michelin Tweel technology report

Seminar report 2015 Michelin Tweel Technology
1
Dept. of .Mechanical Engineering
CHAPTER-1
INTRODUCTION
For more than 100 years, vehicles have been rolling along on cushions of air
encased in rubber. Sometimes, we get so used to a certain product that no true changes are
ever really made for years, decades even. So begins an article discussing the development of
airless tyres, something that has become more prevalent in the past few years. A few tyre
companies have started experimenting with designs for non-pneumatic tyres including
Michelin and Bridgestone, but neither design has made it to mass production.
Creating a new non-pneumatic design for tyres has more positive implications than
one might think. For one thing, there are huge safety benefits. Having an airless tyre means
there is no possibility of a blowout, which, in turn, means the number of highway accidents
will but cut significantly. Even for situations such as Humvees in the military, utilizing non-
pneumatic tyres has a great positive impact on safety. Tyres are the weak point in military
vehicles and are often targeted with explosives. If these vehicles used airless tyres, this
would no longer be a concern.There is also an environmental benefit to using this type of
tyre. Since they never go flat and can be retreaded, airless tyres will not have to be thrown
away and replaced nearly as often as pneumatic tyres. This will cut down landfill mass
significantly.
Because of the benefits, I believe that it is extremely important that research and
production of airless tyres is continued and increased. This type of innovation works well in
conjunction with several engineering codes of ethics, and thus should be embraced by
engineers everywhere. Cars are things that people use every day, so any improvements over
existing designs would affect the lives of the majority of people. Learning about such a
topic, therefore, I believe holds extreme value- especially for us freshmen engineering
students. In doing research into these kinds of topics that hold significant meaning, we can
see that what we will do can make a difference.
Airless tyres can be made with different spoke tensions, allowing for different
handling characteristics. More pliant spokes result in a more comfortable ride with
improved handling

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CHAPTER-2
HISTORY
The pneumatic tyre has served drivers and passengers well on road and off, but a
new design by Michelin could change all that – the Tweel Airless tyre. This report discusses
what such Airless Tyres are, why one would use it in place of traditional tyres, some of the
problems that may occur with an airless tyre and where one might see such Airless Tyre in
the future. When the tyre is put to the road, the polyurethane spokes absorb road impacts the
same way air pressure does in pneumatic tyres. The tread and shear bands deform
temporarily as the spokes bend, then quickly spring back into shape. Airless tyres can be
made with different spoke tensions, allowing for different handling characteristics. More
pliant spokes result in a more comfortable ride with improved handling. The lateral stiffness
of the tyre is also adjustable. However, you can’t adjust a such a tyre once it has been
manufactured. You’ll have to select a different one. For testing, Michelin equipped an Audi
A4 with Tweels made with five times as much lateral stiffness as a pneumatic tyre, resulting
in “very responsive handling”. Non-pneumatic tyres (NPT), or Airless tyres, are tyres that
are not supported by air pressure. They are used on some small vehicles such as riding lawn
mowers and motorized golf carts. They are also used on heavy equipment such as backhoes,
which are required to operate on sites such as building demolition, where tyre punctures are
likely. Michelin is currently developing an integrated tyre and wheel combination, the
"Tweel" (derived from "tyre" and "wheel," which, as the name "Tweel" suggests, are
combined into one new, fused part), that operates entirely without air. Michelin claims its
"Tweel" has load carrying, shock absorbing, and handling characteristics that compare
favorably to conventional pneumatic tyres.
Automotive engineering group of mechanical engineering department at Clemson
University is developing a low energy loss airless tyre with Michelin through the NIST ATP
project. Resilient Technologies and the University of Wisconsin–Madison's Polymer
Engineering Center are creating a "non- pneumatic tyre", which is basically a round
polymeric honeycomb wrapped with a thick, black tread. The initial version of the tyre is
for the SUVs and is expected to be available in 2012.Resilient Technologies airless tyres
have been tested and are used by the U.S. Army.

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CHAPTER-3
TYRES
Airless tyres; Before the technology of airless tyres is discussed, it is important for
the reader to understand how standard pneumatic tyres function, and what advantages and
disadvantages there are to using them. A brief overview of the general concepts of airless
tyres will then follow.
Pneumatic tyres; The basic design of all pneumatic tyres is very similar, even though
there are many different types. They all include an inner core that holds pressurized air
which is then covered with a layer of rubber that comes in contact with the road, called a
tread. The tread helps keep traction with the road and prevents slipping and skidding. The
tread has the tendency to wear down over time, so if the tyre has not gone flat, a person will
usually replace it at this point.
A main reason for using pneumatic tyres is the deformation that occurs during
rotation. As the tyre rolls, the weight of the car pushing down on it causes the tyre to flatten
slightly. This, in turn, causes the tyre to have a larger surface area to be in contact with the
ground, which makes for better traction. It also gives a slight cushioning effect, making
running over small rocks or debris unnoticeable. Or, as writer for How Stuff Works Ed
Grabianowski puts it. If you’ve ever taken a ride in an old-fashioned carriage with wooden
wheels, you know what a difference a pneumatic tyre makes.
Pneumatic tyres have their advantages, but they also have their disadvantages as
well. The possibility of a blowout or flat (when air is let out suddenly from the tyre) is a
major concern because they have the tendency to cause severe accidents. The task of
regulating tyre pressure is also a disadvantage because consumers are usually not very good
at it. Although it may help with traction to have the tyres a little flat, it comes at the price of
handling. When there is not enough air pressure in the tyre, the sidewalls flex causing the
tyre to not quite follow the desired line of steering. It is because of these disadvantages that
tyre companies have taken an interest in designing airless tyres.

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3.1 AIRLESS TYRE (TWEEL)
Airless tyres or Non-pneumatic tyres (NPT), are the tyres that are not supported
by air pressure .These tyres are also called as Tweel which is a merger of the words tyre and
wheel. This is because the Tweel does not use a traditional wheel hub assembly. The Tweel
concept was first announced by Michelin back in 2005. it' s structure is a solid inner hub
mounted onto the vehicles axle, that is surrounded by polyurethane spokes. This forms a
pattern of wedges, which help to absorb the impacts of the road. These spokes look similar
to the ones found on bicycles and plays the shock-absorbing role of the compressed air as in
a traditional tyre. A sheer band is then stretched across the spokes, which forms the outer
edge of the tyre. It is the tension of the band and the strength of the spokes that replaces the
air pressure used on traditional tyres. When a vehicle drives over an obstacle, a sleeping
policeman for example, the tread and shear bands give way as the spokes bend, before they
quickly bounce back into shape.
Fig 3.1: Structural designation Schematic
3.2 WORKING OFAIRLESS TYRE
The Airless tyre (Tweel) doesn’t use a traditional wheel hub assembly. A solid inner
hub mounts to the axle and is surrounded by polyurethane spokes arrayed in a pattern of
wedges. A shear band is stretched across the spokes, forming the outer edge of the tyre. On
it sits the tread, the part that comes in contact with the surface of the road. The cushion
formed by the air trapped inside a conventional tyre is replaced by the strength of the
spokes, Which receive the tension of the shear band. Placed on the shear band is the tread,
the part that makes contact with the surface of the road.

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When the Tweel is running on the road, the spokes absorb road defects the same
way air pressure does in the case of pneumatic tyres. The flexible tread and shear bands
deform temporarily as the spokes bend, then quickly go back to the initial shape.
Different spoke tensions can be used, as required by the handling characteristics and
lateral stiffness can also vary. However, once produced the Tweel’s spoke tensions and
lateral stiffness cannot be adjusted.
Fig 3.2: Tyre on deforming when applying load
Fig 3.3: Tyre regains its shape when load is removed

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3.3 DESIGN APPROACHES
There are many different approaches to the design of the supports. This accounts for
the main differences between the overall designs of each company’s version of the airless
tyre. The following are approaches to making an airless tyre by different companies. Some
solve more problems than others, but it should be noted that all show an extreme amount of
ingenuity that may cross over into different types of engineering.
3.3.1 NASA and the Apollo Lunar Rover
The first major attempt at creating an airless tyre was in 1970 for NASA’s Apollo
Lunar Roving Vehicle. The tyres were made of steel strands woven together to form the
shape, and then were coated with zinc. In order to gain traction, titanium chevrons were
added to the outer surface.
This design worked well on the moon, where comfort of the drivers was not an issue
(i.e. cushioning effect of pneumatic tyres), but it would not have been practical on earth.
The design would also be very expensive for a regular automobile, which is not attractive to
the average consumer.
Fig 3.4: Tyre of NASA and the Apollo Lunar Rover

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3.3.2 Michelin Tweel Tyre
The next main attempt at creating an airless tyre was called the Tweel (combination
of tyre and wheel) by the tyre company, Michelin. Their design consisted of a thin rubber
tread with V-shaped spokes made of polyurethane.
There were extremely high hopes for this model when it came out. Columnist Don
Sherman of Car and Driver writes, introductory claims versus conventional pneumatic
radials were two to three times the tread life and five times higher lateral stiffness with only
a slight increase in rolling resistance. This development has very positive implications
because it means that the tyre would last about two times longer than a standard pneumatic
tyre before it would have to be retreaded. The only major problem with this model is at
highway speeds, the spokes tend to vibrate, causing excessive noise.
When asked about recent developments for the Tweel, Michelin refused comment,
either because they dropped the project, are working with the military, or do not want to
divulge findings to their competitors.
Fig 3.5: Michelin Tweel Tyre

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3.3.3 Bridgestone Tyre
Another model for the non-pneumatic tyre came from the well-known tyre company,
Bridgestone. Although very similar in concept to Michelin’s Tweel, there are some key
differences.
The core is made of rigid aluminum and has thermoplastic spokes radiating outward
at an angle in opposite directions on each side. This creates more stability and less lateral
movement in the tyre. Bridgestone also fixed the vibration and noise problem in this way as
well. The main issue with their design was that debris had the tendency to get caught in the
gaps between spokes. In addition, the materials used in the tyres are recyclable, contributing
to the efficient use of resources. Further, by pursuing extremely low rolling resistance and
contributing to reductions in CO2 emissions through use of proprietary technologies,
Bridgestone believes it is possible to achieve even higher levels of environmental
friendliness and safety.
Bridgestone is pursuing this technological development with the aim of achieving a
cradle to cradle process that proactively maximizes the cyclical use of resources from worn
tyres into new tyres and the use of recyclable resources.
Fig 3.6: Bridgestone Airless Tyre

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3.3.4 Resilient Technologies, LLC
As stated before, the production of airless tyres would be extremely beneficial to the
military. The group Resilient Technologies, LLC is working with the military to develop
such a tyre for Humvees. To meet the requirements of heavy loads and rough terrain, these
tyres are quite industrial-looking. They consist of a thick outer tread with a honeycomb-like
structure inside. This allows for the load to be evenly distributed around the tyre.
The honeycomb design could be adjusted for any application where loss of air
pressure causes problems, where tyres face numerous hazards on a regular basis or where
business want to reduce downtime for tyre issues and maintenance, such as agricultural and
construction equipment.
This design causes the tyre to be very loud, making in unsuitable for regular
automobiles. For military purposes however, it is useful. It can withstand a large amount of
abuse, including blasts when under attack.
Fig 3.7: Tyre produced for military purposes by Resilient Technologies, LLC

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3.3.5Scitech Airless Tyre
The most convenient design for everyday vehicles comes from a company called
SciTech. Their tyre fits on standard rims, unlike all previously mentioned models (which
are really a combination of a wheel and a tyre), and has the look of a regular pneumatic tyre
form the outside. Instead of supports radiating from the center, their supports are spring-
like. There are a hundred supports in every tyre and nine are in contact with the road at any
one time. There is also a secondary support system in order to distribute load to all of the
supports which have 550 pounds of strength each and are made of a thermoplastic glass
fiber composite material.
Because SciTech’s tyre has closed sidewalls and no spokes, there is no noise or
overheating issue as well as no problems with debris. A division of Scitech Industries has
announced a successful test of the company’s non-pneumatic airless tyre at an industry
laboratory in Ohio.
The company says the tyre achieved a cool and uniform 10-hour run at highway
speed at passenger car load. Mounted on a standard rim with a conventional tyre mounting
machine, the airless tyre is self-supporting, with internal glass fiber composite ribs
supporting the load. Built and cured in a conventional steam-bladder mold at a commercial
tyre factory, the composite rib and tyre construction are covered by worldwide patents.
Fig 3.8: SciTech Airless Tyre

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3.3.6 Hankooki – flex tyres
A futuristic design concept, the Hankooki – Flex is an airless wheel and tyre, all in
one. Aiming to keep losses to a minimum when converting energy, Hankook Tyres
engineers have reconceptualised the automobile tyre. With the Hankook Tyres i-Flex, the
company presents the prototype of a non-pneumatic tyre that will help increase the overall
efficiency of vehicles thereby improving their energy balance. With 95 percent of its
construction being recyclable, the Hankooki-Flex is made from polyurethane synthetics,
with the tyre manufactured in conjunction with its rim as one unit. It is considerably lighter
than conventional wheel-tyre combinations and does not require air like conventional
pneumatic tyres, able to offer shock absorbency through the unique design.
Fuel consumption and noise emissions are thus optimized while simultaneously
increasing vehicle safety. it is Displayed at the Frankfurt show on an ABT-tuned
Volkswagen Up, the Hankook i-Flex tyre specification is 155/590 14 (155mm wide, 590mm
diameter, 14-inch ‘simulated wheel size). Through Hankook Tyres hands-on display and
video guides, visitors to the Frankfurt show can alter the colors’ of the Hankook i-Flex. At
the 65th IAA (International Automobile -Ausstellung), September 12-22, in Frankfurt,
premium tyre manufacturer Hankook Tyre will present its latest innovations, production-
ready prototypes and trend-setting tyre concepts designed to meet the demands of future
mobility, in Hall 8, Stand 24.
Fig 3.9: Hankooki -Flex tyres

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3.4 Manufacturing of Tweel Tyre
Tweel tyres are produced in three steps: tread, hub, and polyurethane. In the first
step, the tread is constructed by a similar method as the tyre tread manufacturing process.
The tread on a Tweel tyre is exactly the same as a pneumatic tyre and is extruded in the
same way, and it is mated to layers of belts in the same manner as conventional tyres. The
process of rolling plies onto a drum to achieve the correct diameter currently is performed
manually, but the same basic process that is performed on tyres will be mimicked when the
Tweel production is fully automated. In this fairly simple process, rectangular sheets of
rubber and steel cord are rolled onto a steel drum, and the excess material from each sheet is
removed. Once the desired base thickness is achieved in this manner, the extruded tread is
rolled onto the top, and the entire assembly is vulcanized.
The second step is a very simple 4 kg steel hub casting that is well documented in
several databases including BUWAL250. In the third step, the hub and the tread are secured
concentrically and polyurethane is poured into a spoke and shear band mold while the entire
assembly spins so that the polyurethane will sufficiently fill the mold in the radial direction.
The energy needed to spin the Tweel assembly and polyurethane mold for just 5
minutes while the polyurethane is poured is considered irrelevant compared to the large
amount of energy required to heat and pressurize the ovens needed to cure the shear band
and then cure the entire assembly after the polyurethane is poured, so it can be ignored in
this inventory. Before the pouring process occurs though, all the surfaces that contact the
polyurethane are cleaned and covered with either an adhesive or a mold release for the shear
band and spoke mold, respectively. The quantities of these additives were supplied by
Michelin, and listed in table 3.1
Table 3.1: Cleaning, adhesive, and release agents used during manufacturing of one12 kg
Tweel Tyre
Additive Mass (g)
Ethyl acetate 26.7
Adhesive 3.3
Chemlok 7701 30
Stoner M-804 250

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The polyurathene pre-polymers and curative are stored separately until they are
heated and combined at this point in the manufacturing process, but this chemical process is
considered part of the raw materials production in order to analyze which material is
causing the most amount of environmental harm. The combination of the heated pre-
polymers and curative could be considered in this Tweel manufacturing section, but in order
to organize the impacts of the raw materials it is treated as part of the raw material
production of polyurethane.
After the polyurethane is poured and the assembly is allowed to stop spinning, the
entire Tweel tyre (shear band, spokes, and hub) is placed into another oven. This final
curing occurs at 100°C degrees for 4 hours so that the desired polyurethane properties are
obtained and to assure all the components are securely bonded together. To save some
energy this curing process could take place at room temperature, but it would take much
longer to complete and during this time it would be susceptible to being bumped and
permanently damaged, so this possible environmental benefit to save the energy required to
heat the oven is not a plausible option for Michelin. So, this energy must be considered
along with all the other process inputs mentioned, and all of these are organized with the
rest of the life cycle inventory. The energy required to heat, mix, and cure the polyurethane
is allocated to the raw material production of polyurethane, so this 0.7 kWh is all the energy
that is needed in the Tweel manufacturing inventory.
3.5 Technical description of Tweel
Michelin's resilient, structurally supported non-pneumatic assembly, the Tweel™,
has performance capabilities like pneumatic tyres that are a substantial improvement over
any other airless tyre product. The key component of the technology is a structure called the
shear ring. The shear ring replaces the function of the crown belts and the air pressure that
normally carry the load in a radial tyre. The design of the shear ring consists of three
concentric layered elements.
There is an elastomeric annular band that is called the shear layer. The shear layer is
captured between two composite rings of the same width as the shear layer. The composite
rings have a circumferential tensile modulus of elasticity that is substantially greater than
the shear modulus of elasticity of the shear layer.

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The main characteristic of the shear ring is that deflecting the circular unloaded
shape puts the elastomeric band in a state of shear deformation.
Fig 3.10: Shear Beam Cross Section
The shear deformation of the ring results in a uniform contact patch pressure
distribution again indicated in Figure 3.10. This uniform contact patch pressure is the first
key aspect of the technology. All prior non-pneumatic tyres, which carry load via
compression of structures between the contact patch and the wheel, have parabolic contact
patch pressure distributions that limit a number of performance criteria, such as: traction,
soft-soil flotation and tread life. The uniform contact patch pressure distribution delivered
by shear rings is equivalent to that of pneumatic tyres.
This allows the use of conventional tread materials and tread patterns that result in
traction and wear life similar to pneumatic tyres. Although the current embodiment of the
drive Tweel™ assembly for power chairs is 2¼" in width, the contact areas more
comparable to a 3" wide pneumatic tyre which has a rounded crown.
Further, the contact patch pressure of this technology can be low enough to offer the
prospect of satisfactory mobility in marginal soil conditions. The current estimate However,
any tyre, pneumatic or not, that must operate continuously at a low foot print pressure must
be made larger to provide the necessary footprint area without imposing excessive vertical
deflection. (Excessive deflection would cause too much shear strain and lead to early ring
failure.)The shear ring transmits the contact patch load to the top of the tyre like a
compression arch.

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The ring is attached to the wheel via polyurethane spokes, which act only in tension
to transmit the ring load to the wheel. See the structural schematic in Figure 3.11 to
visualize the load path. The spokes buckle as they pass over the contact patch and therefore
provide little load transmission via compression. The transmission of load via the top of the
shear ring is the second key aspect of the technology.
Fig 3.11: Structural Schematic
The initial version of the Tweel™ assembly concept is shown in Figure 3.12. The
entire structure is utilized to carry the wheel load, making the resulting tyre much more
efficient than classic non-pneumatic tyres in the amount of load carried per unit mass of the
tyre/wheel system. Further, the absence of structures transmitting wheel loads directly to the
road in compression allows much higher levels of deflection without causing excessive
material strains. No prior non-pneumatic tyre design has been able to deliver this
combination of performance characteristics.
Fig 3.12: Tweel assembly

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The design of the spokes and their relationship to the wheel control the forces
transmitted from the shear ring to wheel. Unlike pneumatic tyres, where all the forces
transmitted by the structure are proportional to the inflation pressure, the Tweel™ can be
made soft in one direction and stiff in another.
The lateral depth of the flat, vane style spokes contributes to the high lateral stiffness
of Tweel™ assemblies. This fact removes some of the classic constraints of design that are
inescapable when dealing with traditional pneumatic designs and, therefore, present a
tremendous opportunity for wheel assemblies for many applications with improved
handling and performance.
The shapes of pneumatic tyres are dominated by the constraints of being pressure
vessels. Although the belts in radial tyres allow their basic shape to be flattened into low
aspect ratio, low load carrying sport applications, there are currently no reasonable
structures that lead to tall and narrow pneumatic solutions, such as those in the dimensional
range of rear manual tyres and bicycle tyres. With more understanding and development of
the technology, this could change in the future. Because the spoke loads allow the use of
unreinforced elastomeric materials, the complexity of the spoke design is limited only by
the cost of the mold. This allows substantial design flexibility in meeting the load
transmission characteristics required for each vehicle application. Further, the absence of
inflation pressure loads and simple, robust connections of the spokes to the wheel allow
more freedom in the wheel design.
The wheel can be compliant, carrying its own share of shock loads because the
spokes can be crushed against the outer wheel surface without damage. These additional
degrees of design freedom available to Tweel™ designers make up the third key aspect of
the technology. Tweels™ can be more easily designed to supplement or replace suspensions
in most applications than can pneumatic tyres and are far more tolerant of suspension
bottoming shock loads.
3.6 Components of Tweel Tyre
When mounted on a vehicle the TWEEL is a single unit consists of four pieces they
are The hub, Polyurathene spokes, Shear band, Tread band

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Fig 3.13: Components Of Tweel Tyre
3.6.1 The Hub
The hub is generally made up of steel. Steel is made by reduction of iron, As seen in
the figure the hub is a part of the tweel and perform as a single unit. In a conventional tyre
the hub is a different part of steel made and fixed separately. Polyurathene spokes of a
Tweel tyre are molded directly to the steel hub with a bond that is not easily broken, Both
wheel and tweel use a steel hub weighing roughly 4 kg.
3.6.2 Polyurethane Spokes
Polyurathene Spokes is one of the most important part of the Tweel because it replaces the
air in a conventional tyre thereby avoiding the maintenance due to puncture, reduce the
downtime and provide a cushioned ride for the customers .The construction of the spokes in
the tweel is as follows.
3.6.3 Shear band
A solid inner hub mounts to the axle that’s surrounded by polyurethane spokes
arrayed in a pattern of wedges. A shear band is stretched across the spokes, forming the
outer edge of the tyre (the part that comes in contact with the road). The tension of the shear
band on the spokes and the strength of the spokes themselves replace the air pressure of a
traditional tyre. When the Tweel is put to the road, the spokes absorb road impacts the same
way air pressure does in pneumatic tyres.

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3.6.4 Tread
The tread is constructed by a similar method as the tyre tread manufacturing process.
The tread on a Tweel tyre is exactly the same as a pneumatic tyre and is extruded in the
same way, and it is mated to layers of belts in the same manner as conventional tyres.
The process of rolling plies onto a drum to achieve the correct diameter currently is
performed manually, but the same basic process that is performed on tyres will be
mimicked when the Tweel production is fully automated. In this fairly simple process,
rectangular sheets of rubber and steel cord are rolled onto a steel drum, and the excess
material from each sheet is removed. Once the desired base thickness is achieved in this
manner, the extruded tread is rolled onto the top, and the entire assembly is vulcanized.
Fig 3.14: MICHELIN X TWEEL All terrain Tyre specification
3.7 Material Composition
The material composition of a conventional tyre and a tweel is recorded in the table.
From the following data it’s pretty much clear that the total weight of the conventional tyre
is maximum to be 14 kg but in case of Tweel its slightly more and reach up to 15.75 kg.

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Table 3.2: Pneumatic Tyre Material Composition
Carcass Tread Total tire Hub
Raw Materials Wt % Wt % Wt % Wt%
Synthetic Rubber 15.78 41.72 24.17 0
Natural Rubber 24.56 3.53 18.21 0
Carbon Black 23.40 9.54 19.00 0
Silica 0.80 28.07 9.65 0
Sulpher 1.60 0.80 1.28 0
Zno 1.83 0.91 1.58 0
Oil 4.02 10.64 6.12 0
Stearic Acid 0.87 1.47 0.96 0
Recycled Rubber 0.60 0 0.50 0
Coated wires 17.2 0 11.4 0
Textile 7.0 0 4.7 0
Steel 0 0 0 100
Totals % 100.0 100.0 100 100
Weight (kg) 7.25 2.75 10.0 4.0

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Table 3.3: Tweel Tyre Material Composition
Carcass Tread Spokes Hub Total
Raw Materials Wt % Wt % Wt % Wt% Wt%
Synthetic Rubber 0 41 0 0 1.15
Natural Rubber 0 4 0 0 0.10
Carbon Black 0 10 0 0 0.26
Silica 0 28 0 0 0.77
Sulpher 0 1 0 0 0.02
Zno 0 1 0 0 0.03
Oil 0 11 0 0 0.29
Stearic Acid 0 1 0 0 0.04
Recycled Rubber 0 0 0 0 0
Coated wires 10 0 0 0 0.62
Textile
Polyurathene
0
90
0
0
0
100
0
0
0
8.44
Steel 0 0 0 100 4.00
Totals % 100.0 100.0 100 100
Weight (kg) 6.35 2.75 2.65 4.0 15.75

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CHAPTER 4
DISCUSSION SYNONYMS
4.1 Applications of Michelin Tweel tyre
1. They are used on some small vehicles such as riding lawn mowers and motorized
golf carts and wheel chairs .
Fig 4.1: I-BOT Wheel Chair
2. They are also used on heavy equipment such as Earthmovers, which are required to
operate on sites such as building demolition.
Fig 4.2: Michelin X Tweel SSL in Earth Movers

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3. Military Usage Tweel deflects mine blasts away from the vehicle better than
standard tyres and that the Tweel remains mobile even with some of the spokes
damaged or missing.
Fig 4.3: Michelin Tweel Tyre in US Army Vehicle
4. The airless tyres are also used in All-terrain vehicle (ATV) made by polaris . These
tyres can suffer a shot from a .50-caliber rifle and still travel 350 miles, and also
drive 1,000 miles after running over a railroad spike. It will start at $14,999.
Fig 4.4: All-Terrain Vehicle (ATV) Made By Polaris
5. Six legged robotic lunar developed by NASA used on the moon which is able to roll
and walk over wide range of terrains uses the Tweel as shown in the figure. This
robot is mainly used for climbing hills and terrains.

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Fig 4.5: NASA Lunar Rover
4.2 Advantages of Michelin Tweel Tyre
1. Eliminates air leaks or tyre blow outs.
2. With no air pressure you are left with consistent economy and handling.
3. Its flexibility provides an increase in surface area of contact.
4. No maintenance needed.
5. To lengthen tread life.
6. Facilitate recycling.
7. Makes Vehicle more Efficient have high lateral strength for better handling
without loss in comfort.
8. Vehicle remains under control even in emergency brake.
9. Remains mobile even with some of the spokes damaged or missing.
10. Durability & Long Life.
11. Can take gunfire or explosion.

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12. Less environmental impact.
13 The injection-moulded polyurathene spokes are flexible; this allows them to
effectively absorb impacts by shortening when hitting a bump.
4.3 Disadvantages of Michelin Tweel Tyre
1. Lack of adjustability
One of the biggest disadvantages of the Tweel is that once it has been manufactured,
it cannot be adjusted. In this case if the car needed a different kind of setting, a whole new
set of Tweels will be required. On the plus side Tweels are made with five times the lateral
stiffness compared to pneumatic tyres, enabling very responsive handling.
2. Not as economic as pneumatic tyres
Michelin are currently working on enabling the Tweels to be as fuel efficient as
pneumatic tyres. Currently they are within 5% of the rolling resistance and mass levels.
3. Vibration
This could be one of the Tweels biggest downsides. Vibrations become considerate
once a vehicle is driving above 50 mph, while causing a lot of noise. Also disturbing is the
amount of heat the Tweels generate. Long distance journey with Tweels would be very
unpleasant unless these areas are improved upon.
4. Different Manufacturing process
Another problem is that creating airless tyres requires a totally different
manufacturing process. At this point of time, the tyre industry revolves around the
manufacture of traditional pneumatic tyres. To modify factories and service equipment
would be a major change, and the facilities just don’t exist yet.
4.4 Safety and Environmental Concerns
4.4.1 Safety
As stated before, the main danger of pneumatic tyres is the chance of a flat or blow
out that usually occurs at highway speeds. A blowout is when a tyre basically pops and
deflates rapidly. This causes the driver to lose control of the car and risk the possibility of
hitting another vehicle. With airless tyres, this is no longer an issue.

25
There is no chance for a blowout, and the driver does not have to be concerned
about changing a flat (also eliminates the need for a spare tyre).The assurance of never
having a flat tyre is also beneficial in areas such as construction, where there can be sharp
debris, and in the military. It is especially useful in the military because the tyres of
Humvees are often targeted when under attack, as they are the weakest part of the vehicle. If
the tyres are blown, the vehicle cannot go anywhere. Airless tyres in this sense can save the
lives of troops riding in Humvees because the tyres can take more abuse.
Better handling is also a benefit when it comes to safety. Although it does not vary
by much, it is important to have that extra stability in the tyre to make the car go exactly in
the direction in which it is steered. This is especially helpful in swerving to avoid an
obstacle such as an animal or another car. So for this reason, improved handling is not just
for a better driving experience.
4.4.2 Environmental concerns
Non-pneumatic tyres are also expected to have a positive environmental impact. As
of now, tyre companies must address the growing mountain of bald tyres defiling the
landscape and find a way to recycle or find something that lasts longer and can be recycled.
In the case of airless tyres, it can be the latter. SciTech’s airless tyre is said to be able to
outlast the car. This has enormous environmental implications because with so many cars
on the road, there are many old tyres that have to be disposed of. Because airless tyres
mostly use composite materials, there is only a small amount of rubber that actually goes
into it. Also, since the tread life of most models is longer than that of pneumatic tyres, the
rubber does not have to be replaced very often. This means that there will be less of it to
dispose of later.

26
CHAPTER-5
CONCLUSION
In concluding the goal and scope of this analysis it was found that Michelin's design
goal of a very low rolling resistance Tweel tyre could result in at least equivalent if not
more environmentally friendly performance than the most fuel efficient tyre on the market
today when the overall life cycles of both are considered due to its fuel savings. Both the
EcoIndicator99 and EDIP assessment methods agree that producing and disposing of a non-
pneumatic Tweel tyre contributes a slightly higher environmental load than the baseline
tyre, but the hypothetical Tweel tyre benefits from the10% fuel savings when it is used on a
vehicle. Due to the much higher contribution from the use phase (5 times higher impact
score, 10 times more carbon dioxide emissions, and 100 times more carbon monoxide), this
fuel saving would outweigh the environmental drawbacks of producing a large amount of
polyurethane and the additives needed to mold it and adhere it to the hub and the rubber
tread resulting in an overall environmental improvement if one replaces conventional tyres
with Tweel tyres. With the current knowledge available, the best estimate for the life cycle
comparison would be a 2 to 6% relative environmental savings with a 5.5 kg/T Tweel tyre
as compared to a conventional fuel efficient tyre with a rolling resistance of 6 kg/ton.

27
REFERENCE
[1] Bert Bras and Austin Cobert Life-Cycle Environmental Impact of Michelin
TweelTyre for Passenger Vehicles SAE INTERNATIONAL 2011-01-0093
Published 04/12/2011
[2] Anuj Suhag, Rahul Dayal ,International Journal of Scientific and Research
Publications, Volume 3, Issue 11, November 2013 1 ISSN 2250-3153
[3] Austin Cobert Environmental Comparison Of Michelin Tweel™ And Pneumatic
Tyre Using Life Cycle Analysis Georgia Institute of Technology December 2009
[4] Rhyne T. B., and Cron S. M., 2006, “Development of a Non-Pneumatic Wheel,” Tyre
Science and Technology, 34(3), pp. 150–169.
[5] Asnani, V., Delap, D., and Creager, C. 2009. The development of wheels forthe
Lunar Roving Vehicle. Journal of Terramechanics, Vol. 46, No. xx, pp. 89_103. doi:
10.1016/jjterra.2009.02.005.

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