Modification of pelvic chair with brake support device for descent in

personnel of the Colombian national army

..........................................

Modificación de silla pelvica con dispositivo de apoyo al freno para descenso en

personal del ejército nacional de Colombia

Juan Gabriel Rojas Gonzalez

Jorh Alexander Díaz Tovar

Mónica Estefanía Hernández García

Julian Enrique Barrero García

Nathalie Tarazona Rojas

ABSTRACT

This research article arises from the project

modified pelvic chair with brake support

device for descent, this project is based on the

experiences of contingencies presented in the

first man when descending in the Air Assault

tower of the National Army of Colombia,

seeking to reduce the risk of accident of the

user, implementing a braking device that

consists in the adaptation of a carabiner

located in a specific point (lateral part of the

left or right leg) of the pelvic chair, being a

fixed point with greater adaptability and

anchorage security, allowing to continue with

the tasks that are being performed, giving

orientation and control to the rope, avoiding

knots due to oscillation when releasing the

brake rope.

Keywords: Descent, support device, national

army, pelvic chair.

Received: January 22, 2023

Approved: May 09, 2023

...........................................

Dean, unidadinvestigacion@emsub.edu.co

Military NCO "Sargento Inocencio Chincá".

https://orcid.org/0000-0001-6294-278X

Science and Technology Officer

unidadinvestigacion@emsub.edu.co

NCO Military School "Sargento Inocencio

Chincá". https://orcid.org/0000-0002-5541-

947X

Civil Engineer, Specialist in Project

Management

Investigador.presupuesto@emsub.edu.co

Research Advisor

NCO Military School "Sargento Inocencio

Chincá". https://orcid.org/0000-0001-9802-

2897

Industrial Engineer, Master in Education

Julian.barrero.profesor@emsub.edu.co

Research Director NCO Military School

"Sargento Inocencio Chincá".

https://orcid.org/0000-0003-2143-9461

Electrical Engineer, Specialist in Project

Management, Master in Innovation and

Technologies for Education.

nathalietarazona@cedoc.edu.co

Teacher ESAVE Military Aviation School

https://orcid.org/0000-0002-2113-4724

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

RESUMEN

El presente artículo de investigación surge del

proyecto silla pélvica modificada con

dispositivo de apoyo al freno para descenso,

este proyecto se realiza con base en las

experiencias de contingencias presentadas en

el primer hombre al momento de descender en

la torre de Asalto Aéreo del Ejército Nacional

de Colombia, buscando reducir el riesgo de

accidentalidad del usuario, implementando un

dispositivo de freno que consiste en la

adaptación de un mosquetón ubicado en un

punto específico (parte lateral pierna izquierda

o derecha) de la silla pélvica, siendo un punto

fijo con mayor adaptabilidad y seguridad de

anclaje, permitiendo continuar con las tareas

que estén realizando, dando una orientación y

control a la cuerda, evitando nudos por

oscilación al soltar la cuerda de freno.

Palabras clave: Descenso, dispositivo de

apoyo, ejército nacional, silla pélvica.

Introduction

The Air Assault School trains officers, non-commissioned officers and professional

soldiers of the Colombian Armed Forces in the planning, development and execution

of air assault operations with emphasis on jungle, combining strategic speed with the

tactical mobility of air elements. As a specialty, they have the maneuvers of insertion

and extraction of personnel in the most remote and jungle areas of Colombia. This

implies the descent from helicopters by means of ropes, which generates a risk for the

personnel who descend, especially for the first man, for not having the support of the

rope master who is on the ground.

The Air Assault School of the Colombian Armed Forces seeks to specialize military

personnel in the highest tower in South America, so that the user socializes with the

tower and loses fear, with the above, at the time of certification in aircraft through a

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

simulation of a normal operation, the military can perform their exercise without any

contingency.

In order to continue training military personnel by seeking continuous improvement

of both units and equipment in the training and training of special forces, descent

training is carried out in a tower of approximately 14 meters. In this structure, which

has a cabin similar to that of real helicopters (blajot, MI17, UH) and simulates the

distance of an aircraft over the ground, fast rope maneuvers are performed, used when

there is a high value target on a flat terrain, with the structure of the tower seeks to

optimize the effectiveness of the troops destined in the fight against illegal armed

groups or to capture and hold key positions. It is not trained with aircraft, to avoid

accidents and reduce costs. In a real assault operation, they descend to more than 60

meters (200 feet). (Colombian National Army Aviation, 2012).

The practice of aerial assault has had a great acceptance within the Colombian armed

forces due to the fact that its results in the field have proven to be quite effective. In

the training of personnel assigned to military aerial assault operations, the need to

create an element that avoids accidents due to slipping or falling into the void or

contingencies presented to the first man descending from a helicopter, who faces risks

such as loosening the descent rope or brake, knots, and tangles in the material, is

recognized. The first man is the one who is most exposed to the dangers of the descent

because he does not have someone to provide him with the safety protocol at the end

of the rope.

The project focuses on designing a braking device adapted to the certified pelvic chair,

which can provide greater safety to users of assault teams, an equipment with a

combination of strength and lightness and thus contribute to improve the

development of operations, as is the project called "Modified pelvic chair with brake

support device for descent".

The braking device proposed for the pelvic chair is a second additional friction point

that goes at the height of the leg (right or left depending on the laterality of the

descender), which allows to give an orientation and notion of position of the rope.

Likewise, friction device number two prevents knots from being tied because it is a

control point through which the rope passes. In addition, the vital function in case of

rope release is to have a fixed point to place the hand and recover or pick up the rope

again, avoiding a free fall over the area of operations. Article 348 of the Substantive

Labor and Social Security Code, which was modified by Article 10 of Decree 13 of 1967,

stipulates and regulates the hygiene and safety measures to be adopted by companies

in different areas of the work environment. (Ministry of Labor).

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

This design seeks to reduce the risk of accidents and provide the user with greater

flexibility, adapting the pelvic harness to create a safer and more effective system even

in more demanding situations. This braking device is based on the adaptation of a

carabiner to the pelvic harness at a strategic point, allowing control of the rope. It

should be emphasized that the main function is to allow a higher survival rate of the

first man to descend from a helicopter to a military operations area.

The Universal Declaration of Human Rights in its article 22 (United Nations, 1948)

refers to "everyone, as a member of society, has the right to social security and is

entitled to realization, through national effort and international cooperation and in

accordance with the organization and resources of each State, of the economic, social

and cultural rights indispensable for his dignity and the free development of his

personality".

Materials and methods

According to Cruz, et. al, (2020). The use of artificial intelligence tools minimizes

research data errors.

The methodological development of the project "Modified pelvic chair with brake

support device for descent" will take into account the scope of both the project and the

product. (Project Management Institute , 2012) It states:

• Scope of the project: All the processes and the necessary work that the research

team must do to provide the product (modified pelvic chair) with the required

features and functions.

• Product scope: This refers to the characteristics and functionality that the

product generated by the project should have. This scope will have to include

all the requirements that were gathered through the stakeholders, as long as

they are directly related to the need for which the project was undertaken and

to the strategic objectives of the project.

For a clearer perception, the Work Breakdown Structure (WBS) tool will be used,

which allows a hierarchical decomposition of the total scope of work, in addition to

creating a frame of reference with respect to the sub-deliverables to be delivered.

The scope of the project includes the scope of the product (pelvic chair with modified

brake support device). The scope of the product based on the WBS presented had 4

phases:

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

● Phase 1: Prototype design

● Phase 2: Prototype Construction

● Phase 3: Laboratory Tests

● Phase 4: Redesign and final construction

Results

The "Prototype Design" phase consists of 3 work packages. The first, "CAD Design", is

the realization of a virtual prototype of the pelvic chair, in a design program such as

AutoCAD, SolidWorks or 3D Max. This will detail the shape, location, characteristics,

size, etc., of the brake support device.

Figure 1. Example of a CAD simulated pelvic saddle.

Source: Own

Once the CAD (Computer Aided Design) design was completed, the second work

package, "Dynamic and Static Analysis", was started. This work package is very

important for the development of the pelvic chair, since it allows estimating the

behavior under specific operating conditions.

During the CAD design phase of the prototype, the work packages "analysis and

selection of textile material" and "analysis and selection of carabiners" were carried

out in order to manufacture the first prototype for testing.

For the analysis and selection of textile material, we searched for standards related to

the physical properties of the material, based on this we will analyze which of these is

the most appropriate for the pelvic chair brake support device, which will be selected

for use in the product of the project.

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

For the analysis and selection of carabiners, different types of carabiners are analyzed,

thanks to the CAD design and the dynamic and static analysis, the different loads to

which the carabiners may be exposed can be calculated, thus calculating the resistance

that the carabiners should have, material and thickness.

Through Resolution 3673 of 2008, the Ministry of Social Protection established the

technical regulations for work at heights, a document that at the time became a

fundamental pillar for the regulation of work at heights. (SURA, 2008)

It was planned to perform different types of tests on the prototype. Mechanical tests,

physical tests and functional tests, each of these tests will be carried out in a laboratory

with the necessary equipment and the corresponding report will be obtained.

Mechanical tests:

● Tensile strength: This test is performed to measure the resistance of a textile

material to the applied tensile force, it can be performed directly on the fabric,

to measure its maximum tensile strength or to measure the strength of the

fastening between fabrics (seams), thus validating if the strength meets the

required needs or if it is necessary to change the type of fabric to be used or type

of seam made.

Figure 2. Tensile strength

Source: Web

● Textile fatigue resistance: It is a test to determine the resistance of seam

constructions. For this, a cyclic tension process is performed by means of a

machine (the material is tensioned and then untensioned), in order to analyze

after how many cycles the seam or fabric can fail, break or unravel. This number

of cycles may vary depending on the tension force applied in the cycles.

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

Figure 3. Fatigue resistance

Source: Web

● Static pull test: This test is very similar to the tensile strength test, where an

increasing force is applied until the seam or fabric fails. The difference is that

in this test, a static pull is performed (a specified amount of force in an instant

of time). With this it will be possible to know which is the maximum resistance

of the material before a moment much force applied in a very short instant of

time. (For example, it is calculated if the force with which the product was

designed is necessary to support a person in the descent, if it is entangled any

and stops abruptly).

Figure 4. Example of Static Pull Test

Source: Web

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

Physical Tests:

● Tear Strength: This is a test to analyze the force needed to perform the

tearing, either edge tearing (force needed to initiate the tearing of the material)

or internal tearing (force needed to continue with the tearing). This test is used

for material characterization and subsequent selection. With it we can obtain

criteria to know what would be the durability of the textile.

Figure 5. Textile Tearing Process

Source: Web

● Accelerated aging test: The accelerated aging test is an artificial procedure

that allows to establish what will be the useful life of the product. The procedure

consists in using some conditions, but increased, such as heat, humidity,

sunlight, etc. This makes it possible to increase the aging of the product. This is

done by means of an airtight cabin, where the product is placed for a certain

number of hours, each hour of permanence, according to conditions, will be

equivalent to a certain number of hours under normal conditions.

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

Figure 6. Accelerated aging chamber

Source: Web

• Safety Expert Pilot Test: An expert company in height safety will be in

charge of evaluating the performance of the modified pelvic chair in controlled

conditions (first prototype), which, after having used and analyzed the product,

will issue a concept with comments and recommendations to improve the

product. Based on this and on the results delivered in each of the tests

performed (both physical and mechanical), the next stage of the project,

redesign of the product and construction of a new modified prototype, will

begin.

The redesign and construction of the final prototype will consist of three work

packages, the first "redesign of the product", followed by the "construction of the final

prototype". For the first package, an engineer will redesign the prototype with each of

the recommendations gathered in each of the tests and with the concept of the certified

height safety expert, this work will be done in a CAD design program, and if possible a

3D sample will be reprinted in ABS plastic.

With this redesign, measurements and new features, we proceed with the second work

package, the construction of the final prototype. It will include the observations

gathered in each of the tests performed, such as material, type of carabiner, type of

stitching, stitching material, etc.

Modification of pelvic chair with brake support device for descent in personnel of the Colombian national army

Vol 3 - No 2 July - December e-ISSN 2745-1194 Pages 51-62

Conclusions

The project intends, on the one hand, to raise awareness of the military that performs

this type of training, the risks that may occur with the current pelvic chair taking into

account that the brake is given with the maneuverability of the hand whether left-

handed or right-handed, with the design of the prototype we want to reduce this risk

by means of a braking device,

On the other hand, to try to detect the real needs that arise in the practice of air assault

and to be able to evolve through this design for future air assault training.

The modified pelvic chair with brake device adaptation will serve as equipment to

minimize the indicators of fatalities due to malfunction of the chair in the field of

operation.

The prototype developed vs. the conventional pelvic chair will generate more sources

of strength when used and produced for the different safe works at heights, which

originates a better competitiveness with the occupational health sector.

The impact generated by the modified Pelvic Chair with braking device is obtained

when the prototype is discarded.

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