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Stabilizing Heavy Trucks

Tue, 16 Aug 2011|

Steve White explains why firefighters can't take a small vehicle approach to large vehicle stabilization and examines common cribbing and methods of stabilization. Sponsored by Holmatro.



[MUSIC] [SOUND]. Welcome to fire engineering's training minutes. I'm Steve White, the time chief, Fisher's Fire Department. In this segment we're gonna talk about stabilizing heavy trucks. The one thing we really want to emphasize throughout this whole program, is that you can't take a small vehicle approach to a big truck rescue. We are dealing with vehicles that are taller. Vehicles and their loads that are heavier, and to be able to accomplish this, we have to have good solid stabilization or not capturing the weight of a car. We're gonna start off by talking about four by four cribbing. Four by four cribbing is the most common used cribbing in the fire service. Now, technically we know that it's really three and a half by three and a half. For this segment we're going to call it a 4 x 4. Another key component is the length of the cribbing. We are going to be dealing with 24 inch long cribbing. When we build our box cribs there's two critical factors that we want to make sure we're getting correct. And that is how much weight this crib box can support, and how high we can safely and effectively build this box crib. When we build the box crib we want to ensure that we have four inches of overhand everywhere there's a point of contact. Anything greater than that makes the box unsafe. To be able to figure out how much weight we can establish. We're gonna talk about points of contact, and the point of contact is everywhere the cribbing comes across the top of another piece of cribbing. Each point of contact can support or capture 6,000 pounds. So when we have four points of contact, 6,000 pounds times four is 24,000 pounds. So, as long as the entire load is resting across all four points, we can capture 24,000 pounds of weight. When it comes to height, there's two factors we have to understand. If we capture all four points, okay, we can go up to. Forty-eight inches tall. And we figure that because we're looking at sixteen inches, from outside to outside, times three, is how we come up with forty-eight. So it's not the dimensions or the length of the twenty-four inches, it's the sixteen inches. From where our points of contact are. So, 16 times 3 is 48, four points of contact, we can build this box 48 inches tall. Now we know in some situations, based on the positions of the vehicles, we may not be able to capture all four points. We may be only able to capture. Just two points so that takes our weight to six and six, 12,000 pounds but it's gonna have an impact on our height. When dealing with the same 16 inches, it's 16 times one and a half. That comes to 24 inches. So, when you're only capturing two points of contact. We can go up to 24 inches and no more because then when we build it beyond the safety factor, then it can sway and it's no longer safe. To capture the points of contacts, it's effective to use. Wedges in various positions and again the key point is we want to make sure that where we capture the load, we want to distribute it down and keep our system in line at all times. Here we're gonna build a box crib starting with a good stable base. Now we understand that normally there would be a trailer in the way. We've removed the trailer so that we can demonstrate clearly. What our task is. Understand too that we have to do a size up to our load and understand what can impact at the end where we go to tighten the system up with our wedges. It could be various bolts, mudflaps, and hoses and other items that are in the way. If we can move the hoses without cutting that would be perfect. But any aluminum or metal objects are in the way, we can simply cut off with cutters, chisels, or sawsalls so that we can gain good, positive contact. Here with this box crib, we're capturing two points of contact. So, we're stabilizing 12,000 pounds. At the back points of contact. Using the wedges we're able to tighten that box crib up. Now we have an effective means of stabilization for the back of this frame rail. Now we know that in every rescue situation we're not always gonna have the perfect scenario. Sometimes it's safer to build the box tower outside of an area and slide it in. Working as team, using four by fours to push it, we can get it in place, safely and effectively. When we tighten it, we wanna double check because typically, our vision is gonna be the front. In order to make sure that we're maintaining that four inches of overhang correctly and keeping all of points of contact in line. It's critical that we check the two points of contact that we're capturing in the box so that when we slide the box, it doesn't get out of frame. Here we're dealing with an air ride cab. On size up, it's easy to identify by looking at the back of the cab. Here we have two cushions. That helps the cab rest. The problem is it makes the cab very unstable during extraction operations. So what we want to do is we want to capture the space between the cab and the frame rail, stabilize it so that now the cab is resting on our cribbing. And not the unstable air ride cushions. [BLANK_AUDIO] As another alternative for stabilizing the air ride cab. We're going to use side also known as clutches, this is an option for stabilizing if you have the ability to, other wise you can simply just use the wedges that we just covered, one thing that we want to stress. Is that we are not supporting the load of the entire tractor. We are just simply stabilizing the aluminum cab for movement, taking it off the air cushions, and putting it on our system that doesn't move during extrication operations and patient removal. During this segment of the stabilization, what we're going to do is stabilize the large vehicle, on top of a smaller vehicle. It's critical to point out, that we have, the car stabilized, always have to stabilize from the ground up, having a good base. As well as chalking the tires of the truck. In this scenario we're gonna use the side buttress stabilization devices in two places to be able to stabilize the load. The side buttress stabilization system we're using is the halmotro power strut. It's a combination of making it a mechanical strut after we put it in place with a hydraulic pump. The pump in this scenario is a manual pump. The critical factor is that where the strut makes contact. Is at the frame rail on both sets of struts. We're simply stabilizing the vehicle in this scenario we do not have the intent of lifting the vehicle. Once the struts in place, we're gonna go ahead and back it up. And that makes a mechanical strut. Now we're going to put the driver's side struts in place. the struts we're using on this side are static struts. They are not put in place with a hydraulic pump. One critical factor to remember in all rescue operations, in particular the initial stabilization phase, we're always trying to strive beyond one need. By being on one knee, that allows us to quickly move out of the area in the event the load shifts. [pause] Or he comes out of balance. And it's also important, when you're working on one knee, to make sure that you always have a means of being dressed clear, behind you. You don't want any tools or equipment in your way, if you want to move out from, a load, quickly. [NOISE] The principles of the struts are the same as if you were stabilizing a car. It's an A-frame we're trying to maintain, stay within a 45 degree angle. Good solid positive contact. And this is just to stabilize, not to lift or raise the vehicle. Again our strut is making firm, positive contact with the frame rail and the ground, not to any moving parts on the truck. For this part of the stabilization segment, we want to simulate a common accident. With a car, underneath the semi trailer, known as an under-ride. Looking at our stabilization, we're sticking with our 24 inch long curbing. Building our solid base. All the way up to our points of contact. Which when it reaches the top, the outside section is what we refer to as the rail. Underneath our actual floor joist that run from side to side. Typically, their spaced anywhere from 10 to 16 inches apart. So, it's pretty important that we either read the rivets. So where it's attached, where do we physically go underneath, size up where those floor joists are, because the two outside points of contact will catch the rail, the back two points contact on the crib box will catch the floor joist. By catching all four points. We're able to say that we are be, supporting 24000 pounds without exceeding the max height of 48 inches. As we transition to the other side of the car. We utilized a strut system. One thing that we want to point out about the strut is the placement also should be at the floor joint. Good solid positive contact, maining, maintaining a 45 degree angle and we're tightening our ratchet straps. In this scenario we're using two ratchet straps between the struts on either side of the truck. As we close this stabilization segment, we just wanna emphasize that we've covered just a few basic scenarios. For simple stabilization. Loads, weights, can vary based on the size of the trucks, so being able to use these tools are a good starting point. We'd ;like to thank Homatro for sponsoring this section of the training mimics. Thanks for watching

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