11 62 18 WIND CHIMES - February 2020 version.pdf

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WIND CHIME ASSEMBLIES

SECTION 11 62 18 - WIND CHIME ASSEMBLIES

PART 1 - GENERAL

1.1 SUMMARY

A. Section Includes:

1. Design verification and Fabrication of custom wind chimes and anchorage assemblies

2. Prototype and Production testing of wind chime assemblies

3. Installation of wind chime assemblies

4. Tuning of wind chimes (by others)

5. Commission of chime assemblies

B. Related Requirements:

1. Section 05 05 16 “Powder Coatings” for coating on aluminum surfaces.

2. Section 05 70 00 "Decorative Metal" for stainless steel fasteners.

1.2 DESCRIPTION OF WORK

A. Fabrication and Delivery of forty wind-activated chime assemblies plus three spare assemblies:

Assembly components and configurations shall be generally as described in these procurement documents but may vary subject to approval by the Contracting Officer. Chime assemblies will be installed at the Tower of Voices at Flight 93 National Memorial by others upon delivery by the Fabrication Contractor.

B. Fabricator’s design assist input to the Government’s design consultants in order that they can prepare final engineering designs for the forty wind-activated chime assemblies and spare materials. Fabrication input is required to identify options for component selection, provide input on component and material availability, to request modification to details to facilitate successful fabrication and installation, and to provide feedback from Fabricator’s testing to inform the final design.

C. Prototype demonstration of chime assemblies

1. The Fabricator shall produce one demonstration chime assembly based on the prototype design. The assembly shall meet the requirements of this Specification given in Section

1.5.

2. The Fabricator shall demonstrate the selected damper material options for each of the chime notes in the tuning table. The Contracting Officer will make a final decision about damper materials.

3. The prototype demonstration may be held at the Fabricator’s facility or an alternative location. The Contracting Officer will review the proposed site and confirm suitability of natural wind environment or artificial means of chime activation.

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1.3 REFERENCES

A. Governing Building Code: 2015 International Building Code (IBC)

B. ASCE 7-10

C. Attachments in section 4.0 of the scope of work document

1.4 DEFINITIONS

A. Acoustic Terminology:

1. Sound Pressure Level

a. A measure of the level of energy emitted by a sound source. Sound pressure level is reported in decibels (dB) on a logarithmic scale Pitch

b. The subjective perception of the frequency of vibration of a given sound source.

This perception is affected by the ratio of the fundamental tone and overtones. For example, although a C3 chime has a fundamental frequency of 131 Hz, higher frequency overtones are present in the spectrum, which can cause the C3 chime to be perceived as an F4.

2. Fundamental tone and overtones

a. The fundamental tone is the lowest frequency tone produced by the first mode of vibration of the chime. In this context, the fundamental tone is the desired perceived pitch.

b. Overtones are a result of higher modes of vibration, and thus have a higher perceived pitch than the fundamental tone for a given chime. In this context, the overtones are undesirable and should be damped so that the fundamental is the dominant tone.

3. Timbre

a. The perceived sound quality of a given musical tone. The timbre is defined by the relative strength of frequency components in the spectrum as well as the temporal envelope associated with each frequency component.

b. No metric has been established for this project for describing timbre, so it is assessed subjectively.

4. Sound quality

a. Subjective perception of the timbre as well as the strike pattern over time for a given chime.

b. The subjective perception of the sound output from multiple chimes in the tower.

B. Chime assembly:

1. Chime: An open tube suspended to generate a tone when struck.

a. Dimensions: Chime dimensions include length, outside diameter, and wall thickness, as a general rule, longer chimes create lower pitch fundamental tones and shorter chimes create higher pitch fundamental tones.

b. Material: Mechanically extruded 6063 aluminum alloy shall be used in the fabricated chime assemblies.

c. Chime striking points: Prototype designs used in mock up tests have relied upon a striking point at the bottom end of a chime.

d. Chime nodes: The part of a chime with least vibration located at 22.2 percent of the chime length from either end. Components can be attached to the chime at its nodes with minimal impairment of sound quality.

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e. Chime suspension: Chimes shall be suspended from above at the upper chime nodes.

2. Striker: An object with mass that strikes the chime to generate sound.

a. Striker mass: In this context the striker mass is a 3-inch (75mm) diameter stainless steel circular bar hung vertically inside the chime. The striker is aligned with a chime striking point, in this case the bottom edge of the chime [1.4B1.c].

b. Damping: A material applied to the striker mass over the area of strike contact to improve sound quality. Damping reduces the sound level of the overtones allowing the fundamental tone greater prominence. With too much damping the sound level of the fundamental can be undesirably reduced. Damping materials can be approximately described by their stiffness and thickness.

1) It was observed through concept testing that for higher pitched chimes smaller strikers and less damping can achieve a clean fundamental tone.

Conversely lower pitched chimes require larger strikers and more damping.

c. It was observed through concept testing that lower mass strikers required less damping to obtain a clean fundamental tone.

3. Sail: A wind-activated object that moves the striker.

a. Wind interacts with the sail generating a swinging motion, spinning, or both.

b. The sail is hung from the striker such that motion of the sail generates motion of the striker causing it to strike the chime.

c. Range of motion. Motion of the sail is traditionally considered to be dominated by swinging. At the top of its swing the sail partially rotates, reducing its wind resistance, and allowing it to slice back. During testing for this project it was observed that spinning of the sail can also generate significant striker motion.

Since space constraints are tight in the tower spinning is the preferred type of motion.

d. Surface area and mass: Greater sail surface area creates more wind resistance and leads to a more active sail. The mass of the sail helps to drive the striker.

However excessive mass is likely to reduce the responsiveness to wind.

4. Suspension rods and cables: A means of hanging chime assembly components to allow wind-activated movement. In this arrangement there are four suspension rods and cables:

from the upper corbel to the chime’s top node; from the top node to the striker; from the striker to the sail; and from the sail to the lower corbel. This last cable does not in fact suspend anything but rather it restricts the swinging of the sail to prevent impact with the tower or the other chime assemblies. It is referred to as the ‘tether’.

5. Chime sound: The audible result of the chime vibrating. Chime sounds typically involve three general parts: An initial strike of less than a second. Overtones and harmonics that fade rapidly. A fundamental tone that sustains for several seconds to a half-minute or even longer depending on the chime frequency.

a. Sustain: The duration of chime vibration and sound. Lower fundamental tones sustain longer and higher fundamental tones have less sustain.

b. Tuning (by others): Tuning is the means by which the chime dimension is adjusted to establish a specific frequency and the metered means of verifying the pitch of a chime sound. For chime tuning, a 50 percent chime length reduction generates the same note two octaves higher. One octave higher is obtained from a length reduced to 70.7 percent of the reference length.

c. Tuning range: A range of chime dimensions and materials that best creates good fundamental sound frequencies of usually about two octaves. Long low frequencies begin to have dominant overtones. Short high frequencies begin to clank without resonating.

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1.5 PERFORMANCE REQUIREMENTS:

A. Loads: Structural Design loads shall include most stringent of the following:

1. As required by the 2015 International Building Code and standards referenced therein.

2. Wind loads as required by ASCE 7-10.

3. Chime assemblies must withstand a minimum of 4,730 pounds tensile load (ultimate load) for all materials along the load path from the upper suspension connection down to the bottom attachment.

4. Thermal loading considering the ambient conditions and exposure of the chimes at the site

5. Ice build-up considering the ambient conditions and exposure of the chimes at the site.

6. A 250lb person hanging from a chime or a sail whether accidental or deliberate.

7. Consideration of fatigue over the expected life of the chimes shall be included in any assessment of stresses induced in components of the chimes.

B. Functional limits:

1. It is acknowledged that chimes may not be fully functional during conditions such as ice build-up or in strong winds.

C. Tone and sound quality. The intended fundamental frequency of the respective chime note shall audibly dominate the frequency spectrum. The Contracting officer shall confirm whether timbre produced during prototype and site mockups by the fabricator is acceptable

1.6 QUALITY ASSURANCE

A. Refer to the requirements outlined in 2.3.3 QUALITY CONTROL in the scope of work.

B. PRE INSTALLATION CONFERENCE:

1. Participate in a Pre-Installation conference call.

2. Review methods and procedures related to chime assembly installation including, but not limited to, the following:

a. Proposed sources of chime assembly components.

b. Mockup procedures.

c. Requirements for installation of chime assemblies.

d. Requirements for protecting precast concrete work.

e. Requirements for final adjusting of chime assemblies.

1.7 ACTION SUBMITTALS

A. Product Data: For each type of product used.

1. Include technical data and tested physical and performance properties.

B. Maintenance plan: Develop and submit for review and comment an operation and maintenance manual

C. Shop Drawings: Provide updated shop drawings in accordance with the final design prepared by the designer of record, for each wind chime assembly component and entire assembly.

1. Include plans, elevations, sections, details, and attachments to other work.

2. Detail fabrication, mockup and installation of wind chimes.

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D. Mockups:

1. Production mockup demonstration: Assemble one prototype assembly in accordance with the prototype design and any modifications coordinated prior to a demonstration.

The demonstration shall confirm the fabrication contractor’s understanding of the prototype design as well as provide the means for the fabrication contractor to identify any improvements and/or modifications recommended for the final fabrication assemblies.

1.8 MAINTENANCE

A. Chimes: Fabricator shall provide one additional copy of 3 correctly finished chimes at lengths of approximately 5 feet, 7 feet and 10 feet, matching those installed, packaged with protective covering in boxes with appropriate identification labels.

B. Chime assembly components: Fabricator shall provide 2 additional copy of all chime components, matching those installed for each of the chimes above, packaged with protective covering in boxes with appropriate identification labels.

C. Chime assembly hardware: Fabricator shall provide 5 additional sets of all chime hardware, matching those installed for each of the chimes above, packaged with protective covering in boxes with appropriate identification labels.

PART 2 - PRODUCTS

2.1 MATERIALS

A. General: Refer to Reference Drawings. Use durable materials that have performed satisfactorily in exterior installations. Final sizes, shapes and weights shall be as verified by the fabricator taking into account building code requirements, design life, durability, local environmental conditions. Representative components are indicated in the prototype drawings and below.

Deviations shall be submitted to the Contracting Officer with substantiating results from prototype testing for approval prior to proceeding with production fabrication.

B. Wind Chimes: 8 inch outside diameter seamless 6063 aluminum alloy tubes with 1/2 inch thick walls and eased edges with 1/8” chamfers.

1. Cut for tuned pitches as required in the Tuning Table.

2. Drilled at 2/9 (0.225) length (from top of chime) for suspension rods/cables.

C. Strikers: No. 316 Stainless steel with No. 4 finish.

1. Machined to shape as indicated in the design files for focused strike contact with chime.

2. Machined for provision of connection to suspension element.

3. Machined for 360-degree swivel motion connection with sail.

4. Mass for each striker must be correlated to chime length.

D. Sails: Aluminum plate cut and shaped as indicated in the design documents.

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1. Connection at top of sail to striker/rotator.

2. Connection at bottom to tether.

E. Suspension rods: Stainless steel rod or hollow tube as indicated in the design documents, No. 4 finish.

F. Fasteners: Stainless steel or as noted otherwise in the design documents, No. 4 finish.

G. Damping: Basis of final prototype design is polyurethane material attached to striker.

Durometers of material should correlate to chime assembly size to optimize sound quality.

Material shall be capable of durable operation in exterior environment.

H. Tethers: Industrial rope with connections points at both ends.

I. Mounting assembly: Stainless steel, No. 4 finish as indicated in the design documents.

1. Anchorage through precast concrete corbel as indicated in the design documents.

2. Connection for suspension element to chime assembly.

2.2 FABRICATION

A. Metal Surfaces: For metal surfaces exposed to view in the completed work, provide materials with smooth, flat surfaces without blemishes. Do not use materials with exposed pitting, seam marks, roller marks, rolled trade names or roughness.

B. Chime assembly: Fabricated within the following tolerances:

1. Chime lengths: As necessary to provide the frequencies specified in the tuning table.

2. Drilled holes: Centerline plus or minus 1/16 inch from 2/9 length from top edge.

3. Strikers: Maximum allowable variance from final design template is 1/16 inch.

4. Sails: Maximum allowable variance from final design template is 1/16 inch.

2.3 TUNING

A. Initial Chime Tuning (by others): Modify aluminum tubes to create tuned wind chimes.

1. Cut aluminum tubes to lengths required for specific pitches as defined in the Tuning

Table. The frequencies specified by the Tuning Table are related by the prescribed ratios therein, so that the chimes shall be tuned in just intonation, not equal temperament. The frequency in Hertz specified for each chime should be the primary reference.

2. Verify final tuning of tubes with architectural finish applied and drilled mounting holes.

Coordinate tuning with the Contracting Officer so that representatives of the Government may participate in the tuning activities.

B. Chime Production Testing (by Fabrication Contractor): Before shipping from Fabricator’s production facility, verify final tuning of each chime with architectural finish applied and each chime fully assembled and suspended using proposed suspension components. Coordinate tuning with the Contracting Officer so that representatives of the Government may participate in the tuning activities.

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C. Provide sound recordings and/or metered tuned pitch results to the Contracting Officer for acceptance.

D. Chime Field Assembly: Fabricator shall ship chime assemblies to the site in such a sufficiently complete state that on site assembly and installation steps by the construction contractor are minimized.

1. Tuning may be verified after delivery by representatives of the Government to confirm that assembled components have not distorted chime tuning from required pitches during shipping or installation.

2.4 FINISHES

A. Comply with NAAMM’s “Metal Finishes Manual for Architectural and Metal Products” for recommendations for applying and designated finishes.

1. Aluminum: Powder coated per Section 05 05 16. Government furnished materials includes twenty-seven chime tubes complete with powder coating. As many as sixteen chime tubes furnished by the Government will require powder coating by the Fabrication

Contractor prior to assembly and delivery to Flight 93 National Memorial.

2. Stainless steel: NAAMM No. 4, linear textured finish with an average roughness up to

25 micro-inches.

B. Protect mechanical finishes on exposed surfaces from damage by applying a strippable, temporary protective covering before shipping.

C. Appearance of Finished Work: Noticeable variations in same piece are not acceptable.

Variations in appearance of adjoining components are acceptable if they are within the range of approved Samples and are assembled or installed to minimize contrast.

PART 3 - EXECUTION

3.1 EXAMINATION

A. Examine substrates for compliance with requirements for installation tolerances and other conditions affecting performance of the Work.

B. Proceed with installation only after unsatisfactory conditions have been corrected.

3.2 DELIVERY, STORAGE AND HANDLING

A. Special care shall be taken during delivery storage and handling to minimize damage to chime components and the subsequent need for repairs. Chime components shall be packaged in such a way as to be protected from damage and deterioration. Use special care in handling chime components to prevent twisting, warping, or impact damage.

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3.3 INSTALLATION

A. Installation of chimes shall be by others. Chime Fabrication Contractor will provide support to the Government’s installation contractor during installation. Support may require travel to

Flight 93 National Memorial.

3.4 COMMISSIONING

A. Fabricator shall adjust assembly and confirm tolerances required herein.

B. Fabricator shall support adjustment of wind chime assemblies after installation.

C. Damping: Adjust thickness and/or durometer of damping material to achieve required sound level range and sound quality

END OF SECTION 11 62 18