Article
citation information:
Motrycz, G., Helnarska, K.J.,
Stryjek, P. Continuing
a vehicle fitted with run flat tyres. Scientific
Journal of Silesian University of Technology. Series Transport. 2021, 112, 157-169. ISSN: 0209-3324. DOI: https://doi.org/10.20858/sjsutst.2021.112.7.13
Grzegorz
MOTRYCZ[1], Karolina J. HELNARSKA[2], Piotr STRYJEK[3]
CONTINUING
A VEHICLE FITTED WITH RUN FLAT TYRES
Summary. Modern vehicles are
equipped with many systems that monitor the security of driving. An example is
the tyre pressure monitoring system that shows a fault if the tyre pressure is
lowered. Low tyre pressure or no pressure at all (0 kPa) means that continuing
driving may lead to a dangerous situation. Prolonged driving of the vehicle at
0 kPa in the tyre ends with tyre burst, rim damage, or even loss of stability.
Therefore, on the automotive market, manufacturers offer Run Flat tyres adapted
to emergency driving with a pressure of 0 kPa. This article presents the
results of an experimental research in the field of vehicle dynamics,
continuing driving a vehicle with a loss of tyre pressure. These tests were
carried out not only to confirm the data provided by tyre manufacturers and to
verify the vehicle's driveability but also to analyse the effectiveness of
stopping vehicles equipped with this type of tyres using, for example, police
studs, especially when vehicles are used for crimes or terrorist activities.
Keywords: tyre, Run Flat, vehicle, driving with 0 Pa
pressure
1. INTRODUCTION
Increasingly,
motor vehicles are used by terrorists for attacks. In recent years, there have
been over a dozen attacks in which many people were injured using cars. In the
case of using a vehicle equipped with Run Flat tyres, which, according to the
manufacturers' declaration, despite the lack of air pressure (for an attempt of
a forced stop of the vehicle by the Police, it will be adequate to run into a
road stud or overshoot), it is possible to continue driving. This article
presents preliminary comparative tests of a Run Flat tyre and a standard
construction tyre in terms of the possibility of effective long-distance
driving in the event of loss of tyre shade.
2. TYPES OF RUN FLAT TYRES
The history of Run Flat tyres began
before World War II. The development of the technology took place during World
War II, and further work in this direction was carried out after its end. Tyres
of this type have been used on a larger scale since the end of the 1980s.
Currently, the Run Flat technology is becoming increasingly popular. There are
more cars on the market equipped with this type of tyres, which allow driving
for a distance of 80 km after tyre damage (pressure 0 kPa) at a speed of about
80 km/h. Run Flat tyres can generally be divided into three segments:
- with reinforced structure,
- self-sealing,
- with support ring.
Reinforced construction –
there is a rubber insert in the sidewall of the tyre, which helps to absorb
pressure loss. The tyre bead, directly adjacent to the rim, is also reinforced.
The applied solutions make the sudden loss of pressure almost imperceptible for
the driver. Hence, the necessity to use pressure measuring sensors. The scheme
of operation of such a solution is presented in Figure 1.
Fig. 1. Functional diagram of the operation of a Run
Flat tyre
Source: http://bridgestonesamericas.com
Self-sealing – the structure of the tyre
uses an additional internal sealing layer, just behind its tread, which fills
the places where the air leakage caused by the damage has occurred. The
resulting hole is filled on the inside of the tyre with a sticky, gluey
substance. This solution allows the regeneration of the tyre with a maximum
puncture diameter of 5 mm. Compared to the classic solution, the weight of the
tyre is 15-20% higher. An example of this solution was proposed by Pirelli Seal
Inside presented in Figure 2.
Fig. 2. Diagram of the operation of a
self-sealing Run Flat tyre
Source:
http://www.opony-samochodowe.com/blog/tag/seal-inside
With a support ring – this is technology uses a
special ring inside the tyre. A special part is mounted inside the tyre, acting
as a support, thus prevents the tyre from slipping off the rim. This solution
was introduced by the Michelin concern in a PAX tyre in 1997, shown in Figure 3.
Fig. 3. The Michelin PAX tyre
Source: http://photo blog.netcar.pl
2.1. Comparison of the possibility of
continuing a ride for a RUN FLAT tyre and a standard tyre
|
Fig. 4a. Run Flat Bridgestone |
Fig. 4b. Bridgestone |
The tests were conducted for the
Bridgestone TURENZA ER300 tyre in the standard version and the RFT tyre, size
205/55r16, with the same tread pattern shown in Figure 4a,b. The tyres are
mounted on the rear axle of the vehicle, with an actual weight of 1,320 kg. The
vehicle was loaded with an additional ballast to obtain a rear axle load (on
which the tested tyres were mounted) of 600 kg, which resulted in a vertical
load of a single tyre of 2.94 kN, that is, approx. 50% of the nominal load
permitted by the manufacturer. Figure 5 shows the static radius of the tyres mounted
on the vehicle during the tests (at a pressure of 0 kPa).
|
Fig. 5a. Static radius for the Run
Flat Bridgestone TURANZA ER300 RFT tyre |
Fig. 5b. Static radius for the
Bridgestone TURANZA ER300 tyre |
2.2. Description of the
phenomenon
The basic concepts
of the wheel dynamics presented in this paper are derived from the driven wheel
that is in non-steady state conditions, which is the most general case.
Fig. 6. Forces and moments influencing the driven wheel of
a vehicle driving on a rigid road surface
Source: authors’ study
The diagram of
forces and moments influencing such wheels is shown in Figure 6. The resultant
force between the tyre and the road surface acting in point 01 may
be decomposed into two components: P, Zk. Here, it is anticipated
that the location of point 01 is known. The case is, therefore,
analysed formally.
It is known that the forces and moments acting on the wheel (including
inertial forces and moments) must be balanced. Therefore, the following three
equations may be formulated:
(1)
(2)
(3)
After having considered the directions of forces and moments, the presented
vector equations may be presented as the following algebraic equations:
(4)
(5)
(6)
and
(7)
(8)
where:
mk - mass of the wheel;
Ik - inertia momentum
of the wheel in relation to its axis of rotation.
From (5) and (6), we calculate Mk
(9)
product of eGk we call the rolling resistance
torque, that is:
(10)
The rolling resistance torque Mt expressed by formula (10) is
an abstract notion.
After dividing (9) by rd, we obtain:
(11)
The ratio of driving torque Mk and dynamic tyre radius rd is defined as driving force pn.
Therefore:
(12)
Equation (12) is
especially important in providing the basis for the vehicle's stability. The
driving force provided by the driven wheel depends on the driving torque
supplied by the power train and tyre radius. It is anticipated that the driving
torque is evenly distributed between all driven wheels.
3. TEST
DESCRIPTION
This study aimed to determine the
possibility of continuing driving a vehicle at a pressure of 0 kPa, equipped
with the Run Flat Bridgestone Turanza ER300 RFT tyres and the Bridgestone
Turanza ER300 tyres.
The research was conducted on roads
excluded from public use. To record the longitudinal speed of the vehicle and
accelerations, the Race Technology DL1 recorder was used with the speed and
position sampling frequency of 20 Hz, and other parameters (acceleration and
gyroscope) of 100 Hz.
Fig. 7. View of the measuring
apparatus used during the tests
Source: authors’
study
The tests were conducted under the
following weather conditions:
- temperature 20°C,
- pessure 1010 hPa,
- wind speed 2.6 m/s,
- pavement dry asphalt [-].
The vehicle was subjected to a
controlled air release to a pressure of 0 kPa in the rear axle wheels. Then the
driver covered a measuring distance of about 1000 m from a speed of about 70
km/h, after which the vehicle was stopped, and the condition of the tyres was
checked until one tyre was deformed or completely damaged, preventing further
driving without permanent damage to the vehicle body by defragmentation of the
tyre.
4. DISCUSSION OF RESEARCH RESULTS
The longitudinal speed of the
vehicle during the test was about 70 km/h and was kept at a constant level
(Figure 8). The displayed speed moments, amounting to 0 km/h, resulted from the
need to periodically stop and verify the technical condition of the tyres.
The temperature distribution on the
sidewall of the tyres presented in Figure 9 was made as a mean measurement with
a manual pyrometer at a distance of about 0.025 m from the rim flange.
Measurement was made for solid rubber elements. In the case of the degradation
of the tyre, the exposure of metal elements (belting the tyre) was noticed, and
the steel elements were characterised by a slightly higher temperature,
however, the average value for solid pieces of rubber was still considered as
the tyre temperature.
After covering the distance of 3,000
m, the degradation process of the Bridgestone Turanza ER300 sidewall was
noticed. The successive phases of damage to the tyre wall are shown in Figure
10.
Fig. 8. Characteristics of the
vehicle speed in [km/h] over the distance of 10 km
Source: authors’
study
Fig. 9. Temperature distribution on
the tyre sidewall while driving at 70 km/h:
blue colour - Run Flat
Bridgestone Turanza ER 300 RFT,
red colour Bridgestone Turanza ER 300
Source: authors’
study
After covering a distance of 9,700
m, with a pressure of 0 kPa in the Bridgestone TURANZA ER300 tyre, the sidewall
was abraded. Continued driving with the tyre in this condition resulted in the
occurrence of vibrations in the suspension system, and fragmenting elements
from the damaged tyre caused the risk of damaging the body and suspension
components (for example, breaking the brake lines).
The distance of 9,700 m that was
covered by the Bridgestone Turanza ER300 tyre at a pressure of 0 kPa, loaded
with a pressure of 2.9 kN should be considered relatively long. If the tyre was
loaded to its full extent, the dynamics of vehicle movement were varied
(braking delay, loss of lateral adhesion), the process of destruction would
take place much faster. The experience of the sports research team shows that
tyres operated at a pressure of 0 kPa during, for example, sports trials, are
completely destroyed after covering about 2000-3000 m (Figure 12).
Fig. 10. Phases of damage to
the Bridgestone Turanza ER300 tyre sidewall during the tests
Source: authors’
study
Fig. 11. View of the
process of cutting the sidewall of the Bridgestone Turanza ER300 tyre
while covering the test distance: on the left, the initial phase of the belting
damage on
the right, complete cutting of the sidewall of the tyre
Source: authors’ study
The Run Flat Bridgestone Turanza
ER300 RFT tyre, after covering the test distance of 9,700 m, showed no signs of
damage. It was decided to continue the research at a longer distance. The tests
were completed after covering a distance of 30,000 m. During the tests, it was
found that it is possible to continue driving without any noticeable difference
in the road tyres. This was especially true for straight-ahead driving.
RFT (Bridgestone Run Flat Tyre)
technology stiffens the sidewall of the tyre. Compared to the first generation
RFT tyres produced in 1987-2004 and currently available on the market, a 60%
decrease in the temperature increase index can be observed, as well as an
increase in the comfort of selecting unevenness because the tyre in question
has only about 105% higher stiffness compared to classic tyres.
Fig. 12. View of the destructed
rubber collecting inside the tyre while driving at
a pressure of 0 kPa
Source: authors’
study
In juxtaposition with similar
constructions from previous years, the discussed model of the tyre has an
improved structure of the sidewalls for better comfort when selecting
unevenness, and additionally, has improved cooling of the sidewalls.
Apart from a much greater distance
that can be covered, RFT tyres are characterised by a much lower rolling
resistance at a pressure of 0 kPa. Therefore, even with all tyres punctured,
the vehicle can move with the driving dynamics.
For the Run Flat Bridgestone Turanza
ER300 RFT tyre and the Bridgestone Turanza ER300 tyre, the runway test shown in
Figure 13 was performed. The presented characteristics show that the Run Flat
Bridgestone Turanza ER300 RFT tyre generates a lower rolling resistance of over
50% compared to the Bridgestone Turanza ER300 tyre while driving with a
pressure of 0 kPa.
Fig. 13. Determination of vehicle
rolling resistance using the coast-down method :
green - the Run Flat Bridgestone Turanza ER300 RFT tyre,
red - the Bridgestone Turanza ER300 tyre
Source: authors’ study
During the use of the Run Flat
Bridgestone Turanza ER300 RFT tyre, the parameters related to the longitudinal
dynamics of the vehicle do not deteriorate, while the parameters responsible
for the lateral dynamics deteriorate. Because of pressure loss and increased
lateral acceleration, the bead may slide off the rim edge. Therefore, an
effective method of stopping this type of vehicle may be to use another vehicle
as a measure of direct coercion and ram such a vehicle.
During the tests, basic braking
efficiency tests were carried out for the series tyre and RFT without pressure.
The vehicle maintains a relatively high deceleration during braking, however,
reduced lateral stability must be considered. Interestingly, it results, of
course, directly from the structure of the RFT tyre (the loads in the event of
pressure loss are transferred by reinforced sidewalls) during the braking
process with blocked wheels, and is particularly visible. For the Run Flat
Bridgestone Turanza ER300 RFT tyre, high pressures (a clear trace) are visible
only in the area of the tyre wall with the road surface, while for the series
tyre in a wider footprint.
Fig. 14. View of the emergency
braking marks (blocked wheels) for the Run Flat Bridgestone Turanza ER300 RFT
tyre with a pressure of 0 kPa (right) and the road tyre (left)
Source: authors’
study
4. CONCLUSIONS
According to the manufacturers'
declarations, Run Flat tyres enable effective driving with a pressure of 0 kPa.
This can make it difficult to stop a vehicle equipped with this type of tyre.
In connection with the above, it is reasonable to start research on the
possibility of forced stopping of this type of vehicles by law enforcement
officers. Standard methods that have been used so far, such as the spike, may
be ineffective, and the vehicle, after colliding with it, can still travel for
many kilometres, with high dynamics. In addition, training in not only
effective but also safe stopping of this type of vehicles by the Police,
especially in urban traffic conditions, should be considered.
References
1.
Advertising
materials of Runflat International Limited, Gawne Lane, Cradley Heath, West
Midlands B64 5QY. Available at: http://www.runflatinternational.com.
2.
Caban Jacek,
Paweł Droździel, Dalibor Barta, Štefan Liščák.
2014. “Vehicle tire pressure monitoring systems”. Diagnostyka 15(3): 11-14.
3.
Ejsmont Jerzy,
Jerzy Jackowski, Witold Luty, Grzegorz Motrycz, Piotr Stryjek,
Beata Świeczko-Żurek. 2014. “Analysis of rolling
resistance of tires with Run Flat insert”. Key Engineering Materials
597: 165-170. ISSN: 1662-9795.
4.
Ejsmont Jerzy,
Grzegorz Motrycz, Grzegorz Ronowski, Piotr Stryjek, Sylwia Sobieszczyk.
2012. “Laboratory tests of rolling resistance and temperature of tires
for special vehicles”. In: The
Handbook Experimental and simulation
tests of the dynamics of a multi-axle vehicle in tire damage conditions. P. 1-10. Cracow: Publishing of the
Cracow University of Technology.
5.
Jackowski Jerzy,
Marcin Wieczorek, Marcin Żmuda. 2017. „Analysis of static radial
stiffness of the non-pneumatic tire and the pneumatic tire”. In: Proceedings of 21st International
Scientific Conference. Transport Means. Kaunas University of
Technology, Juodkrante, Lithuania, 20-22 September 2017.
6.
Janulevičius
A., G. Pupinis, V. Damanauskas. 2013. “Effect of tires’ pressure on
the kinematic mismatch of a four-wheel-drive tractor”.Mechanika 19(1): 73-80.
7.
Krmela Jan. 2008.
„Computational Modelling of Tyres Considering Operating and Safety
Requirements”. Communications
10(3): 61-65. University of Zilina.
8.
Motrycz Grzegorz,
Piotr Stryjek, Jerzy Ejsmont, Henryk Kałwa. 2013. “Tire performance
after explosive decompression”. Zeszyty Naukowe Wyższej
Szkoły Oficerskiej Wojsk Lądowych im. gen. T. Kościuszko 3: 134-144. ISSN:
1731-8157.
9.
Motrycz Grzegorz,
Piotr Stryjek, Jerzy Jackowski, Marcin Wieczorek, Jerzy Ejsmont, Grzegorz
Ronowski, Sylwia Sobieszczyk. 2012. “Research on operational
characteristics of tires with run flat insert”. Journal of KONES
Powertrain and Transport 19(3):
319-326. ISSN: 1231-4005. DOI: 10.5604/12314005.113814.
10.
Prochowski Leon.
2016. Mechanics of movement.
Publishing House of Communication and Communications. ISBN: 978-83-206-1957-7.
11.
Regulation No 64
of the Economic Commission for Europe of the United Nations (UN/ECE) —
Uniform provisions concerning the approval of vehicles with regard to their
equipment which may include: a temporary-use spare unit, run-flat tyres and/or
a run-flat system, and/or a tyre pressure monitoring system, Official Journal
of the European Union, L 310/18, 26.11.2010.
12.
Regulation No. 64
UNECE: Homologation test of “run-flat warning systems” (RFWS) for
“run-flat” tyres (RF), Informal document No. GRRF-60-10, (60th
GRRF, 18-22 September 2006 agenda item 5.3).
13.
Sapragonas J., A.
Dargužis. 2011. “Model of radial deformations of protector of
vehicle tire”. Mechanika 17(1):
21-29.
14.
Stryjek Piotr,
Jerzy Grzesiak, Grzegorz Motrycz. 2011. “Braking of passenger vehicles after a tire puncture with a police spike
in the case of standard and Run on Flat tires”. Archives of Automotive Engineering 3:
53-60. ISSN: 2084-476X.
Received 11.04.2021; accepted in revised form 29.06.2021
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Journal of Silesian University of Technology. Series Transport is licensed
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