Why Mandrel Bends?
Bent metal tubing is used in a variety of applications, not just the racing industry. But in racing, every detail matters when it comes to crossing the finish line first. To that end, racers need bent tubing that starts from well-made straight tubing that is then bent in the most effective way possible to minimize wall damage and maximize heat flow through the tube.
The use of a mandrel bend accomplishes this task. The mandrel is used to keep the nominal tube diameter consistent throughout the bend. By maintaining the inside diameter during bending, a mandrel bender prevents wrinkles in the bend. The consistent diameter and round shape (or oval for oval bends) produces a more efficient flow for fluid dynamics to increase horsepower through the tubing and for the benefit of the engine.
The straight tubing is held in place by a die to maintain the outside structure while the mandrel is inserted inside the tubing to maintain the inside diameter during the bend process. The finished bend is then removed from the mandrel and another straight piece is mounted to the machine. In the case of multiple bends in one piece of straight tubing, the machine or the machine operator will tilt and turn the straight tube while still on the mandrel and in the die to form the additional bends where needed.
Mandrel bent tubing has the added benefit of accomplishing tight radii on thin walled tubing without wrinkling or cracking the tube in the process. This allows for a center line radius of 1.625” on a 1.625” diameter tube. Not all gauges of material are capable of achieving that tight radius, but a mandrel bend allows for the tightest CLR possible on any given gauge of material.