WHEN NHTSA wrote its underride regulations five years ago, the agency did so with the underriding assumption that guard manufacturers and trailer manufacturers would not necessarily be one and the same.
Trailer manufacturers generally responded by designing, building, and installing underride guards themselves. However, the National Research Council Canada has developed a generic rear underride guard for the Canadian Transportation Equipment Association (CTEA). The purpose of the project was to help manufacturers comply with underride regulations by developing a guard that would meet the following criteria:
- Make a structure, not a device
- Adaptable to trailers and trucks
- Attached by welding or bolting
- Achieve FMVSS 223 performance with materials of minimum properties
- Distribute FMVSS 223 test forces without yielding vehicle rear-end structure
- Adaptable to allow support for a step, pintle hook, or other equipment.
Other requirements were that the guard be as strong as possible, use common sections and grades of steel, and have a 4" x 4" x 3/16" bumper made of 50,000-psi steel tubing. It also had to be repairable to restore strength and energy absorption requirements of FMVSS 223 and provide performance through a standard yielding element in the support.
John Billing, senior research officer for the National Research Council Canada, provided details of the project at the Society of Automotive Engineers International Truck & Bus Meeting December 6 in Portland, Oregon.
"Many manufacturers found it onerous to qualify rear impact guards to FMVSS 223," Billing said. "CTEA determined a generic, prequalified rear impact guard would assist these manufacturers in compliance."
The project, a cooperative effort between NRC and CTEA, resulted in a guard that meets FMVSS 223 easily, Billing said.
"It is cheaper, lighter, simpler, and stronger than most manufacturers' own designs," he said. "It can be fabricated and installed for less than the purchase cost of many kits."
For its part, CTEA defined the needs of the project, gathered investors from its members, issued a request for proposals, and selected NRC/CSTT to perform the design and engineering work.
National Research Council Canada simulated the FMVSS 223 tests using ANSYS for a nonlinear collapse analysis. The council developed and tested four candidate designs.
"One design clearly met the objectives better than the others," Billing said.
The result is a design that will pass even if built from materials of minimum properties, Billing said.
The generic underride guard comes with an application guide on CD-ROM. To use the generic guard, individual trailer manufacturers must design the attachment, do a brace strength calculation, make drawings, manufacture the guard per instructions, put on the compliance sticker, and keep records for compliance purposes.
CTEA has plans for additional development of generic underride guards, including the use of aluminum and stainless steel. For additional information, contact CTEA at Canadian Transportation Equipment Association, 49 Pearl Street, St Thomas, Ontario N5P 2P5 Canada. Telephone: (519) 631-0414 or (519) 637-1955.