Design and Analysis of Food and Drinks Crutch Accessories Report

This report details the design process of crutch accessories, specifically focusing on detachable food and drinks holders. The project involved clarifying customer needs and constraints, including the requirement for 3D printable materials. The design process included conceptual design, material selection (ABS plastic), and embodiment design using SolidWorks. The drinks accessory featured a cup holder, ring, base, and counterweight, while the food accessory included a plate base, ring, and pod. Finite Element Analysis (FEA) was conducted to assess the structural integrity of the designs under load. The report also includes cost analysis and concludes with a discussion and references. The report covers aspects of design modeling, environmental considerations, user needs, and the application of industry standards, aiming to create functional and user-friendly crutch accessories.

CONTENTS
ABSTRACT..............................................................................................................................................2
1. INTRODUCTION.............................................................................................................................2
2. AIMS AND OBJECTIVES..................................................................................................................2
3. TASK CLARIFICATION.....................................................................................................................2
4. CONCEPTUAL DESIGN....................................................................................................................3
5. MATERIAL SELECTION....................................................................................................................4
6. EMBODIMENT DESIGN 1................................................................................................................4
6.1. DRINKS CRUTCH ACCESSORY.................................................................................................5
6.1.1. Cup Holder.....................................................................................................................5
6.1.2. Ring................................................................................................................................5
6.1.3. Base...............................................................................................................................5
6.1.4. Counter Weight..............................................................................................................5
6.1.5. Cup Pod Assembly..........................................................................................................6
6.2. FOOD CRUTCH ACCESSORY....................................................................................................6
6.2.1. Plate Base......................................................................................................................6
6.2.2. Plate Ring.......................................................................................................................6
6.2.3. Plate Pod........................................................................................................................7
6.2.4. Food Crutch Accessory...................................................................................................7
7. EMBODIMENT DESIGN 2................................................................................................................7
7.1. FEA ANALYSIS.........................................................................................................................7
7.1.1. Drinks Accessory............................................................................................................8
7.1.2. Food Accessory..............................................................................................................8
7.2. COST ANALYSIS......................................................................................................................9
7.2.1. Drinks Crutch Accessory...............................................................................................10
7.2.2. Food Crutch Accessory.................................................................................................10
8. DETAIL DESIGN............................................................................................................................11
9. DISCUSSION.................................................................................................................................11
10. CONCLUSION...........................................................................................................................11
REFERENCES........................................................................................................................................11
APENDICES...........................................................................................................................................12
APPENDIX I. DRINKS CRUTCH ACCESSORIES....................................................................................12
APPENDIX II. FOOD CRUTCH ACCESSORY.........................................................................................15
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ABSTRACT
This report aims at describing a crutch accessories design process. In this design,
the task was clarified and all the all the considerations given by the customer
were looked at. In this report, various concepts for crutch accessories were
discussed and their pros and cons investigated. The functions of the parts of the
model that was designed were discussed. It is a good practice to use appropriate
codes of practice when detailing a product. This report shows details of the
designed crutch accessories.
1. INTRODUCTION
Crutch accessories are products that helps to customize the crutches to suit the
unique desires of the customers. (Kujath, 2018). They include hand pads, grips,
coffee pods, bottle pods, torches, covers and replaceable tips. (Harpham, 2018).
People who use the crutches should not get more burden when moving or when
doing their day to day activities. Using crutches doesn’t mean that your life
becomes harder. The use of crutches is made easier by use of crutch accessories
that aid in mobility, and other support. Engineers and designers have come up
with various products to help and carry drinks in containers such as bottles,
coffee cups and cans, to carry food in small dishes and plates and to carry other
personal items such as mobile phones. (Samsonaite, 2019). They make people
using Crutches more independent since they carry their own personal items.
(Frescura, 2014).
2. AIMS AND OBJECTIVES.
This project aims at meeting the following objectives.
a) To design detachable food and drinks pod crutch accessories.
b) To illustrate knowledge of design modelling tools.
c) To define environmental and sustainability constraints and restraints.
d) To define and investigate the needs of the user and other crucial
considerations.
e) To apply the appropriate code of practice and industry standards.
3. TASK CLARIFICATION
There is a common challenge with individuals who use crutches in carrying food
and drinks around. We have been challenged to design two accessories that can
be attached to the crutch to carry food and drinks without spilling.
The accessories are limited to some constraints. Below are some of the
important considerations that governed the design synthesis.
a) The design must be able to accommodate a range of different styles of
cups, cans, bottles, dishes, and bowls.
b) Does not spill any of the contents while using the crutches.
c) Attachable and detachable to a standard crutch.
d) Cup attachment must hold at least 400 ml of liquid.
e) Dish attachment must hold at least up to 1 kg of food.
f) 3D Printable.
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The product needs to be strong in order to be able to carry heavier foods. It
should include mechanisms that does not allow food or drinks spillage. A
temporary way of attaching the accessories on to a crutch was necessary so that
the accessories can be detachable. Use of 3d printable plastics was also
necessary.
4. CONCEPTUAL DESIGN
Having understood the customers needs, various design solutions were
developed. The first concept used a plastic pod for carrying the food and the
drinks. The crutch passed through the pod. Two fasteners were used to fasten
the pod to the crutch.
Fig: Concept one.
The accessory had a simple design. Very few parts were used. Plastic pod means
that the accessory can be 3d printed. However, the solution had a couple of
problems. According to the way the pod is attached to the crutch, when you tilt
the crutch, the pod will tilt also in a similar manner since the pod is attached
directly and rigidly to the crutch. This means that the chances of spilling the food
and drinks is high.
To cater for spillage of food and drinks, another concept was idealized. In this
concept, the pod was not directly attached to the crutch but instead through a
ring and a holder. The rings and holder had revolute joints that permitted the
rotation of the ring and holder with respect to one another. The cup or plate
would be placed inside the ring. This concept is illustrated by the sketch below.
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Fig: Concept two.
Although this design reduced the chances of spilling, the 4 revolute joints
introduced would allow swinging of the cup when the person using the crutches
is walking. This would also reintroduce possibilities of spilling. The cup should
remain upright at most of the time. This design was modified to counter this
swinging behaviour. A counterweight was added to the design. The inner ring
was modified in order to look like a pod a round removable plastic solid placed
inside. This solid is the counterweight. the figure below illustrates this concept.
Fig: Concept three.
A basket like plastic pod was used in order to reduce the weight of the
accessory. Using 4 joints allowed for rotation in two axes and thus permitted the
pod to stay upright. The counter weight balanced the forces to lower the centre
of gravity of the pod. Unlike the previous design, this design ca be used to carry
both bottles, cups and other items such as the phone. For the food accessory,
similar mechanisms were used but the rings and the housings had bigger
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diameters to accommodate plates. A counter weight was not used for the food
accessory.
5. MATERIAL SELECTION
The design is limited to customer specification such as use of 3d printable
materials and the food weight capacity. Only plastics which are 3d printable were
considered during the material selection process. ABS plastic, nylon and PBT
plastics in this case. Nylon has a lower yielding point than both ABS and PBT, and
therefore it was ruled out. Though PBT has a bibber yielding point than ABS, it is
more expensive than ABS plastic and as a result, it was ruled out. (Sidestix,
2011)
For the pod, the holder and the rings, any plastic would have been used but the
same material for all of them was chosen. This is advantageous sine one buys
only one type of 3d print filament and thus reducing on the cost.
6. EMBODIMENT DESIGN 1
Having idealized a concept and selected materials, the design was modelled on
Solidworks. The modelled parts and assemblies are discussed below.
6.1. DRINKS CRUTCH ACCESSORY.
6.1.1. Cup Holder
The cup holder is a basket like part that
hold the bottles and cups. It is large
enough to accommodate 500 ml bottle
of drink. The bottles can rest on a
counter weight that is installed at the
bottom of the holder while the cups do
not touch the bottom of the cup but
hang on the top surface of the cup. The
two wholes at the top of the holder are
for pivotal revolute joints that joins it to
a ring.
The joint member is shown below.
It is an ABS plastic member and can be
3d printed. They are four of them in this
accessory. Two for holder and two for
the base.
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6.1.2. Ring
This is the accessory part that makes it
possible for the cup to remain vertically
straight even if the crutches are tilted in
any angles especially during walking. It
has 4 holes arranged orthogonally to
one another. Two are for joining to the
holder while the other two are for
joining to the base.
This ring is made of ABS plastic and is installed between the holder and the base.
6.1.3. Base.
The base is the part that is attached to
the crutches. It has two holes for
attaching to the crutch. All the weight of
the food plus the accessory acts on this
member and thus needs to be strong.
The principle of triangulation has been
utilized to make it withstand large
weights of the drinks.
The base is made of ABS plastic.
6.1.4. Counter Weight.
As explained at the conceptual design,
there is the tendency of the suspended
cup to overturn during walking. A
counter weight is used to balance the
forces by keeping the centre of gravity
as low as possible when the cup is
swinging. It is installed inside the cup
holder. It is 3d printable since it is made
of ABS. The part is solid and not hollow.
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6.1.5. Cup Pod Assembly.
Fig: Forward tilting of the crutch. Fig: Side tilting of the crutch.
The figure above shows the orientation of the cup pod accessory when the crutch
is tilted forward and sideways. Note that the cup stays vertical even when the
crutch is tilted thus reducing the chances of the drink spillage.
6.2. FOOD CRUTCH ACCESSORY.
6.2.1. Plate Base
The plate base is similar to the cup base
only that it has a large diameter to
accommodate a plate and it is thicker to
withstand the large weight of a plate
with food. It is made of ABS. Similar
methods to the cup plate of fastening to
the crutch are used.
6.2.2. Plate Ring
The plate ring is similar to the cup ring
only that it has a large diameter to
accommodate a plate and it is thicker to
withstand the large weight of a plate
with food. Two holes are for joining with
the plate while the other two holes are
for joining to the plate base.
6.2.3. Plate Pod.
The plate pod is also a basket
like pod just like the cup pod.
One places his plate on this
pod. It is ABS and has two holes on the
sides for joining with the plate ring.
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6.2.4. Food Crutch Accessory.
The whole food accessory is shown below. The crutch has been tilted forward
and sideways to show the various orientation of the plate pod.
Fig: Forward tilting of the crutch. Fig: Side tilting of the crutch.
The plate pod stays vertical even when the crutch is tilted
7. EMBODIMENT DESIGN 2
7.1. FEA ANALYSIS
Having done the modelling, the Assemblies were simulated in order to see
whether they will fail when food and drinks are placed on top. A static analysis
was conducted on Solidworks simulator. The materials were selected and applied
appropriately. Fine meshes were generated for both the assemblies in order to
give more accurate results.
7.1.1. Drinks Accessory.
A coarse mesh was generated. The points of attachment with the crutch were
restrained. A force equivalent to weight of drinks, 4N, was applied above the
revolute joints. The analysis was simulated and the results probed. The figure
below shows the mesh and loads for the plate base.
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Fig: Mesh, restraints and loads of drinks base static analysis.
The Von Mises stresses were probed. The figure below shows the deformed
results.
Fig: Von Mises stress distribution.
The maximum stress 0.511 MPa while the minimum Von Mises stress is 0.1696
Mpa at the location indicated on the figure above.
7.1.2. Food Accessory
A coarse mesh was generated. The points of attachment with the crutch were
restrained. A force equivalent to weight of food, 10N, was applied above the
revolute joints. The analysis was simulated and the results probed. The figure
below shows the mesh and loads for the plate base.
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Fig: Mesh, restraints and loads of food base static analysis
The analysis was simulated and the results probed. The von Mises stresses were
probed. The figure below shows the Von mises stresses distribution.
Fig: Von Mises stress distribution.
The maximum stress 1 MPa while the minimum Von Mises stress is 9.798 Mpa at
the location indicated on the figure above.
From the simulation data, For the plate base, the maximum Von Mises stresses is
1 MPa. Comparing it with the Yield Strength of ABS (42 MPa), we can conclude
that the plate beam will not fail. For the drinks base, the maximum Von Mises
stress is 0.511 MPa. Comparing this with the Yield strength of ABS, we can
conclude that the base will not fail also.
7.2. COST ANALYSIS
Both accessories were simulated. During analysis, a bunch of 100 assembly for
each accessory were used.
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7.2.1. Drinks Crutch Accessory
Below is an excerpt of the drinks cost analysis report.
Calculated Parts Method Quantit
y
Part Cost
(USD/Asse
mbly)
Total Cost
(USD /
Assembly)
CUP BASE Printing 1 16.64 16.64
CUP HOLDER printing 1 10.28 10.28
CUP RING Printing 1 0.25 0.25
PIVOT Printing 4 0.15 0.60
COUNTERWEIGH
T Printing 1 0.46 0.46
Total 28.23
The cost of producing the 3d printable drink accessory is USD 28.23. The cup
base is the most expensive since it has the largest volume of material. The cup
holder follows.
7.2.2. Food Crutch Accessory.
Below is an excerpt of the drinks cost analysis report.
Calculated Parts Method Quantit
y
Part Cost
(USD/Asse
mbly)
Total Cost
(USD /
Assembly)
PLATE BASE Printing 1 24.73 27.73
PLATE HOLDER printing 1 16.24 16.24
PLATE RING Printing 1 0.75 3.00
PIVOT Printing 4 0.36 0.36
Total 47.33
The total production cost of one food accessory assembly in a bunch of 100 is
USD 47.33. Just like the drinks accessory, the plate base is the most expensive
due to its large volume of material.
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The above analysis was done for a bunch of 100 items. Meaning that the cost is
for large scale production. The cost is thus higher when producing small number
of assemblies.
Another method that could be used in producing the parts is injection moulding.
8. DETAIL DESIGN.
The drawings for both assemblies were generated. See the appendices.
9. DISCUSSION
These accessories are able to withstand forces of the food and drinks as seen
from the stress analyses. The mechanism of using the revolute joints helped in
making it possible for the pods to stay in vertical position even after the crutch is
inclined to angles.
Use of ABS has also made the accessories to be light weight. The food accessory
weighs just 533 grams while the drinks accessory with a coffee cup included is
396.78 grams which is light.
10. CONCLUSION
Crutch accessories are products that helps to customize the crutches to suit the
unique desires of the customers. Both the drinks and the food crutch accessories
prevent the spillage of drinks and food by maintaining the food container in
upright position when the crutch is inclined. Light materials are used when a light
product is desired.
REFERENCES
Sidestix, 2011, “A brief overview of the SideStix line of crutch attachments”.
Retrieved from: https://youtu.be/NesG34tFHx4. Retrieved on: 30 June 2019.
Frescura, 2014, “New innovative accessory for Crutches”, Retrieved from:
https://youtu.be/tq5_hCz5tE0?t=4. Retrieved on: 30 June 2019.
Shinde, 2017, “crutches with accessories for plate and glass”. Retrieved from:
https://youtu.be/AnzlTyh_LWI?t=3. Retrieved on 30 June 2019.
Fairley, Miki, 2008. "Innovative Crutch Designs”: Retrieved from:
https://opedge.com/Articles/ViewArticle/2008-04_06. Retrieved on 30 June 2019.
Samsonaite, 2019, “Tranformable crutch”. Retrieved from
https://lup.lub.lu.se/student-papers/record/1501554/file/1501570.pdf. Retrieved
on 30 June 2019.
Harpham, 2018, Beautiful Crutches. Retrieved from:
https://www.researchgate.net/publication/328101161_Beautiful_Crutches?
_sg=iSS6uUv4hDfAYkjU0UHQ9W7SKwvTaBgsBmJR-
Ew1nLcTwXfprRqziQG7wuEisbxpYpHr-da0kDoQ3pY. Retrieved on 30 June 2019.
Kujath, 2018, “Crutch Fitting”. Retrieved from:
https://www.researchgate.net/publication/326510362_Crutch_Fitting?
_sg=t6H6JusOgLzxefsAsDQ_dDMevE05SHpiVI3MNHStZjGD1Sn5SmQgR0mZaUWA
MvhShiotXKpqFdxUP40. Retrieved on 30 June 2019.
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