Hydroformed side rail for a vehicle frame and method of manufacture

A method of making a frame side rail for a vehicle frame comprising:

• pre-bending a constant diameter cross-section tubular member to a configuration having first and second end sections, a center section and first and second transition sections joining the respective ones of the first and second end section and the center section to substantially the same as a desired final shape of the frame side rail;
• pre-expanding said center section to an increased diameter and said transition sections of said pre-bent tubular member to a new configuration, having one end portion thereof with a diameter equal to the respective end section and another end portion thereof equal with the increased diameter of said center portion, in a single hydroforming process;
• and
• hydroforming the pre-expanded tubular member into a side rail of substantially rectangular cross-section with said end sections having first and second wall thicknesses, said center section having a third wall thickness less than said end sections and said transition section having a varying wall thickness which is equal to the respective end section wall thickness at a first position adjacent thereto and equal to the center section wall thickness at a second position adjacent thereto.

A hydroformed frame side rail for a vehicle frame comprising:

• spaced end sections having a first and second rectangular cross-sectional area with respective first and second wall thicknesses and having a first height to width ratio;
• first and second transition sections having each having a first end rectangular cross-sectional area integrally hydroformed contiguous with respective ones of said first and second end sections and a second end rectangular cross-sectional area;
• and
• a center section having a third rectangular crossectional area having a third wall thickness and a second height to width ratio greater than said first height to width ratio and having first and second portions thereof being hydroformed contiguous with respective ones of said first and second transition sections.