Wrecker FramesApr 26th, 2013 | By Editorial Staff | Category: Jack Schrock's Blog
Before hydraulic wreckers the wrecker crane assembly on HD Holmes mechanical wreckers mounted directly to the truck frame as did the body, if there was one. However, most hydraulic designs now include a continuous sub frame that sits directly on top of the truck frame and the winches, boom, underlift, everything now attaches to that sub frame. And, for obvious reasons, this sub frame is usually very robust, leading some to believe that reinforcement of the truck frame is no longer necessary… Well, read on.
In a European study involving over 200 HD hydraulic wreckers, frame failures often occurred several feet behind the truck cab in an area that was/is not usually reinforced by the shorter sub frame.
Super heavy-duty truck frames are available from the truck manufacturer of new chassis. But if the tower chooses to select a used road tractor chassis, frame reinforcement must be done in the field and that can be very tricky. First, it is necessary to remove all that “stuff” from the rear brackets of the front spring hangers back and that’s a big task in more ways than one. Then the reinforcement should be a complete glove, though some try to fishplate with a single, flat piece of continuous metal, or an inverted “L” which is some better. I’ve known towers who have used double gloves resulting in a triple frame. But, that really is expensive as well as very heavy, which makes a bad problem worse. And, over the years, rust begins to take its toll between the surface(s) of the gloved frame.
Assuming that the 25-ton wrecker is primarily a tow truck, it is my recommendation that everything above that rating should have a double frame for a higher Resisting Bending Moment (RBM) as recommended by the wrecker manufacturer. How you get there is entirely your choice.
And yes, Capt. Whitaker was right. You can fly a commercial airliner upside down, but not for very long.