TWISTS AND TURNS OF MOTION SIMULATOR RIDE REPLICATED USING NEW
ACTUATOR SIMULATION TECHNOLOGY
||Iwerks Entertainment, Inc., Burbank, California, is one of the worlds
leading suppliers of location-based entertainment attractions, such as the TurboRide
cinematic simulator shown here. This type of simulator was the subject of an engineering
analysis by amusement ride expert Ed Pribonic using Mechanical Event Simulation software
from ALGOR, Inc., Pittsburgh, Pennsylvania.
By: Edward M. Pribonic
President, Edward M. Pribonic P.E. Engineering and Consulting, Seal Beach, California, www.aimsintl.org/pribonic.htm
As an engineering consultant specializing in amusement rides, theme park design and
water parks, my job often seems more like play than work. I have worked on countless theme
park simulations -- flight, free-fall, explosions, train rides and space travel, just to
name a few. While it is fun and exciting, engineering in the entertainment industry is
also a very serious business. Millions of people take tens of millions of thrill rides
each year in amusement parks. Assuring their safety as they roar through the loops of a
roller coaster at 60 mph, or as they dive and dodge exploding asteroids in a flight
simulator, is a demanding engineering responsibility.
Fortunately, rapid advances in science and computer technologies, especially simulation
software, now support engineering analysis. However, for slide rule-trained engineers like
myself, realizing the benefits of the latest simulation tools can require some extra time
and training. My efforts paid off recently when my firm created an engineering simulation
using physics-based Mechanical Event Simulation (MES) software from ALGOR, Inc.,
Pittsburgh, Pennsylvania, to verify the integrity of a cinematic motion simulator ride.
A family entertainment complex in Edinburgh, Scotland, purchased a new TurboRide from
Iwerks Entertainment, Inc. (Iwerks), headquartered in Burbank, California. Iwerks
contracted Edward M. Pribonic P.E. Engineering and Consulting (Pribonic Engineering and
Consulting) to verify that the American-built simulator would meet requirements set by the
British Fairground Standard for amusement ride safety. After recognizing the inherent
limitations of using traditional linear static stress analysis to analyze a dynamic event,
my firm researched alternative FEA and kinematic analysis solutions and concluded that MES
provided the best solution for the engineering analysis needs of the project. Ultimately,
the MES enabled the installation of the ride to move forward and provided my client with a
virtual prototype for future product developments.
The Iwerks TurboRide consists of two, four or eight seats mounted on motion bases that
are arranged before giant flat or domed 180° theater screens. The motion bases move in
synchronization with action-packed Point of View movies. The
large screens, coordinated movement and booming digital audio transport riders through the
virtual twists and turns of a space voyage, whisk them through the human body or race them
across the finish line of an Indy Car-type race.
The Edinburgh installation consists of 12 four-seat motion bases. The fiberglass seats
are supported by a welded steel frame of rectangular tubing, known as the flying platform.
Six double-acting hydraulic cylinders connect the flying platform and floor-mounted base unit. Each cylinder is fastened at one end to the base unit
via a cast iron bearing. The base unit has three mounting
plates, each with two bearings to accept the lower ends of the cylinders. The
computer-controlled hydraulic cylinders extend or retract independently, providing the
seat and occupants roll, pitch, yaw, heave, surge and sway motion with six degrees of
freedom in coordination with the on-screen adventure action.
After reviewing the simulator design, Iwerks, their client and I determined that all
components of the ride should be structurally analyzed with the bearings as the main focus
of the engineering analysis. We needed to verify that the simulators would safely
withstand the dynamic loading caused by the actuating cylinders, the weight of the entire
assembly and presence of four adult passengers. Of special concern was a portion of the
iron bearing housing beneath the bearing inserts. We needed to prove that there was no
possibility of a catastrophic failure of this part.
||Cast iron bearings, similar to this one, were the focus of the linear static
stress analysis, which aimed to verify that the bearings could withstand stresses
resulting from the motion of six actuating hydraulic cylinders and provide extended
While the goal of the project was straightforward, the method of achieving it was not.
Our first approach to the problem was to perform a linear static stress analysis. However,
we discovered that the inherent limitations of static analysis made it unsuitable for
studying the dynamic nature of the simulator. The problem arose in determining loads
created by the accelerations of the multiple double-acting cylinders to use as input into
a linear static stress analysis.
Control valves connect to the top and bottom of each cylinder. As the ride begins,
computerized controls lift all six cylinders to their neutral positions at half the
cylinder extension capability (maximum extension is 25.25 inches) by raising fluid levels
in the lower portion and releasing fluid in the upper portion of the cylinder. Computer
commands conduct unique multi-directional extension and retraction sequences for each of
the cylinders. An accumulator provides for fluid surges, while a central HPU provides a
constant fluid pressure of 2000 PSI.
Due to the complexity of movement, calculating the loading on the bearings from the six
independently moving cylinders was not feasible. A detailed solid model of the bearing was
created in SolidWorks and captured directly in ALGOR using InCADPlus for
SolidWorks, without translation to a neutral file format. The model was fully constrained
at the stainless steel inset in the center of the bearing. We decided to analyze a worst
case scenario, applying an artificially high static load to the bearing.
In addition to the bearing analysis, Iwerks requested another analysis to verify that
the welds of the motion base also would withstand the dynamic loads created by actuator movement and the presence of simulated passengers. A detailed
solid model of the motion base was created in SolidWorks and transferred to ALGOR in the
same manner as the previous model. A load that would have been distributed to three
mounting plates was applied to just one mounting plate in the vertical and horizontal
directions. The points where the seat is attached to the frame were fully fixed for the
static analysis. The results showed only moderate stress levels in the structure despite
an artificially high load case. The welds in the seat frame performed well under the
||The linear static stress analysis results showed that a bearing could withstand
loading 2.5 times the maximum-recommended load for the component. Because of the number of
assumptions and simplifications made in the analysis, Mr. Pribonic was not convinced that
the results portrayed an accurate picture of the mechanical system behavior.
The static analyses conducted separately on the bearings and seat frame yielded low to
moderate stresses as well. While the results were favorable, both my firm and our client
were not convinced that the results portrayed an accurate picture of the mechanical system
behavior because of the number of assumptions and simplifications made in the static
Consequently, my firm decided to go beyond traditional
static FEA methods to take advantage of the high level of engineering simulation and
computing power available with ALGOR. I recommended that we build a complete, fully
detailed, full-motion computer model of the simulator that could be used to run the motion
profile at hand as well as new motion profiles as they are developed for future films.
Stresses on the equipment can change with every new motion profile so Iwerks needed an
engineering model that could run each motion profile and produce results.
With the help of ALGORs technical support, we determined that replicating the
actuating movement of the hydraulic cylinders using ALGORs new actuator element
technology and Mechanical Event Simulation (MES) software was the best method of
evaluating real dynamic loads over time. In addition, a reliable computer model based on a
detailed CAD solid assembly would help all involved to better understand the dynamics of
the design and apply this knowledge to future programming and simulator design decisions.
At the onset of the MES, the dynamic load calculation problems encountered in the linear
static stress analyses were eliminated. MES simulates motion and flexing simultaneously to
calculate stresses over time, thus forces are determined intrinsically by the software.
MES is physics-based, not assumptions-based; therefore, we could rely on the
"known" physics of the event -- the weight of the simulator and passengers,
gravity, pressure and displacement of each cylinder over time -- to unfold as the event
was processed. Using this data, Pribonic Engineering and Consulting was challenged to
simulate the six degrees of freedom motion capability of the simulator ride in order to
determine dynamic stresses in the bearings.
For a simple MES, such as a manually shifted lever, the engineer simply specifies a
prescribed displacement or, if it is known, the force needed to set up the MES. Then the
software will compute the acceleration and resulting stresses. In the case of the
simulator, applying prescribed displacements for each cylinder to get dynamic motion and
stress results over time was not feasible. At best, we could determine stresses at just
one instant in time if we used this approach with the available software capabilities.
Such an analysis would yield a similar result as a motion load transfer analysis, in which
loading determined in a kinematic analysis is applied to a static stress analysis. My
client had already agreed that this would not meet the safety analysis requirements for
The complex actuating movement could be simulated using a new actuator element
technology invented by ALGOR. Actuator elements are engineering elements (like contact or
dashpot elements) that replicate linear extension and contraction movement in
three-dimensional space, typical motion for hydraulic and pneumatic cylinders and electric
solenoids. An actuator element, which appears as a line, was used to represent each
cylinder in the finite element model.
To proceed with the MES, we created a detailed CAD assembly of the simulator that would
be captured in ALGOR for finite element modeling. Using SolidWorks once again, engineers
at Pribonic Engineering and Consulting modeled more than 100 individual components based
on Iwerks drawings and merged the components into five subassemblies.
|To create an accurate representation of the simulator, a SolidWorks assembly was
created and captured in ALGOR using InCADPlus technology. The hydraulic
cylinders were represented with ALGORs actuator elements. The inset shows the
construction of the base unit with three mounting plates containing pairs of bearings. The
center bracket holds the accumulator, which handles fluid demand peaks. Hydraulic pressure
for the system is provided by a central HPU at a constant 2000 PSI.
The surfaces of the subassemblies were meshed separately by choosing the InCADPlus
menu selection in SolidWorks, which activates ALGORs surface meshing. InCADPlus
captures the exact CAD geometry, and group information is preserved in the
finite element model.
Once the subassemblies were meshed, they were merged into one model in Superdraw III.
While some detailed surface matching was needed to align welded components in the seat
frame, we performed very little surface mesh enhancement. The initial finite element model
contained approximately 500,000 elements -- far too many for a reasonable analysis
With the help of ALGORs technical support, my firm was able to reduce the overall
number of finite elements in the model to approximately 141,000 elements. This was due in
part to ALGORs solid mesh engine, which automatically creates better aspect ratios
for each solid element based on the quality level chosen by the engineer. We also replaced
flexible brick elements with ALGORs kinematic elements where possible to reduce the
analysis computation time. Kinematic elements behave just
like flexible finite elements, but do not produce stresses. Engineers can insert kinematic
elements in areas of the assembly where dynamic effects are essential but for which
stresses are of secondary importance. This saves time and the engineer can focus the
analysis on the part of the mechanism being optimized -- a set of bearings in our case.
After the model size was reduced, my firm defined the analysis type, unit system,
element and material properties by group. A translator program was used to read in the
displacement vs. time load curves for each actuator element. The program extracted the
load curves for an 11.6-second segment of the motion profile provided by Iwerks. We chose
this particular segment because it contained the most extreme range of accelerations
across all of the load curves. Material properties for steel and cast iron were defined
using ALGORs Material Library Manager. Global analysis parameters included the
duration of the event and capture rate. A rate of 30 captures per second was chosen to
match the Iwerks motion file data points. Gravity also was applied to the model.
During processing, ALGORs built-in visualization capabilities and Monitor utility
were activated so we could watch the event unfold as it was processed. ALGOR enables
WYSIWYG visualization by showing the movement of the mechanism and stresses as they occur
over time. Had we found an error at the beginning or during the run, we could have stopped
the analysis and fixed the problem without waiting for the entire run to complete.
ALGORs Monitor utility works like a virtual oscilloscope, displaying velocity,
displacement, acceleration, reaction forces or maximum stresses vs. time for a specified
node. Using Monitor, we viewed acceleration vs. time data for the six cylinders.
||Created using ALGORs Monitor utility, this graph shows the acceleration vs.
time curve for each of the six independently moving actuator elements used in the
Mechanical Event Simulation.
As soon as the processing was finished, we viewed analysis replays of the MES in .avi
format. These served as visual aids, helping my firm explain to Iwerks the dynamics of the
event in terms that non-engineers could understand.
||A Mechanical Event Simulation (MES) with built-in actuator element technology of
the motion simulator replicated the movement of computer-controlled hydraulic cylinders.
The cylinders were represented with actuator elements (shown here as blue lines). Replays
of the MES show the cylinders extending and retracting independently, providing the seat
and occupants with roll, pitch, yaw, heave, surge and sway motion in coordination with the
on-screen adventure action. ALGORs actuator elements (shown here as blue lines) were
invented to simulate axial extension and retraction movement in three-dimensional space,
typical motion for hydraulic and pneumatic cylinders and electric solenoids.
Using ALGORs built-in visualization capabilities, we reviewed the tensor stress
output normal to the base of the bearings and axially through the pivot point for the MES.
Tensor stress output was chosen because of the brittle properties of cast iron; however,
von Mises stress output was used in a general comparison with the linear static stress
analysis to pinpoint timesteps with high relative stresses in the MES.
The MES results showed that the stresses experienced by the bearings under loading from
the six cylinders were within the acceptable range. A comparison of the maximum stresses
found in the MES with those of the linear static stress analysis showed the static results
to be very conservative. The accuracy of the MES stress results for the simulator was
important to ensuring that the ride met the assigned British Fairground Standard.
||ALGORs Mechanical Event Simulation (MES) software results showed that the
stresses experienced by the bearings were within the acceptable range. A comparison of the
maximum stresses found in the MES (shown left) with the linear static stress analysis
results (shown prior) showed that the linear static stress analysis was quite
conservative. Much lower loadings (and therefore stresses) were found in the dynamic
analysis of the MES. As predicted by the MES results, the bearings performed well in
The actuating motion produced by the MES appeared to be very realistic when we viewed
the analysis replays in real time. However, to verify the accuracy of the actuator
elements used to produce the motion, we compared the MES output to actual test data. Using
one of the motion bases produced for the Scottish TurboRide, engineers placed
accelerometer test equipment at key areas of the simulator. One such point was placed in
the left rear seat of the motion base. Data acquisition software compiled the acceleration
data as the motion program was run on the simulator.
Acceleration vs. time data for a node in a similar location as the accelerometer
testing was acquired from the Monitor program. We found that the MES and physical
acceleration testing results for the same timeframe correlated very well, giving my firm
and Iwerks a high confidence in the accuracy of the results.
||The ALGOR Mechanical Event Simulation acceleration vs. time data for the X, Y and
Z directions (right) correlates well with the acceleration data acquired through
laboratory testing using accelerometers (left). Both sets of data were captured at similar
points in the motion base.
Through this engineering challenge, Pribonic Engineering and Consulting has recognized
the value of developing virtual prototypes using ALGORs MES. We can represent
product designs using detailed CAD assemblies and simulate complex, dynamic behavior. In
this case, the virtual prototype verified that the ride would withstand stresses caused by
the high-speed actions. Just as importantly, its true-to-life form will enable it to serve
as a virtual prototype for future product developments by Iwerks.
About the Author
Ed Pribonic is President of Edward M. Pribonic P.E. Engineering and Consulting, Seal
Beach, California. He has over 30 years of experience in entertainment engineering,
including serving as Manager of Engineering and Architecture at Disneyland and as Senior
Design Manager of Walt Disney Imagineering. He has contributed his expertise to some of
the best-known amusement destinations and attractions in the country. Past projects
include Splash Mountain, Disneyland, Anaheim, California and Jurassic Park, Universal
Studios, Hollywood, California. He travels frequently, consulting worldwide, and is
presently busy developing a series of permanent magnet brake systems for roller coasters
and other industrial equipment. He is also an active member of ASTM, AIMS, IAAPA and
NAARSO, industry organizations which develop amusement ride design standards and promote
industry safety. Mr. Pribonic may be contacted via e-mail by clicking
here or visit his web site at