Pyramidal Balance

AEROLAB supplies Pyramidal Force/Moment Balance to meet all needs.

During the early years of wind tunnel testing, Forces and Moments were literally measured through pan-type “balances.” Although technology has advanced dramatically since those early days, the term “balance” is still applied to the devices used for Force and Moment measurements today.

Balances can be divided into two main groups: internal and external. The group names are derived from their location relative to the test model and wind tunnel test section – internal balances reside inside a test model, while external balances reside outside the test section.

AEROLAB external balances are of the “pyramidal” type. The name is derived from the architecture of the supporting members. Although the four supporting members do not actually converge to form the “peak” of a pyramid, Forces and Moments are measured about their projected convergence – known as the “resolving center” of the balance.

AEROLAB offers pyramidal balances with either three or six measured “components.” Three-component balances provide Lift, Drag and Pitching Moment information while six-component balances also provide Side Force, Rolling Moment and Yawing Moment.

AEROLAB Pyramidal Balances are available in three sizes: small, medium and large. Size selection is based on test section size and application.

Performance Specifications

Small Pyramidal Balance

• Approximate resolving center height – 12 inches (30.48cm)
• Minimum required height below test section – approximately 13 inches (33.02cm)

Medium Pyramidal Balance

• Approximate resolving center height – 16 inches (40.64cm)
• Minimum required height below test section – approximately 46 inches (116.84cm)

Large Pyramidal Balance

• Approximate resolving center height – 40 inches (101.6cm)
• Minimum required height below test section – approximately 40 inches (101.6cm)

Load Limits

Detailed Description

AEROLAB offers individually handcrafted pyramidal balances in three sizes: small, medium and large. Size selection is based on test section size, expected aerodynamic loads and application.

Pyramidal Force/Moment balances employ a series of beams, flexures and turnbuckles to separate Forces and Moments. As such, Forces and Moments are read directly as Lift, Drag, Side Force, Pitching Moment, Yawing Moment and Rolling Moment. In contrast, internal balances require output data to be reduced to these basic values.

Aerodynamic loads experienced by a test model are transferred to the balance “spider” subassembly. Forces are then transferred to the balance “cradle” via machined rods and flexures. Moments are measured directly from the spider while Forces are measured directly from the cradle. AEROLAB installs high-accuracy load cells to measure spider and cradle output.

Hand-cranked pitch/yaw control is standard; however, high-accuracy stepper motors are available as an option.

AEROLAB Pyramidal Force/Moment Balances are made from anodized 6061 aluminum, high-quality carbon steel and stainless steel. Stainless steel fasteners are used throughout.

Pyramidal Balances are supplied with calibration fixtures and a first-order calibration matrix.

Optional Features

• Data Acquisition and Control (DAC) System
• High-accuracy stepper motor drives for pitch and/or yaw
• Motor-driven fairing table

Related Products

• Open Circuit Wind Tunnel
• Closed Circuit Wind Tunnel
• Traverse System
• Test Models and Probes