Building a Banked Track Is a Balancing Act

Mitchell Machine Works is in the business of building complex machines. Hailing from Dalton, Ga., the company has been known the world over for its Magic Carpet, a hydraulically driven roller system that can roll up, or roll out, an entire sports field of turf in a matter of minutes.

Mitchell Machine Works was founded in 1967 by the company’s self-described “chief engineer, owner and just about everything else,” Mark Mitchell, who has gained a reputation for being someone who can design and deliver complex machines. Because of this pedigree and his previous experience building the Magic Carpet, Mitchell picked up the phone one day and found himself with some surprise business. On the other end of the line was a company that needed Mitchell to build an indoor running track.

Taken at face value, building an indoor running track doesn’t seem all that mechanically complex. A track’s essentially an oval. A flat oval.

But there was a catch.

Instead of being flat, the indoor running track that Mitchell was being asked to build had to be hydraulically driven, because, you see, some indoor track events use a banked surface, not a flat one like its outdoor counterpart.

As you can imagine, building a banking hydraulic indoor running track isn’t a straightforward endeavor. In fact, building such a machine requires some 200,000 pounds of steel and 72,000 components (including 72 hydraulic actuators)—and that doesn’t even take into account the 7,000 work hours required to build the machine. What’s more, for an indoor track to work properly, it has to work in perfect harmony, with each of the hydraulic drivers that lift the track’s banks working in unison with its nearby neighbors.

As Mitchell described it, one of the biggest issues facing the design of this track was figuring out the complex control system that would be used to govern how each hydraulic actuator worked, because as Mitchell noted, “given the torsion in the system, no cylinder could be more than 10 mm out of line with its neighbor.” To transform this seemingly intractable problem into something more manageable, Mitchell looked to IronCAD.

Mitchell's Hydraulic Track in IronCAD

Although Mitchell is familiar with CAD, he turned much of the actual CAD work over to RJ Saucier of Genesis Technology Systems. Working in concert with Saucier, Mitchell was able to create a robust CAD model using IronCAD that gave him great insight into how the hydraulic system worked.

Once Mitchell’s vision for his indoor track had been modeled, Saucier and his team set out to analyze how the track’s movement would affect its overall performance. Using IronCAD’s finite element analysis (FEA) tools, each component in the assembly was tested, and when errors that would affect the performance of the track were found, the design was slightly modified.

“One of the best parts about IronCAD is the fact assemblies are so easy to use,” said Saucier. “You’re never hung up with constraint sets, so when a client comes in and needs a quick change, say, this component needs to be moved over one-sixteenth of an inch, IronCAD can do that quickly without having to untangle an assembly connected mess.”

With this analysis at hand, Mitchell and Saucier were able to articulate their assembly and move the track as it would move in reality. Because of the integrity of the geometry in their model, Mitchell could accurately measure how much each hydraulic cylinder would move at different points along its path as it was raised and lowered. With those numbers in hand, Mitchell was able to give the programmers developing his control system detailed instructions describing the positions of each hydraulic cylinder as it moved through the banking operation.

“Trying to make 36 cylinders dance together is tough, but with IronCAD we were able to simplify the design control system design process,” noted Mitchell.

CAD as an Installation Tool

Beyond the fact that IronCAD was instrumental in designing Mitchell’s track, it also played a role in making the assembly of his track much easier. Not only was Mitchell able to use detailed drawings to transform those 72,000 parts into one working whole, he also used IronCAD’s software to give instruction to the workers assembling the track. Whenever communication problems would arise during the assembly process, Mitchell was able to bring up a detailed 3D model directly in IronCAD and specify exactly how a subsystem should be assembled and why. 

Given that level of communication, Mitchell was able to cut down his time on site and have his track built efficiently.

With one completed track behind him and a second nearing completion, Mark Mitchell is confident that his hydraulically articulated indoor track’s design represents the shape of things to come in multipurpose sports facilities being built around the world. Still, Mitchell realizes that each and every track design will be different, requiring minor tweaks and work-arounds that will alter his original design. Fortunately, Mitchell is confident that he can meet any design requirement thanks to the robust design and analysis tools that he has in IronCAD today.

IronCAD has sponsored this post. It had no editorial input. All opinions are mine. —Kyle Maxey