Sway Bar Prototype Production Process
Manufacturing a sway bar has been done by various methods throughout the years. The traditional method of making a bar is to take the raw bar stock, and bend it into the shape you want by using a press and bend dies. This is generally a cheap way to make them, and there are several drawbacks to this method. The first such detriment is that each bend is done separately. With each bend the tolerance increases, i.e. inaccuracy, in making the part. This allows for increased human error in production.
As cars become more complex, the packaging of the sway bar tightens. There is less room for error, and thus, the part needs to be more accurate to fit in the car. The second drawback is that all of the additional handling adds extra time to the manufacturing process. This can lead to extended production times and higher costs. One final disadvantage is that the press bends can add several extreme tooling dents or ‘marks’ to the product. Dents such as these are acceptable on a solid bar, but they make the part less eye pleasing to look at. Tubular material cannot be bent in this traditional way. The press will either kink or crack the tubing when bending the material.
All of our sway bars are meticulously designed on a fully parametric CAD system. This insures that the sway bars are designed for the proper fit and handling characteristics of the vehicle. Hotchkis Performance uses a “state of the art” high tech CNC (Computer Numerically Controlled) bending machine. This machine does essentially all of the bends in one handling process. Raw material is loaded into the machine, which then goes through a series of motions to produce a smoothly bent part. A computer keeps track of each bend in relation to all of the other bends. This produces a very high tolerance part, typically in the 0.050″ range or tighter, and with consistent reliability. During the manufacturing run, a Laser Vector inspection system is employed to measure the parts being bent by the machine. This measures the shape of the bar, and compares it to a computer file of the part print. The laser’s computer sends any necessary corrections to the bending computer. This is done because each batch or raw material varies and bends slightly different than another.
Tubular Anti-Roll Bar Design Philosophy
Many people are confused by the modern use of a ‘hollow’ ARB. Technological advancements in racing designs are finally being used by many suspension designers throughout the world. Companies such as, Porsche, Daimler-Chrysler, Ford, and many others have started to include hollow anti-roll bars on factory produced cars and trucks. There are many advantages to using a tubular ARB rather than a solid bar. The foremost advantage is the weight reduction that can be achieved by using hollow technology. For the suspension designer, the flexibility of using a tube greatly increases the ability to really ‘fine-tune’ the design. All one has to do is change the wall thickness of the material to give an incremental change in stiffness. A designer can then adjust the stiffness of a bar using the same vehicle packaging in this way for a number of different bars.
There are many misconceptions floating around about the hollow bar designs. One major one is that a solid bar is stronger than a hollow one. This is only partially correct. If a solid bar and a hollow one of the same diameter are compared, then the solid bar is stiffer than the hollow version. By increasing the outer diameter of the hollow bar, and fine-tuning the wall thickness, you can yield the same performance while reducing weight. How many racing designers try to cut every ounce out of the chassis? They all do! Reducing weight acts like adding horsepower. Another expressed concern is the durability of the part when using a hollow bar. Under the same loading conditions, a properly designed hollow bar will see virtually the same stress levels that a solid bar does, yet provide the equivalent handling performance or improve upon it.