January 19, 1998 Design News
Raise the Titanic!
Titanic's scale models weren't just for show. Despite their enormous size, engineers had to move them up and down as much as 34 feet
Charles J. Murray, Senior Regional Editor
ROSARITO BEACH, MEXICO--The steel for the Titanic set began arriving on trucks late in 1995. One by one, an endless parade of flatbeds pulled into this oceanside town, dumping loads of wide-flange beams, steel plates, angle iron, and countless bolts for the throngs of construction workers that followed. In all, there was enough steel to fill the downtown of a medium-sized city. Assembled, it would yield three massive structures, the biggest of which was about the size of a 77-story building tipped on its side. Ultimately, that set alone would weigh more than two million pounds.
That, however, was not the most remarkable aspect of Titanic. The most amazing part was that when the last bolt had been locked down and the final board was nailed in place, the film's director looked at the massive scale model and said: Now move it.
Move it: Most engineers have never imagined using those words in reference to two million pounds. But that was what Titanic director James Cameron wanted, and it was what the movie's special effects coordinator, Tom Fisher of T.R.I.X. Unlimited, planned to do. After considering several options, including the use of barges to hold up the loads, Fisher called engineers at Mayo Hydraulics, Bakersfield, CA and Parker Hannifin's Motion and Control Group in Irvine, CA. "When I first called and told them I wanted to move more than a million pounds, they thought I'd gone crazy," Fisher recalls. "But they studied it, called me back, and said: 'You can do it if you can pay the price.'"
Indeed, Paramount Pictures and Fox Filmed Entertainment, co-makers of the film, will pay the price for a long time to come. Already, Titanic is regarded as the most costly film ever made, having come in at about $200 million. But from the outset, Cameron was determined to spare no expense when it came to technical realism. That was why he built three massive sets in huge, man-made, concrete-lined "lakes" for the movie's shooting. It was also why he rented a submersible to dive down to the real Titanic wreck and photograph it. And it was why he demanded that the set designs--from the style of the carpeting to the patterns on the wood moldings--faithfully re-create the original.
Given those demands, giant scale models were the only viable option. Unlike most sea-based films, which make heavy use of models measuring a mere 10 or 15 feet long, Titanic would come as close as possible to the real article. Engineers on the project ultimately built a scale model measuring 775 feet long--about 90% of the size of the original. "In terms of sheer size, no single movie set has ever compared to this," Fisher states. "And no one has ever moved a piece this big for a movie."
Record-setting lift. The 775 ft-long structure, however, was not the only scale model at the Rosarito site. It was joined by two others: a 200 ft-long interior set; and a 100 ft-long, hinged poop deck set, which had to be tilted from 6 degrees to 90 degrees.
Because Cameron intended to re-enact the sinking of the legendary ocean liner, all sets needed to be capable of movement. The concrete-lined tanks, or "lakes," in which the structures were built, were up to 40 feet deep, and the models needed to travel from the water's surface to near-bottom.
To begin, crews built the steel structures at the tank bottoms, before seawater was added. The first of the models, the indoor set, measured 200 feet long by 120 feet wide. Built within the confines of an enclosed building, it housed such indoor sets as the Titanic grand ballroom, dining room, and the grand entranceway. "From the outside, it looked like an unfinished house," notes John Rothas of Mayo Hydraulics, a member of the technical team.
Ultimately, the indoor set would be used for the movie's sinking sequences, which meant that the structure would have to be tilted, then lowered into the water. Some scenes would be filmed by dumping large quantities of water onto the set; for example, special effects experts used trailers filled with water to simulate the scene where water bursts onto the grand entranceway. By tilting the trailers backward and equipping their doors with explosive charges, they created a sudden rush of water through the entranceway's skylight and down its grand staircase.
But for most of the key sinking sequences, the special effects team needed to slowly immerse the sets in seawater. "To achieve the shots we needed, we had to sink the set," explains Fisher. "You can't make an 8 million-gallon dump tank."
Moving the set at a prescribed speed and tilt angle, however, took extraordinary power and control. "We talked about putting the set on barges, then sinking it," Fisher says. "But we wouldn't have had enough. In terms of cost and practicality, the only solution was hydraulics. To raise and lower it 15 times a night, there was no other way."
Hydraulics the key. To move the 1.4 million-lb indoor set, engineers employed a combination of power media, including: a diesel generator set; electric motors; and a mechanical pulley system; as well as hydraulic pumps, reservoirs, valves, and cylinders. The diesel generator, a 2,500-hp unit made by Caterpillar, was necessary because of the lack of electrical power available from the local grid. Thousand gallon-capacity reservoirs for the huge hydraulic system were built on site by engineers from Mayo Hydraulics.
To prevent damage to the steel structure, engineers John Rothas and Mark Force from Mayo Hydraulics and Greg Paddock from Parker Hannifin Corporation selected eight attachment points (instead of four, as they might otherwise have done), and divided the power media into two equal systems. Each system consisted of four 200-hp electric motors made by Lincoln Electric, Cleveland, OH, which powered eight Parker Hannifin PAVC100 axial piston pumps. The eight 100-cc piston pumps, operating at 3,200 psi, transported hydraulic oil through four Parker D41FH valves, which fed the hydraulic cylinders. Each of the 12-inch diameter Parker Series 3H cylinders had a 17-foot stroke, but a pulley configuration attached to them provided a 2:1 mechanical advantage. As a result, when the cylinders moved 17 feet, the pulley system moved the model 34 feet.
Using four cylinders and eight pumps on each side of the structure, engineers provided about 1.2 million lbs of lifting force. Because the set weighed about 1.4 million lbs, they supplemented the system with foam flotation, which was placed under the platform. The foam flotation provided enough additional lifting capacity to move the set as desired. It also added a measure of safety, engineers say. "It wasn't safe to try to lift that much weight with a single system--hydraulic or otherwise," Rothas says. "The flotation system was a good back-up."
Power and control. Lifting, however, was only half the battle for the movie's technical staff. The other half was control. Although they were moving the 1.4-million-pound load at a rate of six inches per second, they wanted to synchronize the movement of all eight cylinders to within ±1.0 inches of the commanded position and velocity.
To accomplish that, they employed an eight-axis motion controller and a master/slave control scheme. The "master," a 1/20th scale model of the platform, was controlled by a two-axis joystick and a pair of hydraulic cylinders. By moving the miniature, then sending its command signals through an eight-axis digital motion controller, engineers were able to create an identical motion profile for the real model.
To synchronize the two, the motion controller compared the eight command signals with electronic feedback signals from the eight, 17-ft stroke cylinders. The motion controller then processed the signals and sent an output drive signal to each of the cylinders' servo valves. The cylinders on the full-sized model then traveled to the desired position at a pre-determined speed dictated by the master. "The master-slave technique allowed us to create an initial profile for the motion we wanted to achieve," notes Greg Paddock, a Parker Hannifin applications engineer and veteran of several large movie projects. "Once we had a feel for the platform movement, we directly programmed the controller."
Programming for the system was done by engineers from Distributed Motion, Inc. (DMI), a Parker Compumotor distributor in Irvine, CA. DMI engineer Greg Stewart, who did most of the programming, ultimately selected an eight-axis motion controller made by Delta Tau Data Systems, Inc., Northridge, CA. Use of the Delta Tau technology enabled engineers to control all eight axes with a single controller.
The big one. When they finished moving the 1.4 million-pound interior model, engineers dismantled the power systems and prepared for the big job--moving the 90% scale model of the Titanic. A 6.6-acre outdoor "lake," located about 500 yards away from the indoor set, served as the site for a two-million- pound scale model of the ship. Built atop a 30-foot cliff overlooking the Pacific Ocean, the outdoor model provided the look and feel of an ocean liner at sea. "When you stood on the deck and looked out, you saw the ocean," Fisher recalls. "You felt you were in the middle of the Atlantic."
In truth, however, the outdoor set wasn't a ship at all. Rather, it was a bolted steel web of wide flange beams, columns, and trusses, like those in the skeleton of any office building. Steel plates were bolted to the sides of the steel skeleton to give it the appearance of a ship. But below the water line, the steel facade