SAFE recovery explained
61 - 80 of 114 Posts
Joined
·
14,427 Posts
sorry I missed that. I must have skipped over it the other day when the thread started.Miffy said:
I finished up the 2/3 training today. so the next level will be out to our shop in the fall. the teacher was outstanding for his knowlage of recovery operations.
I ran into issues with Donnie some years ago . Donnie Cruise was the orginal wreck master . He and i met up in Baltimore several years ago , at that time a few towing brains including Donnie and I were brain storming the removal of a sunken barge above the Niagra falls . Lets just say He and I didnt see eye to eye and apparently no one else liked his calculations on the barge as its still sunk there :sonicjay:Yetti said:
Some of there instructors are excellent but its a crap shoot with them some times . While they have a lot of neat tricks and good information , dont challenge them , They will never admit when there off on something .
Before i got on the boards or the internet i decided to shrink my company about 50% , back away from the big shot big shit work and settled back to dumb ass ******* . Its a more enjoyable way of life :hacksaw:
Joined
·
31,375 Posts
Several of the folks at GLFWDA either already have or are working towards their ham's. Primarily for the runs in Canada where it is so remote. Haven't heard too much about ham's for local wheelin. I also hear they use them alot out west.victorymike said:
Marv, early on, you mentioned a minimum of a 3" strap. I have found that WHEN USED PROPERLY, a 2" will work better in most cases for a Jeep. A light weight Jeep gets very little stretch out of a 3" strap unless it is hit really hard, which I don't recommend. Jeep to Jeep with a 3" almost seems like a chain at times. I have never broken a 2" strap. But I never hit it very hard. If you can't pull someone with a mild pull with 5 ft of slack max, do something different! Time to use a wire.
I like a 30 footer since is allows much more stretch without reaching it's limits. Make sure it is a 20,000 pound minimum. (not an arguement.....just an observation)
Something else that has not been mentioned is when using a shackle attachment in a trailer hitch, make sure you know the quality of the cross pin holding the shackle into the hitch. Many of the "cheap" pins are not good quality.
2" strap is somthing i have never used . I dont even know the rating on them . I can see your point about the stretch .
You mention jeep to jeep but often the larger rig will do the pulling so if some one with a full size is near by and he hooks onto the strap you could easily see a 16,000 lb force put on the strap . You mentioned 20,000 lb rating , thats new a used strap i think you would be really pushing the straps limits .
2" can be safe if it is inspected often and you dont let some one with a full size go nuts with it . I hate to call thinks close , im an over kill sort of guy :tonka:
You mention jeep to jeep but often the larger rig will do the pulling so if some one with a full size is near by and he hooks onto the strap you could easily see a 16,000 lb force put on the strap . You mentioned 20,000 lb rating , thats new a used strap i think you would be really pushing the straps limits .
2" can be safe if it is inspected often and you dont let some one with a full size go nuts with it . I hate to call thinks close , im an over kill sort of guy :tonka:
Joined
·
31,375 Posts
A good 2" strap is generally rated at 20,000 pounds. Yes, a full size rig pulling a jeep is possible to over load the strap but only if the pulling rig was hitting it too hard or the stuck vehicle is really mired down. Use a 2" strap for light tugs & you won't have a problem.
Joined
·
14,300 Posts
whiterhino said:
Thats the problem though... people carry a 2" strap then take it balls to the wall and snap it.
I was at the mounds and watched them break 4 - 2" straps in a row doing this with a mild stuck. Too many people assume you have to really yank ANY strap
Bullfrog came in with a 6" strap and slow and easy yanked him out.
Joined
·
14,427 Posts
http://www.niagarafrontier.com/accident.html
Hey Gman, read this and see if your barge is listed here. I was told it was removed in 2001 , that is why the lake levels have dropped about 4 feet.
Hey Gman, read this and see if your barge is listed here. I was told it was removed in 2001 , that is why the lake levels have dropped about 4 feet.
Joined
·
12 Posts
More on winching safety
Just a couple more thoughts on winching safety.
Never step on or push against a winch cable that is under tension. The increase in strain (force) in the cable is increased far more than you might think. If the cable is already near its strain limit, it could snap with deadly results. To get an idea of the added strain from just a small amount of force being applied perpendicularly to the cable, get about a 4 ft. length of really stout fishline. Hang a small weight---just 3-4 lbs---in the center of the line and taking an end of the line in each hand, see how much force you need to exert to bring the line back to perfectly straight, from the “V” shape caused by the small weight. The small weight represents someone stepping on a winch cable and the force needed to pull the line straight again represents the increased strain on the cable. You can see why tightrope walkers need to be so careful!!
If you’re so inclined, run some numbers:
the Tension = (Force/ sine of angle)/2.
E.g. A 175lb person steps on the middle of a winch cable that is under tension and displaces the cable 5 degrees (as measured from either secured point). This increases the strain in the cable by (175/.0872)/2 or about 1000 lbs! (the “2” is there because we have two lines---kinda like a single pulley with one rope going around it---each end supports half the load). In fact, if you pulled the cable out 90 degrees (totally fictitious here) you’d end up with (175/1)/2 or 87.5 lbs, just what the tension would be in each rope of the pulley system if you hung a 175 lb weight on the two ends of a rope suspended over a pulley. The tightrope walker would be better off to have some “sag” in the rope.
Another one: Throw a “winch blanket” over the cable when winching.
When Captain Kirk told Scotty to fire up the Impulse Engines, Scotty was, in effect, applying an engine Force for a length of Time or (Force X Time). A fellow by the name of Isaac Newton said that this was what caused a change of momentum----which is what they called the product of an object’s mass times its velocity. Since the mass couldn’t change, the velocity changed when a force was applied for a length of time. Thats why the expanding gasses in a rifle barrel increase the velocity of a bullet more in a long barrel than in a short barrel----the Force acts on the bullet for a longer Time in a longer barrel. So: Force X Time = (change in momentum----considering here only the object’s velocity). More importantly for us, Force = (change in “velocity")/Time---(of course the mass is still there but for this purpose we're ignoring it because it remains constant). Everybody knows that the LARGER the number in the denominator of a fraction, the SMALLER the piece of pie (or anything else). If a winch cable snaps, the Force doing the snapping is going to propel a hook & cable at deadly velocities (acceleration = Force/mass if you’re interested). What we need to do is make "TIME" in the denominator as LARGE as possible and still be practical about it. The easiest way is to throw a blanket over the cable to absorb the energy that produces the Force-----make the change in momentum of the cable/hook take as long a TIME as possible. Increased TIME = reduced FORCE = safety! Padded dashboards, airbags, carpet vs. hardwood floors when a wine glass is dropped. Think of how much “Force” your foot needs to exert on the brakes when you compare running right up to the stop sign or braking way back from the stop sign, i.e. you change your momentum by exactly the same amount either way, but the TIME it takes makes all the difference in how hard you push on the brake pedal-----all the same principle.
Just my three-cents worth and probably more than you wanted to read.
Papa
_____________________________________________________________
"If you can read this, thank a teacher.
If you're reading this in English, thank a veteran."
Just a couple more thoughts on winching safety.
Never step on or push against a winch cable that is under tension. The increase in strain (force) in the cable is increased far more than you might think. If the cable is already near its strain limit, it could snap with deadly results. To get an idea of the added strain from just a small amount of force being applied perpendicularly to the cable, get about a 4 ft. length of really stout fishline. Hang a small weight---just 3-4 lbs---in the center of the line and taking an end of the line in each hand, see how much force you need to exert to bring the line back to perfectly straight, from the “V” shape caused by the small weight. The small weight represents someone stepping on a winch cable and the force needed to pull the line straight again represents the increased strain on the cable. You can see why tightrope walkers need to be so careful!!
If you’re so inclined, run some numbers:
the Tension = (Force/ sine of angle)/2.
E.g. A 175lb person steps on the middle of a winch cable that is under tension and displaces the cable 5 degrees (as measured from either secured point). This increases the strain in the cable by (175/.0872)/2 or about 1000 lbs! (the “2” is there because we have two lines---kinda like a single pulley with one rope going around it---each end supports half the load). In fact, if you pulled the cable out 90 degrees (totally fictitious here) you’d end up with (175/1)/2 or 87.5 lbs, just what the tension would be in each rope of the pulley system if you hung a 175 lb weight on the two ends of a rope suspended over a pulley. The tightrope walker would be better off to have some “sag” in the rope.
Another one: Throw a “winch blanket” over the cable when winching.
When Captain Kirk told Scotty to fire up the Impulse Engines, Scotty was, in effect, applying an engine Force for a length of Time or (Force X Time). A fellow by the name of Isaac Newton said that this was what caused a change of momentum----which is what they called the product of an object’s mass times its velocity. Since the mass couldn’t change, the velocity changed when a force was applied for a length of time. Thats why the expanding gasses in a rifle barrel increase the velocity of a bullet more in a long barrel than in a short barrel----the Force acts on the bullet for a longer Time in a longer barrel. So: Force X Time = (change in momentum----considering here only the object’s velocity). More importantly for us, Force = (change in “velocity")/Time---(of course the mass is still there but for this purpose we're ignoring it because it remains constant). Everybody knows that the LARGER the number in the denominator of a fraction, the SMALLER the piece of pie (or anything else). If a winch cable snaps, the Force doing the snapping is going to propel a hook & cable at deadly velocities (acceleration = Force/mass if you’re interested). What we need to do is make "TIME" in the denominator as LARGE as possible and still be practical about it. The easiest way is to throw a blanket over the cable to absorb the energy that produces the Force-----make the change in momentum of the cable/hook take as long a TIME as possible. Increased TIME = reduced FORCE = safety! Padded dashboards, airbags, carpet vs. hardwood floors when a wine glass is dropped. Think of how much “Force” your foot needs to exert on the brakes when you compare running right up to the stop sign or braking way back from the stop sign, i.e. you change your momentum by exactly the same amount either way, but the TIME it takes makes all the difference in how hard you push on the brake pedal-----all the same principle.
Just my three-cents worth and probably more than you wanted to read.
Papa
_____________________________________________________________
"If you can read this, thank a teacher.
If you're reading this in English, thank a veteran."
Joined
·
3,166 Posts
The math might lose some of us, but I think I'll listen anyway.
He's a Physics professor!
I love it when we have the chance to learn from those more knowledgeable that ourselves.
I'd like to thank EVERYONE who has posted help and hints, especially Grandman for starting it.
Let's hope that EVERYONE reads them . . . and USES them!
He's a Physics professor!
I love it when we have the chance to learn from those more knowledgeable that ourselves.
I'd like to thank EVERYONE who has posted help and hints, especially Grandman for starting it.
Let's hope that EVERYONE reads them . . . and USES them!
Joined
·
15,563 Posts
Quick Question.
What can you safely use to clean a recovery strap? I jut got a "new" tree strap and it is filthy, something like Simple Green maybe?
Thanks
What can you safely use to clean a recovery strap? I jut got a "new" tree strap and it is filthy, something like Simple Green maybe?
Thanks
Joined
·
17,905 Posts
Basic mechanics, really.Trail_Fanatic said:
Actually, you'd find thats an old-school method for recovery as well. I have used that method for getting vehicles off trailers and tow dollies and such:
Hook my straps together with a ratchet strap, and tie one side to said broken vehicle, and the other 6 ft up a tree. Ratchet as tight as possible, then sit with full weight on the middle of the strap.
usually with practical rope lengths, its a 10-50 x multiplication.
Of course, I've done some tightrope walking in my time, and understand the subject better than most..
Joined
·
12 Posts
Jason is absolutely correct. Its one of the oldest tricks in the book-----and a standard problem found in most "Mechanics" sections in physics books. Since he's done some tightrope walking, he has real "feets-on" experience with the idea........can't beat practical experience!
Joined
·
46,076 Posts
I beg to differ.Haggar said:
I just read this complete site:
http://www.darylscience.com/Demos/TightRope.html
61 - 80 of 114 Posts
