Raising the front
- Thread starter gonervn
- Start date
porthole
Retired
There is only one way to do that correctly and safely - cribbing.
Get yourself some 4x4's, non pressure treated and DO NOT paint. A standard two tier (meaning 2 pieces of cut cribbing at each level) has a load capacity of up to 24,000 pounds, Over 50,000 if you use 3 pieces at each level.
Some 3/4" plywood as well, make a couple of 18" square "wafers"
At the top, use two extra 4x4's then use the plywood so your jack pad has a solid surface.
You do not need to fill all the gaps with extra wood. Although it gets stronger as you increase the number of cribs, you also reduce the friction load on each piece. You need both, load capacity and friction to work.
Rather then go through all the details here, I attached a cribbing worksheet which goes into all the details.
This is what we do in the Fire service to pick up - support just about anything. Done correctly you can lift a train.
For the height you want I would suggest keeping your landing gear retracted and crib right up to the height you need then adjust with the landing gear. You should be nice and stable then
Get yourself some 4x4's, non pressure treated and DO NOT paint. A standard two tier (meaning 2 pieces of cut cribbing at each level) has a load capacity of up to 24,000 pounds, Over 50,000 if you use 3 pieces at each level.
Some 3/4" plywood as well, make a couple of 18" square "wafers"
At the top, use two extra 4x4's then use the plywood so your jack pad has a solid surface.
You do not need to fill all the gaps with extra wood. Although it gets stronger as you increase the number of cribs, you also reduce the friction load on each piece. You need both, load capacity and friction to work.
Rather then go through all the details here, I attached a cribbing worksheet which goes into all the details.
This is what we do in the Fire service to pick up - support just about anything. Done correctly you can lift a train.
For the height you want I would suggest keeping your landing gear retracted and crib right up to the height you need then adjust with the landing gear. You should be nice and stable then
Last edited:
porthole
Retired
JohnDar
Prolifically Gabby Member
No, I hadn't seen that. But after watching it a couple of times, it looks like they overextended the struts. You see how little of the piston was left in the strut by where the collar is after it came apart. They should have added an extension so as not to do that. We have enough equipment to do that (L-trench corner) and now have the aluminum wales, along with the corner blocks and thrust plates. No more cutting lumber for it. I've been converting a 36 ft. cargo trailer into a Trench/Structural Collapse response trailer. It's still a work in progress.
View attachment 30441
This was back when I did my technician level training a few years back, taught by Chase Sargent. We didn't have all the gear we have now.
View attachment 30437
View attachment 30441
This was back when I did my technician level training a few years back, taught by Chase Sargent. We didn't have all the gear we have now.
View attachment 30437
traveler44
Well-known member
I think I would want the top layer of blocks close together and running in the same direction as the rv. Maybe add an extra block in the top row to make a better platform for the jack plate. Sounds like a very steep incline to be camping on. My wife would be too nervous to let me do that.
porthole
Retired
John - that video was intentional, showing what can happen if do not follow the proper guidelines.
Cribbing as depicted above works. Friction is needed, so the cribs need to be built just as the PDF file shows.
I suggested using a 3rd crib at the top to support the plywood and trailer jack lower plate. Probably should have a 3 crib on the 2nd from top as well.
And if it was a rescue situation, and using a 3rd crib at the top, the whole pile would be 3 on 3
Cribbing as depicted above works. Friction is needed, so the cribs need to be built just as the PDF file shows.
I suggested using a 3rd crib at the top to support the plywood and trailer jack lower plate. Probably should have a 3 crib on the 2nd from top as well.
And if it was a rescue situation, and using a 3rd crib at the top, the whole pile would be 3 on 3
JohnDar
Prolifically Gabby Member
Got it and will use it for training. When I teach this stuff, I don't allow for any shortcuts or "good enough's." I held a small rope rescue practice a few days ago. Guy rigging the belay line felt we didn't need the LRH in installed. Short version, it got rigged in. Sometimes, this LT reverts to his old E-8 persona.
porthole
Retired
Cost
Pressure treated can be slick when wet, especially when newer
The chemicals injected - we deal with enough chemicals already.
Many times at an extended scene we are also cutting wood as we go. So there is that issue with the saw dust
Splinters with pressure treated double the suck factor.
Pressure treated tends to bend and warp if not "built" into something.
Ever buy 4x4's and let one sit for awhile before using?
The stability on the crib concept comes from both the crush resistance and the friction between components.
I don't have any knowledge one way or another but I would think injecting the chemicals has to weaken the wood some.
gonervn
Bill & Sallie
Duane,
Sorry about the second question, just want to make sure I understand it correctly. I did read the pdf and i'm guessing wood should be untreated for the friction part. My question is in your example you said cut 18 in wafers. Would that wafer cover the entire stack including the over hangs?
Sorry about the second question, just want to make sure I understand it correctly. I did read the pdf and i'm guessing wood should be untreated for the friction part. My question is in your example you said cut 18 in wafers. Would that wafer cover the entire stack including the over hangs?
porthole
Retired
Bill, yes. Although I don't have any real reason other then to just have the wafers the same size as the crib lengths.
During an "event" telling the cutter to give you 18" 4x4's and wafers to match seems easier.
BTW, we typically use 24" lengths.
Cribbing is a very stable way to lift and support large heavy objects. Been quite popular in the New jersey area since that brat Sandy reared her ugly side 2 years ago.
During an "event" telling the cutter to give you 18" 4x4's and wafers to match seems easier.
BTW, we typically use 24" lengths.
Cribbing is a very stable way to lift and support large heavy objects. Been quite popular in the New jersey area since that brat Sandy reared her ugly side 2 years ago.
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