DEVELOPMENT of generic rear impact guards to meet US standards and other trailer related issues were discussed in Toronto in October at the Canadian Transportation Equipment Association's (CTEA) 35th annual meeting and manufacturers conference.
"We will be discussing United States standards, because at this time there is no standard in Canada for rear impact guards," said John Billing, senior research officer for the National Research Council (NRC) of Canada in Ottawa, Ontario.
For more than 33 years, the NRC has conducted vehicle engineering studies and test evaluations on rail vehicles, road vehicles and offroad vehicles, Billing said.
On-site at the NRC are two tilt tables, a suspension test rig, shaker test facility, and a climatic test chamber, Billing said. Parking brake tests are performed on a 60-degree hill. To support this testing, the facility has instrumentation, data acquisition, and data processing.
"Tilt tests are done to order, and all manner of vehicles have have been tested," Billing said.
Rear Impact Guard Standards The Canadian standard developed by the NRC and CTEA will most likely be the same or very similar to the US standard for rear impact guards, Billing said. The CTEA, which has about 80 Canadian trailer manufacturer members, is developing some recommendations for generic rear impact guards.
"It will be onerous for the CTEA to qualify one guard for each product line, or guards for all their various product lines," Billing said.
Billing explained how the NRC and CTEA are developing recommendations for a generic rear impact guard. First, a priority list is made of what needs to be done. Billing said this process will lead to designs, qualification, and reporting.
The recommendations will be reported in the form of a manual that presents the design, what must be done, and how the rear impact guard is installed, Billing said.
The NRC will provide the CTEA with a book based on its findings and surveys from trailer manufacturer members of the CTEA, he said. The NRC wants survey responses and drawings of current rear impact guards.
"We want to understand what people are doing with existing nonqualified rear ends and with the qualified designs," Billing said.
Current Trailer Designs Billing discussed some of current trailer designs and how to best accommodate them with a rear impact guard. He said rear frames on 53-ft vans are basically cookie-cutter production.
"It is impractical to come up with a design that says this is how your trailer must look," Billing said. "The objective should be to have a design that is adaptable to any trailer required to have a guard."
A recommendation for a rear impact guard would be impractical if every manufacturer were required to redesign the rear frame of a trailer, Billing said. The design for the generic rear impact guard needs to preserve as much of the rear frame as possible, and it needs to be repairable so it meets the requirements of FMVSS 223.
The most important interface is between the rear impact guard and trailer. The new generic rear impact guard design may require some stiffening of the rear frame and a standard beam connection between the frame and the guard, Billing said. This will provide the needed energy absorption capability and strength.
"We need to understand the stiffness and the strength of these interfaces so we can make the connection work," he said.
Trailers Exempt From Regs Under regulations in the United States, some types of trailers are exempted from the requirement for rear impact guards, Billing said. The exempted vehicles include wheels-back trailers.
To be defined as a wheels-back vehicle, the rear-most tire must be within 12 inches of the rear of the vehicle, he said. That typically includes many heavy-haul vehicles that operate within Canada and 28-ft van trailers.
By definition, the lead unit of a B-train is a wheels-back vehicle, Billing said. The trailer would not be required to have one of these bumpers because the tires usually are right at the back.
A bumper on a trailer must be within 22 inches of the ground, Billing said. If the rear of the trailer is below 22 inches, then a rear underride guard is not required.
On a typical dropdeck platform trailer, the deck height is 40 inches and the rear frame extends 18 inches below that deck height to 22 inches, he said. If the rear frame of the trailer is higher than 22 inches, the structure must either be moved down or moved up and a bumper added.
Repairing the Guards Repairs to rear impact guards must comply with the dimensional and certification requirements under the Federal Highway Administration's proposed rule, he said. A certification label must be affixed to the replacement bumper.
"But regulators are not requiring compliance with the strength or energy absorption requirements," Billing said.
The repair of rear impact guards was recently an issue at The Maintenance Council meeting in Kansas City, Missouri, said G Allan Tucker, general manager of the Canadian Transportation Equipment Association in St Thomas, Ontario, Canada. The trucking industry wanted standardization so repairs to the guards can be completed reasonably fast and be dimensionally correct.
"They were quite happy to hear about what the CTEA is trying to do up here -- to have a design for a generic rear underride guard that's going to look universal instead of having every one look different," Tucker says.
"The design approach we are taking has the potential to make repairs quite simple," Billing says. In most cases, repairs to the generic rear impact guard will not involve the upper structure.
"The other dilemma happens if the bumper is destroyed where the label is attached," Tucker said. "Trailer manufacturers said they will not mail certification labels to affix to repaired rear underride guards."
Guard Certification Labels When a certification label is destroyed by the elements or ripped off during repair, the compliance of the rear underride guard cannot be checked, Tucker said.
"This is why there is sort of a moratorium on enforcing this regulation in the states," Tucker said. "There are a lot of gray areas here."
The targeted completion date for the generic rear underride guard proposal is April 30, Billing said.
Other Issues Several other seminars at the CTEA seminar covered additional trailer issues. Another seminar given by Billing discussed the certification of anchor points on platform trailers.
"The objective is to produce a performance-based requirement for cargo securement that is implemented and applied uniformly throughout North America," Billing said.
Billing identified several issues regarding cargo securement:
About two thirds of US states automatically adopt federal motor carrier safety regulations for intrastate carriage, he said.
Research used to write Canadian Motor Vehicle Safety Standard (CMVSS) 905 showed that anchor points varied from quite weak to very strong, Billing said. Anchor points designed for light-duty service were quite weak. Other anchor points that were strong when pulled in one direction were weaker when pulled in the other direction.
Platform Anchor Points Several issues exist regarding anchor points. Transport Canada proposed CMVSS905 about three years ago. The new proposal becomes effective in September 1999. It requires anchor points on trailers with a gross weight over 10,000 kilograms, Billing said.
The National Highway Traffic Safety Administration (NHTSA) does not intend to introduce a similar standard in the United States, Billing said. But the Truck Trailer Manufacturers Association (TTMA) does recognize the issue.
"Many manufacturers don't know the capacity of the anchor points they are testing," Billing said. "Testing shows the actual strength of anchor points is quite variable. It may be that some trailers just don't have enough crossmembers.
"It's going to be onerous for many trailer manufacturers to qualify their anchor points. So again the generic process seems a candidate."
First, determine the responsibility of the generic design and its responsibility to the trailer manufacturer, Billing said. The design of the trailer structure should remain the domain of the trailer manufacturer.
"It is necessary to define this interface (between the generic design and the trailer manufacturer)," Billing said. "We don't have a clear idea what's going to come out from the manufacturers."
Brake Drum Tests One of the last trailer subjects covered at the CTEA meeting was a report on the CTEA brake drum evaluation test project. The presentation was made by Richard Radlinkski, president of Radlinski & Associates Inc (RAI) in East Liberty, Ohio.
The CTEA, as part of its generic brake approval program, asked for testing to prove that brake drums make no difference as far as parking brake performance, Radlinski said.
The testing program evaluated whether brake drums make a difference in parking brake performance as defined by CMVSS 121, Radlinski said. The second area Radlinski covered were performance-based brake testers.
The brake drum testing program was initiated because of Transport Canada's request that the CTEA show whether or not brake drums make a difference in terms of the certification of parking brake performance, Radlinksi said. RAI's involvement was as the program manager, and the testing was paid for by the brake drum manufacturers.
Six brake drums were tested, Radlinski said. Meritor provided the axles, brake assemblies, and linings. Additional linings were provided by Brake-Pro.
Two different brake linings were tested, he said. Each series of tests were performed three times to study the repeatability. A series of 36 tests were completed. The order of the tests were random so there were no work-history effects.
Brake Assemblies Tested The test procedure was carried out using a single-ended inertia dynamometer, Radlinski said. A 20,000-lb lining was tested with 5 1/2-inch slack adjusters. The other lining tested had a 22,500-lb GAWR, and was tested with six-inch slack adjusters.
The new brake assembly components, including bushings and camshafts, were given a CMVSS or FMVSS dynamometer burnish, Radlinski said. Immediately following the burnish, a simulated draw-bar test was performed.
"A winch was wrapped around the dynamometer inertia weights and the shaft on the brake assembly was pulled in 90 degree increments," Radlinski said.
The overall conclusion is that brake drums make no difference in parking brake performance, he said.