What dimensions are your cribbing sets?
What type of hard wood do you use for cribbing?
I am not a fan of the plastic cribbing so we are trying to build our own. We just received a grant for cutter, spreader, combi tool, air bags, rams, stabiliztion struts, and all accessories. Just no cribbing. So any help would be appreciated.
Our cribbing is all 24" long. We have 2x4, 4x4, and 4x6. The wedges are just made out of a 24" 4x4 that we cut 6" from one end to the same distance from the other end, making them about 18" long with 12" of it being wedge.
Ours are all made of red oak that we got from a local sawmill. They're a valuable asset if you've got one nearby.
same as you, but we just use any kind of oak. we also have the plastic step cribbing that we never use lol:D
Originally Posted by Catch22
We just happened to get red oak, I'm really not that picky as long as it's hardwood.
Originally Posted by RS1606
thats what she said! :D
Originally Posted by Catch22
Doug fir or Southern Pine, stay away from the real hardwood, it is expensive and doesn't crush, like doug fir. when a crib crushes it gives you an indicator that it might fail. If hardwood is overloaded to failure it may just fail without crushing.
We have 18" and 24" cribbing, don't forget not to exceed 3 times the width of the crib (not the length of the members) so an 18" 4X4 can make a crib around 30 inches tall. 24" can make a 48" crib
I agree with ADSN. When I teach classes, the #1 point of ignorance is on how to correctly use a ratchet strap. #2 is on how to use cribbing. This link will give you a PDF on cribbing that you can print, laminate and put in your cribbing compartment. It is from the FEMA Heavy Rescue Technician manual and the Field Operations Guide (FOG). Its ratings are based on 500 lb per square inch of crossgrain load capacity, which is Douglas Fir or Yellow Pine.
Not only will the softer woods make noise to let you know when they are getting overloaded, but they develop better stability under load because they deflect easier and lock together better than hardwoods.
Height is a big point of confusion for most beginning Firefighters. If you review the cribbing page you will notice that heights are based on the width of the FOOTPRINT of the cribbing stack, NOT the length of the cribbing. A square box crib has a maximum height limit of 3 times the footprint (length of cribbing minus 2 times the thickness of the wood due to overlap).
A box made of "4X4's" (actually 3.5X3.5") 18 long wood has a maximum height limit of 33. 24 long 4X4s can go up to 51. This is why most departments are dumping their old 18 cribbing and going to 24 long cribbing.
Note that those numbers are only for 4 points of contact. Max height for 2 points of contact (typical extrication scenario) is only 1.5 times the width of the footprint. Thats 16.5 high for 18 wood, and 25.5 high for 24 long wood. One point of contact is limited to 1 times the footprint.
Thanks for that link Tim. That's very useful.
Like I say, the biggest reason we went with the hardwood cribbing is that we have a sawmill that gave it to us (free isn't a bad thing most of the time). There's some other benefits, as well, in that the oak will withstand more PSI of force and it's rough-sawn, so it grips to itself better. At one time I knew where a chart was showing the strengh of different kinds of wood for cribbing, but I can't find it now.
My biggest problem is going to the local lumber yard and buying lumber for cribbing. I've seen several departments that have the CCA-treated lumber they've cut for cribbing. not only can it be soft and knotty, it's slick as snot. Around here it's very hard to find anything that's not treated, save going to a sawmill.
With the majority of the lumber that's cut around here being oak and walnut, it's rather easy to find someone that'll give you some scraps or lengths of oak for cribbing.
its the same way with the plastic step cribs. it wont give any warning but just collaps.
Originally Posted by ADSNWFLD
Does anyone carry anything larger than just 24" 4x4s?
The compliment that I work with is as listed:
80 - 24" 4x4s
40 - 24" 2x4s
24 - 24" 6x6s
20 - 36" 6x6s
6 - 36" 4x4's
The larger cribbing can be used to create platforms for High and Medium pressure lifting bags.
It is also important to remember that it is more flexible to carry all 24" (or greater) cribbing instead of a mix of 24" and 18". You can make a 24" piece of cribbing 18"s by using a chain saw, but you can't make a 18" piece of cribbing 24"s.
i was taught never go more than 4 levels high. unless there is no other option
Sorry but that is incorrect.
An 18" 4X4 can make a crib around 30 inches tall. 24" can make a 48" crib
That is right out of the SOG /FOG http://www.disasterengineer.org/Libr...7/Default.aspx
ok. im going by TARS standards. thats who im taught by. i think they say that to try and be on the safe side.
Cribbing dimensions should be 24". Our lumber comes from lumber yards and Home Depot. It gets beat to hell and we've never had any problems. Just remember always build the crib stacks correct. All pieces should line up and the overhang should be no more than the dimension of the lumber.
We go with rough cut hard wood. Generally we have oak, but some maple and a local saw mill is going to get us some hickory this summer.
We go with 24" lengths and make sure that we have a stap on the outward facing ends. I have also seen in many classes where departments color code the ends for lengths.
Timber Cribbing Info
If anyone is interested, please email me on firstname.lastname@example.org and I'll send you a handout specifically for timber cribbing that may help.
We have used Douglas fir because of it's characteristics: great strength..has rough surface rather than a glaze like some harder woods, less tendency of slippage. Wood is audible over plastics that if things are moving you have a audible indicator. The length has been 18"inches which gives us a safe working height of approx. 30 inches. Another factor in relation to length to keep in mind is where the cribbing is to be stored? All said!!! Work within your budget and resources!!