MGM offers insight into spring brake actuators manufactured with welded yokes.
MGM offers insight into the benefits of utilizing a welded yoke clevis. This paper gives the history and benefits of the welded yoke clevis.
The Benefits of Spring Brake Chambers Utilizing a Welded-Yoke Clevis History
For as long as there have been heavy-duty vehicles with air brakes, there have been concerns ensuring the proper length of a replacement brake chamber’s push rod, when changing chambers on commercial vehicles. Maintaining proper replacement brake chamber push rod length (as determined by the vehicle’s manufacturer) is not only a critical maintenance procedure, but is also a crucial step in maintaining the performance and efficiency of the vehicles braking system. Properly installing the correct brake chamber, with the correct push rod length, is vital in assuring the vehicles ability to firmly hold while parked on grade, as well as the overall vehicle brake system capacity to stop the vehicle within a safe distance. For many years, all spring brake chambers installed on heavy-duty vehicles utilized a threaded push rod that is cut to the proper length as specified by the manufacturer. These rod lengths may vary between vehicle manufacturers. Even different models within a single manufacturer could differ in the correct push rod length. Many variables contribute to the varying push rod lengths, including differing suspensions and axle configurations. To allow quick installation during production, heavy-duty vehicle manufacturers had OEM brake chamber suppliers pre-cut the push rod to the proper length, thereby necessitating brake chambers at the factory with varying push rod lengths depending on the models of heavy-duty vehicles built. When brake chamber replacement becomes necessary in the aftermarket, aftermarket brake chamber manufacturers typically produced chambers with a universal 8-inch threaded push rod as a “one size fits all” replacement part. This allowed for a universal replacement part, whereby a mechanic usually compared the push rod length of the previous chamber, and cut the push rod of the replacement chamber to match the length of the chamber being replaced. The issue then arose where mechanics failed to use proper procedures when cutting the threaded-rod. This resulted in the vehicle brakes being set up improperly, causing problems such as inadequate parking brake performance (vehicles rolling when parked), increased vehicle instability during panic stops, or increased stopping distances during brake events. In the case of earlier model year vehicles that utilized manual brake adjusters, the push rod length wasn’t as critical as the brake adjuster was set manually, and could somewhat compensate for push rod length error. This was an industry-accepted practice which masked this problem before the advent of automatic brake adjusters (ABA’s). The automatic brake adjuster, mandated on all air brake vehicles in 1995, didn’t allow room for error in the proper cutting of the push rod, and depends on the proper push rod length in order to maintain automatic adjustment as designed.
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