1. #1
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    Default Flipping step chocks upside down?

    Hey all, We did an extrication class the other day and it came up about many pics we've seen where the chocks were placed with the steps down and the car rested on the flat side of the chock.
    Can someone explain if it is better or worse or if it will comprimise the step chock?

    Here is a link to a picture of what I mean.
    http://www.flickr.com/photos/nilsplace/393129932/


    (I tried to search the forums but found nothing at all related, post a discussion link if found)
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    Last edited by ffmedcbk1; 12-09-2007 at 07:41 PM.

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    There should be no problems, It's acting like a giant wedge. In that particular scenario, the steps on the chock could not be used as a normal step chock would be. I've done it before as well, and it works fine. It would be no different that placing a 4x4 on top of the step chock to fill space under a taller vehicle.
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    We do this routinely, both at work and the VFD. It works well ... it allows a larger contact point with the vehicle (espically if it's on it's top or side) and the steps will make contact with the ground just fine.

    Come to think of it, we just did it a couple of hours ago on an overturned vehicle.
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    It also looks like in the picture provided that it would provide more traction against the ground, the steps look like to be acting as teeth into the ground.

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    Default Step Chocks

    The advantage of using step chocks is that they can be used either as a "step" or a wedge. Either way, the strength does not really change. For the upright vehicle (on wheels) the rescuer can place the chocks under the frame and stabilize the vehicle. The rescuer can go as far as deflate the tires so that the vehicle is resting entirely on the chocks. By using the chocks in this fashion, the vehicle is stabilized in the vertical aspect, meaning the vehicle will not lower. When the step chock is inverted and used as a wedge, the chock takes on additional capabilities. The rescuer places the chock in the same location but simply inverts it; turns it upside down. When 4-point stabilization is utilized, the vehicle now has both vertical and horizontal stabilization provided. The vehicle will not lower, nor will it move side to side because you now have created a "wedge" on both sides basically pinching the vehicle between the chocks.

    Now, one word of caution when performing this techinque. As you may understand, using "step chocks" in their normal position, the vehicle simply rests on the chocks and you can practically forget about them; although we know we must continually keep watch on the stabilization. When inverting the chocks, you MUST watch them more carefully especially when there is a lot of movement in and around the vehicle. I've seen the chocks become dislodged and become ineffective. As noted previously, the inverted step chocks do provide "teeth" on the ground thus providing additional bite to "wedge" or pinch the chocks into the vehicle. Inverting the chocks is dependant on the terrain you're working with. Dirt, grass, gravel will allow great grip, however pavement and clay will sometimes prevent the chocks from gripping thus allowing them to slip out.

    Basically it takes practice and technique. As in the photo, the step chocks are a composite material (plastic) which slides easily as compared to wood which can wear and create a better grip both on the terrain and the vehicle. One other use of "step chocks" is to invert when you have an inverted vehicle. Take the chocks, invert them and place under the "A" and "C" posts of the vehicle. This prevents the vehicle from rocking. When performing this technique, you MUST back up the chocks with box cribbing to prevent the roof from collapsing.

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    I've always taught and been taught that step-chocks are stand-alone devices. They do not go on top of cribbing and cribbing does not go on top of them. If the step-chock does not fit as it is, resting on the ground, then it doesn't get used and you revert to conventional cribbing techniques.

    As for inverting the step-chock, I would think that is up to the manufacturer to decided if it is acceptable or not. Those composite ones I can't see having a problem with it. However if you have wooden ones built with nailed/screwed together pieces, i wouldn't be doing that. The forces being applied to it are completely opposite than it was designed for.... tensile and lateral rather than vertical weight. I wouldn't want to be a test-pilot for that under load.
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    Quote Originally Posted by nmfire View Post
    I've always taught and been taught that step-chocks are stand-alone devices. They do not go on top of cribbing and cribbing does not go on top of them. If the step-chock does not fit as it is, resting on the ground, then it doesn't get used and you revert to conventional cribbing techniques.
    The composite ones are actually designed to be used with a companion wedge. The reason each step is angled backwards is to allow for the step to sit level under the frame once shimmed up into position from the bottom.

    There is no way to ensure vehicles are exactly the right height to match the 2 or 3 inch increments on a step chock so they must be wedged to make then tight (unless you use the tire deflation or body lift techniques).

    IMO, the upside down method is fine for the application shown above and other situations where the body-panel/frame is not parallel to the ground, but less desireable for level frame stabilization. There is much less weight-bearing ability and stability when you are tyring to support a flat object on top of an angled object.
    Last edited by mcaldwell; 12-10-2007 at 05:06 AM.
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    I prefer the wedge method instead of the step. Its inevitable every time you go to slide a step under a vehicle, its either too high or too low for the chock to make contact, so I flip it over for a constant contact point. Plus you can kick it in easily as the car is going up

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    like plastix said, i like to be able to "kick adjust" the inverted step block. I can't stand using them the conventional way - time consuming and sloppy fit.

    the resqjack site shows a lift of a side resting car in a video http://www.res-q-jack.com/Online-Vid...ting-Lift.html where you can see the convenience of the upside down step block. no need to bend over and get your hands in as well.

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    Quote Originally Posted by nmfire View Post

    As for inverting the step-chock, if you have wooden ones built with nailed/screwed together pieces, i wouldn't be doing that. The forces being applied to it are completely opposite than it was designed for.... tensile and lateral rather than vertical weight. I wouldn't want to be a test-pilot for that under load.
    Realistically, the weight you're working with on a vehicle extrication is minimal and is normally not a concern. If you're dealing with collapse rescue, that's another issue...

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    And why couldn't/wouldn't you use a step on a crib if necessary on a SUV or similar?Both are intended to be vertically loaded.We see/do this a lot up here with the SUV's and tall tires. T.C.

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    Default inverted step chocks

    Our department has been practicing this method for a few years now. It works fine, especially when there is gravel, glass, etc. on the asphalt. It allows for better contact with the ground. You do need to ensure there is an opposing chock on the other side of the vehicle in order to oppose the angle of the chock. By this I mean, when you turn a chock upside down it puts a wedge toward the vehicle, when you do this you must put another one on the other side. This creates opposing force for better stability.

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    Quote Originally Posted by nmfire View Post
    I've always taught and been taught that step-chocks are stand-alone devices. They do not go on top of cribbing and cribbing does not go on top of them. If the step-chock does not fit as it is, resting on the ground, then it doesn't get used and you revert to conventional cribbing techniques.
    Routinely taught by many, inlcuding manufacturers
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    We do it routinely. Also we will push the chock in loosely grab the strap and apply a gentle upward pressure, then slide (not kick) a wedge under it.

    When you release the pressure the chock is held by the wedge giving a firmer support. This negates the need to p!ss around letting down tires which is a complete waste of time.

    The object is to stabilise the vehicle, not carry its full weight.

    The reason for not kicking the chock is obvious, it is unnerving to the trapped people as well as causing pain if they have broken bones.
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    It depends on the situation. We will flip them upside down or we will use them upright and have a few guys lift the car by hand a little to get it onto a step level if needed (only if it needs to go up about 1" or so). One reason we love the step chocks is because of their versatility.

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    The down side of a step chock is the trip hazard they can pose, given that they can stick out a bit depending on their size and the placement...
    Luke

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    Also with step chocks on lower to the ground vehicles they are too tall and actually block the use of the doors. We ran into this in a training exercise last weekend. It of course is just something that the person handling the stabilization needs to notice before all is done and ready to start cutting. Great thread btw!

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