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TTMA-100 Trailer Mounted Impact Attenuator: How it works
Tube Bursting Technology
The TTMA-100 uses a patented tube bursting technology to safely dissipate the energy of the impacting vehicle. The basic concept is quite simple. When a tapered mandrel with a square cross-section is forced into a square tube with smaller inside dimensions, the mandrel pushes against the inside of the tube. The outward forces on the inside of the tube concentrate stresses in the corners, creating a controlled cracking of the steel. As the mandrel proceeds forward, the tube is split into four flat straps of metal that are curled outward by the flared portion of the mandrel. See below.
Tube Bursting Process
This bursting process, i.e., cracking of the tube at the corners and splitting it into four straps of flat metal, dissipates the energy of the impacting vehicle. The level of energy dissipation can be regulated by using different thickness and lengths of tubing and scoring the tube, i.e., cutting grooves into the tubes at the corners reducing the energy dissipated during cracking. By adjusting the level of energy dissipation the rate of vehicle deceleration can be controlled to bring the impacting vehicle to a gradual and safe stop.
Tube bursting technology allows the TTMA-100 to use the trailer frame as the energy absorber, thus eliminating the need for a separate energy absorbing material. This simplifies the design and reduces the costs of the TTMA-100. Also, the straps of metal have no structural strength and curl up and away from the impacting vehicle, thus eliminating any hazard posed to the impacting vehicle. Furthermore, the straps of metal remain securely attached to the un-bursted section of the tube. Thus there are no detached elements that can be thrown forward at the construction site and pose hazard to workers and adjacent traffic.
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- How It Works (PDF file, 360 KB, opens in separate window or tab)
The TTMA-100 incorporates several innovative design features that render it superior to other Truck Mounted Attenuators (TMAs) in the market today. The patented tube bursting technology utilizes the tubular trailer frame as the energy absorber. Thus, there is no need to use a separate bulky energy absorbing material like other TMAs. The end result is an affordable trailer that is simple in design, light weight, and highly effective. Another innovative feature is the use of a simple hitch mount which allows the TTMA-100 to rotate upon impact, unlike competing trailer attenuators that utilize rotational restraints to prevent the attenuator from rotating. The impact head is designed to produce a mechanical interlock with the front of impacting vehicle. Thus, the rotation allows the trailer to be aligned with the impacting vehicle, maximizing the energy dissipation and minimizing the risk to the vehicle occupants. The TTMA-100 is the only TMA on the market today that was tested with the support vehicle blocked against all forward movement in all the required and optional crash tests set forth in NCHRP Report 350. Hence, there is no upper limit on the weight of the support vehicle and the TTMA-100 can be used with any support vehicle weighing 10,000 lbs or more in GVW. More detailed description of these innovative features, including the tube bursting technology and the pintle hook attachment that allows for rotation are provided in this document.
- Features and Benefits (PDF file, 26 KB, opens in separate window or tab)
The innovative design features incorporated into the TTMA-100 provide for more features and benefits, particularly in terms of its flexibility in field applications. A list of the features and benefits is outlined in this document.
Gregory Industries, Inc. • 4100 13th Street, SW • Canton, Ohio 44710 • Phone 330-477-4800
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