Winching

[ken white]

Originally posted by ken white
Actually, you are still incorrect. The mechanical advantage is basically defined as the length of the cable retrieved divided by the length the load moved.

So if we look at your dynamic pully block diagram, there are two limits for the distance traveled.

One limit occurs where the traveling block is fixed at the load, and we see the mechanical advantage will be 3 for an increase to 48,000lbf.

The other limit is when traveling block is fixed at the winch, in which case the mechanical advantage will be 2 for an increase in to 24,000 lbf.

So, this system will operate somewhere between 24,000 lbf and 48,000 lbf depending on where the pully is located.

Without a reduction in distance traveled by a factor of 4, there is no way to get to 96,000 lbf.

Ken

Tried to edit my earlier post, and found I couldn't, so for the 3 line limit I posted above, it would actually only be 36,000 lbf not 48,000 lbf. Sorry for the quick response mistake.

Oh, and the line tension for the fixed pully block scenerio, the lines have the forces equally distributed, so each line will see the same lbf.

For the floating pully block scenario, this is not true. The floating pully block single point connected line will see twice the tension the pully end sees, so be very careful using this set-up.

Ken

[mudpup]

http://web.utk.edu/~sbratto1/Jeep/VE...dynamic-ed.jpg

am I wrong in thinking this is how the forces add up?

[ken white]

Actually, that is a very interesting question.

The sum of the vector tensions must still balance between the connection points at the pulley. So I'm guessing the floating pulley will move towards the winch as force is applied until the system eventually becomes a 2 line system.

So, maybe my assumption about the line forces for the floating block system is wrong...

[Robert A.M. Stephens]

You may wish to verify, since that setup is how a 12,000 lb winch pulled out a 66,000 lbs. concrete truck, with 4 yards of concerete on board for a gross of nearly 80,000 lbs., uphill at a 5% grade for a distance of some 60 feet horizontal, with the truck stuck to the axles at the twin screw rear end (twin axle). That was the original pull, not the staged re-pull.

A traveling rig-up is a common rig in industry, logging, mining, quarry, steel mills, cranes, hoists etc, and is no more dangerous than any other rig up.

[ken white]

Robert, all I can say is that the Cement truck's rolling load isn't the same as it's weight - it is much, much less even at 5% grade.

As for your block and tackle set-up being able to pull 96,000 lbf, the winch would have to recover 8 feet of line for every foot the truck moved and the winch would have to be at it's rated capacity.

The mechanical advantage is simple, (8' recovered/1' moved)*12,000lbf = 96,000 lbf. If you can prove the block and tackle set-up you described does this, then you are correct. If not, then you have made an error.

Ken

[derf]

Originally posted by Robert A.M. Stephens
You may wish to verify, since that setup is how a 12,000 lb winch pulled out a 66,000 lbs. concrete truck, with 4 yards of concerete on board for a gross of nearly 80,000 lbs., uphill at a 5% grade for a distance of some 60 feet horizontal, with the truck stuck to the axles at the twin screw rear end (twin axle). That was the original pull, not the staged re-pull.

A traveling rig-up is a common rig in industry, logging, mining, quarry, steel mills, cranes, hoists etc, and is no more dangerous than any other rig up.

If you were dead lifting the concrete truck off the ground, you'd need the 80,000 pounds of force to do so.

But hell, even rolling 80,000 pounds up a 10% grade only requires about 16,000 pounds of force. A 5% grade requires even less force. It is a rolling load after all. (I only remember a 10% grade is roughly a 5:1 reduction in force required because it's easy to remember. I can't remember what a 5% grade factor is because it's not a linear equation...)

Add in the resistance of the surface it was sitting on and that would bump up the force required significantly. But the 48,000 pounds of force your setup had would be more than sufficient to roll that truck off the gravel it was stuck in.

[Robert A.M. Stephens]

Huh uh......

Here is how it was back then......sometimes.....whoa!!!



Read it here at the top:

http://behold-the-rage.com/jeep_page22.html

Okay fellas, based on your amazing experience, get your Warn (whatever it is) 8000 lb. winch and a little Warn snatch block, and find a concrete or any other truck of about 80,000 lb., stuck on a 5% grade up to the axles in mud, and yanker 'er out with your rigs , based on your "math".

Report back here and how it all went down.

Fair is fair.

Oh well, that is the internet...........

[mudpup]

I give up

[derf]

Originally posted by Robert A.M. Stephens
Huh uh......

Here is how it was back then......sometimes.....whoa!!!



Read it here at the top:

http://behold-the-rage.com/jeep_page22.html

Okay fellas, based on your amazing experience, get your Warn (whatever it is) 8000 lb. winch and a little Warn snatch block, and find a concrete or any other truck of about 80,000 lb., stuck on a 5% grade up to the axles in mud, and yanker 'er out with your rigs , based on your "math".

Report back here and how it all went down.

Fair is fair.

Oh well, that is the internet...........

So when you can't dispute the figures and the engineering facts, you just throw up your hands and declare victory?


I have no doubt it took 48,000 pounds (gross) of pulilng force through the 3 snatch blocks to get that truck unstuck. But, unlike you, I understand the dynamics of that system and know what was actually going on.

And it doesn't matter if you're a high schooler who just took physics or Albert Einstein. Facts are facts. Age and experience don't change the laws of physics.

Oh well. The text books are still right at least...

[Robert A.M. Stephens]

Originally posted by mudpup
I give up

So do I.

Have it your way, just like Jeep fourm. Sounds great......

[Robert A.M. Stephens]

Originally posted by derf
So when you can't dispute the figures and the engineering facts, you just throw up your hands and declare victory?


I have no doubt it took 48,000 pounds (gross) of pulilng force through the 3 snatch blocks to get that truck unstuck. But, unlike you, I understand the dynamics of that system and know what was actually going on.

And it doesn't matter if you're a high schooler who just took physics or Albert Einstein. Facts are facts. Age and experience don't change the laws of physics.

Oh well. The text books are still right at least...

What a lame response. What do you think the data I have supplied, with facts, diagrams, the math, and verification contact points have accomplished? Nothing.

Unbelievable response above. You're the experts so I give in. I have nothing to offer. Without a war with you folks, I run like hell, since I have nothing to offer you on the topic.

Oddly, you have not made the same effort to support your claims whatosever and your math application is in error.

Sorry.

[Jeeper]

Please read the "Mechanics of Winching" section of this link http://www.peak-recovery.fsnet.co.uk..._in_safety.htm
which you site in your "Incedence of winching" report on page 22. It outlines the formula to find the force necessary to move a rolling object out of various terra and includes gradient degrees.

Jeeper

[derf]

Originally posted by Robert A.M. Stephens
What a lame response. What do you think the data I have supplied, with facts, diagrams, the math, and verification contact points have accomplished? Nothing.

Unbelievable response above. You're the experts so I give in. I have nothing to offer. Without a war with you folks, I run like hell, since I have nothing to offer you on the topic.

Oddly, you have not made the same effort to support your claims whatosever and your math application is in error.

Sorry.

I cited encyclopedias, physics texts, engineering resources and other relevant accepted data.

You cited basically your own website and unknown persons on the internet.

Which would you believe in my situation? The text books and recognized authorities or just some guy on the internet who says he knows the answer because he's older?

[Robert A.M. Stephens]

Originally posted by Jeeper
Please read the "Mechanics of Winching" section of this link http://www.peak-recovery.fsnet.co.uk..._in_safety.htm
which you site in your "Incedence of winching" report on page 22. It outlines the formula to find the force necessary to move a rolling object out of various terra and includes gradient degrees.

Jeeper

Understood. Why do you think it is there.

[Jeeper]

Originally posted by Robert A.M. Stephens
Understood. Why do you think it is there.

I posted the link because it confirms what the others have been saying when you do the math on your cement truck recovery.

You said that no one bothered to read your information...I did, and came to the conclusion that you do not double the pulling power each time you add a block.

[Robert A.M. Stephens]

Originally posted by derf
I cited encyclopedias, physics texts, engineering resources and other relevant accepted data.

You cited basically your own website and unknown persons on the internet.

Which would you believe in my situation? The text books and recognized authorities or just some guy on the internet who says he knows the answer because he's older?

I would do whatever you are convicted of, since it is all hyperbole anyway. Nothing i can offer is going to assist in the learning curve, so it must all be a mirage.

It's funny, when I showed up to that pull after a D-4 failed, a 5 ton wrecker broke it's boom, and finally, the concrete company and the homeowner where the truck was doing the pour, Dane Shortt (a fellow 4 wheeler), called, and said, "we gotta stuck, Robert, and the mud is cooking off in the drum, you wanna try it. It's the last chance to save the drum on the new truck and you're only a mile away....."

When I showed up and did some quick calculations and decided the Jeep could handle it, I began to rig up.

Many famers, neighbors of Dane and onlookers also showed up. When they saw what we were going to do, they actually got mad and taunted with all the retorts based on the fact it couldn't be done, the blocks were wrong, the weight was too much, that 12,000 lb winch and three blocks weren't going to pull out a buried concrete truck and so on, like a mob almost. They even told me to get out of there and quit being stupid. I, Dane and the driver continued to rig up.

After the truck was out, they all went away, never said anything either.

So, like here, I really don't have a thing to offer you whatsoever. I am wrong and you are right and I have nothing further to offer. You're all the experts and that is that. I surrender totally to your expertise.

Interesting though. Very familiar experience for me, this thread.

[derf]

Originally posted by Robert A.M. Stephens
I would do whatever you are convicted of, since it is all hyperbole anyway. Nothing i can offer is going to assist in the learning curve, so it must all be a mirage.

It's funny, when I showed up to that pull after a D-4 failed, a 5 ton wrecker broke it's boom, and finally, the concrete company and the homeowner where the truck was doing the pour, Dane Shortt (a fellow 4 wheeler), called, and said, "we gotta stuck, Robert, and the mud is cooking off in the drum, you wanna try it. It's the last chance to save the drum on the new truck and you're only a mile away....."

When I showed up and did some quick calculations and decided the Jeep could handle it, I began to rig up.

Many famers, neighbors of Dane and onlookers also showed up. When they saw what we were going to do, they actually got mad and taunted with all the retorts based on the fact it couldn't be done, the blocks were wrong, the weight was too much, that 12,000 lb winch and three blocks weren't going to pull out a buried concrete truck and so on, like a mob almost. They even told me to get out of there and quit being stupid. I, Dane and the driver continued to rig up.

After the truck was out, they all went away, never said anything either.

So, like here, I really don't have a thing to offer you whatsoever. I am wrong and you are right and I have nothing further to offer. You're all the experts and that is that. I surrender totally to your expertise.

Interesting though. Very familiar experience for me, this thread.

Again, I'm not challenging the fact that you did it. This is not, and has never been about me questioning that you were able to get the truck unstuck. I'm not challenging the ability of that rig to get the job done. I'm sure it worked. I'm merely pointing out that the equations you are doing to explain the details of the pull aren't correct. That is all.

The fact that the equations aren't applied correctly doesn't take away from the fact that you accomplished a difficult pull. I doubt many people have the rigging to do what you did.

It worked, but not exactly the way you think it did.

If you want to stick to debating the physics of the pull and stop wasting time trying to turn this into a personal attack on you so you can cry foul, which it is not, I'd love to show you the right way to apply the correct equations so that you can accurately portray what happened. If you insist on distracting from the discussion with personal anecodtes and irrelevant calls for other, lesser equipped vehicles to accomplish the same feat, there's no point in continuing.

It's up to you.

[ken white]

Robert, connect your 3 pulley blocks in any configuration you want and then measure how much line is recovered when the load moves 1 foot. The amount of line recovered will be the mechanical advantage multiplier.

It is that simple.

If you recover 8' of line for the 1' of load movement, then your hypothesis on pulling power is correct assuming perfectly parallel lines and lossless pullies. However, experience shows you will only be about 80% to 85% efficient for 3 pulley blocks. So, multiply the length of line recovered by .85 for your mechanical advantage.

[mudpup]

The reason I give up is because I am tired of arguing. Jeep forum...never heard of it.

[Robert A.M. Stephens]

Originally posted by ken white
Robert, connect your 3 pulley blocks in any configuration you want and then measure how much line is recovered when the load moves 1 foot. The amount of line recovered will be the mechanical advantage multiplier.

It is that simple.

If you recover 8' of line for the 1' of load movement, then your hypothesis on pulling power is correct assuming perfectly parallel lines and lossless pullies. However, experience shows you will only be about 80% to 85% efficient for 3 pulley blocks. So, multiply the length of line recovered by .85 for your mechanical advantage.

You are correct, and it is actually slightly less due to natural mechanical resistance also, like bearings, electrical, the winch gear train, pulley and roller fairlead resistance, and so on.

You are correct in your statement.

[BMRisko]

Hey Robby, are you a liberal?

[Chuck K.]

My only question in pulling such massive loads with a jeep is how do you anchor the jeep? If securing the rear of the jeep to a tree or such and using multiple blocks with the winch line do you stand a chance of damaging the frame This might be a cheaper alternative than buying a new unlimited .

I would imagine before the 481,856.026 pounds of pull the frame would begin to stretch.

[Robert A.M. Stephens]

Originally posted by derf
Again, I'm not challenging the fact that you did it. This is not, and has never been about me questioning that you were able to get the truck unstuck. I'm not challenging the ability of that rig to get the job done. I'm sure it worked. I'm merely pointing out that the equations you are doing to explain the details of the pull aren't correct. That is all.

The fact that the equations aren't applied correctly doesn't take away from the fact that you accomplished a difficult pull. I doubt many people have the rigging to do what you did.

It worked, but not exactly the way you think it did.

If you want to stick to debating the physics of the pull and stop wasting time trying to turn this into a personal attack on you so you can cry foul, which it is not, I'd love to show you the right way to apply the correct equations so that you can accurately portray what happened. If you insist on distracting from the discussion with personal anecodtes and irrelevant calls for other, lesser equipped vehicles to accomplish the same feat, there's no point in continuing.

It's up to you.

I did the last diagram as that is the way the first pull was performed and then had the Crosby Group Engineers check it for accuracy, though I knew when I did the pull, and know it is correct now. It doesn't matter, it is still wrong so let it be wrong. That was the 'changes' "mrblaine" spoke of in earlier posts.

I understand perfectly that there is no personal attack against me, I know that. It is just you have all the answers so I have nothing to rebutt. The engineers I consulted to make sure I was correct and those in the trade, differ with your dissent, so I am a loss as to how to reply.

If possible, you can get a tension scale for leverage and failure. Rig some blocks in a static and traveling pull arrangement and see what the pull raito is. Might be fun.

Is that a better response?

Thanks.

[Robert A.M. Stephens]

Originally posted by BMRisko
Hey Robby, are you a liberal?

Flame away asshole. I am 7 steps to the right of Ghengis Khan and feel Pat Buchannan is a flaming liberal. Liberalism is akin to Nazism.

I should burn you to death with Pentex and ARCO High Test.

[Robert A.M. Stephens]

Originally posted by Chuck K.
My only question in pulling such massive loads with a jeep is how do you anchor the jeep? If securing the rear of the jeep to a tree or such and using multiple blocks with the winch line do you stand a chance of damaging the frame This might be a cheaper alternative than buying a new unlimited .

I would imagine before the 481,856.026 pounds of pull the frame would begin to stretch.

Great post!!! Actually by adding 7 more blocks the pull is close to 9,499,000, and the break away point and that pesky frame stretching event you've mentioned begins at about 1,345,000,000 lbs, so we're all safe.

Is that helpful?

[mudpup]

which diagram did the crosby folks say was correct, all of them or was there just a certain one you showed them?

[ken white]

Originally posted by mudpup
which diagram did the crosby folks say was correct, all of them or was there just a certain one you showed them?

I'm interested in which diagrams are correct as well...

BTW, I am a registered Professional Engineer, electrical, but still feel I know my fundamental mechanicss very well. So, this has peaked my interest.

Ken

[Robert A.M. Stephens]

For mud pup and Ken, the whole page in description for a re-reference, and the last diagram on the bottom of the page whereby I presented the traveling block arrangement verses the static block arrangement since that is how I pulled out the truck, and too, Rig it that way asI wanted to use more cable to get down on the 1st wrap on the drum to give me an actual 12,000 lb pull at the winch, in the initial stage of breaking the truck free so it would perhaps roll uphill toward VEX at the start.

Too, I think there is confusion in available pull, by numbers, verses actual pull availbale by application. For instance, yes, the pull availability is high, but in actual applied recovery rating, factoring in all failure areas for resistance, it is always about 15 to 35% LESS than rated, since all those items by nature deceases available pull ratio as a gross number.

With that said, and I am guessing since I had no way to scale the pull in acutal pull rating lbs., I had about 65,000 to 72,000 lb, available pull to work with.

But, in the real, it was truly a strain, since all the air in the tires on the Jeep got squeezed out, plus the two 20 ton dead man throw chains on the back of the Jeep, tied to the huge White Pine behind VEX, got so hot one couldn't touch them. The truck was heavy, especially in the mud as it was, and winching it uphill also.

[Matt Pascoe]

But, in the real, it was truly a strain, since all the air in the tires on the Jeep got squeezed out, plus the two 20 ton dead man throw chains on the back of the Jeep, tied to the huge White Pine behind VEX, got so hot one couldn't touch them. The truck was heavy, especially in the mud as it was, and winching it uphill also.

This story just keeps getting better




Ever see the movie "Big Fish"?

[Chuck K.]

Originally posted by Robert A.M. Stephens
Great post!!! Actually by adding 7 more blocks the pull is close to 9,499,000, and the break away point and that pesky frame stretching event you've mentioned begins at about 1,345,000,000 lbs, so we're all safe.

Is that helpful?

Yes very helpful, my resources had the frame molecular tensile shear strength at 1,345,000,000.0475


:

Flame away asshole. I am 7 steps to the right of Ghengis Khan and feel Pat Buchannan is a flaming liberal. Liberalism is akin to Nazism.

I should burn you to death with Pentex and ARCO High Test.

That is what I like to see, diversity and inclusion on all grades of fuel Dont forget to address the hammer also