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Designing the Team Roll Cage (Part 1)

For racing, a well-built roll cage is much more than a mandatory requirement. The roll cage is a central piece of any machine- it occupies a significant portion of the overall weight, allows for safe competition, defines the appearance of the vehicle, and must be planned ahead of the build to prevent interference with other critical components (radiators, factory plastics, rear-mount fuel cells, etc.). Optimizing these constraints can be time consuming as the fulfillment of one requirement, weight reduction for instance, impedes that of another, such as less structural triangulation. Even in absence of these considerations, anyone who has built a roll cage understands the complexities inherent with construction such as proper notching, placement of compound bends, and ‘square’ construction.

Prior to actual construction of the roll cage, several test components will be constructed (as featured above) to understand the nuances and special considerations needed with operation of each tool. In the case of using our JD2 Model 3 tube bender, steel memory or ‘bend-back’ is a major consideration that can easily throw off the connection of dependent pieces. Another determination from this phase in construction is that of material thickness- in the case pictured, the wall was too thin for the dye and kinking resulted beyond 85 degrees of bend. Currently, we intend to use 1.75″ DOM with a wall thickness of 0.120″ for primary hoops and 1.75″ DOM with a wall thickness of 0.095″ for triangulation and accessory members (spare tire carrier, rock-sliders, etc.).

Another pivotal feature of construction is in the weld quality at each joint. Porosity, experience, and notch-quality / fit-up are major contributors to the quality of our roll cage build. We will be working with MIG and expect to use a Pro-Tools or JD2 hole-saw notcher to hone in the quality of each and every weld (this is especially prevalent for the larger race series such as SCORE, SXS Sports, and BITD). Before undertaking the build in October, we will have welded hundreds of practice joints and fit-ups in order to fluently grasp the art of welding tube.

Another portion of our build, arguably the most exciting of all the stages of planning, will be in the CAD rendering of the roll cage. Greg is well accustomed to using CAD systems (AutoCAD, Autodesk Inventor, and Autodesk Civil 3D to name a few) and will be working to produce several iterative versions for final decision. From here, we will use the digital rendering to model race-induced rollover loads and optimize the cage for weight and strength. Zero-force members, redundant interactions at nodes, and over-triangulation will be studied specifically in order to keep the cage as light as possible.

Stay posted for the next version of our roll cage write-up and learn the tricks to designing custom roll cages on the computer instead of by hand. We will show how this method is much faster and more accurate than the conventional approach and can streamline the manufacturing process to eliminate wasted material and wasted time!

Categories

The How To

Greg Torney View All

Driver of the #428 Draco Motorsports Polaris RZR. Co-Driver for the #804 Can-Am X3 during King of the Hammers. Ultra4!!

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