Delft Germany FD's Stepchocks

[rmoore]

During a visit to fire stations in Delft, Germany, I found these stepchocks. They are interesting for several reasons. They are rugged. They have wedges carried inside them. The wedges easily insert into the bottom to tighten the cribbing. They also build upon one another for high ground clearance vehicles. I'm going to build some and try them out.

[rmoore]

Here is a close-up of the wedges adjusting the height of the German stepchock.

Also, when turned vertically, two stepchocks can be used by the firefighters for stabilization of high ground clearance vehicles..

[billyleach]

Looks good. I bet several folks with build them with variations.

[ffmedcbk1]

sir ron, did they have a build sheet for you? are they glued and clamped or is there screws involved? 3/4" plywood?

[Rescue101]

Marine grade Plywood? Interesting design,I like the all in one feature. T.C.

[rmoore]

There was a set of bolts and recessed nuts/washers binding the layers together. Nothing stuck out; everything was flush.

I do not know if each layer of the body of the stepchock was glued or not. There was no evidence of any glue but typical of German engineering, I'd bet that each layer was glued to the other and then the big bolt put in place.

[rmoore]

I did ask why the wedges had recessed 'holes' along their sides. Answer was that when the wedges are stored inside the stepchock, the two recessed shallow holes were for grip. Your thumb and one finger can grab the wedge and pull it out of the stepchock without the need for any rope or strap handle.

[Theusje]

Are you sure that was in Germany? The only Delft I know is in The Netherlands.

Anyway we use a plastic version of such a block but with seperate wedges. Allthough we can't place two on top off each other like they do.

Edit: we use these kinds of blocks: http://brandweerduffel.be/145/#c852

[TimatRescue42]

Hey Ron,

You know me; I love cool stuff, and these are cool!

However... I see a few problems.

First, they have forgotten one of the fundamental rules of a free-standing support. There needs to be a base that is at least as wide as 50% of the height. If you go measure a jackstand (for example) you will see that it will not go any taller than twice the width of the base. The same goes for a Turtle Plastics, Rescue 42 or any correctly made wooden step chock. This rule gets stretched to 3X the base in box cribbing because it is built of separate structures tied together with cross ties. In this case the base looks like it is about 4" wide, but you have it well over a foot tall. This does not meet the rule and should not be used above 8" (or 2X) the width of the base. This could be fixed by adding a wide baseplate to the bottom of the chock.

Your stack job in the last picture... well, picture doing that with 4X4's all stacked on top of each other in the same direction. This is the too-narrow base problem compounded.

I will be interested to see how strong it is. In the close-up of the wedges it appears that all the load is felt where the top of the wedge meets the chock. While I see a metal crosstie plate up higher, the point where the wedge is touching seems to just be an I-Beam glue joint in "double shear". It does not look very strong. For a European sedan it may be ok. An American 350/3500 truck will probably crush it. You might run a bolt through the part right at that point to reinforce the glue. I am also curious how that top step will hold up under load as it is cantilevered over the cutout section.

Interesting design!

-Tim

[jbrescue]

Are you sure that was in Germany? The only Delft I know is in The Netherlands.

Anyway we use a plastic version of such a block but with seperate wedges. Allthough we can't place two on top off each other like they do.

Edit: we use these kinds of blocks: http://brandweerduffel.be/145/#c852

Wood is cheap and easily changed on the fly with a saw. Those plastic ones tend to slip when wet and are very expensive, especially if you have to leave them on the scene for some reason.

[johnsb]

While the concept is cool, as a woodworker, I would double up the outside layers of the plywood so there were two layers not just one. As for glue, my choice would be liquid nails or a polyurethane glue like Gorilla glue. And for using the second stepchock for high clearance, I'd drill some holes in both so that I could insert some metal pins that would align the two for less chance of it slipping out.

[Catch22]

I don't know what kind of plywood they're using, but it looks like that bottom plate has 14 plies. They definitely aren't using the cheap stuff.