Vacuum assisted altitude scaling device

International Journal For Research & Development in Technology
Volume: 1, Issue: 2, JUNE 2014 ISSN (Online):- 2349-3585
28 Copyright 2014- IJRDT www.ijrdt.org
Vacuum Assisted Altitude Scaling Device
________________________________________________________________________________________________________
Aswin Mathen Kottarathil1,Bijal George2,Binoj K. George3,
George Jose Kuttemperoor4, George T.S5
12345
Department Of Mechanical Engineering ,Saintgits College of Engineering,
Kerala.
Abstract-Vacuum Assisted Altitude Scaling Device
(VAASD) defines a new way in scaling vertical surfaces
which is mainly limited to ladders, ropes, robots etc.
The main problems associated with the existing
methods of scaling are it requires an external help and
is constrained to move in specified directions. Vacuum
Assisted Scaling Device (VAASD) mainly consists of
Suction Pads, Suction Lines, and Vacuum Backpack
with Vacuum Generator, Harness Belt (for body
support) and Leg Support (with chain). Vacuum
pressure is created in the Vacuum Generator with the
help of vacuum pumps and reaches Suction Pads
through Suction Lines.
The mechanism uses the pressure gradient between
vacuum pressure and atmospheric pressure as the
source of force. The mechanism was able to carry a
load of 250 kg (at normal conditions). It could hold a
single average human’s weight and allow vertical
movement on the wall. The mechanism can also be
operated to a height of 2300 meters above the sea level.
This mechanism enables users to climb up walls and
remain suspended with no handholds. A prototype
mechanism has been fabricated for testing and
visualization purposes utilizing a few basic calculations
and rules of thumb.
Keyword:- vacuum pump, suction pad
I.INTRODUCTION
An increasing interest in the development of special climbing
has been witnessed in last decade. Climbing mechanisms with
the ability to maneuver on vertical surfaces are being strongly
requested by various industries and military authorities in
order to perform operations such as inspection of high-rise
buildings, spray painting on top of building, cleaning outer
walls of buildings, aircraft inspection surveillance,
reconnaissance, assistance in firefighting and rescue
operations etc. The project was aimed at proposing a new way
of scaling vertical surfaces.
The problem definition and background are:
Existing methods of climbing walls are limited to ladders, rope
pulley mechanisms and elevators. They have the drawbacks of
limited flexibility of movement, unsafe operations and bulky
character of equipment. Also in these equipments, the
operators cannot have a hands free operation during the
climbing motion. Although rope pulley mechanism can have
hands free operation, the motion is constrained during
climbing. It has limited flexibility. The main concern was to
design and develop a mechanism based on proper adhesion
technique to ensure that the wall climbing can be done reliably
without sacrificing mobility. The mechanism should support
an average human body weight. A compact mechanism with
the above characteristics was desired.
The solution to the problem is “wall walking systems”. Wall
walking systems are specific mechanisms which can adhere to
the walls and move like a lizard. The wall walking
mechanisms can move anywhere on flat surfaces without any
external aid.
II.METHODOLOGY
A literature survey was conducted to collect data regarding
standard design calculation practices in designing a vacuum
assisted system for wall climbing systems. Since there were no
journal papers about human wall climbing equipment available
at the moment, an investigation into the climbing techniques
of wall climbing robots was conducted. After some research, a
human climbing mechanism known as PVAC (Personnel
Vacuum Assisted Climber) engineered by Utah University UG
students was found. As papers about their work were not
available, a from-the-scratch approach was adopted for
designing.
The next step was an experiment to check feasibility of the
idea. So a suction pad with ply wood was fabricated and tested
with the help of a home vacuum cleaner pump. The initial
prototype system could bear a load of up to a 100 kg, which
was encouraging. The next step was to design a model of the
suction pad. After which a design for vacuum generator was
made based on trial and error method and connected suction
lines to it. The dimensions of the suction pad were obtained
from design analysis. Reverse engineering approach was
adopted in designing the equipment.
III DESIGN OF SUCTION PAD
The performance of VAASD (Vacuum Assisted Altitude
Scaling Device) entirely depends upon the area of suction pad.
The pressure force generated depends upon the area of the

suction pad. In order to determine the dimensions, a prototype
must be fabricated. For making a prototype, ply woods were
chosen as the pad material (since the design needs to be
changed frequently). Half inch ply woods were chosen for
making suction pad. Based on the initial observations and
study, a suction space inside 46 cm  30 cm ply wood was
created. The shape of the suction pads was rectangle. The
figure is given below.
Fig.1 First iteration
A vacuum cleaner for suction purposes was taken and
connected to the suction pad. The vacuum cleaner was of 1300
W and the suction pressure was unknown. The pad was tested
on various surfaces such as vertical walls, ceilings, glass,
granite and wood. Of the surfaces tested, the equipment
showed a higher adhesion with granite and glass surfaces. The
reason was very clear. It was due to the uneven surface
texture of the walls, ceilings and wood. There were leakages
of air into the system due to unevenness of the surface. The
above result led to the need of a sealing material. The sealing
material must possess higher flexibility and adaptability. Of
the different material tested, a layer of foam showed high
flexibility. So a foam layer was attached to suction pad and
was tested on the surfaces mentioned before. The result was
positive. It gave a perfect sealing to the suction pad and the
leakage was reduced.
On vertical walls the design failed as force was applied
vertically. This was due to the absence of friction materials
along the boundary. The normal component of the force was
strong but the shear component was very weak. As to solve
the problem, materials for friction were tested. Of the different
compound tested, the rubber showed higher friction
characteristics. A small test on natural and vulcanized rubber
was conducted. The test was loosely based on angle of repose
method. The natural rubber showed better frictional
characteristics than vulcanized rubber. So a lining of natural
rubber was provided along the boundary of the suction pads.
The resultant suction pad was very effective in holding vertical
and shears forces. A test was conducted on the suction pad for
determining load carrying ability in vertical surface. The result
was positive. It was having good adhesion in smooth surfaces.
Fig.2 Second iteration
In second iteration, a square suction pad was made.
The dimensions were 30 cm  30cm. A load of 100 kg was
applied and the system was able to hold the force. Different
tests were conducted on suction pad. Results were
encouraging. So, the dimensions were finalized as 30 cm  30
cm.
IV DESIGN PARAMETERS
The main parameters in the design are maximum normal force
at suction pad, maximum altitude of operation of equipment
and coefficient of friction of the friction material.
In order to find the maximum normal load acting on the
equipment, the vacuum pressure generated by the motor is
measured. A vacuum gauge is used for finding the pressure at
the suction end.
The vacuum pressure at the end of the suction line
=0.26675 bar (200 mmHg)
Absolute pressure at the end of suction line Pin
= 1.013 - 0.26675
= 0.74625 bar
Standard atmospheric pressure Pout
= 1.013 bar
Area of the suction pad
Inside area (Ain ) = 0.230.23 m2
Outside area (Aout) = 0.300.30 m2
Pressure force = Pout
Aout – Pin
Ain
= (1.013105 0.09) – (0.746251050.0529)
= 5169.33 N
Maximum normal load (in Kg) = 5169.33/9.8
= 527.4 ~ 500 Kg
There is a safe altitude up to which the
equipment can be safely operated. Also it depends upon the
load acting on equipment. Since the machine has an ultimate
normal load capacity of 500 kg, a margin of 200 kg is given.
So, the ultimate load capacity of 300 kg (safe load -150 kg)
can be assumed.

Equation for air pressure above the sea level
ph = 101325(1 - 2.2557710-5 h) 5.25588
Where ph = air pressure at height h(Pa)
h = altitude above sea level (m)
Weight of 300 kg = 3009.8 = 2940 N
Then pressure required by atmosphere to hold the weight is
given by
2940 = (ph
1050.302
) – (0.746251050.232
)
On solving,
ph = 76529 Pa
Putting the value of ph in equation for air pressure and solving
for h,
h = 2305 m
i.e. the equipment can be operated anywhere up to 2.3 km
from ground level.
V FABRICATION
The working design consists of halt linkage, leg linkage and
handle bar. The position of each linkage is shown. The
designing was aimed at producing equipment which can hold
above 125 kg on to the wall surfaces. A design analysis
(section 3.2) was conducted, which is based on the vacuum
pressure created by the vacuum pump. Using a vacuum gauge,
vacuum pressure at the suction end was tested. By relating the
area pressure force relations, normal force which suction pad
can bear for a given pressure was found out. Different linkages
are placed around outer surface of the suction pad. A
pushbutton switch is provided in the suction pad for operating
the equipment.
Fig.3 Suction pad
The vacuum space is created using layers of wood, foam
and rubber. Foam and rubber is used for proper sealing of the
suction space. The suction lines are attached to the suction pad
by flexible pipe.It consists of a chain, MS Rod and a wooden
bar directly attached to the suction pad using M5 bolts. The
dimensions of the MS Rod are 10 mm in diameter and 160
mm in length. The linkage is designed in such a way that the
load is transmitted directly to the center of the MS Rod via
chain. The MS Rod transmits the weight to the wooden bar
which in turn transfers the applied load as shear load in the
bolts. In order to reduce the moment caused by the forces, the
leg linkage is provided at the bottom position of the suction
pad.
The halt attachment consists of an eye bolt of 8 mm diameter,
dorsal ring of 8 mm diameter and a handle made of steel. The
halt linkage is for supporting body during the halt position. In
order to reduce the moment created by the force, the halt links
are attached closely to the center position of the suction pad.
The dorsal rings are attached to the halt & harness belt.
Fig 4 Sectional view of seal
Sealing is provided at the suction pad to reduce the air leakage
into the system. Sealing ensures the minimum differential
pressure in order to hold the weight. For sealing purposes a
thick lining of plywood is provided. Above the wood, a layer
of foam is placed. The foam has excellent flexibility so that it
will deform when force is exerted. So it can be effectively
used as a sealing material in different contours. The
irregularities of different surfaces are compensated by the
deformation of the foam.
Backpack houses the vacuum motors which are used to
generate the vacuum force required. It consists of two vacuum
motors each of 1400 watts enclosed in a specially designed
casing.
Fig.5 Backpack
The casing which accommodates the vacuum motors is made
from plywood. Proper ventilations are provided to the casing
to reduce the back pressure and also for the circulation of air
to carry away the heat generated by the electric motor powered
vacuum pump. The motor is packed tightly inside the casing
made from plywood using a rubber seal. The rubber seal
damps the vibrations produced during the operation of the
motor. A rigid plastic square frame attached directly to the
rigid frame of plywood absorbs the initial torque of the electric
motor powered vacuum pump.

The Vacuum motors (1400 watts each) used require adequate
ventilation in order to operate properly and meet their
expected life targets. Improper ventilation will cause the motor
to run hot and will contribute to reduced operating life. Also it
will lead to a high back pressure. As per manufacturer‟s
specification, a minimum of 3 inch * 2 inch area should be
provided for ventilation air inlet and discharge. The
Ventilation is provided to the backpack casing (Vacuum
Generator) by drilling holes
Cooling air should not be allowed to re-circulate. The path of
cooling air in the equipment should not restrict the minimum
areas. Otherwise, this will have an adverse effect on the unit.
Fig.6 Circular holes for ventilation
Ventilation are needed to reduce the back pressure developed
by the vacuum motor in the casing made from plywood and
also to cool the motor from becoming red hot. The circular
holes provided on the plywood casing or backpack was able to
reduce the back pressure and the heat developed in the small
space inside the casing made from plywood.
VI FORCE ANALYSIS
The Vacuum Assisted Altitude Scaling Device has two
linkages, Leg linkage and Halt linkage. At any instant during
the climbing motion, the weight of the load is transmitted to
these linkages. Force analysis was done to find out the
magnitude of forces acting on each of the links.
The halt mode of operation is converted into a three bar
linkage (shown in figure above). The suction pad end and leg
end assumed as fixed ends. The link is now converted into a
structure. The human body is assumed as an inclined link and
the load acting on the link is the weight of the body. The
center of gravity of the body is approximated at 0.57 L (where
L- height of human) from the bottom of human body.
Fig.7 Halt mode converted to three bar link
Software used:-Autodesk Force Effect
Load applied :- 125 kg
The resultant force diagram generated by „Force
Effect‟ is shown below.
Fig.8 Result of force analysis
1) Force acting on chain = 0.287 kN
2) Force acting in halt rope = 0.139 kN
3) Reaction force provided by wall
= 0.422cos (40) = 0.323 kN

VII PERFOMANCE TEST IN VARIOUS
SURFACES
The objective of this analysis is to analyze the performance of
the equipment in different surfaces. The surface roughness of
wall surfaces may vary. The performance of the equipment
depends upon the roughness of the surfaces. More the surface
roughness, the less will be the load carrying capacity due to
the air leakage into the system.
The apparatus for carrying out the test is given in the figure
above. The apparatus consists of a vacuum gauge and a
suction tube on the end to which the vacuum gauge is
attached. A hole is drilled on the suction pad for inserting the
tube into the suction space. All joints are sealed properly to
prevent air flow into the system. The suction pad is attached to
various surfaces for testing.
Fig.9 Apparatus for testing performance
The apparatus for carrying out the test is given in the figure
above. The apparatus consists of a vacuum gauge and a
suction tube on the end to which the vacuum gauge is
attached. A hole is drilled on the suction pad for inserting the
tube into the suction space. All joints are sealed properly to
prevent air flow into the system. The suction pad is attached to
various surfaces for testing. The tested surfaces are
1) Concrete
2) Wood polished
3) Wood unpolished
4) Granite
5) Glass
6) Aluminum
The result of the test conducted is shown in the table.
Table.1 result of the test conducted
Surface Vacuum
pressure
(mmHg)
Max.
normal
load (kg)
Max.
lateral
load (FOS
=2)
Concrete 120 469 234
Wood
(polished)
140 484 242
Wood
(unpolished)
130 477 238
Granite 140 484 242
Glass 140 484 242
Aluminum 140 484 242
From the table it is concluded that the equipment has its lowest
pressure built up in concrete surface. This is due to the high
roughness of the surface. Due to the low pressure, the load
carrying capacity of the equipment at concrete surfaces
reduces from 250kg to 234 kg. In smooth surfaces, the
pressure inside suction pad was found out to be 140 mmHg.
So the load carrying capacity on smooth surfaces is 242 kg.
From the test it can be concluded that the equipment has
satisfactory performance on all surfaces. Load carrying
capacity at all surfaces is approximately same. Slight
difference is due to the surface roughness.
VIII CONCLUSION
The Vacuum Assisted Altitude Scaling Device (VAASD) is an
equipment designed for climbing wall surfaces. It is an efficient
wall walking system. The equipment provides high load
carrying capacity (125 kg). The operating altitude of the
equipment ranges up to 2.3 km. No other existing equipment
provides such a large load carrying capacity with a high
altitude of operation. The designing and testing stages were
successful and performance of the equipment was found
excellent. Different tests conducted on the equipment ensure
that the equipment can bear up to 125 kg safely. The
performance of the equipment on various surfaces was tested.
The performance was satisfactory on concrete and found to be
excellent on smooth surfaces.
The equipment has various applications ranging from common
household applications to military applications. As scaling of
the walls is one of the basic job in gas tank industries, aircraft
maintenance industries and building industries, this device
would be helpful to them. Another main application of this
device is in fire rescue operations since existing methods (such
as rope-pulley, ladder, etc.) are highly inconvenient.
The future scope of equipment includes addition of individual
pressure sensors in each suction pad and addition of compact
batteries. Each time suction pad adheres to surface, the pressure
inside the suction pad varies. It is necessary to ensure that the
suction created is sufficient for holding the weight. Another
scope is addition of compact high power batteries. This will
increase the flexibility of operation. Also addition of battery
level sensors is a need to indicate battery level.
REFERENCE
[1] Development of a Wall Climbing Robot; Surachai Panich,
Srinakharin wirot University, 114, Sukhumvit 23,
Bangkok. Journal of Computer Science 6 (10): 1185-1188,
2010, ISSN 1549-3636, © 2010 Science Publications.
[2] City-Climber: A New Generation Wall-climbing Robots;
Jizhong Xiao and Ali Sadegh The City College, City
University of New York USA; Climbing & Walking
Robots, Towards New Applications, ISBN 978-3-902613-
16-5, pp.546, October 2007, Itech Education and
Publishing, Vienna, Austria.

Vacuum assisted altitude scaling device

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