Cribbing Questions

Replies to This Discussion

Permalink Reply by lutan1 on January 12, 2009 at 4:46am

Here's a couple of links I just came across that may be of interest:

Destructive testing of box cribbing
http://www.cribpac.com/cribtest.html

Mechanical properties of wood
http://www.cribpac.com/woodspecs.html

▶ Reply to This

Permalink Reply by Mark Montgomery on January 12, 2009 at 5:03am

To me the cribbing does not look right.

From a basic engineering viewpoint once you get a dynamic load, such as a car on pneumatic tyres on an angle you need to brace against the force push back towards you (the side of the vehicle).

Looking at the base of the cribbing we can see from top to bottom in the photo it appears that the base cribs are too narrowly set out having been placed side by side, so we end up with a very unstable inverted pyramid. General instructions for safe cribbing have "the height should not be more than three times the width."

▶ Reply to This

Permalink Reply by Asst. 29 on January 12, 2009 at 12:37pm

Mark hit it right. The base of the crib needs to be wider. with a narrow box crib the higher you go the less stable it becomes. Also you can not make it out in the picture but has anything been done on the other side of the vehicle? I would have at least deflated the tires to reduce the possibility of the vehicle moving sideways thus causing it to fall off the box crib.

▶ Reply to This

Permalink Reply by lutan1 on January 12, 2009 at 1:29pm

The other consideration is keeping members out of the firing line of lifting airbags.

There was a case over here where a career firey got pretty seriously injured on a training drill when the airbag became dislodged and flew out at him at a great rate of knots! Using this picture as an example, the operators would wear the impact in the face...

▶ Reply to This

Permalink Reply by john mueller on January 13, 2009 at 1:25pm

i agree the hight is way to tall , and even though this is training you would most likey not need to lift this high .plus by the picture it dont look like the other side is stablized in any way the tire on the front still looks to have air in it and you cant see any other cribing on that side if you look at the rear bag it looks to be on two 2x4S that could spread apart with the curve of the bag , causing it to dislodge and hitting the firefighter in front of it . personal safty must come first .

▶ Reply to This

Permalink Reply by Asst Chief Tim Cook on June 5, 2009 at 9:09pm

It's NOT textbook! Base too narrow,stack too high,it doesn't appear that the wheels are chocked in any fashion. If I were doing this lift I'd use one lifting point just forward of center and use BOTH bags stacked. Crib as you go.

▶ Reply to This

Permalink Reply by Ben Waller on June 7, 2009 at 10:00am

Tim is correct on all counts. Another way to use this is to use struts that have jacking capability or to use a single cribbing stack with double-stacked air bags and to use struts instead of the additional stacks of safety cribbing.

▶ Reply to This

Permalink Reply by Jeff Burr on July 21, 2009 at 9:07pm

My question what are they trying to do? If they want to lift the car. Res-Q-Jacks all the way!

▶ Reply to This

Permalink Reply by Ben Waller on July 21, 2009 at 9:16pm

If they started with the car on all four tires, good luck finding a ResQJack short enough to start the lift.

▶ Reply to This

Permalink Reply by FETC on July 21, 2009 at 9:35pm

Using a "sling" chain lift regardless of manufacturer would allow the height needed. But I agree with Ben and Tim airbags re-centered. I would use the struts to stabilize the bag lift.

▶ Reply to This

Permalink Reply by Ben Waller on July 21, 2009 at 9:36pm

How would this work if you needed to lift only one side, or if you only had access to one side?

▶ Reply to This

Permalink Reply by FETC on July 21, 2009 at 10:07pm

You can sling the undercarriage and carry the chain to the airbag side at the height needed, I would use one in the front and rear quarter panels. (the new space saver jacks are very short)

As the bags lift, have someone crank or extend the struts to take up any collapse space created from the bag lift. (dual kick stands)

▶ Reply to This

• First
• Previous
• Next
• Last