Burbank, CA--Deep within the cavernous Warner Brothers facility that serves as Batman's lair in the just-released Batman and Robin movie, engineers late last year found themselves scratching their heads over a vexing Bat-problem: How to rotate, pivot, and extend a massive 45-ft-long telescope for the movie's key scenes. After scribbling out some rough calculations, they realized they'd be moving as much as 97,000 lbs.
While engineers struggled with the problem, however, one aspect of it became clear: The prime movers must be hydraulic. "At the time, it was the largest and heaviest moving prop in film history," notes Mark Yuricich, an independent special effects engineer who worked on Batman and Robin. "The only way to move it accurately was with fluid."
Indeed, "fluid" has become the answer to a growing variety of special effects riddles. Before the dust began to settle on the Batman set, engineers had already used fluid power to break cinematic engineering records on two other films: Speed 2 and Titanic. For sheer mass, both movies exceeded Batman and Robin, with Titanic hoisting an incredible 1.8 million lbs.
The use of fluid power in such movies as Batman and Robin has surprised no one in the industry, having long been used to move big movie props. But now, with special effects growing more realistic and props growing bigger and bulkier, fluid power has taken on a greater role. In many cases, no other power medium can replace it.
"Electrical drives don't have the required power," notes Greg Paddock, hydraulic territory manager for Parker Hannifin Motion and Control Group, Irvine, CA. "And if they did, you still wouldn't have the luxury of placing an electric actuator near the item that you are moving. Size prohibits it. That's the real advantage of hydraulics--power density."
†For the movie Batman and Robin, hydraulics not only provided power density, but supplied speed. Cylinders for the telescope's extend function, for example, needed to move huge loads as fast as 48 inches per second. A special platform for close-up shots needed to move at 60 inches per second.
On the telescope, the movie's engineers faced four main tasks: design a lower pivot; design an upper pivot; extend the telescope; and rotate it, along with an attached 50-ft-diameter platform. Hydraulic power accomplished all these critical tasks:
Lower pivot. The telescope, located in the fictional Gotham City Observatory, was attached to two huge counterbalance arms. The arms counterbalanced the weight of the fully extended, cantilevered telescope. But they also provided two pivot points, from which the telescope could swing up and down. The lower pivot points, located at the base of each counterbalance arm, employed Parker Series 2H Heavy Duty hydraulic cylinders. The cylinders attached to the platform beneath each arm. By pushing up on the bottom surface of each arm, they could swing the telescope up. To provide the lifting force, each cylinder used a 72-inch stroke, six-inch-diameter bore, and a four-inch-diameter rod, providing a travel speed of seven inches per second.
Upper pivot. A cross member spanning the distance between the two counterbalance arms served as the upper pivot point. Engineers employed a single Parker 2H Heavy Duty cylinder on top of the cross member at the centerline of the telescope. The cylinder, which had a six-inch bore and four-inch-diameter rod, tilted the telescope up at a rate of 19 inches per second by pushing on its bottom surface.
Extension. The telescope, which consisted of a smaller tube nested within a larger one, needed to extend at speeds reaching 48 inches per second. Engineers accomplished that by pushing on the inner tube with another heavy-duty cylinder. Fully extended, the cylinder pushed the nested inner tube out a distance of 111 inches.
Rotation. The 45-ft-long telescope, along with the 50-ft-diameter platform that supported it, was required to rotate at a speed of 3 rpm. The solution: four Parker MZG hydraulic motors, each mounted to their own rubber wheels through planetary gear reducer hubs. Powered by the hydraulic motors, the wheels rode on a circular metal track, providing the torque to move the 97,000-lb structure. A key element of the rotating platform design included the use of modulating control valves at each actuator port and Parker proportional valves. The modulating control valves provided a measure of safety for actors and stunt people during the movie's fight scenes, which take place atop the telescope. The proportional valves also supplied smooth control over acceleration, deceleration, velocity, and position of the platform.
By taking such pains in the construction of the telescope and the design of its motion systems, engineers attained the scientific look that the movie's producers sought. "The telescope had to move on camera and the movie's principal actors had to stand on top of it," Yuricich says. "It needed to have the look and feel of authenticity."
Special effects challenges. Movement of the Gotham City telescope wasn't the only problem facing the picture's special effects engineers. Warner Brothers also called on them to build a special gimbal for close-up scenes and a "Batlift" to lift the Batmobile and Batcycle.
The gimbal, designed to replicate the top portion of the telescope where the fight scenes take place, was initially constructed as a safety measure. Actors, who would have stood more than 40 ft above floor level on the telescope, needed only to stand about seven ft up on the gimbaled platform. The design also enabled the production's camera crew to take tighter shots of the actors, because it kept cameras closer to the action.
The gimbaled platform, which measured about 25-ft by 25-ft square, tilts back and forth at an angle of Ī22 degrees at speeds up to 60 inches per second. Because it was a half-replica version of the telescope, it also needed to rotate like the original.
Lift and rotate a 45-ft-long, 97,000-lb telescope and platform at 3 rpm, and extend telescope at 48 inches per second.
Move a half-size replica of the telescope at 60 inches per second.
Simultaneously raise and rotate at 3 rpm a 50-ft-diameter, 65,000-lb platform holding the Batmobile, Bat Cycle, and 50 people.
Design a sealing system that would be 100% leakproof.
To facilitate all those movements, Yuricich worked with Parker Hannifin engineers to create a gimbaled platform that could be actuated from each side. The team placed one Parker Series 2H cylinder at opposite edges of the platform, then tilted it back and forth like a teeter-totter. To achieve the necessary forces and motion angles, they employed four-inch-bore cylinders with 41.5-inch strokes. Rotation of the platform was achieved in the same manner as the real telescope: four hydraulic motors mounted on rubber wheels and controlled by proportional valves.
From an engineering standpoint, however, the Batlift may have been most challenging of the film's special effects. Unlike the telescope, the Batlift was designed to lift and rotate. The 50-ft-diameter platform needed to elevate the Batmobile, Batcycle, and up to 50 people, while rotating at 3 rpm. Including the weight of the support structure, engineers estimated that a loaded Batlift would weigh more than 65,000 lbs. During the movie, the Batlift elevates the vehicles from unseen depths up to the Batcave floor.
Engineers achieved all the goals for the Batlift by designing a support structure, or "lifting ring," that hoisted the Batlift's upper platform into place. The lifting ring was essentially a 50-ft-diameter circular steel truss structure supported by eight steel towers. A metal track on the ring's outer perimeter enabled the upper platform to sit atop the lifting ring and rotate independently from it. As a result, the platform rotated while the lifting ring raised and lowered the load.
Lifting action was generated by a large Parker Series 3H Heavy Duty cylinder with a 10-inch bore and a 4.5-inch-diameter rod. The cylinder, which had a 96-inch stroke, hoisted the platform by attaching to steel pulleys on the towers, which, in turn, lifted the ring. When the cylinder extended, the Batlift moved eight ft at a speed of 12 inches per second. When it retracted, the Batlift moved back down.
Torque for the Batlift's rotation was provided by four hydraulic motors. These were attached to the rubber wheels that rode on the lifting ring's track.
Sealing a key. Although the ability to generate forces was key to the use of hydraulics in Batman and Robin, engineers say that sealing technology proved equally critical. The reason: Big budget productions can stand no downtime.
"You have to design for 100% reliability on these films because downtime can cost between $10,000 and $100,000 per hour," Yuricich explains. "If you lose one hour due to unreliable components, people get very upset."
Led by Paddock, Parker's crew dealt with the issue of potential leakage by employing TS-2000 seals on glands and Hi-Load piston seals. The latter are specially designed for situations in which side-loads can potentially be applied to the pistons. They employ a pair of phenolic wear bands on two outer grooves in the piston and a pair of PTFE primary pressure seals on the inner grooves. Parker engineers also used face Seal-Lok fittings on all hoses and plumbing connections to allow for thermal expansion and to provide resistance against vibration.
The combination of reliability, speed, and power density made hydraulics an obvious choice for Batman and Robin, as well as for scores of upcoming films. "The need for high force and control capability narrows your choices down in most cases to hydraulics," Paddock says. "But in these props, space is also at a premium. And hydraulics allows you to mount the actuator in a nice, convenient package."
How to match fluids with seals
Parker Hannifin engineer Richard Swanson keeps a boxful of failed seals in his office, the better to illustrate the problems of material and fluid incompatibilities. "I regularly receive seals that have been damaged, simply because they've been placed in the wrong fluid," says Swanson, product manager for Parker Hannifin's Packing Div., Salt Lake City, UT.
Seal failures, relatively common when lifting huge loads such as those in Batman and Robin, can be dramatically reduced, says Swanson. "Selecting the right material for a given fluid is critical to the performance of the seal," he notes.
Software programs, such as Parker Hannifin's inPHorm, or the Elastomer Compatibility Guide from Green, Tweed & Co., helps engineers pick the proper material for a given fluid. Six different Parker Hannifin divisions offer specialized versions of the inPHorm software, including the Packing Div. and the O-Ring Div.
To use such programs, engineers typically designate the fluid, temperature range, and maximum pressure for their applications. For certain situations, programs may ask for such information as shaft speed or shaft length. Programs such as inPHorm offer a scrollable list of more than 1,000 fluids from which to choose. Typically, they respond with five or six potential materials, then steer the user to a single one. The advantage of such systems, Swanson says, is that they take the guesswork out for the engineer. Ultimately, they also make seals perform more effectively.