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Overview

The Hydraulic Arm (Brazo Hidráulico Educativo) is an impressive engineering project that demonstrates how hydraulic systems transmit force through incompressible fluids. This hands-on prototype validates Pascal’s Principle and shows the same technology used in excavators, cranes, and industrial machinery.
Project Cost: S/. 35.00 - The most complex project with the highest material cost

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Scientific Principles

This experiment demonstrates fundamental hydraulics and mechanics:
  • Pascal’s Principle - Pressure applied to a confined fluid is transmitted equally in all directions
  • Force Multiplication - Small input force creates larger output force through different piston sizes
  • Incompressible Fluids - Liquids maintain constant volume under pressure, enabling force transmission
  • Mechanical Advantage - Hydraulic systems provide leverage without traditional levers or gears
  • Energy Conservation - Work input equals work output (force × distance)

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Materials List

All components serve specific mechanical functions:
MaterialQuantityFunction
10ml syringes4 unitsMaster actuators (control)
5ml syringes4 unitsSlave actuators (arm joints)
IV tubing1.5 metersHydraulic fluid transmission
Reinforced cardboard2 sheetsStructural framework
Colored water200 mlHydraulic fluid
Zip ties and wireVariousRotation axes and connections
Hot glue5 sticksIndustrial adhesive for assembly
The 10ml/5ml syringe ratio provides mechanical advantage - small movements on the control create larger movements on the arm.

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Team Members

  • Sebastian M.
  • Ariana L.
  • Felix A.
  • Gianella Y.
  • Luciana E.

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How It Works

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Pascal’s Principle in Action

1

Closed System

Each master-slave syringe pair forms a closed hydraulic system filled with incompressible fluid (water).
2

Pressure Transmission

When you push a master syringe plunger, pressure increases throughout the connected tubing.
3

Equal Pressure

According to Pascal’s Principle, this pressure transmits equally to the slave syringe.
4

Motion Transfer

The slave syringe plunger extends, creating mechanical motion at the arm joint.
5

Coordinated Control

Four independent hydraulic circuits control: base rotation, lower arm, upper arm, and gripper.

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Force Multiplication

The syringe size ratio provides mechanical advantage:
Force Calculation
Force_out / Force_in = Area_out / Area_in

For 10ml master → 5ml slave:
- Smaller slave area means less force but more displacement
- System trades force for precision control

For 5ml master → 10ml slave:
- Larger slave area multiplies force
- System trades displacement for power

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Construction Guide

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Structural Design

The arm consists of four main sections:
  1. Base Platform - Stable foundation with rotating mechanism
  2. Lower Arm - Connected to base with hydraulic pivot
  3. Upper Arm - Articulates from lower arm via second hydraulic joint
  4. Gripper - Hydraulically controlled claw for grasping objects

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Assembly Instructions

1

Cut Cardboard Pieces

Measure and cut cardboard pieces for:
  • Base platform (15cm × 15cm)
  • Lower arm (20cm × 5cm)
  • Upper arm (15cm × 5cm)
  • Gripper components (2 pieces, 8cm × 2cm)
  • Control base (20cm × 15cm)
2

Create Pivot Points

Use zip ties or wire to create rotation axes:
  • Base rotation pivot
  • Lower arm joint
  • Upper arm joint
  • Gripper hinge
3

Mount Slave Syringes

Attach 5ml slave syringes to each joint using hot glue:
  • Position so plunger movement creates joint rotation
  • Ensure plunger can extend and retract fully
  • Secure barrel firmly to prevent movement
4

Prepare Control Base

Mount four 10ml master syringes to control platform:
  • Arrange in ergonomic pattern for easy access
  • Label each control (Base, Lower, Upper, Gripper)
  • Secure barrels with hot glue
5

Connect Hydraulic Lines

Attach IV tubing between master-slave pairs:
  • Cut tubing to appropriate lengths (avoid excess)
  • Ensure airtight connections at syringe nozzles
  • Use hot glue to seal if needed
6

Fill Hydraulic System

Fill each circuit with colored water:
  • Remove air bubbles by pushing plungers slowly
  • Fill until water appears at both ends
  • Close system with caps or clips
  • Check for leaks
7

Test and Adjust

Test each hydraulic circuit:
  • Verify smooth plunger movement
  • Check for leaks at connections
  • Ensure joints move through full range
  • Adjust pivot points if binding occurs
Air bubbles in the hydraulic system reduce efficiency and cause spongy control. Take time to remove all air during filling.

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Video Tutorial

Watch this excellent step-by-step construction guide:

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Educational Resources

Download the theoretical foundation:
  • Fundamentos Teóricos: Hidrodinámica - Complete hydraulics and Pascal’s Principle guide (PDF)

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Scientific Conclusion

The experiment successfully demonstrates:
“El brazo hidráulico demostró la transmisión eficiente de fuerza mediante fluidos incompresibles, validando el principio de Pascal y permitiendo la manipulación precisa de cargas a través de movimientos articulados.”
This validates that hydraulic systems efficiently transmit force through incompressible fluids, enabling precise control of mechanical loads through articulated movements.

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Real-World Applications

Hydraulic systems power countless machines:

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Heavy Machinery

  • Excavators - Multiple hydraulic cylinders control boom, stick, and bucket
  • Cranes - Hydraulic telescoping arms lift heavy loads
  • Bulldozers - Hydraulic blade control and track drive
  • Forklifts - Hydraulic lift mechanism

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Vehicles

  • Brake Systems - Foot pedal pressure transmits to all four wheels
  • Power Steering - Hydraulic assist reduces steering effort
  • Suspension - Hydraulic dampeners absorb shocks

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Industrial Equipment

  • Metal Presses - Hydraulic rams apply tons of force
  • Injection Molding - Hydraulic clamps hold molds closed
  • Aircraft Controls - Hydraulics move ailerons and flaps

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Everyday Items

  • Car Jacks - Hydraulic bottle jacks lift vehicles
  • Barber Chairs - Hydraulic height adjustment
  • Trash Compactors - Hydraulic rams compress waste

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Advanced Modifications

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Improvements to Try

  • Include a wrist rotation joint
  • Add a base height adjustment
  • Create a 6-axis arm for complex movements
  • Use larger slave syringes (20ml or 50ml)
  • Replace cardboard with plywood or acrylic
  • Add support braces at joints
  • Use stronger adhesives (epoxy instead of hot glue)
  • Use smaller master syringes (3ml or 1ml)
  • Add mechanical stops to limit joint range
  • Install graduated scales on control syringes
  • Use clear tubing to monitor air bubbles
  • Use PVC pipes instead of cardboard
  • Replace syringes with pneumatic cylinders
  • Add pressure gauges to monitor system
  • Implement actual hydraulic fluid (oil) instead of water

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Troubleshooting

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Common Issues

Cause: Air bubbles in hydraulic linesSolution:
  • Disconnect tubing and refill system
  • Push plungers very slowly to avoid trapping air
  • Tap tubing gently to dislodge bubbles
  • Hold connections upward while filling
Cause: Friction at pivot points or misalignmentSolution:
  • Enlarge holes at pivot points
  • Use smoother wire or add washers
  • Check that joints are perpendicular to cardboard
  • Ensure slave syringes are aligned with joint motion
Cause: Poor seal between tubing and syringeSolution:
  • Apply hot glue around connection
  • Use smaller tubing for tighter fit
  • Wrap connection with electrical tape
  • Replace damaged tubing sections
Cause: Cardboard too weak for loadSolution:
  • Double layer the cardboard
  • Add diagonal support braces
  • Use corrugated cardboard with ridges perpendicular to stress
  • Reinforce joints with additional glue

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Performance Specifications

Typical performance for cardboard hydraulic arm:
MetricValue
Maximum reach~30-40 cm
Lift capacity50-100 grams
Degrees of freedom4 (base, lower, upper, gripper)
Control precision±5 degrees
Response timeImmediate (no lag)
Operating pressureLess than 5 psi (low pressure)
Document your arm’s specifications and create a technical drawing. This adds engineering rigor to your presentation!

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