometer. Testprototype brakingsystem underdistressed conditionson dynamometer.

Responsivebraking

Braking action must be responsive to driverdemand.

Test individual brakingcomponents underdistressed conditionson dynamometer. Testprototype brakingsystem underdistressed conditionson dynamometer.

No noticeablefading There must be no noticeable brake fade. Limitfade to 10% of maximum braking torque forall reasonable driving conditions and specifiedlife of braking systems.

Test prototype brakingsystem ondynamometer.

Materials Readilyavailable.

The materials and out-sourced componentsmust be readily available. Use existingdeveloped materials.

Source examplecomponents andmaterials at outset ofdesign activity.

Safety Maximise There must be no exposed sharp, hot orrotating components. Lubricants must becontained within the casing.

Test prototype to anyrelevant nationalstandards.


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ASPECT OBJECTIVE CRITERIA TEST CONDITIONSPatents No royalty

payments tocompetitivecompanies.




The constituent components for the producthave to be recyclable. Compliance to EU and

other national standards for recycling andsustainability.


Environment Compatibility The brake must operate at temperatures from-15

oC to 110

oC.

Test individual brakecomponents attemperature extremes.Test prototype brakingsystem at temperatureextremes.

Cost Minimise The cost of the braking system componentsand installation must be below 150 Euros.

Obtain quotations forconstituentcomponents fromOEMs and estimatesfor in-house

manufacturedcomponents andassembly costs.

Noise Minimise The braking system must not developnoticeable noise to the vehicle occupantsunder normal braking conditions or followingextreme conditions. Noise of braking must belimited to below 56 dB.

Measure brakingsystem noise ondynamometer.

Shelf life Long The braking system must be able to be storedand suitable for sale for up to 12 years withoutidentifiable degradation in visual appeal orfunction.

Test packaging andproduct underdistressed conditionsto simulate rapidaging.

etc.

1.8) to 1.11) No solution provided.


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1.12) No unique solution. The following chart is potentially suitable.

Function MeansSupport Track spikes wheels air

cushionslides pedipulato

rsPropulsion Driven

wheels

air thrust moving

cable

linear

inductionPower electric fuel cell diesel petrol bottled

gassteam

Transmission

belts chains gears andshafts

hydraulics flexiblecable

Steering turningwheels

air thrust grippers airpaddles

Stopping air thrust frictionbrake ontransmission

frictionbrake onground

grapple cable grip

Driver/operator

standing towed seated inmiddle

sealed atfront

seated atrear

Aggregatestorage

hopper compress box bladder

Aggregateloading/unloading

tip out blow out lift openhopper


FEATURE MEANSsupport track wheels air cushion slides pedipulators

propulsion drivenwheels

air thrust movingcable

linearinduction

power electric diesel petrol bottled gas steam

transmission belts chains gears andshafts



air thrust rails magnetism

stopping brakes reversethrust

ratchet magnetism anchor

Lifting hydraulicram

rack andpinion

screw chain orrope hoist

linkage

operator standing walking seated atfront

seated atrear

remotecontrol

1.14) to 1.17) No solution provided


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Function MeansSupport track Spikes wheels air

cushionslides Pedipulato

rsPropulsion driven

wheels

air thrust moving

cable

linear

inductionPower electric Fuel cell diesel petrol bottled

gasSteam

Transmission

belts chains gears andshafts



air thrust grippers airpaddles

Stopping reverse airthrust

frictionbrake ontransmission

frictionbrake onground

anchor sail

Driver/passenger

standing towed seated inmiddle

seated atfront

seated atrear

1.19) Ideas might include:squeeze tubetub and spoonpowdercylinder and pistonpivoted lever with prong bearing down onto a tube containing pastetwist tubesuctionratchet and pawl mechanismbottlewater degradable capsulebite a capsule containing paste.


1.22) Ideas might include:voice activated seal breakercompartments to preserve freshnesscompartments for flavoursseparate mouth pieces (could be re-useable)bear keg spoutpush in cap to cut foil sealsports top optionheat degradable layer that responds to body heat?diamond shape spoutre-useable sticky sealscrew topperforated


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acidtappull-ringgunpowdertupperware style pop off lidscrew lid (jar)

scissorschemical reactionpressure to perforate weak spotzip bag top (cf freezer bag/pencil case)swing arm pivot.


chapter01 worksheet

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