Equilibrium of Parallel Forces Apparatus | FrixoDynamics FX-525

The SCIENTICO FrixoDynamics FX-525 Equilibrium of Parallel Forces Apparatus is a frame-mounted statics unit for the experimental verification of parallel coplanar force equilibrium conditions — ΣFv = 0 and ΣM = 0 — using two acrylic truss models and a 12-point Perspex circular disc. Warren and N-truss acrylic models, each counterbalanced to eliminate self-weight, accept vertical loads and reactions applied through nylon cords, hanging weights, and double pulleys. Force lines are recorded on A1 paper clipped to the force board for graphical link polygon construction and moment equilibrium verification. The circular disc provides 12 attachment points for couple equilibrium experiments across a range of couple arm positions. A comprehensive weight set — 10 pieces each of 5 N, 2 N, 1 N, and 0.5 N — supports a wide range of loading configurations. Suitable for undergraduate statics, structural mechanics, and applied mechanics laboratories, the FX-525 is supplied complete with all models, weights, rings, thread, and instructional manual. Manufactured by SCIENTICO, available for institutional supply and international distribution.

The SCIENTICO FrixoDynamics FX-525 Equilibrium of Parallel Forces Apparatus is a frame-mounted experimental unit for the verification of equilibrium conditions for sets of parallel coplanar forces acting on a rigid body. Using two acrylic models shaped to simulate Warren and N-type truss structures, and a 12-point circular Perspex disc for couple experiments, students investigate the conditions for vertical force equilibrium, moment equilibrium, and the equilibrium of opposing couples. Force lines are recorded graphically on paper clipped to the force board, enabling direct verification of the link polygon and the conditions ΣFv = 0 and ΣM = 0. Manufactured by SCIENTICO, the FX-525 is suitable for supply to engineering institutions and distributors worldwide.

Product Overview
 

The equilibrium of parallel forces is a foundational topic in statics and structural mechanics. For a rigid body acted upon by a set of parallel coplanar forces to be in equilibrium, two independent conditions must be satisfied simultaneously: the algebraic sum of all vertical forces must equal zero (ΣFv = 0), and the algebraic sum of all moments about any point must equal zero (ΣM = 0). A special case arises when two equal, opposite, and non-collinear parallel forces act on a body, forming a couple — a pure moment with no net resultant force. The equilibrium of opposing couples requires that their moments are equal and opposite.

The FX-525 provides a direct, physically observable and graphically verifiable demonstration of all these conditions. The apparatus is mounted in a Universal Frame and Stand, with a force board as the working surface. Two acrylic models are provided — one shaped and engraved to simulate a Warren truss geometry, and one shaped to simulate an N-type truss. Each model has counterbalancing weights that render the model effectively weightless in the experimental setup, ensuring that only the deliberately applied loads and reactions influence the force system under investigation.

Forces are applied to the acrylic models using nylon cords tensioned by calibrated dead weights on hangers. Double pulleys redirect the cord directions as required, turning upward reaction forces downward so that all forces in the system are applied via hanging weights. The lines of action of all cords are transferred onto a sheet of A1 paper clipped to the force board, providing a permanent graphical record of the force geometry for each experiment. Students then apply the link polygon method to verify ΣM = 0 graphically, and check the algebraic sum of the recorded vertical forces to verify ΣFv = 0.

The circular Perspex disc, fitted with twelve equally spaced peripheral attachment points, is used for the couple equilibrium experiments. Opposing couples are applied at selected attachment points using cords and weights, and students verify that equilibrium requires the two couple moments to be equal and opposite — regardless of the position of the couple arms. The twelve attachment points allow a wide range of couple arm geometries to be tested within a single experiment session.

Parameter Specification
Model FrixoDynamics FX-525
Mounting Universal Frame and Stand
Truss Models 2 acrylic models — Warren truss, N-truss (engraved)
Circular Disc Perspex, 12 peripheral attachment points
Counterbalancing Each acrylic model fitted with counterbalancing weight
Force Application Nylon cords, dead weights on hangers, double pulleys
Force Recording Cord lines transferred to A1 paper on force board
Weight Set 5 x 0.5 N hangers, 10 x 5 N, 10 x 2 N, 10 x 1 N, 10 x 0.5 N
Rings 2
A1 Paper Not supplied
Scope of Delivery 1 experimental unit, 5 sets of weights, 2 rings, 1 thread, 1 instructional manual

Key Features

  • Two acrylic truss models — Warren and N-type — engraved with structural geometry for realistic parallel force loading scenarios
  • Each acrylic model counterbalanced to render it effectively weightless, isolating the deliberately applied forces as the sole variables in the experiment
  • Circular Perspex disc with 12 peripheral attachment points for systematic couple equilibrium experiments across a range of couple arm positions
  • Double pulleys redirect cord directions, allowing both downward loads and upward reactions to be applied using hanging weights throughout
  • Force lines transferable directly onto A1 paper clipped to the force board for permanent graphical record and link polygon construction
  • Large, comprehensive weight set — 10 pieces each of 5 N, 2 N, 1 N, and 0.5 N — supports a wide range of load combinations across all experiment configurations
  • Supports graphical verification of link polygon (ΣM = 0) and algebraic verification of vertical force equilibrium (ΣFv = 0)
  • All assembly and operational tools provided with the unit

Applications

  • Experimental verification of the conditions ΣFv = 0 and ΣM = 0 for sets of parallel coplanar forces on a rigid body
  • Investigation of the special case of a couple — equal, opposite, and non-collinear parallel forces acting on a body
  • Verification of the equilibrium of opposing couples using the 12-point circular Perspex disc
  • Graphical verification of the link polygon for parallel force systems
  • Application of parallel force equilibrium principles to Warren truss and N-truss structural geometries
  • Study of the relationship between applied loads, reactions, and moment equilibrium in simply supported structural models
  • Undergraduate laboratory practicals in statics, structural mechanics, applied mechanics, and civil and mechanical engineering

Construction and System Design

The FX-525 is mounted in a Universal Frame and Stand that holds the force board in a fixed upright position. The force board provides a flat, stable surface to which A1 paper is clipped for recording cord lines during experiments. The two acrylic models are attached to the force board in turn, with the counterbalancing weights ensuring that each model contributes no net force or moment to the system beyond those intentionally applied through the cords.

Nylon cords are attached to the model’s load and reaction points and routed over double pulleys fixed to the frame. The pulleys redirect the cord directions as needed, ensuring that all forces — including upward support reactions — are generated by hanging dead weights rather than by spring or mechanical loading mechanisms. This approach maintains the simplicity and accuracy of the force application, and ensures that every force in the system is precisely known from the hanging weight value.

The circular Perspex disc is fixed to the force board at its centre for the couple experiments. Twelve equally spaced attachment points around the perimeter allow cords to be attached at any combination of positions. Opposing couples are formed by applying equal and opposite forces at symmetrically selected points, and the equilibrium condition is verified by confirming that the net moment about the disc centre is zero. The two rings provided are used for cord attachment at the model’s node points and disc periphery attachment positions.

The comprehensive weight set — with 10 pieces each of 5 N, 2 N, 1 N, and 0.5 N across five hangers — provides sufficient range and resolution to construct multiple distinct load configurations on the same model within a single session, supporting both introductory parallel force experiments and more complex multi-load moment verification exercises.

Export and Supply Capability

The SCIENTICO FrixoDynamics FX-525 is available for supply to engineering colleges, technical universities, civil and mechanical engineering departments, research institutions, and industrial training centres. SCIENTICO manufactures and exports laboratory equipment to institutions and distributors across multiple regions. Standard packaging is suitable for international shipment. Bulk orders, customised configurations, and institutional procurement enquiries are welcomed. Please contact SCIENTICO directly for pricing, lead times, and shipping terms.

Q1: What is the equilibrium of parallel forces apparatus used for?

The FX-525 is used to verify the conditions for equilibrium of parallel coplanar forces acting on a rigid body — specifically that the algebraic sum of all vertical forces equals zero (ΣFv = 0) and the algebraic sum of all moments about any point equals zero (ΣM = 0). Students apply controlled loads and reactions to acrylic truss models using cords and hanging weights, record the force lines on paper, and verify equilibrium using both algebraic calculation and graphical link polygon construction.

Q2: What is a couple, and how does the FX-525 demonstrate couple equilibrium?

A couple consists of two equal, opposite, and non-collinear parallel forces acting on a body. The net force of a couple is zero, but the net moment is non-zero and equal to the product of one force and the perpendicular distance between the two force lines. The FX-525 demonstrates couple equilibrium using the 12-point Perspex disc, where opposing couples are applied at different peripheral attachment points. Equilibrium requires the two couple moments to be equal and opposite, verified by confirming ΣM = 0 about the disc centre.

Q3: Why are the acrylic truss models counterbalanced?

The counterbalancing weights render each acrylic model effectively weightless in the experimental setup. Without counterbalancing, the model’s own weight would act as an additional downward force in the system, complicating the force balance and introducing an uncontrolled variable. By neutralising the model’s self-weight, the counterbalancing ensures that only the deliberately applied cord loads and reactions contribute to the force system, making the experimental conditions consistent with the theoretical parallel force equilibrium problem.

Q4: What is the link polygon method, and how is it verified using the FX-525?

The link polygon is a graphical method for verifying moment equilibrium in a parallel force system. It involves constructing a force polygon from the known vertical forces and then drawing a series of rays from a chosen pole point, generating link lines that form a closed polygon when the system is in moment equilibrium. The FX-525 supports link polygon construction by allowing students to transfer cord lines onto A1 paper on the force board, providing an accurate graphical record of the force positions and magnitudes from which the polygon is constructed and closure verified.

Q5: What is included in the scope of delivery for the FX-525?

The FX-525 is supplied as a complete experimental kit including: one parallel forces experimental unit with Universal Frame and Stand, force board, two counterbalanced acrylic truss models (Warren and N-type), Perspex circular disc with 12 attachment points, double pulleys, and nylon cords; five sets of calibrated weights (5 x 0.5 N hangers, 10 x 5 N, 10 x 2 N, 10 x 1 N, 10 x 0.5 N); two rings; one thread; and one comprehensive instructional manual covering assembly, experimental procedures, example results, and graphical verification methods. A1 paper for the force board is not supplied.

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