Stair climbing hand truck

By: Group 7
Stephen McLoughlin
Shiyas Basheer
Conor Tiernan
Due Date: 30th
October 2012
Dublin Institute of Technology Bolton St.
Faculty of Engineering
Head of Department Supervisor Details
Dr. David Kennedy Mr. Gerard Nagle

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Table of Contents
Introduction.......................................................................................................................................5
Objective.........................................................................................................................................5
History.............................................................................................................................................5
Benefits and Problems ..............................................................................................................6
Design Objectives.............................................................................................................................7
Marketability .....................................................................................................................................8
Literature review:............................................................................................................................9
The Cargo Master:.......................................................................................................................9
Ease-E-Load Stair Climber Trolley Truck Carrying Capacity 150kg.................... 11
Stair Robot SR Express........................................................................................................... 12
Motor Type Selection .................................................................................................................. 16
DC motor...................................................................................................................................... 16
Advantages............................................................................................................................. 16
Disadvantages....................................................................................................................... 16
Applications where a DC motor is used:..................................................................... 16
AC motor...................................................................................................................................... 16
Advantages............................................................................................................................. 16
Disadvantages....................................................................................................................... 17
Applications where an AC motor is used:.................................................................. 17
Two main types of DC motors............................................................................................. 17
Brush:....................................................................................................................................... 17
Brushless:............................................................................................................................... 18
The Design....................................................................................................................................... 19
Considerations taken while designing............................................................................. 19
Mechanism....................................................................................................................................... 20
Mechanism free body diagrams ......................................................................................... 21
The free body diagram below illustrates the point where the most force is
needed to lift the trolley ................................................................................................... 21
The free body diagram below illustrates the point where the second most
force is needed to lift the trolley.................................................................................... 21
The free body diagram below illustrates the point where the force is at the
point where the trolley is on the next step and force is not needed anymore
.................................................................................................................................................... 21

Initial design ................................................................................................................................... 21
Final Design..................................................................................................................................... 25
Base of the Trolley:.................................................................................................................. 26
Arm Frame.................................................................................................................................. 27
Arm frame (x2) (female part) ............................................................................................. 27
Arm frame (x2)(male part) .................................................................................................. 28
Arm frame total height: ......................................................................................................... 28
Wheel Attachments................................................................................................................. 29
Handle........................................................................................................................................... 30
Rotational shaft with key way (for the motor and rotational support).............. 31
Crank (which is attached to the motor to the rotational shaft) ............................. 33
Large Rotational Arm (attached to wheels that sit on step) ................................... 34
Wheels that sit on step........................................................................................................... 35
Mechanism.................................................................................................................................. 36
Stage 1: .................................................................................................................................... 36
Stage 2: .................................................................................................................................... 36
Stage 3: .................................................................................................................................... 37
Stage 4: .................................................................................................................................... 37
Final design of the mechanism: .......................................................................................... 38
Supports (which support the motor, mechanism and rotational shafts)........... 39
Ansys: ................................................................................................................................................ 39
Material............................................................................................................................................. 41
Price ............................................................................................................................................... 42
Calculation....................................................................................................................................... 42
Selection of motor.................................................................................................................... 42
Selection of battery.................................................................................................................. 43
Torsion in the arm........................................................................................................................ 45
Selected Motor............................................................................................................................... 45
Design problems....................................................................................................................... 48
Weight and Cost........................................................................................................................ 48
Selection of battery ...................................................................................................................... 49
Battery Life Cycle ..................................................................................................................... 50
Battery Size................................................................................................................................. 51
Battery capacity retention characteristics:.................................................................... 52
A 10Ah battery...................................................................................................................... 53
Varying the speed ......................................................................................................................... 53

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The initial reaction .................................................................................................................. 53
Pulse Width Modulation........................................................................................................ 54
Speed controller............................................................................................................................ 61
Recommendation:......................................................................................................................... 62
Conclusion ....................................................................................................................................... 63
Roles of the group......................................................................................................................... 64
Stephen McLoughlin: .............................................................................................................. 64
Tasks done:............................................................................................................................ 64
Shiyas Basheer .......................................................................................................................... 64
Task done:.............................................................................................................................. 64
Conor Tiernan............................................................................................................................ 65
Tasks done:............................................................................................................................ 65
Reference ......................................................................................................................................... 66
Appendix:......................................................................................................................................... 68
Electrical stair climber assembly 2D drawing.............................................................. 68
Base 2D drawing....................................................................................................................... 68
Female tube 2D drawing ....................................................................................................... 69
Male tube 2D drawing............................................................................................................ 69
Pin 2D drawing.......................................................................................................................... 70
Handle component 1 2D drawing...................................................................................... 70
Handle component 2 2D drawing...................................................................................... 71
Handle Component 3 2D drawing ..................................................................................... 71
Main support 2D drawing..................................................................................................... 72
Selected battery 2D drawing ............................................................................................... 72
Overhead battery support .................................................................................................... 73
Bottom of battery support 2D drawing........................................................................... 73
Rotational Support 2D drawing.......................................................................................... 74
Support for motor and rotational support 2D drawing ............................................ 74
Overhead support for rotational support 2D drawing.............................................. 75
Shaft for rotational support and motor 2D drawing .................................................. 75
Rotational Arm of Motor 2D drawing............................................................................... 76
Rotational arm for rotational support 2D drawing .................................................... 76
Crank 2D drawing.................................................................................................................... 77
Mechanism and motor support component 1 2D drawing...................................... 77
Mechanism and motor support component 2 2D drawing...................................... 78
Mechanism component 1 2D drawing ............................................................................. 78

Wheel attachment component 1 2D drawing ............................................................... 81
Wheel 2D drawing ................................................................................................................... 83
Description...................................................................................................................................... 84
Assumptions ................................................................................................................................... 85
Model Information........................................................................................................................ 85
Material Properties...................................................................................................................... 86
Loads and Fixtures ....................................................................................................................... 87
Mesh Information ......................................................................................................................... 88
Mesh Information - Details................................................................................................... 88
Study Results .................................................................................................................................. 90
Conclusion ....................................................................................................................................... 93
Ergonomics................................................................................................................................. 96

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Introduction
“By definition the mechanical process defines a device that will carry out a specified
task when appropriate inputs are given. In reality, however, this definition provides a
tunnel-visioned view into the world of design. Mechanical engineers who design
consumer products have a twofold responsibility. In addition to designing functional
machines, successful product designers must create devices that consumers will want
to purchase and use. While there are many possible factors that can make a product
appealing to a buyer, perhaps the most important factor is an ability to make the user's
life easier in some small way. In this way, product design is a service profession. In
this design project we are trying to do the same, by designing a stair climbing hand
truck that will ease anyone’s workload.”
Objective
Every single year, thousands of adults worldwide, both at home and in workplaces,
injure themselves while attempting to lift/move heavy objects. Devices such as hand
trucks can be used to relieve the stress of heavy lifting on flat ground, however, can
fail when it comes to negotiating a short flight of stairs.
The objective of this design project is to design and test a consumer hand truck
capable of climbing stairs – for use in homes and small businesses. Having
brainstormed a number of designs that could travel over stairs, curbs or uneven
terrain, the authors decided on a variation on the motorised chair climber. As a result,
several models were researched and the group came up with a tweaked design.
History
A hand truck (also known as a two-wheeler, stack truck, dolly, trolley, trolley truck,
sack barrow, sack truck, or bag barrow) is essentially an L-shaped box handcart that
has handles at one end, wheels at the base, with a small ledge to set objects on and sits
flat against the floor when it’s upright. Objects that require moving are tilted forward
while the ledge is inserted underneath, and then tilted back to rest on the ledge. The

truck and object(s) are then tilted backward until the weight is balanced over the large
wheels, facilitating the movement of heavy or bulky objects. A motor mechanism is
attached to this hand truck to lift it up the stairs.
Benefits and Problems
Hand trucks can be made from many different types of materials – such as tube steel,
aluminum tube, aluminum extrusion and high impact plastics. Most commercial hand
trucks that are used for service deliveries are very light weight. A motorized hand
truck can completely eliminate the hardships of carrying objects up stairs. Its light
weight means that it can be easily transported, moved around and lifted. It also has the
ability to reduce or even eliminate the health problems that can arise by using
conventional had trucks that still require a lot of manual labour. However, stair
climber wheels can sometimes be problematic when trying to turn on flat ground, as
four wheels in a fixed position will be in contact with the ground.

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Design Objectives
The functional requirements for this stair-climbing hand truck include:
 The device should be able to provide most or all of the upward force necessary
to ascend a flight of stairs
 The device should be able to bear a weight of up to 100kg
 The cost of the device should be comparable to that of a conventional
consumer grade hand truck
 The product should be ergonomic and easy to use
 The weight of the product should be comparable to that of conventional
models
 The appearance of the product should be similar to that of conventional
models
 A lightweight design
 Focus on standard house stairs
 Interchangeable toe plates
 Interchangeable- rechargeable battery
 Adjustable handle.

Marketability
Being a consumer hand truck, this design is primarily targeted towards end consumers
who need to bring heavy or awkward items up and down stairs on a regular basis –
whether in a domestic home environment or in a small business environment.
For example, older people having to bring laundry, food trays, shopping or other
items up and down the stairs, would find a solution like this very appealing. Stair lifts
are quite a prominent feature in the homes of older people – however, they are
expensive and require an extensive amount of installation to work. With the Stair-
Climber Trolley, older people who are still of nimble agility, who do not want a Stair
Master ensemble in their homes but struggle to lift weighty items up and down stairs
can simply install this solution into their homes. In this way, they and their families
can have the extra peace of mind in knowing that they are not lugging heavy objects
up or down stairs, which can contribute to potentially dangerous or even fatal falls.
Other target markets include: small businesses or people living in apartments without
the use of a lift.
This product will be priced competitively against other solutions (as outlined here)
with a view to making it as affordable as possible for a consumer segment, whilst
ensuring the highest price that can be tolerated by the market.
If targeting a consumer segment, the main ways to promote this is through –
advertising (TV, radio, publications targeting the older generation or family
publications (as many children of older parents may worry about them carrying
excessive weights up and down). Distribution can also be possible through authorized
dealers who also cater for the needs of older people. Additionally, research could also
be conducted to determine if there are any grants available for older people to install
these motorised gadgets into their homes to prevent falls and serious injuries.
However, there is another potential buyer for this type of product design – other
companies in the market that provide Stair-Master type solutions, who already have
the target market, the market reach, an established customer base and the marketing
and sales budgets required to market this to a mass consumer segment – worldwide.

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Literature review:
During the research phase of this project, the authors have conducted a literature
review of conventional industrial hand trucks that are used today.
The Cargo Master:
The Cargo Master essentially does the same job as the electrical stair-climbing trolley
which is the focus of this project, with the exception of operating in a different way
with additional features. This particular stair-climbing trolley aims to reduce or
eliminate health problems and accidents caused by lifting heavy goods up a set of
stairs. It also enables one person to lift heavy objects up stairs, eliminating the need
for a second person to help. This can be very cost-beneficial in environments such as
service delivery (delivery of beverage and food items), saving valuable time and
resources for companies. The trolley’s mechanism for lifting objects up stairs could
feasibly be used on the likes of winding stairs (which would be even more difficult to
manually lift heavy objects up that type of stairs compared to the traditional set of
stairs), which means that the trolley itself would be adaptable to most stairs. The
design of the mechanism ensures that the trolley can be used on practically all types
of surfaces and also that the edge of the step will not be damaged in the process.
The Cargo Master has a built-in speed control system, ensuring that the trolley can be
adjusted around the different types of users (e.g. users that prefer to be on the higher

speed setting compared to the lower). Also, a safety brake system is applied to this
trolley to ensure that when the trolley is close to the edge of the step that the safety
brakes can be activated to prevent the operator from moving any further and, as a
result, prevent a potential accident e.g. trolley falling down the stairs.
The battery used on the trolley is a sealed vapour-proof battery which is capable of
being charged by any 240v supply current. This is an additional battery pack that
comes with the product and a car charger so the trolley can be continuously used,
eliminating the need to wait for the product to charge before using it again. The lifting
wheels on the trolley are made of rubber.
As seen in the pictures above, the trolley’s mechanism basically pushes the trolley up
the next step from the previous step so that the mechanism is vertically pushing the
trolley up to the next step with a very powerful motor.
Key features of this product include:
 An adjustable handle
 The centre of gravity depends of the load applied
 The trolley weighs 27kg
 Its dimensions are 1060 x 450 x 300mm
 Toe plate has the ability to be folded
 The lift has the capability of lifting objects 100kg x 1200mm high.

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Ease-E-Load Stair Climber Trolley Truck Carrying Capacity
150kg
This is a manual stair-climbing trolley. With the same objective of the electrical stair
climbing trolley, this trolley allows the carrying of objects up stairs easily, doable
with just one person. The difference between this mechanical trolley and the electrical
trolley is that the electrical one does all the hard lifting through the motor and
mechanism, whereas this manual trolley, while facilitating the lifting of heavy and
awkward objects up stairs, still requires the operator to put in significant effort and
back-breaking work to get them up the stairs. As can be seen from the picture, the
mechanism of the manual trolley moves around the steps of the stairs when being
pulled up, making it possible for the trolley to lift heavy objects up the stairs. This
particular product fetches 222.62 euros.
 Free- running pyramid wheels which makes mounting kerbs easier to
accomplish.
 The trolley is durable
 Foot size: 225 x 330mm
 Carrying capacity = 150kg

Stair Robot SR Express
This is an electrical, battery-powered stair-climbing trolley that distributes power to a
powerful motor, which enables the trolley to travel up the set of stairs with ease. This
electrical stair climber is designed for day-to-day distribution, so it can be used quite
frequently. This particular product was designed as a compact and lightweight stair
climber with the ability to lift a weight of up to 150kg.
It contains two basic techniques that enables the trolley to move up and down a set of
stairs:
 Step-by-step
 The trolley being laid flat on the surface of the stairs and sitting on two or
more steps.

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This particular trolley was designed for single operators. The design of this trolley
is very similar to the wheels of a tank or digger with its teeth-shaped wheels
capable of gripping the edges of the stairs, enabling the trolley to climb the stairs.
 Fast removable battery pack
 Remote control functionality
 Height adjustable platform
 Adjustable handles
The same concept underpinning this electrical stair climbing trolley is now being
adapted to wheelchairs (giving wheelchair-confined users more freedom). The above
picture illustrates the electrical stair-climbing wheelchair in use. As the picture
illustrates, this wheelchair can descend and ascend steps easily, ensuring the safety of
the person. This particular electrical wheelchair climber is fairly similar to the
previous electrical stair climbing trolley. The wheelchair uses its teeth like wheels that
enable the wheelchair to grip the edge of the steps and gives the wheelchair operator
the manoeuvrability to negotiate a set of stairs with ease. This concept in now ready
for commercialisation, so it won’t be much longer till electrical wheelchairs that are
capable of climbing stairs are seen all around the world.

The above electrical stair climber trolley is specially designed for the transportation of
manual wheelchair users up and down a set of stairs safely. This electrical stair
climbing trolley has a motorised electronic traction control that grips the edge of the
steps at a constant speed, which ensures safe travelling up and down the stairs every
time. This particular product goes for 3595 dollars.
 Battery with long-life span
 Manual emergency device so that if the battery fails, for whatever reason, the
safety of the wheelchair user is not jeopardised
 Mechanism operates smoothly and quietly ensuring that nobody will be
disturbed when the electrical stair climbing trolley is in use
 Key control

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 Compatible to be used with various stair types
 Travels at 16ft/min
 Can lift up to 250 pounds capacity.

Motor Type Selection
DC motor
Advantages
 Speed control: dedicated switches that can vary speed of rotation of the DC
motor from higher and lower speeds. At the same time, taking into
consideration that it cannot be too fast or too slow on the ascending of the step
of stairs.
 High starting torque: DC motor has a high starting torque. This will be
essential for a steady start for lifting a load of approx. 100kg of weight. The
starting torque can reach up to 500% in comparison to normal operating
torques, which is what we needed to get the heavy load up the stairs.
 When the speed drops the torque is constant: over a given speed range, the
torque of the DC motor will remain constant.
Disadvantages
 Initial cost is high.
 DC motor uses commuter and brush kit which are known for wear and tear. As
a result, there will be a higher maintenance cost and will eventually need
replacing altogether.
 Wear and tear of the commuter and brush will result in production of dust.
 DC motor cannot be used in explosive or hazardous areas because of the DC
motor sparkling.(Hughes 2006)
Applications where a DC motor is used:
DC motors are generally used in steel mills, paper mills, cranes, elevators, and electric
trains etc. Electric trains are a perfect example for a starting torque, as a high level of
torque is needed which is provided by the DC motor.
AC motor
Advantages
 The construction of an AC motor is simple.
 They are cheap to buy.
 An AC motor is reliable.

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Disadvantages
 Normally only used at a fixed speed. To apply a variable speed function to an
AC motor, it could be very complex compared to that of the DC motor. An
additional expense would also result if it were to be carried out this way (e.g.
multiple winding or gearbox).
Applications where an AC motor is used:
An AC motor is generally used in fans, washing machine compressors, audio
turntables etc. From looking at both the advantages and disadvantages, it is clear that
the DC motor is the best motor to be applied to the electrical stair climbing trolley.
The next step is looking into the different types of DC motors available.
Two main types of DC motors
Brush:
The motor, as a result of DC power being supplied to the DC motor, produces torque.
This is achieved with the internal commutation, stationary magnets (which can be
permanent or electromagnets) and also with the spinning electrical magnets. Torque is
generated as a result of Lorentz force and this applies to all electrical motors and
electrical generators. Lorentz force states that any current-carrying conductor placed
within an external magnetic field will, as a result, experience torque.
Advantages:
 They are cheap to buy.
 They are highly reliable motors.
 The speed of the motor can be simple controlled.
Disadvantages:
 High level of maintenance required (this would entail changing brushes and
springs which are the components that carry the electrical current. Also, the
commutator may require to be cleaned or, in some situations, changed.).
 If the motor is in continuous use, then this will result in the lifespan of the
motor being very low.

Brushless:
This is essentially an AC motor with an electronic controller built-in so it acts like a
DC motor but is not a DC motor. It is referred to as a DC motor to avoid confusion.
The brushless motor uses a spinning magnet or soft magnet core that is located in the
motor, as well as a fixed electrical magnet that can be found on the motor’s housing in
order to rotate. A controller is applied to the motor that converts DC to AC.
Compared to the brush motor, the design of the brushless motor is simple. This is as a
result of the disregard of the complexity of transferring power from the outside of the
motor to the rotating rotor.
Advantages:
 This motor has a long lifespan.
 Little or no maintenance is required for this motor.
 High efficiency.
Disadvantages:
 They are expensive to buy.
 The speed control is a lot more complicated compared to the brush motor.
From the two types of DC motors examined above, the motor that was decided to be
adapted to this electrical stair-climbing trolley was the DC brush motor (with the
permanent magnet). This decision was taken based on how both motors work, the
advantages and disadvantages of both, with the permanent magnet was the best
choice.

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The Design
Considerations taken while designing
When undertaking the design for the electric stair-climber, the first thing that had to
be taken into consideration was an actual set of stairs, as this is what it had to be
designed around. With the help of the internet and a few books which can be found in
the references, the authors obtained a greater understanding of stair terminology and,
most importantly, the origin of where the dimensions of stairs come from was also
figured out. Stair dimensions must follow building regulations and codes of practice
in an effort to keep hazards of tripping or falling to a minimum. Obviously, it is not
the case where every staircase in Ireland is exactly the same in dimension and just has
a different finish. The designers of stairs have a range of values for each different
component of the staircase (which can be seen in the picture below). With these
regulations and codes of practice in place, it makes it easier to negotiate the design
and dimensions being applied to the staircase.
In different types of buildings
e.g. (flats, shops etc.), rules are
stricter. As seen from the
diagram on the right, the pitch
(the angle at which the
staircase rises) of a staircase is
restricted to a 42 degree
incline. Limitations are also
applied to the size of the risers
and threads etc.
A flight of stairs should not have more than sixteen rises. If this is the case, a landing
should be incorporated into the staircase. This ensures that if individuals get tired
from going up the 16 steps, then they have a resting place that will give them a chance
to catch their breath in safe manner. This also discourages individuals that are
climbing more than sixteen steps to keep going when they become exhausted, as this
could result in a fall and injury. The minimum width of a stair case is 860mm.

Mechanism
The above sketch (initial design of the lifting arm and mechanism) represents the
overall look of the arm that is going to be taking the weight of the trolley and lifting it
up the stairs. By just looking at the sketch, there is an indication of how it works.
Point A shows the bar that is connected (pivoted) to the crossbar of the actual trolley.
This gives the mechanism the ability to move up and down the y-axis. Point B
connects Point A with the large rotational arm (A is pivoted off B, which is pivoted
off the large rotational arm). Point B gives the overall lifting arm the ability to move
up and down the x-axis. The combination of points A and B (which are essentially the
main parts to the mechanism) gives the overall lifting arm the ability to move up and
down the x- and y-axes, which is essential in order for the crank of the motor to
complete a full 360-degree rotation and still provide stability to the overall lifting
arm. Stability is important because if the electrical stair climbing trolley is to climb a
set of stairs smoothly, it needs to have the appropriate supports to account for any
imbalances. This is achieved with the above diagram.
A
B

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Mechanism free body diagrams
The free body diagram below illustrates the point where the most force
is needed to lift the trolley
The free body diagram below illustrates the point where the second
most force is needed to lift the trolley
The free body diagram below illustrates the point where the force is at
the point where the trolley is on the next step and force is not needed
anymore
Initial design
This is the initial design of the electrical stair-climber housed two motors, whereas the
final design has one motor applying the force needed to climb the stairs. The team
initially wanted to design a stair-climbing trolley with two motors, as the force could
be evenly distributed between the two motors and by two shafts. Of course, as a result
of using two motors, there would have been a need for a bigger battery to cope with
the extra load of the additional motor but since there was two motors doing work, the

additional force needed to lift the extra weight of the battery wasn’t much of a worry
for the team. There are a few reasons why this was not the final outcome of the
design.
1. The motor that was used was designed to come out one direction. So to have
two of the same motor, their shafts would have to be in line with each other
and this wasn’t as simple as putting the two motors back-to-back to each
other. To achieve alignment of the shafts of the two motors, housing had to be
designed to secure the two motors in place and align the shafts of the two
motors. The housing was designed and the two motors where secured in it. But
when the housing with the two motors was applied to the assembly, it was
clear that it was way too big to be put onto the electrical stair-climbing trolley.
The main reason why it was so big was because aligning the two shaft motors
led to a lot of lost space in the housing in order to support the motors in the
right position. Also, because the housing of the motors was so big, it was
clashing with the lifting arms (used to lift trolley up stairs). With the
dimensions at the time applied to the lifting arms and mechanism, the lifting
arms were cutting into the housing of the two motors. No matter how many
times the dimensions of the lifting arm and mechanism were changed (trying
to get the right dimension that would allow the trolley to climb the stairs with
ease and not cut into the housing), it was not preventing the lifting arms from
cutting into the housing of the motors and it became clearer that a revised
design was going to have to be looked into just in case this problem couldn’t
be resolved. The smaller the dimensions were for the lifting arm and
mechanism, the decreased risk of the lifting arm cutting into the housing.

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However, the down side to this was that it had less chance for the electrical
stair-climbing trolley to climb the stairs (which is what this project is all
about). An initial revised design of just the lifting arms was first looked into
and can be seen below with the initial design.
The left-hand screenshot shows the initial design for the lifting arm, while the right-
hand-side shows the revised design for the lifting arm (designed to prevent the arm
from cutting into the housing of the two motors). The revised design looked good on
paper and was thought to be the solution that was needed to solve this big problem.
However, once the design was drawn into SolidWorks, it was clear that it only made
the problem worse. Because the arm dips downwards, this meant that when the lifting
arm was rotated around, the lifting arm came nowhere near the housing of the two
motors – success. But when a standard set of stairs was put into the overall assembly,
it was clear that this design was not going to work. This was because, while the
redesign achieved what it set out to achieve (i.e. prevent it from hitting off the
housing of the two motors), it caused another problem. Because the redesign lift was
at an angle downward, it prevented the lifting arm from being able to reach the next
step. No amount of change to the dimensions of the lifting arm could be made to
rectify the problem. The dimensions of the lifting arm are limited - as in the crank and
large rotational have an overall limit of 200mm in order to continue using the motor
that was already selected. Anything bigger than the 200mm value would result in the
motor being having to be changed for a bigger motor, which was not a feasible option
– it was hard enough finding the chosen motor as there were very few motors that the
team came across that ticked all the boxes in terms of what was needed from it. Also
the motor that is being used was hard to position on the trolley with its size and

orientation, therefore, to use a bigger motor for the trolley would make the design
more cumbersome.
2. The housing that’s attached to the trolley is very bulky and is just a big lump
sticking out of the back of the back of the trolley. This means the trolley
would be at a tilt when climbing the stairs and could, potentially, come into
contact with the step of the stairs, preventing it from climbing the stairs
effectively.
3. The design would include the additional weight of using two motors and the
increased battery weight (as a result of using two motors a bigger battery
would have been selected) that will be present on the trolley. While the motor
would be able to handle the weight of the additional motor and bigger battery,
it would make the trolley difficult to wheel and manoeuvre for the operator.
At the end of this trial and error process with SolidWorks, it was decided that the
revised design for the lifting arm would be scrapped and instead of having two motors
housed together, one motor would be sufficient to carry out the task of lifting the
trolley up a set of stairs. This was carried out below and can be seen in the final
design of the electrical stair-climber.
Two
motors
supported
in the
housing
Supports (

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Final Design
When designing what the trolley was going to look like, it was decided to go with a
basic trolley to start off the initial design process, with a view to modifying it to
complement the final design to achieve a fully working, ergonomic electrical stair-
climber. So with the initial design in mind, the team applied the dimensions to the
design. This was done with ergonomics in firmly in the forefront of mind.
Ergonomics allowed the team to design a trolley, taking into account average height
of potential users to ensure ease of use, ensuring it was not too big or small, so that
pretty much everybody can use it comfortably and with ease.
When designing the trolley, it was known that these stair-climbing trolleys were
already readily available in the commercial world. This provided the team with a
valuable reference point in the face of encountering challenges with design, allowing
them to see how other electrical stair-climbers designed – and the benefits and
drawbacks of each. Design doesn’t necessarily mean a radically new design - it can
also mean taking an old design and trying to improve on it to benefit the users. Most
designs deployed by companies are of the improving variant – with companies
competing against each other on the basis of having the best designs so they can
charge the highest prices for their products.
………………..

Base of the Trolley:
The width of the base is 600mm and the length is 200mm. When applying these
dimensions, a step of an average set of stairs was taken into consideration to avoid the
base being wider than a set of stairs, which would prevent the trolley from being able
to get up a set of stairs. As it turned out, the width of the trolley base was less than
the minimum width of a set of stairs, which is 860mm, so the trolley can go up and
down the stairs with ease. When applying the length to the base, the going (min
220mm) of the step was taken into account, so that the length (which is less than the
going) isn’t bigger than the dimension of the going so that the trolley can sit
comfortably on the step. The dimensions for the base can also be seen in the 2D
drawing which can be found in the appendix.
Base of the
Trolley

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Arm Frame
Arm frame (x2) (female part)
When designing the female part to the frame arm, the team wanted to use a hollow
cylinder design with an outer diameter of 40mm and an inner diameter of 30mm,
giving it a thickness of 5mm. The length of the arm is 1200mm. This is because
allowance had to be taken into account for the length of the male part of the arm (so
that the combined height of the arm frame’s male and female parts would result in a
decent sized trolley), which sits in the female part and will add to the total height of
the trolley. Therefore, the total height of the trolley was split between the two parts
appropriately. The dimensions for the arm frame of the female part can be found in
the appendix
Arm
Frame
(Male
part)
Arm
Frame
(Female
part)

Arm frame (x2)(male part)
The male part to the arm frame sits in the female part of the arm frame. This was done
to allow for the electrical stair-climber trolley to adjust its height depending on what it
is carrying up or down the stairs. The outer diameter is 30mm and the inner diameter
is 20mm, giving it a thickness of 5mm. The height of the arm frame’s male part is
600mm. The dimensions for the arm frame of the male part can be found in the
appendix
Arm frame total height:
Combining the height of both the male and female part of the arm frame gives a total
height of 1800mm (180cm), which is applied to the trolley
Pin
The pin is used to lock the adjusted height in place. A clearance fit is applied to the
male and female part of the arm frame, allowing the male part to move freely up and
down the female part, with the pin applying force to lock the male part in a set place
along the female part.
Pin (that locks
the arm frame
both male and
female parts in
place)

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Wheel Attachments
The wheel attachment comes in three parts (part A and B (x2)), which grips the
female part of the tube. It is then bolted to the female part of the arm frame, which is
offset from the base by 100mm, with the wheel being positioned 50mm up from that
point so that it is positioned 150mm up from the bottom. When the 300mm wheel is
attached, these three dimensions allow it to sit flush to the step and to be wheeled like
all other two wheeled trolleys are wheeled. The dimensions for the Component A and
B can be found in the appendix
B: These
two
individual
wheel
attachment
parts lock
the main
wheel
attachment
in place
A: Main part
of wheel
attachment

Handle
The handle is designed so that it is not sitting in line with the female and male frame
arms - it is offset by approximately 140mm to enable a long objects to be comfortably
carried up stairs (without the offset, it would be awkward to hold as it would be where
the user places their hands when holding the trolley). So the handle is offset away
from the arm frame so that the trolley can be handled comfortably (i.e. fingers aren’t
getting crushed and good grip isn’t being sacrificed), which is key in designing
anything. The dimensions for the handle can be found in the appendix.
Extended
handle bar

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Rotational shaft with key way (for the motor and rotational
support)
The rotational shaft was designed with a key way so that power from the motor can be
effectively transmitted to the crank. The dimensions for the rotational shaft can be
found in the appendix.
For finding the size for the key way, the following table below is used to work out the
dimensions of it. The dimensions that were selected for the key way were width 6mm
and the height 3mm which can be seen in the 2D drawings in the appendix.
Rotational
shaft
attached
to the
motor
Key way
transmitting
power from
the motor to
the small
rotational
Arm

Relevant
key way
dimensions
for a 19.05
mm
diameter
shaft

33 | P a g e
Crank (which is attached to the motor to the rotational shaft)
This is the part that enables the trolley to climb the height of the stairs. But when
designing it, the length was fairly awkward to pick. If the length is too small, the
trolley will not be able to climb the stairs. Also the length of the crank cannot be too
big, as the arm with the wheels that sit on the step moves in an out, it will end up
cutting into the motor and the rotational support which is fixed onto the trolley. So the
trolley had to be modified to allow the overall arm to move freely and have an
efficient and effective length on the shaft that would be able to lift the trolley up the
stairs and not cut back into the motor. The dimensions for the crank can be found in
the appendix.
Small
Rotational
Arm

Large Rotational Arm (attached to wheels that sit on step)
The length of this arm also affected whether or not the arm would cut into the motor
and rotational support. So the length (132.5mm) was chosen because it was long
enough to reach the step of the stairs and, when rotated, doesn’t cut into the motor and
rotational shaft. The dimensions for the large rotational arm can be found in the
appendix
Overall length of the crank and large rotational arm
The overall length of the two arms was restricted to an overall length with a range of
180-200mm, which ended up being 200mm. This is because the greater the length of
the arms, the more force that was needed to lift the trolley. From the calculations that
was done for the motor, it worked out that the overall optimum length of the arms was
180mm-200mm, which was applied for the overall length.
Large
Rotational
Arm
Overall
Length
measured
from here
To
here

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Wheels that sit on step
These are the two wheels that sit on the step which assume the weight of the trolley as
it is being lifted up the stairs. The wheels have a 50mm diameter and thickness of
15mm. The tube connecting the two wheels has a diameter of 40mm and the length of
the tube is 360.292mm. The material that will be used for these two wheels will be a
solid rubber material. This will ensure that the tyres will never have a flat and, most
importantly, they will provide the grip necessary to lift the trolley up the stairs
without slipping (which could result in an injury or damage). The dimensions for the
wheels that sit on step can be found in the appendix.
Wheels
that take
the weight
of the
trolley and
objects
being
carried.

Mechanism
Stage 1: The starting position of the lifting arm and mechanism.
Stage 2: The lifting arm and mechanism are positioned on the stairs but are not
taking the weight of the trolley just yet.

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Stage 3: The lifting arm and mechanism has lifted the trolley halfway up the step.
Stage 4: The lifting arm and mechanism has lifted the trolley up a step on the stairs
and is going to start the whole cycle again until the top of the stairs is reached.

Final design of the mechanism:
When designing the mechanism, the team got a little carried away with existing
electric chair-climbing mechanisms. This was both positive and negative. On the
positive side, it showed the team exactly how the arm works (lifting the trolley up a
set of stairs), giving them confidence in going off to make their own design. However,
the problem was that the team didn’t understand how the arm stayed parallel to the
step (when the machine was being illustrated in online videos, the actual mechanism
wasn’t shown, preventing the team from seeing it in action). As a result of this, the
team wasted time trying to understand what was already done. In the end, it came
down to thinking outside the box to come up with a new design that had the same
principles (keeping the arm parallel to the step).
The mechanism is attached to the support of the motor which can be seen above, with
the other end being attached to the arm that sits on the step of the stairs, which can
also be seen above. At that point, the mechanism is fixed to the arm that is sitting on
the step (allowing the arm to constantly be parallel to the going of the step of the
stairs), while the rest of the mechanism (which is attached to the support of the motor)
moves up and down the x- and y-axes to allow the fixed point to move along the x-
and y-axes. This also prevents the large rotational arm from twisting so that the motor
can effectively transmit its power to the crank and large rotational arms. The
dimensions for the individual parts of the mechanism can be found in the appendix.

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Supports (which support the motor, mechanism and
rotational shafts)
The supports ensure the stability of all the components on the trolley. The dimensions
for the supports can be found in the appendix.
Ansys:
Ansys could not be done on the SolidWorks 3D drawings (of the overall assembly), as
no member of the team had the required skills to operate the software with any
proficiency. So the team decided to go down an alternative route and do a
SolidWorks simulation instead. This was achieved successfully, however, the only
downside was that it could not be applied to the overall assembly but to only one
single part of the assembly. So it was decided that the whole mechanism would be
made up as one single part. Again, this was successfully achieved, however, when the
simulation was run on it, the component reacted weirdly and the results obtained from
the simulation were useless – so in the end, that idea had to be scrapped. The next
option was to perform it on the most important part of the mechanism, which was the
large rotational arm (as it was the part that the motor transmits power to and that the
mechanism holds together and, most importantly, it is the key reason how the trolley
Support for
motor and
mechanism
Supports
for Motor
and
Rotational
Shaft
Battery
support

can get up the stairs). So the simulation was done on that part and the results and
conclusions from this can be found in the appendix.

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Material
Considering weight of the trolley and different types of users, the authors decided to
use aluminium alloy 6061, which is a precipitation alloy containing magnesium and
silicon as its major alloying elements, as the material for our hand trolley. The high-
strength aluminum alloys rely on age-hardening: a sequence of heat treatment steps
that causes the precipitation of a nano-scale dispersion of intermetallics that impede
dislocation motion and impart strength. This can be as high as 700 MPa, giving them
a strength-to-weight ratio exceeding even that of the strongest steels.
It has good mechanical properties and exhibits good weld-ability. It is one of the most
common alloys of aluminium for general purpose use. It is commonly available in
pre-tempered grades such as 6061-O (solutionized) and tempered grades such as
6061-T6 (solutionized and artificially aged) and 6061-T651 (solutionized, stress-
relieved stretched and artificially aged). 6061 is widely used for construction of
aircraft structures, such as wings and fuselages, more commonly in homebuilt aircraft
than commercial or military aircraft. 6061 can be easily worked and remains resistant
to corrosion even when the surface is abraded. It is used for yacht construction,
including small utility boats, in automotive parts, such as wheel spacers, in the
manufacture of aluminium cans for the packaging of foodstuffs and drinks, in scuba
tanks (post 1995) and was the material used for the pioneer plaques.
Consideration was also taken for another two types of materials -one of which was
aluminum. These composites are metals reinforced with ceramic particles. The most
widely used are based on aluminum reinforced with particles of silicon carbide or
alumina. The reinforcement increases the stiffness, strength and maximum service
temperature without seriously increasing the weight. It has a cost of 2 - 5 €/kg. The
other one was stainless steel - Grade 304 is the standard "18/8" stainless; it is the most
versatile and most widely used. Even though it had a higher yield strength than
aluminium, it was decided to go with aluminium as it was widely available and
provided more ease with which to work, giving it a winning vote.
General properties
Density 156 - 181 lb/ft^3
Price * 1.07 - 1.17 USD/lb
Date first used ("-" means BC) 1916
Mechanical properties
Young's modulus 9.86 - 11.6 10^6 psi

Shear modulus 3.63 - 4.06 10^6 psi
Bulk modulus 9.28 - 10.2 10^6 psi
Poisson's ratio 0.32 - 0.36
Yield strength (elastic limit) 13.8 - 88.5 ksi
Tensile strength 26.1 - 89.9 ksi
Compressive strength 13.8 - 88.5 ksi
Elongation 1 - 20 % strain
Hardness - Vickers 60 - 160 HV
Fatigue strength at 10^7 cycles 8.27 - 30.5 ksi
Fracture toughness 19.1 - 31.9 ksi.in^0.5
Mechanical loss coefficient (tan delta) 1e-4 - 0.001
Price
At the latest, according to the www.metalprices.com it is priced at 1.485 euro per Kg.
Calculation
Selection of motor
To select a motor, the team had to find the power it needed to lift a weight (100 kg)
up the stairs. Due to its specific design, when the arms push the load up the weight,
force acts through the small tires at the end of the arms down the body. The safety
factor was taken to be 4, therefore, the minimum weight it needed to lift was found to
be 100kg. The first calculation was the work acting and then using the time (3sec) it
needed to push the weight the team found the power output. (Direct 2012)
First the force was calculated using the rise height as 220mm:
Then using the arm length to be 20cm, the team found the torque acting at the joint of
the arm by the motor:

43 | P a g e
Assuming there are 40 steps to climb and taking one revolution to climb each step, it
was assumed that 40 RPM (revolutions per minute) would be needed for the motor
and, in doing so, found the angular velocity. Then using angular velocity and torque,
the power needed for the motor was calculated as follows:
From above, it can be concluded that any motor with a power output higher than
822W can be used.
Selection of battery
Using the power and voltage (24V), the team found the current needed to run the
motor.
The equation is as follows:

Using the current and voltage, kWh was calculated:
Using the current and the minimum time needed for the battery to run, the charge was
found:
The above charge was converted to amp hours and was calculated using:
It was found that to run the present motor of .024kWh for 20 minutes, a battery of
minimum 10.7 Ah was needed. Therefore, it was decided to get a two 12V 5Ah sealed
lead acid battery which will give a time as follows:
As it was a reasonable time, it was decided to proceed with this.

45 | P a g e
Torsion in the arm
The arms had to be of adequate diameter to ensure that it didn’t cause failure
due to torsion. The diameter was calculated as follows:
Using the previous calculations obtained, the torque was found to be 196.2
Nm, that the shear strength of Aluminium 6061 is 190MPa and a safety factor
of 4:
Solving for d, gives a diameter of 27.5mm. This was rounded up to 30mm in
our actual arm diameter.
Selected Motor
For the selection of the motor, the team considered two different motors from two
different companies listed below:
The first came from Prestolite motors. With the specifications outlined below, it was
considered first because of its size and the way it could be fitted onto this design.

The next one was from Dongyong motors:
With 90:1 gear ratio, 40 RPM and 900W optional power, this was the best choice.
With an inbuilt gearbox, this could be fitted straight on to this project’s product
design without needing any tweaking.

47 | P a g e
On the basis of price, reliability and the fact it had the exact specifications that was
needed, the team selected the second motor option (Tarp gear motor) for its design.

Design problems
In the beginning, the team focused on using two motors side-by-side to give more
power to the arms. However, in the later stages, it was found to be too difficult and
was making the design far more complicated than it needed to be, so it was decided to
go with single motor which was enough to produce the required torque as stated
below:
Weight and Cost
With DC motor, battery and complex design, the total weight of the product was
found to be around 20kg (without battery). The rechargeable lead acid battery would
weigh around 4kg.

49 | P a g e
Selection of battery
The company that supplied the battery is called Battery Sharks and position
themselves as the replacement battery specialists. As a result, they have a huge variety
of every battery in the market, making the process of finding the perfect battery even
easier. The chosen model turned out to be the 12V-5AH NB12-5 battery. This was
perfect for what was needed, as it not only met the desired power requirements but
was also an ideal size at approx. 70mm deep, 90mm wide and 110mm high. It is very
light at approximately 1.65 kg. NB12-5 is a rechargeable, maintenance-free, non-
spillable and a highly efficiently designed battery. This model has an expected life of
up to 5 years in standby use, with low self-discharge rate and lower than 3% capacity
loss per month. However, national batteries can be stored for up to one year at 25oC
but then a freshening charge is recommended. This type of battery is commonly used
for emergency light, mobility and alarm and securities, but can be used for almost all
purposes. As mentioned previously, the hand truck will require two of these batteries
as they have only a 5ah output.
One might question the cost of using two batteries instead of just one 10ah battery,
but these batteries are surprisingly cheap and actually work out cheaper than its
equivalent 10 ah battery.

Battery Life Cycle
The battery has a lifecycle, as seen below. Assuming that the temperature is kept
constant at 25o
C, the rates of discharge can be calculated easily. As the number of
cycles increases to 450, the discharge capacity drops by 50%. As the battery is used
more, the discharge continues to decrease but at a slower rate. The battery can be used
over 600 times before it loses 20 percent. However, after these 1,150 uses, the
discharge will have dropped all the way to 30 percent and will need to be changed.

51 | P a g e
Battery Size
Above you can see a drawing of the
form of the battery. Its height is approx.
107mm.
Above is a drawing of the top of the
battery. The two terminals can be clearly
seen and the dimensions are approx. 70mm
deep by 90mm wide.
This is a drawing showing clearly all the
dimensions of the terminal of the battery.
This is a basic side view of the battery
to give a finished idea of the size of the
battery. The dimensions are given in the
drawings above.

Battery capacity retention characteristics:
When the battery was chosen, the team looked into all the information available and
found that the capacity characteristics depended on the temperature as follows. The
graph shows that as the temperature increases, the capacity retention ratio of the
battery is less efficient. A simple example of this can be seen on the graph. It takes the
battery almost four months to reach a ratio of 50% at 30 degrees, but at 40 degrees it
takes only two months. This graph shows the user the importance of the temperature
at which the battery is kept. Fortunately for the specific use of this design, the battery
will not be kept at high temperatures like this so it is not a big concern.

53 | P a g e
A 10Ah battery
The 10 ah battery that was selected was the same model as the 5ah battery that was
originally selected. Its specs were very similar. The only properties that changed
were, obviously, its weight and size.
Varying the speed
The initial reaction
The initial idea was to insert a variable resister in the circuit to vary the speed,
however, there were numerous reasons why this idea was not used. The initial
thoughts were as follows. These figures have been completely made up and are purely
for an explanation purpose. If the no-load motor current at 5V is 88 mA, the apparent
resistance has to be 56 ohms (5V / 0.088 A). The question was - can the speed of the
motor be lowered to 1/3 if a 112 ohm resistor was inserted to take up 2/3 of the
power?
After a lot of research the following conclusions were made:
If a 200ohm potentiometer (a variable resistor) between the motor and GND was
inserted, then this theory could be tested. The variable resistor was first powered up
and set to 0 ohms. Then with the resistance set to 112 ohms, the motor was a little
sluggish, but seemed to work – albeit at a slower pace. The circuit was turned off, but
the pace continued, however, it was turned back on (still set to 112 ohms), the motor
didn’t turn on at all.
The problem was that a motor is a varying electrical load. A motor needs a lot more
power at start-up than it does when running. When the 112 ohm resistance is set, the
motor turning power needed to start up is not met. Since the motor is going up stairs
and will need to draw a lot of additional power, this solution wouldn’t work.
There is another reason why a resistor is not a good choice for controlling the power
delivered to a large load. As the power requirements increase, it will quickly exceed
the power rating on a resistor or potentiometer. The electronic component will get
very hot and then will likely fail permanently.

Furthermore, a resistor wastes excess power as heat. As with all projects, an
inefficient methods must try be avoided.
Pulse Width Modulation
So it is now known that using a resistor to change the speed is inefficient, as holding
back the power makes the resistor hot and energy is lost. Therefore, a better way to
vary the voltage is needed and, by doing so, vary the speed. The best way to do this is
with a pulse width modulator (pwm). For the project, an understanding of exactly
how pwm’s work is needed and how they are wired, as one will be added to the
circuit. Below is an outline of how pulse width modulation works and how its wired.
When a circuit runs at 10v, an oscilloscope will show its voltage as shown below:
This voltage is constant just like 0V shown below:

55 | P a g e
But what happens when there is a 10v supply being turned on and off? The wave form
is 10V half the time and 0v half the time. This is a 50% duty cycle, so called since it’s
on 50% of the time and off 50% of the time.
The 10V is only there half the time so what is seen is an average voltage of 5 volts.
Because the motor takes time to change between sudden changes in voltage, a steady
voltage of 5 is achieved, which is unexpected at first.
Now look at the screen show below. The 10v is only on 10% of the time so it is seen
that it has a 10% duty cycle and an average voltage of 1V is seen.
So by changing the pulse width, the average voltage is changed seen by a circuit. This
is where the name pulse width modulation comes from for this method.
Building a pulse width modulation (pwm) generator circuit is reasonably easily and
very cheap, requiring only few parts.

The overall circuit looks as follows:
The key component is the 555 chip shown below. It can buy one for approximately 2
euro.
The 555 chip has eight connection points - each one is described below. For the
project, there is no need to worry too much about the exact detail of how it works, as
the variable speed switch will be bought in and fitting it in the simple circuit.
Pin Description Purpose
1 Ground Dc ground
2 Trigger The trigger pin triggers the
beginning of the timing
sequence. When it goes
low, it causes the output

57 | P a g e
pin to go HIGH. The
trigger is activated when
the voltage falls below 1/3
of +V on pin 8.
3 Output The output pin is used to
drive external circuitry. It
has a "totem pole"
configuration, which
means that it can source or
sink current. The output
pin is driven high when the
trigger pin is taken low.
The output pin is driven
low when the threshold pin
is taken high, or the reset
pin is taken low.
4 Reset The reset pin is used to
drive the output low,
regardless of the state of
the circuit. When not used,
the reset pin should be tied
to +V.
5 Control Voltage The control voltage pin
allows the input of
external voltages to affect
the timing of the 555 chip.
When not used, it should
be bypassed to ground
through a capacitor.
6 Threshold When the voltage rises
above 2/3 of the +V the
threshold pin causes the
output to be driven low

7 Discharge The discharge pin shorts to
the ground when the
output pin goes high. This
is normally used to
discharge the timing
capacitor during
oscillation.
8 +V DC power 12V here
When the chip is constructed in such a way, it gives out a square wave that is pulse
width modulated.
But how to change the duty cycle? By changing the potentiometer, the duty cycle
changes in proportion. So by twisting the potentiometer, this enables the varying of
the average power.
In order to get a wider speed range an ideal 100K pot will be used.
The diodes in the circuit are used to stop current flowing in the wrong direction.
Zener diodes are very poor voltage regulators and so the team will avoid using them.
Thirty percent more gets the user a proper regulator. A basic 1N34 diodes will be
used.

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The capacitors in the circuit are 10nF ceramic capacitors. The best way to identify
them is by the number 103 written on them.
Another very important part of the circuit is the npn transistor. The transistor allows
the user to deal with heavier loads than just the 555 chip can handle. A basic tip 31
transmitter can be picked up easily. The only thing to watch is that the transistor
might heat up with heavier loads. If the transistor heats up too easy all that is needed
to be done is put a heat sink on it and our problem is solved.

The final diode is put in to make sure the inductive loading of the motor doesn’t blow
something up.
Applications where pwm circuits are used include dimming the lighting on your
laptop or changing the speed on a remote control car.
In general, a pwm supplies full power to the motor but only in short pulses. A motor
takes a little bit of time to respond to abrupt changes. So by powering it with a pulse
wave that varies between 0Va and 12V at a fast rate, the motor will behave as if it is
getting a steady voltage somewhere between 0 and 12 depending on the duty cycle.

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Speed controller
With this understanding of how pwm works, it can now be applied to this project. For
the design, two speeds are needed, however, it was decided that a variable speed of
greater range will be applied because it is unknown where it will be used. For
example, older people may want to use the trolley and want to work at a slower rate.
There is a better understanding of the motor speed controller, but for building the
design, the team would just buy a variable speed controller. The images below
illustrate how to wire the battery and motor into the side of the variable speed
controller.

Recommendation:
If more time was given to the project, then additional work would be done on the
following:
 Look into applying safety brakes onto the trolley that would prevent the
electrical stair climbing trolley from falling down the stairs, which would
result in an injury or damage.
 Make the base of the trolley with interchangeable bases so that it can cope
with almost any situation.
 Look more into the design of the trolley and making sure that the objects
being lifted by the trolley is sitting evenly on the trolley so that objects won’t
fall out of it (which could result in injury or damage).
 Look into adapting an interchangeable battery onto the design of the trolley so
that, while one battery is being charged, the trolley can still be used with the
other battery which should be fully charged. The interchangeable battery will
need to be secured onto the trolley when in use, so that it doesn’t fall off and
cause a potential accident.
 A breaking system should be applied to the mechanism that climbs the stairs,
ensuring that if the battery goes flat or the motor just dies that the trolley
won’t simply just fall down the stairs as a result, but will be in a fixed position
till somebody can come to help.

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Conclusion
Overall, this project proved to be a great learning experience in terms of working in a
team. It showed the three members of the team what it is like working in a team of
people you don’t really know, ensuring there is sufficient scope to share the work
evening among the team and to adhere to deadlines and timescales.
The process of deciding as a team to design an electrical stair-trolley took a while to
reach, as each member of the team had to agree to pursue this particular project. The
team had its up and downs but, in the end, the team came together and designed the
electrical stair-climber in as most efficient and effective a manner as possible, and
compile the learnings, experiences rationale of it into a report.
In terms of actually designing the stair-climber itself, the team believes it has
achieved a reasonably good design that can be manufactured quite cost competitively
and marketed to the segments outlined in the marketability section (older people,
people living in apartments with no lifts, small business owners). The team is of the
opinion that a product like this could, and should, be more readily available for this
segment of the market and its design is specifically made to ensure excellent
ergonomics and ease of use.
Overall, the team is happy with the outcome in terms of the final design of the electric
stair-climber and that it has achieved what it set it out to achieve.

Roles of the group
Stephen McLoughlin:
Tasks done:
 Designed the overall trolley.
 Write up on the design of trolley.
 Solid Works: did all the solid works 3D and 2D drawing of the trolley.
 Solid Works simulation was done on mechanism arm.
 Did free body diagrams of the mechanism.
 Write up was done on simulation.
 Literature survey.
 Looked into the construction of Stairs (and incorporated it into the design).
 Looked into AC and DC motors (Advantages and Disadvantages and different
types of DC motors and chose best type of DC motor to use for the project).
 Looked into Calculations (Power, Torque, Back EMF, Speed etc).
 Looked into mechanism and came up mechanism design to use in the project.
 Marketability.
 Compiled report
 Proof read report
 Conclusion.
 Did presentation Sides for appropriate sections.
 Compiled presentation.
Shiyas Basheer
Task done:
 Introduction section (Introduction, History, Benefits and Problems).
 Material Selection.
 Looked into different types of mechanism already out there (this was done to
try on deciding what the team wanted their electrical stair climber to look
like).
 Did initial and Finalized Calculations (Battery and Motor calculations).
 Motor selection.
 Torsion on arm calculations

65 | P a g e
Conor Tiernan
Tasks done:
 Looked into variable speed switches.
 Initial Calculations on motor selection
 Motor selection.
 Battery Calculations.
 Battery selection.
 Did presentation slides for appropriate section

Reference
Encyclopedia, 2012. hand truck -- Britannica Online Encyclopedia. Britannica.
Available at: http://www.britannica.com/EBchecked/topic/254117/hand-truck
[Accessed October 20, 2012].
Dongyang, Small AC/DC Motors & Gear Motors | DYD MOTOR. Available at:
http://www.dongyangmotor.com/ [Accessed October 20, 2012a].
Liftakar, Stairclimber Sales from Sano UK Powered Stairclimbers - Home. Available
at: http://www.liftkardirect.com/ [Accessed October 20, 2012b].
Journal, stairclimber.pdf. Available at:
http://courses.washington.edu/art483/site/images/stairclimber.pdf [Accessed October
20, 2012c].
Direct, L., 2012. Stairclimber Sales from Sano UK Powered Stairclimbers - Home.
Liftkar Direct. Available at: http://www.liftkardirect.com/ [Accessed October 20,
2012].
Finney, D., 1991. Variable frequency AC motor Drive system,
Hughes, A., 2006. Electric Motors and Drives Third.,
Niku, S., 2010. Introduction to Robotics Second.,
D Marshall & D Worthing (2006). The Construction of Houses. London:EG Books
A Engel(2007). For Pros by Pros, Building Stairs, United States: The Taunton
Press.
DC and AC Advantages &Disadvantages[Online].Available:
http://electricalquestionsguide.blogspot.ie/2011/05/dc-motors-advantages-
disadvantages-ac.html - Last Accessed 26th September 2012
DC and AC Advantages and Disadvantages[Online].Available:
http://www.wdtl.com/pdf/WT4706AdvantagesandDisadvantages.pdf - Last
Accessed 26th September 2012

67 | P a g e
AC diagram [Online].Available:
http://www.tt-itbu.com/technology/20090309/DC.html - Last Accessed 26th
September 2012
Voltage current torque etc in a dc motor[Online]. Available:
http://www.societyofrobots.com/actuators_dcmotors.shtml - Last Accessed
27th September 2012
Cargo Master [Online].Available:
http://www.materialshandling.com.au/pc-2254-53-cargomaster-electric-stair-
climbing-trolley.aspx -Last Accessed 27th October 2012
Manual Stair Climbing Trolley[Online].Available:
http://www.fileone.ie/Ease-E-Load-Stair-Climber-Trolley-Truck-Carrying-
Capacity-150kg.html -Last Accessed 27th October 2012
Stair Robots [Online]. Available:
http://www.hercules.com.au/index.php?srexpress –Last Accessed 27th October
2012
Stair Climbing WheelChair [Online].Available:
http://marketplace.sibaya.com/2007/05/18/topchair-stair-climbing-
wheelchair-ready-for-commercialization/ -Last Accessed 27 October 2012
Stair Climbing Trolley Designed around Wheel Chairs [Online]. Available:
http://www.ameriglide.com/item/AmeriGlide-AG-CLIMBER.html -Last Accessed
27th October 2012

Appendix:
Electrical stair climber assembly 2D drawing
Base 2D drawing

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Female tube 2D drawing
Male tube 2D drawing

Pin 2D drawing
Handle component 1 2D drawing

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Handle component 2 2D drawing
Handle Component 3 2D drawing

Main support 2D drawing
Selected battery 2D drawing

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Overhead battery support
Bottom of battery support 2D drawing

Rotational Support 2D drawing
Support for motor and rotational support 2D drawing

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Overhead support for rotational support 2D drawing
Shaft for rotational support and motor 2D drawing

Rotational Arm of Motor 2D drawing
Rotational arm for rotational support 2D drawing

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Crank 2D drawing
Mechanism and motor support component 1 2D drawing

Mechanism and motor support component 2 2D drawing
Mechanism component 1 2D drawing

79 | P a g e

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Wheel attachment component 1 2D drawing

Simulation of
Alternative mechani
attached to motor
Date: Tuesday, October 23, 2012
Designer: Solidworks
Study name: SimulationXpress Study
Analysis type: Static
Table of Contents
Description 84
Assumptions 85
Model Information 85
Material Properties 86
Loads and Fixtures 87
Mesh Information 88
Study Results 90
Conclusion 93
Description
No Data

85 | P a g e
Assumptions
Model Information
Model name: Alternative mechanism attached to motor
Current Configuration: Default
Solid Bodies

Document Name and
Reference
Treated As Volumetric Properties
Document Path/Da
Modified
Cut-Extrude1
Solid Body
Mass:0.134618 kg
Volume:4.98584e-005 m^3
Density:2700 kg/m^3
Weight:1.31925 N
E:3rd year level
8Engineering Design
Works up to dateAlter
mechanism attached
motor.SLDPRT
Oct 23 00:14:56 20
Material Properties
Model Reference Properties Components
Name: 6061 Alloy
Model type: Linear Elastic
Isotropic
Default failure
criterion:
Max von Mises Stress
Yield strength: 5.51485e+007 N/m^2
Tensile strength: 1.24084e+008 N/m^2
SolidBody 1(Cut-
Extrude1)(Alternative
mechanism attached t
motor)

87 | P a g e
Loads and Fixtures
Fixture name Fixture Image Fixture Details
Fixed-2
Entities: 1 face(s)
Type: Fixed Geometry
Load name Load Image Load Details
Force-1
Entities: 1 face(s)
Type: Apply normal force
Value: 981 N

Mesh Information
Mesh type Solid Mesh
Mesher Used: Standard mesh
Automatic Transition: Off
Include Mesh Auto Loops: Off
Jacobian points 4 Points
Element Size 3.68177 mm
Tolerance 0.184088 mm
Mesh Quality High
Mesh Information - Details
Total Nodes 11501
Total Elements 7166
Maximum Aspect Ratio 8.2839
% of elements with Aspect Ratio < 3 98.8
% of elements with Aspect Ratio > 10 0
% of distorted elements(Jacobian) 0
Time to complete mesh(hh;mm;ss): 00:00:02
Computer name: BST-390-G-02

Study Results
Name Type Min Max
Stress VON: von Mises Stress 3681.27 N/m^2
Node: 9282
6.9433e+007 N/m^2
Node: 11377
Alternative mechanism attached to motor-SimulationXpress Study-Stress-Stress
Name Type Min Max
Displacement URES: Resultant
Displacement
0 mm
Node: 38
0.359234 mm
Node: 1

91 | P a g e
Alternative mechanism attached to motor-SimulationXpress Study-Displacement-Displacement
Name Type
Deformation Deformed Shape

Alternative mechanism attached to motor-SimulationXpress Study-Displacement-Deformation
Name Type Min Max
Factor of Safety Max von Mises Stress 0.794269
Node: 11377
14980.8
Node: 9282

93 | P a g e
Alternative mechanism attached to motor-SimulationXpress Study-Factor of Safety-Factor of Safety
Conclusion
From the above report, the team generated SolidWorks simulations of the force being
applied to the large rotational arm and the effects it has on the arm. The hole that is
used to connect the large rotational arm to the crank is used as the fixed point in this
simulation. The force of 981N (100(kg) x 9.81(gravity) = Force applied) is applied all
along the large rotational arm and the results above were obtained. With the mesh
applied to the large rotational arm, the simulation to find the yield strength is then

completed. The yield strength came out at 55148500 N/m^2, which is very strong.
Also, starting with the color blue (least amount of stress) and working its way up to
the color red (most amount of stress), this illustration shows the different levels of
stress being applied to the large rotational arm. From the diagram above, it can be
seen that the large rotational arm has a slight deformation. In the team’s opinion, it is
doubtfull that this will have any impact on the performance or safety of the electrical
stair-climbing trolley. The report generated results that were, in some way, expected
and the team feels that the simulation was a success. This part has been recently
updated but when the simulation was initially run and the report generated, the report
came out the way it was supposed to. There is no real difference between this report
and the updated part report, meaning so this report is sufficient in showing the
simulation of the large rotational arm. Screenshots can be seen of the updated part
below.
So as can be seen, the yield strength is the same as the previous simulation

95 | P a g e
Different displacement values have been obtained compared to the previous part

Ergonomics
Calculating the average height and reach of a person to help decide on the
height of our trolley.
In order to calculate how big our trolley should be we need to decide what the
average height of a person should be. Below are some of the interesting facts we
found.
The tallest man
The tallest man living is Sultan Kösen (Turkey, b.10 December 1982) who
measured 251 cm (8 ft 3 in) in Ankara, Turkey, on 08 February 2011.
The part-time farmer was the first man over 8 ft. (2.43 m) to be measured by
Guinness World Record in over 20 years.
Indeed, GWR only knows of 10 confirmed or reliable cases in history of humans
reaching 8 ft. or more.
Sultan also holds the records for widest hand span and largest feet on a living
person.
From this we can take that since there have only been 10 men over 8 ft. in the
world ever that if the product we are carrying is of average size we will not need
to exceed this limit of 8 foot when designing the height of our trolley. However,
we want to accommodate for extra-long product so we have decide that we are
going to make our arms extendible to a reasonable length anyway.
Average height in different countries
Growth and height have long been recognized as a measure of the health and
wellness of individuals. In order to decide the average height of a man or women
using the trolley we must consider this chart and where the product will be sold
most. This chart shows the average height of males and females in various world
countries
Chart showing the average height of males and females in various world countries.
Country Average male height Average female height
Argentina 174.46 cm (5 ft. 8.6 in) 161.03 cm (5 ft. 3.4 in)
Australia 178.4 cm (5' 10.2") 163.9 cm (5' 4.5")
Bahrain 165.1 cm (5' 5") 154.7 cm (5' 1")
Belgium 176.6 cm (5' 9.5") 163.3 cm (5' 4.3")
Brazil 169.0 cm (5' 6.5") 158.0 cm (5' 2.2")
Cameroon 170.6 cm (5' 7.2") 161.3 cm (5' 3.5")
Canada 174 cm (5' 8.5") 161.0 cm (5' 3.4")
China (PRC) 164.8 cm (5' 4.9") 154.5 cm (5' 0.8")
China 169.4 cm (5' 6.7") 158.6 cm (5' 2.5")
Colombia 170.64 cm (5' 7.2") 158.65 cm (5' 2.4")
Cote d'Ivoire 170.1 cm (5' 7") 159.1 cm (5' 2.7")
Czech Republic 180.3 cm (5' 11") 167.3 cm (5' 6.0")
Denmark 180.6 cm (5' 11.1")
Dinaric Alps 185.6 cm (6' 1.0") 171.0 cm (5' 7.2")
Estonia 179.1 cm (5' 10.5")
Finland 178.2 cm (5' 10") 164.7 cm (5' 4.7")

97 | P a g e
France 174.1 cm (5' 8.5") 161.9 cm (5' 3.7")
Ghana 169.46 cm (5' 6.7") 158.53 cm (5' 2.4")
Gambia 168.0 cm (5' 6.1") 157.8 cm (5' 2.2")
Germany 178.1 cm (5' 10") 165 cm (5' 4.9")
Guatemala (Maya people) 157.5 cm (5' 2") 142.2 cm (4' 6")
Hong Kong 170 cm (5' 7") 158.8 cm (5' 2.6")
Hungary, Debrecen 179.14 cm (5' 10.4") 165.84 cm (5' 5.2")
Iceland 181.7 cm (5' 11.5") 167.6 cm (5' 6")
India 165.3 cm (5' 5") 165.3 cm (5' 5")
Indonesia 158.0 cm (5' 2.2") 147.0 cm (4' 10.0")
Indonesia, East Bali 162.4 cm (5' 3.9") 151.3 cm (4' 11.5")
Iran 174.24 cm (5' 8.6") 160.0 cm (5' 3")
Iraq 165.4 cm (5' 5.1") 155.8 cm (5' 1.3")
Israel 175.6 cm (5' 9.2") 162.7 cm (5' 4.1")
Italy - Middle & North 176.9 cm (5' 9.7") 163.2 cm (5' 4.2")
Italy - South 174.2 cm (5' 8.0") 160.8 cm (5' 3.3")
Japan 171.2 cm (5' 7.4") 158.8 cm (5' 2.6")
Korea, South 175.26 cm (5' 9") 162.56 cm (5' 4")
Lithuania 176.3 cm (5' 9.4")
Malaysia 164.7 cm (5' 4.8") 153.3 cm (5' 0.4")
Malta 169 cm (5' 6.5") 159 cm (5' 2.6")
Malawi 166 cm (5' 5.3") 155 cm (5' 1.1")
Mali 171.3 cm (5' 7.4") 160.4 cm (5' 3.2")
Mexico, State of Morelos 167 cm (5' 5.7") 155 cm (5' 1.1")
Netherlands 184.8 cm (6' 0.8") 168.7 cm (5' 6.4")
New Zealand 177.0 cm (5' 9.7") 165.0 cm (5' 5")
Nigeria 163.8 cm (5' 4.5") 157.8 cm (5' 2.1")
Norway 179.9 cm (5' 10.8") 167.2 cm (5' 5.9")
Philippines 163.5 cm (5' 4.4") 151.8 cm (4' 11.8")
Portugal 172.8 cm (5' 8")
Singapore 170.6 cm (5' 7.2") 160 cm (5' 3")
South Africa 169.0 cm (5' 6.5") 159.0 cm (5' 2.5")
Spain 170 cm (5' 7") 161 cm (5' 3.3")
Sweden 180 cm (5' 10.9") 166.9 cm (5' 5.7")
Switzerland 175.5 cm (5' 9") 164.0 cm (5' 3.8")
Taiwan 171.45 cm (5' 7.5") 159.68 cm (5' 2.75")
Thailand 167.5 cm (5' 5.9") 157.3 cm (5' 1.9")
Turkey 173.74 cm (5' 8.4") 161.4 cm (5' 3.5")
United Kingdom 176.8 cm (5' 9.6") 163.7 cm (5' 4.4")
U.S. 178.2 cm (5' 10.2") 164.1 cm (5' 4.6")
Vietnam 167 cm 156 cm
The only gene so far attributed with normal height variation is HMGA2.
Genetically speaking, the heights of mother and son and of father and daughter

correlate, suggesting that a short mother will more likely bear a shorter son, and
tall fathers will have tall daughters.
Today the tallest race of humans is the Nilotic peoples of Sudan such as the Dinka
they have been described as the tallest in the world, with the males in some
communities having average heights of 1.9 m (6 ft. 3 in) and females at 1.8 m (5
ft. 11 in).
Disabled World - Disability News for all the Family: http://www.disabled-
world.com/artman/publish/height-chart.shtml#ixzz27NbbvGJF
Average height
The estimated average height of the human male in the overall worldwide
population currently stands at 1.72 m or 67.7 in. Economic advantages lead to an
increase in the average height, although genetic background does set higher
standards for some ethnic populations. American men 20 years and older
currently average 69.4 in. in height.
In other words the average height of a man using are trolley we can presume to
be 5.75 foot or 175cm
http://www.livestrong.com/article/289265-what-is-the-average-adult-male-
height/#ixzz27NhzqAib
Arm length
The average male arm, from shoulder to finger, is about 75 cm or so, slightly less.
Women come in at about 71 cm, not that much shorter than men. Therefore the
trolley does not need to vary a lot for it to be at ideal height for both men and
women. Having said that, if a large object is being carried adjustable arms will be
very helpful. The final design chosen has arms of a considerable variation in
length.

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