Winching

[Robert J. Yates]

Originally posted by Joe Dillard
Hehehe, can I use that phrase Robert? Or is it going through the patent pending process?

Have at it Joe - that would make for a good signature

[Robert A.M. Stephens]

Originally posted by derf
Yup.

Back in high school, we rigged up multiple pulleys with fish scales between them and the bar it was pulling. We also had a fish scale connecting the bar to a fixed point. We were able to see the force applied at each pulley, the force applied to the end of the string and the total force applied to the bar. It was very educational.

In the cited example, if one were to put some way to measure force on all the attachment points, you would find that:

1) each snatch block applied roughly 24,000 pounds of force to the object it was attached to.

2) each end of the cable applied roughly 12,000 pounds of force to the object it was attached to.

Given that the truck had two snatch blocks on it, it would have 48,000 pounds of force applied to it.

Given that the Jeep had 2 cable ends and one snatch block, we would have the other side of that 48,000 pounds of force applied to it.

The forces equal each other so this system can exist in real life.

Q.E.D.

I'll be damned. Thank you.

And then, as in the original pull by using 3 blocks and 4 lines, all blocks static (not traveling, single sheave), what is the rated gross available pull?

Additionally, if you would like to speak with an engineer at The Crosby Group, who I interface with, with their's and other HD industrial products and applications, the contact person and point is here below (a super knowlegeable guy, I might add):

Brad Beall
Product Engineer
bradbeall@thecrosbygroup.com
phone: 918-834-4611 x322
fax: 918-834-9447

And, sadly, I am correct, of you will check and listen to Brad very carefully. I have invited him to post here and verify.

I've also added more information at Behold, here, if this is of interest to you and others:

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

[Robert A.M. Stephens]

Originally posted by Jeff Weston
Cool pics Joe. My dad made the crossing from an oiler to his carrier in a similar matter while travelling on the open seas. He had visions of the two ships veering apart, snapping the line and him sinking to the bottom of the ocean in this steel cage. I'll have to show him these pics.

Yes, amazing photos Joe and thank you.

[mudpup]

Originally posted by Robert A.M. Stephens
And then, as in the original pull by using 3 blocks and 4 lines, all blocks static (not traveling, single sheave), what is the rated gross available pull?

That would be 48k lbs, just use the formula I posted above, ofcourse it would change with angles involved and what not.

As long as its all straight line stuff, a real easy way to figure it out and just draw a line normal to the direction of force (winch line) and however many times the line crosses the winch cable is the # you multiply by to get total pulling capacity

[derf]

Originally posted by Robert A.M. Stephens
I'll be damned. Thank you.

And then, as in the original pull by using 3 blocks and 4 lines, all blocks static (not traveling, single sheave), what is the rated gross available pull?

Are you talking about attaching the snatch blocks to fixed points where the blocks themseves don't pull anything? If you're doing that for the purposes of lining up a pull on something where you can't get a straight pull, all you're doing is changing direction and you should have just the 12,000 pounds of force on the line end wherever it snakes out.

If the blocks are moving, you get all sorts of math involved and some or all of the math you listed applies.


If you're talking about fixing the snatch blocks to the pulling vehicle and the vehicle being pulled, the total avalable force with 3 snatch blocks (2 on the pulled vehicle, 1 on the pulling vehicle) is 48,000 pounds gross pull (assuming you're on the inner most layer of cable). That's assuming the blocks get the line as close to parallel as possible.

[Joe Dillard]

Thanks Jeff & Robert.

I don't recall where I was when I snaped those pics. The oiler was the USNS Walter S. Diehl (T-AO 197). I believe I was on the USS John S. McCain (DDG-56), two days prior to Gulf War-II. Perhaps I was somewhere in the Northern Arabian/Persian Gulf. When you're out at sea for 6 months at a whack - you tend to forget sometimes where certain pics were taken because there's no land to judge things by - just LOTS of open ocean.

[Robert A.M. Stephens]

Originally posted by derf
Are you talking about attaching the snatch blocks to fixed points where the blocks themseves don't pull anything? If you're doing that for the purposes of lining up a pull on something where you can't get a straight pull, all you're doing is changing direction and you should have just the 12,000 pounds of force on the line end wherever it snakes out.

If the blocks are moving, you get all sorts of math involved and some or all of the math you listed applies.


If you're talking about fixing the snatch blocks to the pulling vehicle and the vehicle being pulled, the total avalable force with 3 snatch blocks (2 on the pulled vehicle, 1 on the pulling vehicle) is 48,000 pounds gross pull (assuming you're on the inner most layer of cable). That's assuming the blocks get the line as close to parallel as possible.

Boy, not being caustic and such, or in any way negative, but if you can go back and study the diagrams and study and read the text carefully, you will discover I am correct. I don't know what else to present as facts. I am correct.

Also, please call Brad at The Crosby Group, since they are one of the world's authority on heavy lift and pulling devices as well as applications.

It would be really helpful for you and mudpup as a new learning curve for you. I've been doing this stuff a very long time, in the 'real', not only in Jeep stuff but logging, heavy equipment, and so on, and I really do know what I am talking about. In no way bragging or boasting however.

I am correct.

Just a thought, as best I can offer.

BTW- on the 'pull strap' subject, you stated you were an engineer. What type if I may inquire.

Thanks.

[cbassett]

Interesting read.

Robert, who copied whom without giving credit?

http://www.dodgepowerwagon.com/glovebox/snatch.html

[Robert A.M. Stephens]

Originally posted by cbassett
Interesting read.

Robert, who copied whom without giving credit?

http://www.dodgepowerwagon.com/glovebox/snatch.html

Reid got that from me on the Jeep BBS, New Horizon, which is gone now, back in 2000 I believe. Same discourse we're doing here now, back then.

I included the link on the reference links at the bottom of page 22, since I no longer had the copy other than the Crosby catalog-tech data.

Does that help?

[derf]

Originally posted by Robert A.M. Stephens
It would be really helpful for you and mudpup as a new learning curve for you. I've been doing this stuff a very long time, in the 'real', not only in Jeep stuff but logging, heavy equipment, and so on, and I really do know what I am talking about. In no way bragging or boasting however.

I am correct.

I look at most of the work you present and 90% or more of it discusses using only a single pulley. And in those cases, everything you're saying is true.

However, every resource I can find that talks about multiple pulleys in the block-and-tackle arrangement, including the Encarta reference I posted earlier, shows that using multiple pulleys only adds 1x the force on the line for each wrap around a pulley. The fact that using a single pulley happens to double the force doesn't mean that using additional pulleys in a block and tackle arrangment will keep doubling the force. It just doesn't work that way.

Who am I going to believe? The writers of text books and encyclopedias or some guy on the internet?

Again, no offense intended.


But here it is again:

Work = force * distance.

If I have a 12,000 pound winch that pulls 40 feet worth of cable, I have done 480,000 pound-feet of work.

Work = 12,000 * 40 = 480,000

Running the cable through 3 snatch blocks as you have shown, I will have moved the truck 10 feet because that 40 feet worth of cable is removed equally from all lengths. Each length shortens by 10 feet, meaning the truck moves 10 feet.

So, with 480,000 pound-feet of work and 10 feet of distance, what's the force on the truck?

480,000 = force * 10

Apply basic algebra

480,000 / 10 = force

48,000 = force

Who's right?

[Croaker]

Originally posted by derf
Who am I going to believe? The writers of text books and encyclopedias or some guy on the internet?

This forum is generating great quotes for signatures today!

[cbassett]

Originally posted by Robert A.M. Stephens
Reid got that from me on the Jeep BBS, New Horizon, which is gone now, back in 2000 I believe. Same discourse we're doing here now, back then.

I included the link on the reference links at the bottom of page 22, since I no longer had the copy other than the Crosby catalog-tech data.

Does that help?

Yup.

[ken white]

Originally posted by derf
I look at most of the work you present and 90% or more of it discusses using only a single pulley. And in those cases, everything you're saying is true.

However, every resource I can find that talks about multiple pulleys in the block-and-tackle arrangement, including the Encarta reference I posted earlier, shows that using multiple pulleys only adds 1x the force on the line for each wrap around a pulley. The fact that using a single pulley happens to double the force doesn't mean that using additional pulleys in a block and tackle arrangment will keep doubling the force. It just doesn't work that way.

Who am I going to believe? The writers of text books and encyclopedias or some guy on the internet?

Again, no offense intended.


But here it is again:

Work = force * distance.

If I have a 12,000 pound winch that pulls 40 feet worth of cable, I have done 480,000 pound-feet of work.

Work = 12,000 * 40 = 480,000

Running the cable through 3 snatch blocks as you have shown, I will have moved the truck 10 feet because that 40 feet worth of cable is removed equally from all lengths. Each length shortens by 10 feet, meaning the truck moves 10 feet.

So, with 480,000 pound-feet of work and 10 feet of distance, what's the force on the truck?

480,000 = force * 10

Apply basic algebra

480,000 / 10 = force

48,000 = force

Who's right?

You are...

By definition the mechanical advantage will be determined by the length of the line recovered divided by the distance traveled for a straight line pull. So 4 lines, or 3 pulleys, would equal 4 x 12000 = 48,000 lbf assuming an initial pull of 12000lbf. This also assumes the pulleys are ideal and the forces are in the exact same plane. However, since three pulleys were used the efficiency of the system would be somewhere between 80% to 85%, so with losses the actual pull would be closer to 38.4k to 40.8k.

Ken

[mudpup]

with your theory on acheiving 96,000 lbs from the setup in the picture you somehow made you winch capable of pulling 24k lbs. It is simple physics. Each of the four attached lines to the vehicle is carrying an equal load....96k divided by 4 equals 24k lbs.

[derf]

http://www.howstuffworks.com/pulley.htm

[mrblaine]

If you ever want to talk to a nice and extremely knowledgeable gentleman in the recovery and rigging business, Mr. Brad Beall is phenomenal.

He cleared up many areas of myth and confusion for me.

First off, snatch blocks and winching. It matters only how many lines are in the rigging that are parallel.

1 = x1
2= x2
3= x3
4=x4

It's that simple.

Wire rope is dangerous when it breaks.

[derf]

Originally posted by ken white
You are...

By definition the mechanical advantage will be determined by the length of the line recovered divided by the distance traveled for a straight line pull. So 4 lines, or 3 pulleys, would equal 4 x 12000 = 48,000 lbf assuming an initial pull of 12000lbf. This also assumes the pulleys are ideal and the forces are in the exact same plane. However, since three pulleys were used the efficiency of the system would be somewhere between 80% to 85%, so with losses the actual pull would be closer to 38.4k to 40.8k.

Ken

Yeah, that's true. The slight angles and losses due to friction, etc would have that effect. And not all winches operate at peak efficiency for many reasons so even if the winch is on the first layer, it may not be operating at the full 12,000 pounds. The practical force being applied to the truck was probably closer to 35,000 pounds in reality. Each layer you step up as you spool the cable drops the pulling force by whatever factor (depending on the diameter of the drum and the thickness of the cable) and you lose even more.

The gross pull rating (i.e. without the above losses factored in) would be 48,000 pounds. And we're talking about theoretical pulling capacities.

[mudpup]

look at the picture I posted, it shows exactly how the forces work in that setup. There is no need to bother calling people up about a simple physics problem, besides this knowledge is a 1000 yrs old, everyone knows me and derf are correct

[BMRisko]

I'm not going to read this entire thread right now, but R.A.M. Stephens, where are you getting that extra 48,000 lbs of pulling power from? Just curious because it should be 48,000 total, not 98,000lbs, as you have drawn out. Draw a simple FBD and you will see. High school physics stuff here.

[mrblaine]

Originally posted by mudpup
look at the picture I posted, it shows exactly how the forces work in that setup. There is no need to bother calling people up about a simple physics problem, besides this knowledge is a 1000 yrs old, everyone knows me and derf are correct

Yes, true, but if I call and verify to everyone's satisfaction, then the discussion remains civil, entertaining, and a pleasure to keep around and read. Besides, I always enjoy discussions with folk in various specialty areas of knowledge. It at least entertains me.

btw- He did relate to me that he and Mr. Stephens have arrived at a consensus and the drawings on Behold are being modified as we speak.

[mrblaine]

Originally posted by BMRisko
I'm not going to read this entire thread right now, but R.A.M. Stephens, where are you getting that extra 48,000 lbs of pulling power from? Just curious because it should be 48,000 total, not 98,000lbs, as you have drawn out. Draw a simple FBD and you will see. High school physics stuff here.

It's actually simple if you look at only one aspect of the equation.

One snatch block and two lines will typically be interpreted as doubling the power of the winch. Unfortunately the doubling is a function of two lines and not one snatch block.

That's where the error came in. If you figure that a snatch block doubles each time one is used and it doubles the total before it, you wind up with Robert's calculations.

The correct way is to ignore the blocks and count the lines.

[derf]

Originally posted by mrblaine
Yes, true, but if I call and verify to everyone's satisfaction, then the discussion remains civil, entertaining, and a pleasure to keep around and read. Besides, I always enjoy discussions with folk in various specialty areas of knowledge. It at least entertains me.

btw- He did relate to me that he and Mr. Stephens have arrived at a consensus and the drawings on Behold are being modified as we speak.

Most excellent. It's always best to see the truth win out without people getting their feathers ruffled too much.

[BMRisko]

Originally posted by mrblaine
It's actually simple if you look at only one aspect of the equation.

One snatch block and two lines will typically be interpreted as doubling the power of the winch. Unfortunately the doubling is a function of two lines and not one snatch block.

That's where the error came in. If you figure that a snatch block doubles each time one is used and it doubles the total before it, you wind up with Robert's calculations.

The correct way is to ignore the blocks and count the lines.

Ah, so Mr. Stephens was grossly mis-informed all along. Tis' a shame considering he has all that real life experience, not just good 'ole Jeepin'.

[mrblaine]

Originally posted by BMRisko
Ah, so Mr. Stephens was grosely mis-informed all along. Tis' a shame considering he has all that real life experience, not just good 'ole Jeepin'.

I wouldn't consider it grossly misinformed.

It's kinda like tossing leaves under the rear of a TJ, it looks good on paper.

[mrblaine]

As much as I'd like to continue this conversation, I hear the desert calling. Ya'll behave while we're gone.

[mudpup]

heh, I was just poking some fun, taking a line from his website, just good nature ribbing.

[Robert A.M. Stephens]

Originally posted by derf
I look at most of the work you present and 90% or more of it discusses using only a single pulley. And in those cases, everything you're saying is true.

However, every resource I can find that talks about multiple pulleys in the block-and-tackle arrangement, including the Encarta reference I posted earlier, shows that using multiple pulleys only adds 1x the force on the line for each wrap around a pulley. The fact that using a single pulley happens to double the force doesn't mean that using additional pulleys in a block and tackle arrangment will keep doubling the force. It just doesn't work that way.

Who am I going to believe? The writers of text books and encyclopedias or some guy on the internet?

Again, no offense intended.


But here it is again:

Work = force * distance.

If I have a 12,000 pound winch that pulls 40 feet worth of cable, I have done 480,000 pound-feet of work.

Work = 12,000 * 40 = 480,000

Running the cable through 3 snatch blocks as you have shown, I will have moved the truck 10 feet because that 40 feet worth of cable is removed equally from all lengths. Each length shortens by 10 feet, meaning the truck moves 10 feet.

So, with 480,000 pound-feet of work and 10 feet of distance, what's the force on the truck?

480,000 = force * 10

Apply basic algebra

480,000 / 10 = force

48,000 = force

Who's right?

I see where you are coming from exactly. In the case of our winching discussion we have two different applications here and I doing a diagram for both that may help. The issue is static load pull, and traveling load pull.

Please bear with me and I should have those up at the site shortly.

Thank you for your input.

[Robert A.M. Stephens]

Originally posted by BMRisko
Ah, so Mr. Stephens was grossly mis-informed all along. Tis' a shame considering he has all that real life experience, not just good 'ole Jeepin'.

No. I am correct to the letter. I replied that about being il-informed, as I thought this would be a war as on Jeep Forum, and its easier to let people believe what they wish, and then run like hell...............

In light of that, with all these good posts, I am continuing and in the diagrams for both loads, you will learn something knew I hope, as it is intended.

The two issues are static line pull, in which Mr. "Derf" and "mudpup" are correct, and a traveling line load, for which how the concrete truck was originally pulled out (not the re-pull), and I am correct.

Watch the page 22 for updates here shortly an I think it will help.

Thank you.

[Robert A.M. Stephens]

If possible, please go to the page 22 again for the diagram of traveling verses static block usage. Might help.

Thanks.

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

[ken white]

Originally posted by Robert A.M. Stephens
No. I am correct to the letter. I replied that about being il-informed, as I thought this would be a war as on Jeep Forum, and its easier to let people believe what they wish, and then run like hell...............

In light of that, with all these good posts, I am continuing and in the diagrams for both loads, you will learn something knew I hope, as it is intended.

The two issues are static line pull, in which Mr. "Derf" and "mudpup" are correct, and a traveling line load, for which how the concrete truck was originally pulled out (not the re-pull), and I am correct.

Watch the page 22 for updates here shortly an I think it will help.

Thank you.

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