High-speed sports car chases, fast and furious aerobatics, imaginative trips into volcanos, and snow skiing — these are just a few of the simulated experiences you may encounter at a shopping mall, entertainment complex, tourist attraction, or amusement park. Motion simulators provide these thrills and spills by reproducing the sights, sounds, and feelings of motion to create the impression of any of dozens of fast-paced experiences. Unlike their larger, more sophisticated cousins you'll find permanently installed at major theme parks around the world, portable motion simulators can be moved from one location to another and cost but a fraction of their high-end counterparts.
At the low-end of these portable simulators are models with enticing high-tech graphics and low-tech, electromechanical motion bases. These units require the lowest monetary investment from owners and are inexpensive to operate, but they can only handle one or two people per cycle. They also provide an entertainment experience that leaves a lot to be desired because motion may be sluggish and participants may not be completely enveloped by visual and audio effects..
On the other hand, multiple-passenger portable motion simulators provide a much more sophisticated and believable experience. Highly-responsive, multi-axis actuation produces realistic perceptions of motion, and participants are isolated from the outside environment and completely surrounded by the sights and sounds of the simulated experience. Furthermore, these simulators have a much higher throughput — 12 or more people per cycle — but carry a much higher price tag and can be cumbersome to transport from one location to another.
A market left untapped lies somewhere in between — an easily transportable simulator that can handle more than one or two people at a time, but has a purchase price and operating cost in the neighborhood of a two-person electromechanical simulator. This hole in the market has been filled by the Transport 6 portable motion simulator from Doron Precision Systems Inc., Binghamton, N.Y. The Transport 6 holds six people, so it boasts a much greater throughput than one- or two-person simulators. However, the Transport 6 carries a price tag competitive with a high-end, two-person simulator.
Donald Wenzinger, vice president of domestic entertainment simulator sales at Doron, says the Transport 6 is light enough to be rolled on its casters from one location to another by only two people and is small enough to fit through standard double doors. David C. Byerly, senior mechanical systems engineer, adds that once the Transport 6 arrives at its destination, setup is simple because its low center of gravity means it does not have to be bolted to a foundation, and it operates from widely available single-phase, 230-V power.
Advantages of hydraulics
Motion simulators that handle one or two people at a time generally are actuated electromechanically. Loads are light enough that a variable-speed motorized ballscrew provides an economical drive package for each axis. Hydraulics could work in these applications, but would cost more and offer little or no performance advantage. Once power requirements enter the 3- to 5-hp range, however, hydraulics can drive multiple axes at higher performance, lower cost, or both.
Doron engineers evaluated electromechanical systems when they first entered the entertainment market in the mid 1970s. According to Byerly, hydraulics was the clear choice for most applications. "Electromechanical systems definitely have gained some ground. But even when an electromechanical drive offers the performance we need at a reasonable price, we have found hydraulics to be the most reliable and responsive drive system. Hydraulic actuators also take up less space than a motor and ballscrew, and we can always find space to locate the hydraulic power unit."
Byerly also cites service life as an advantage hydraulics has over electromechanical systems for these applications. "Life of a ballscrew is rated like a bearing: a finite number of cycles, distance traveled, or hours of operation. Maintaining proper lubrication, cleanliness, and alignment is essential to a ballscrew achieving its rated life. A carefully engineered hydraulic system, on the other hand, excludes contaminants and filters out those that do happen to get into the oil. Ballscrews do not have this opportunity to remove contaminants unless a sophisticated pressurized lubrication system is incorporated."
Wenzinger explains that manufacturers of electromechanical motion simulators often attempt to gain a competitive edge by presenting leakage and noise as major disadvantages inherent to hydraulically powered motion simulators. "But," reveals Byerly, "leakage has not been a problem with our simulators as long as they are installed and maintained properly. We use O-ring type fittings to prevent leakage, and rod seals hold up well because they normally are not subjected to anything real hostile. It's not like a backhoe, where mud and sand get caked onto the rod. Our literature specifies that the simulators should be installed in relatively clean environments. One operates near an ocean-side boardwalk. But because it is inside a tent, it is not exposed directly to the sandy, salty atmosphere of a marine environment — and it doesn't leak. So our systems are helping to dispel the myth that hydraulic systems have to be messy.
"Also, noise has not been a big concern. With hydraulics, most of the noise is generated by the hydraulic power unit. Granted, the power unit makes more noise than a single ballscrew and motor assembly. But with hydraulics, noise comes from a single source, so it is easier to isolate than noise coming multiple sources and different directions, as is the case with a simulator using multiple motorized ballscrews."