[Grandman]

Here is an EXCELLENT article on offroad recovery. It is from Bill Vista over at pirate4x4. This has many excerpts from the military recovery manual and other quality sources of information like wire and strap suppliers.

Also has the charts that were mentioned above.

http://www.pirate4x4.com/tech/billavista/Recovery/

well damn that would of saved alot of time . Very well done post . Thanks for the link .

 

[Yetti]

Here is a work sheet chart to help with calculations to over come resitance in a pull. you have to observe each axle to know how to figure load. use the chart to give each axle a % of resitance and then you can gauge the pull base on it and the axles estimated weight. add the axles on the second page which is the work sheet with an example to help you figure restance load

use the center section of the above chart to start out with. just assmue the car is on a level surface to figure out how to use it.

I'll check back later to see if you figured out how to use this chart.

 

[Yetti]

http://secure.cartsvr.net/catalogs/catalog.asp?prodid=342664&showprevnext=1

if you want to cheat and buy a nice recovery calculator have at it.

 

[97xj]

Because a picture can be worth a 1000 words...

Don't mess around with cheap and wornout recovery equipment.

Clevis comes in the back window... though the Head Rest... Out the windshield... Jeep rolls forward onto the end of the strap.

 

[Yetti]

that is the worst picture ever! I can only hope no one died or was injured.

 

[mudd_jumper]

proper connection , make sure you and the rig you hook to have a solid hook point , do not turst the other person that there bumper is solid , tow hook and so on . 2 bolts grade 8 3/8 or larger thread size are minimum to secure a tow point for a lite weight rig .

Then does this mean that you do not recomend weld on d-rings? I ask becuase I need to upgrade my front bumper and want to do it right.

 

[Yetti]

here is the cable & chain selection charts. hope it helps

 

[whiterhino]

Marv,
Good post. No arguements from me. As already stated, there are actually 2 different ways to attach two straps together but I don't have any pics. (this makes my post lame I know)

Regarding the chrome hook breaking.... I would agree with Marv that it is probably a cheap aftermarket hook. But, the chrome platint DOES NOT weaken the material underneath. Chrome plating does not use heat and therefore will not anneal or draw back a hardened material. In addition, cosmetic chrome is only .0005" to .002" thick.

 

[Grandman]

Welding on D rings . I dont have a problem with welding them on " IF " it is done by a competent welder . Some one who knows how to get the proper penetration on the weld . A weld can look pretty and have no strenght .

If this is a tube bumper , like 2x6 retangular steel then no dont weld then on the face of it . You would want to bolt all the way through the bumper so both sides of the tube was holding .

whiterhino , i seldom frequent other boards so im not sure of your post you mention !

 

[DetR6oit]

Some explanation of the differences in straps; i.e. a "jerk" strap vs "tow" strap vs air "sling" strap.

I don't think there are exact rules or specifications for it but this seems to be the general guide lines.


Tow strap - Usually the ones with hooks and rated for 7-10k lbs. Like the name states its intended for towing, meaning more static loads like for example, towing a vehicle not moving under its own power, down the road and not stuck, or held back in any significant way. It is NOT for recovery or freeing stuck vehicles if any serious force is needed such as yanking. Basicly if you have to have slack in the strap and use momentum of the recovery vehicle to move the immobile rig then its the wrong applicaton for a tow strap.

Recovery strap - The ones with loops at the ends and designed for yanking or a kinetic type of load. Ones for offroad use are normally rated for 20k or 30k lbs. You might want a higher rating if you have fullsize trucks. They are intended to use momentum of the recovery rig, by having a little slack in the strap, accelerating to gain the momentum, then when the slack is pulled tight it streches to absorb the hard initial impact, and then acts somewhat like a rubber band where it wants to contract helping to pull out teh stuck vehicle.

 

[Deaner]

Hey Marv or anyone who can help. im kind curious. through my rigging experiance and Classes. What about using a properly rated pully or two. example in operating a crane over the years on my block and takle the more pully I have the more I can lift or reduce the tension/weight of lift on my cable. Say its a single pully I reduce the weight/Friction of my lift(pull/recovery) by half via doubling the cable increasing its strengh and weight capabilities. is this an ok method to use on the trail? or am off in left field.


For instence hook a Block and takle with a single pully to the vehicle to be recoverd. Loop cable through pully back to the recovery vehicle and secure. reducing the friction/weight of pull, and increasing load a bility of your cable.


I will dig through my book for some answers.

 

[mudd_jumper]

If this is a tube bumper , like 2x6 retangular steel then no dont weld then on the face of it . You would want to bolt all the way through the bumper so both sides of the tube was holding .

No I have not decided what I am going to build it out of or call jcr or what yet. Still looking at options and ideas have any:tonka: ??

 

[Kawierider]

Marv,
Good post. No arguements from me. As already stated, there are actually 2 different ways to attach two straps together but I don't have any pics. (this makes my post lame I know)

Regarding the chrome hook breaking.... I would agree with Marv that it is probably a cheap aftermarket hook. But, the chrome platint DOES NOT weaken the material underneath. Chrome plating does not use heat and therefore will not anneal or draw back a hardened material. In addition, cosmetic chrome is only .0005" to .002" thick.

It does not weaken the material due to a change in heat treatment. It weakens the material because when the hook (in this case) flexes the chrome plating will form small cracks (because it is so brittle). these cracks concentrate stresses on a very very small area. this intense area of stress will propogate a crack more readily than a non-plated piece. Usually, this is a theory applied to fatique fractures, but without knowing the history of the hook I can't obviously tell you if this was the case or not.

I also concurn though. it probabley was a cheap aftermarket hook.

 

[Grandman]

Deaner , the same principles apply but theres more to it . If you use a block and double your line yes you reduce the load on the winch my 50% only if the lines are running straight like this

-----------------
-----------------

If the line is running at a < angle then its less then 50 % reduction .

Lets say your pulling out a larger truck with your lighter rig . Use a dead man and here is how to set that up .

put the block or pulley on the stuck rig , your winch line goes out to the block then back near you but hook it to a tree of other solid object . This method will give you nearly double the winch power plus the the tree will hold 50 % of the load being pulled . This way you dont drag your rig forward . If a second pulley is needed that goes to the tree and the winch line goes to the stuck rig once again . stuck rig has one pulley and the hook attached at that point . Your winch is 4 times the pulling power and your rig is only holding 1/4 of the load .

 

[Deaner]

cool, preciate the insight Marv. I was thinking that might have been right but wanted a wiser more experianced opinion on it.

Cheers

 

[brewmenn]

I've seen a couple of different ways to use a stick when attaching 2 straps, and even a way to use one to attach a strap to a "D" ring without using the shackle. I'll have to get some pictures one of these days...

 

[Grandman]

Ill take some photos of rigging a dead man set up , mulitple pulley set ups tomorrow to post .

To often i see a rig tied to another rig when a deadman set up would be easier to do . Im guessing not to many know what i mean . Picture is worth a thousand words they say .:gman:

 

[TJrockdogg]

:rock: :rock: very good post Grandman.:rock: :rock: :rock: :rock:

 

[General Lee]

:rock: :rock: very good post Grandman.:rock: :rock: :rock: :rock:

I agree 100%.

Thanks for helping me keep my friends and family safe!!!

 

[whiterhino]

It does not weaken the material due to a change in heat treatment. It weakens the material because when the hook (in this case) flexes the chrome plating will form small cracks (because it is so brittle). these cracks concentrate stresses on a very very small area. this intense area of stress will propogate a crack more readily than a non-plated piece. Usually, this is a theory applied to fatique fractures, but without knowing the history of the hook I can't obviously tell you if this was the case or not.


I also concurn though. it probabley was a cheap aftermarket hook.

I don't want to hijack this thread because it is a good dialog. But, I have to politely disagree. All chrome has micro cracks in it from conception. This is sometimes called "cracked Chrome". We sell hardened steel rolls all over the world that are chrome plated. These are used under very high loads. These rolls are intentionally "bent" in order to correct shape defects in rolled steel products. Chrome up to .003" thick will bend with the roll. Chrome over ".003 thick will chip off WITHOUT affecting the parent material underneath. The parent materials (typically 1050, 8620, 52100 or D2) are never affected by the chrome.

Back to the real issue: If you have a broken hook, look at the material where the break appeared. A new break will show shiny material with sharp edges. A crack that has been propogating will show duller or dirty in the area where the crack is old and the sharp points will be less defined. This will tell you whether this was a single "event" or a growing problem.

Marv, I was talking about my above post. No pics = worthless.

Jim