The Bill of Rights Tour: safeguarding freedom's symbol.

Two hundred years ago, the Founding Fathers spelled out our basic American freedoms in a remarkable document called the Bill of Rights. These first 10 amendments to the U.S. Constitution were elegantly inscribed on sheepskin parchment by scribes wielding quills dipped in ink made from iron sulfate

and the galls of oak trees. The honeyed patina of age now coats the 12 remaining originals, whose words are as relevant today as when they were penned. All but one of those fragile originals are stored away in darkened climate-controlled security vaults, rarely seen except by hostorians and rare-document conservators. (The exception is the Congressional copy, which is on permanent exhibition at the National Archives in Washington, D.C.)

In 1989, curators and historians at the National Archives began planning an exhibit that would explain the heritage of liberty guaranteed by the Bill of Rights to Americans, many of whom know little about it, according to polls. Their intention was to celebrate the 1991 bicentennial of the adoption of the Bill. They decided that the best way to accomplish this goal in a dramatic and personal way was to take the Bill of Rights on the road to all 50 states--an odyssey of more than 40,000 miles. The Virginia State Library and Archives (Richmond) offered its recently restored copy of the Bill of Rights, while tobacco and processed-food giant Philip Morris Companies Inc. (New York) agreed to put up $60 million over three years to finance the project, which would include the exhibit, touring and promoion costs, the printing of three million copies of the document, and an educational program for schools.

Faced with the daunting demands of rare-document conservation, the difficulty of mounting a lengthy road show, and the then-looming threat of Persian Gulf-inspired terrorism, the project planners had to answer the question: How do you safely bring this living symbol of American freedom to the people? "Very, very carefully," said Bran Ferren, who leads the 50-person design and engineering firm commissioned to create the Bill of Rights exhibit. "After all, nobody wants to be responsible for losing the Bill of Rights."

Taking that charge to heart, the 15,000-square-foot Bill of Rights pavilion was developed over a seven-month period by Ferren's engineering and design firm, Associates & Ferren (Wainscott, N.Y.). The pavilion uses the state of the art in document-preservation systems; lightweight traveling exhibit structures; robotic motion and lighting controls; television, audio, and communications technology; and security systems to safeguard the document as it moves across the country.

The multimedia show took to the road in September 1990. To date, almost one million people have viewed the exhibit. It will complete its 16-month journey this December. It cruises around in a caravan that includes 10 tractor-trailer trucks, a bus, four vans, three Jeeps, a six-wheeled armored vehicle, and a contingent of 26 former Marine embassy guards and 35 other personnel.

Careful Planning

In creating the pavilion, Associates & Ferren drew on its experience as a leading producer of special effects and display technologies. The company has created special effects for movies such as Star Trek V: The Final Frontier and Little Shop of Horrors and for Broadway plays including Cats and Evita. Associates & Ferren also does research and development in robotics and advanced optical and imaging technology for clients including the ABC television network, the U.S. Navy, and NASA. The firm also consults for entertainment industry clients such as Walt Disney Imagineering.

Ferren described the initial design guidelines developed by the firm's project team: "First, expert document conservators impressed upon us that it was crucial that the parchment not 'know' that it's out of its protective vault, so our handling of the document had to be equal to the best archival treatment, even on the road," he said.

"Second, given the possibility of terrorist attacks, we had to make security a priority. Ironically, the closest paradigm we could come up with for transporting this valuable sensitive object was the shipment of nuclear weapons in the United States.

"Third, we realized that the exhibit apparatus, which would be rapidly erected and disassembled by stage hands as it traveled from venue to venue by road and air, should be as automated and bulletproof as possible. As we've found over the years, there are military specifications, NASA specifications, and then there are road specifications, which are much more stringent," Ferren said.

"Finally, we recognized that our audience would be the general populace of the United States, not the typical museum crowd, so the show had to be accessible to a wide range of attendees. And though high viewer-throughput was a goal, we wanted each person to find something personal to relate to as he or she walked through the exhibit, something that would bridge the 200-year gap between the signers of the Bill and people's experience today. The result, according to one newspaper account, is something of a cross between the Smithsonian and Disneyland."

That description suits the show's climax well: patriotic music swells as a recorded voice announces authoritatively, "The Bill of Rights of the United States of America." The circle of schoolchildren and adults assembled in the darkened hexagonal viewing room leans expectantly toward the wood-railed ballistic steel/aramid-armored viewing pod in the center. Lights activate on cue, gradually revealing the 200-year-old parchment and its historic words, which lie below a bulletproof high-optical-transmission acrylic window that blocks destructive ultraviolet and infrared radiation. The 28-inch by 34-inch document rotates slowly inside the pod, allowing everyone to see it as the dramatic music continues. After a minute, the lighting shifts to direct the crowd's attention to the exit ramp. Meanwhile, the Bill of Rights and its protective stainless-steel capsule drop silently out of sight into the now-darkened viewing pod. While the audience files out, the capsule and its precious cargo trundle on rails to an identical viewing room several yards away, where another circle of expectant visitors awaits its arrival.

Document Conservation

The 600-pound protective stainless-steel capsule was built to the specifications of the consulting conservators, Nathan Stolow and Donald Etherington. Designed to keep the delicate parchment in optimal condition, the capsule contains a purged nitrogen atmosphere to prevent oxidation. The document is mounted on "inert" (nonoutgassing) cloth with special hinged archival clips. A Macintosh IIfx computer inside the capsule monitors temperature, relative humidity, vibration, light level, and nitrogen pressure. The data are also transmitted every 13 minutes via satellite link to Washington, D.C. This allows experts from the Virginia State Library and other institutions to evaluate any emerging conditions that may damage the document.

A layer of silica-gel humectant inside the capsule and strict temperature control provided by the exhibit's 40-ton heating and cooling system maintain the correct environmental conditions. "It's crucial to the document's well-being that it be kept at 56 percent humidity (+ or -2 percent) and at a temperature of 68 degrees F (+ or -1 degrees F)," explained Louis Manarian, state archivist for the Commonwealth of Virginia. "If the humidity were to rise, the edges could curl as the skin goes taut, making the parchment look like it wants to get back on the animal." If the moisture level were to drop too low, the parchment could crack and ink could flake off, he said.

The amount of light permitted to strike the parchment's surface must be strictly limited to 5 foot-candles. This prevents the iron gall ink from fading. Ultraviolet and infrared exposure must also be prevented.

Vault on Wheels

Associates & Ferred produced a custom-built blast-resistant armored car they call the secure transit vehicle (STV) to protect the Bill of Rights as it travels across the country. Basically a bank vault on wheels, the STV looks like a scaled-down Brinks truck with an extra pair of wheels in the center.

"We would have gladly bought an armored car of some sort off the shelf," said Clint Hope, an engineer at Associates & Ferren, "but the wheelbases of standard security vehicles are too wide to fit inside a tractor trailer or a 40-foot shipping container, which is where the STV is placed to transport it from city to city. So starting with a stripped-down chassis, we built a vehicle that met our needs from the puncture-resistant run-flat tires up." The result is an 18,000-pound six-wheel-drive diesel-powered composite-armored car capable of speeds up to 90 miles per hour over rought terrain, which allows quick exit from any situation that might place the Bill of Rights in danger. The STV is equipped to act as the document's self-contained motherbase. It features its own ac power generator, cooling system, security installation, global positioning satellite navigation and communications apparatus, and Halon fire-extinguishing system.

The rear vault, where the document capsule is stored, is armored against blast, projectiles, and fire. "We got in touch with experts at the Naval Surface Warfare Center, Lawrence Livermore National Laboratory, and Los Alamos National Laboratory for advice on how they protect nuclear weapons in transit," Ferren said. "Though we can't talk about it in detail for security reasons, the armor scheme performed well on the firing range."

"Basically, the vehicle vault is lined with an effective but lightweight sandwich of double-hardened battleship steel, du Pont Kevlar aramid spalling armor, Allied-Signal Spectra compressed aramid blocks, and ballistic and refractory thermal ceramics able to withstand 2000 degrees F," Hope explained.

Automated Handling

The designers' intent that the document capsule remain untouched by human hands was satisfied by an automated tubular rail and 16-wheeled motion-control system similar to those used in amusement and theme parks. The tracked "sled" takes the capsule out of the vehicle vault (where its base serves as the integral rear door of the vault) to the display pods and back again. If a security problem arises, the sled automatically returns to the vault under its own power and closes itself within the STV.

"Motion control of the sled is a fairly complex task involving unlocking and exiting from the vault, driving out down the curving track, and locating itself within a few millimeters so it can position itself under the viewing pods. Then a servo hydraulic scissor lift raises the sled to the audience and a rotary table makes it revolve," Ferren said. "We used pulse width-modulated dc servos under digital logic control with optical encoder and position sensor feedback." Custom ride-control software written in the C programming language drives the computer's safety and error-monitoring tasks. "We don't want the document to raise up in the middle of the track or rotate to the wrong position so it can't go back down under the floor. Multiple levels of fault-tolerant interlocks resolve questions such as: 'Do I agree with the position sensor data?' and 'What do I do now?'"

The sled, which is propelled by a low-backlash harmonic drive servo motor connected to an autonomous uninterruptible power supply, is continually monitored by infrared television cameras as it moves beneath the exhibit's floorboards. Multiple reduntant communications systems, including modulated infrared signals and radio communications on the power rail, maintain constant contact.

Several obstacles had to be overcome in developing the sled/rail system, according to Phillip Cullum, Sr., welding and fabrication that runs from the STV to the pods was originally envisioned as having a simple flat 90-degree turn connecting sections of straight track. Then we discovered that there wasn't enough room in some of the venues to accommodate that arrangement, so we had to switch to a compound elevated curve, which entailed a tricky problem: how to drive up and around the corner with the traction-drive system we planned when precise encoder feedback control is needed?"

Traction drive, Cullum explained, is fine for the straight sections where low noise levels are required, but it cannot negotiate the elevated turn with sufficient precision. "We decided on a silent chain drive that automatically engaged when the sled reaches the curve," he said. "With its positive timing chain sprocket, it can't slip, so everything maintains its relative position, which keeps the encoders from going haywire."

Cullum noted that a high-durability synthetic rubber compound was used in the traction wheel for the friction drive so that wheel wear would not disrupt the position-encoding system. In addition, the sled's front axle is designed to flex to provide better control at onset of the turns.

The scissor lift, which would run every day all day long, posed its own concerns, Cullum said. Its cycling requirement of 300,000 to 400,000 raisings and lowerings over its lifetime was too much for the off-the-shelf device Associates & Ferren purchased. To meet the cycling specification, the lift was modified by removing the original bearings, boring out the seats, and installing needle bearings. Linear encoders were used for positioning. With a maximum traversing speed of 64 inches per minute, the original hydraulic-drive unit on the scissor lift was too slow to support the desired visitor throughput, so a special servoed hydraulic drive was built, which operates at twice the speed.

To bear the heavy load of the sled, the 12-inch rotary table that swings the Bill of Rights around for the audience to see was also beefed up with new bearings and a dc servo drive system with encoder feedback. Depending on the size of the audience, the rotation rate ranges from one to three revolutions per minute.

Pavilion Structure

At each venue, prior to the erection of the show structure, a computerized Zeiss master station theodolite (surveyor's instrument) is used to precisely locate some 50 or 60 points on the floor so the structural components can be positioned within 0.1 inch. The premeasurement allows the setup to proceed rapidly as several teams of stage hands can work simultaneously on different parts of the exhibit. First the technicians lay down the tracks and viewing pods, then they fit the understructure and raised flooring over those components. Finally, the teams erect the exhibition structures. Currently, the tour's staff can unload and set up the 15,000-square-foot show in from 8 to 10 hours and pack up in 2 1/2 hours, an important feat, given the tour's heavy schedule.

The entire exhibit, according to Ferren, was first constructed mathematically as a computer model using AutoCAD. Then a working scale model was produced in plastic, wood, and metal. Designers had to ensure that the pavilion structures were failureproof and would work both indoors and out. Another important design consideration was the strict adherence to the many code requirements--building, construction, electrical, and handicapped-access--the tour would encounter on the road.

Much of the exhibit's architecture is based on technology developed for rock and roll concert tours, which require lightweight durable structures that go up and down quickly, Ferren said. "We designed welded truss systems of 2.5-inch-diameter 6061-T6 aluminum tubing that link together with quick-engagement pin-release or bolt and cam-lock connectors." The structures are designed to be supported, because the venues could not be relied on to have strong overhead structures on which to hang things. Significant portions of the exhibit were constructed by FM Productions, California-based scenic design house.

Another concern was audience throughput, which gained greter emphasis when the projected numbers of attendees became larger than first estimated, Ferren said. To handle a maximum of 2000 people per hour, two document-viewing rooms capable of housing an audience of about 50 were included. The dual rooms allow crowds to be "pulsed" from an antechamber--one room fills as the other empties.

The hexagonal shape of the viewing rooms stemmed from the need to accommodate the audiences that ring the document pods, said Paul Jordan, vice president for engineering at Associates & Ferren. For each viewing room, six 25-foot-long truss members with curved ceiling segments on hinges fold over to connect to a central compression ring. Each room has a "chandelier," which contains overhead lighting, audio, and security equipment, that drops into a central hole in the roof.

The exposed trusses run up outside the walls of the viewing rooms, which are composed of 13.5-foot-span Plascore aerospace-type honeycomb aluminum panels with added soundproofing. These lightweight, durable, and strong wall panels clamp easily onto the truss system.

In the entrance area, where three high-resolution television projectors and screens play news clips such as Martin Luther King's famous "I Have A Dream" speech, a triangular truss structure was used, Jordan said. "The truss members in the entrance area support thousands of pounds of articulated lighting instruments, video projectors, screens, and audio equipment. It would be very time-consuming to put them up with ladders and scaffolds, so the trusses are fitted with motorized winching equipment and wheels," he said. "The instrumentation is fixed to the trusses on the ground, and chain hoists are used to lift each corner structure simultaneously. When everything is in place, they are cam-locked into position. Afterwards, the walls are filled in with quarter-inch-thick, extruded polyvinylchloride accordion scenery panels that hang from headers."

A cross-beam tube structure is used in the post-show area, where a collection of simple banner displays dedicated to each of the Bill's articles hangs from the cross beams, which stand near big "monolith" structures bearing large-scale backlit photo reproductions (including color, ultraviolet, and computer-enhanced images) of the parchment. Television monitors on freestanding supports show film clips from old movies that explore the rights of Americans, including His Girl Friday, Mr. Smith Goes to Washington, Born Yesterday, Talk of the Town, Fury, Twelve Angry Men, and Gentlemen's Agreement. If the visitors wish, they may record their personal impressions of the Bill of Rights in a video message booth that produces a living record of the tour. Selected statements made by past visitors run continuously on nearby monitors. Before leaving, visitors can also pick up facsimiles of the Bill as souvenirs.

Ferren stressed that all the information presented to the audiences was selected by museum curators and specialists on American history, who acted as advisors to the project.

Distributed Control

The pavilion is crammed with computers, lights, security, and audio-visual equipment. A heavily distributed control system with separate Fluke Instruments' touch-screen terminals is responsible for motion and lighting control, audio-visual scheduling and queueing, and security monitoring. It is linked by local area network to an 80386-based PC that serves as a master control computer. "One reasons we used distributed control technology is so that many programmers can work simultaneously on different parts of the system," Ferren said. "In addition, you never run out of processing, because all you need do is add more."

One of the shipping containers that travels with the show is lined with five equipment racks of Texas Microsystems rack-mountable PCs that control the show, said Eric Rosenthal, audio-visual engineer for the project, who is based in Freehold, N.J.

The master computer, which runs proprietary software, controls the robotics, motion control of the sled, and the overall coordination of everything in the show, Rosenthal said. The control system, which was developed by Associates & Ferren, is similar to that used at a theme park or for TV studio automation.

The audio-visual computer controls a lighting system, audio amplifiers, and eight Pioneer 4200 high-definition lase disk players. The computer's custom software allows an untrained person to control the complex system with little technical support, Rosenthal said. Its interactive-script module provides the operator with a time line divided into seconds, which is used to fine-tune the show. Depending on the conditions at a particular venue, commands can be entered that change the show routines. If a large crowd shows up one day, for example, shorter film clips could be queued on the laser disk players so that people can move through the exhibition faster.

Ferren said that the audio-visual system has 250 lighting control channels for the articulated lighting equipment. The pavilions's extensive audio system, which features 100 speaker channels, sophisticate equalization and level controls, and nine audio zones, was provided by suppliers including JBL Bose, the Grass Valley Group, Electro-Voice, and Krell. Three Barco 1500 high-definition television projectors are used in the preshow area. The message kiosk's automated taping system was provided by Digital Ovations.

Security is pervasive around the pavilion, Ferren said. Though vague about the details, he noted that the security and safety system includes intensified-color surveillance cameras, digitally encrypted communications units for the show managers and guards, and microwave and laser perimeter fences for overnight parking, as well as a minibackup generator, a 20-kilowatt uninterruptible power system, and a sophisticated power management system.

"Throughout its four, the Bill of Rights exhibit has been a magnet for protesters," Ferren noted. "But being a show about freedom and liberty, we thought it appropriate to provide all attendees with a soapbox from which to speak. Ironically, the soapbox may be the strongest symbol of freedom in the show."