This is very interesting and a good demo of something we don't normally think about or are taught with pulleys. I like to think of it this way. Advantage for one end of the system must always be disadvantage for the other end. The 3rd setup produces mechanical disadvantage as described because it is the mirror of the 2nd setup whereby the moving pulley is now attached to the moving hauler as distinct from the moving load. In the 3rd setup, if the roles of the red and yellow vehicles were reversed, the MA would be restored.
Gotta love working demonstration models. This is tricky stuff to teach because of ….three completely different sets of rules for…. A. Simple systems B. Compound systems C. Complex systems Almost all recovery setups are simple systems though, so beginners don’t have to sweat it too much. There is one confusing exception in a simple system when it comes to self recovery with your own mounted winch. The optional way of figuring MA is count the number of pulleys that are moving and multiply by 2. Stationary pulleys are just redirects, not MA. And I just created confusion for the self recovery situation, which has a redirect pulley at the anchor and no moving pulleys, but still makes 2:1 MA because……..are ya ready for this…… The power source is “anchored” to the load. The winch is pulling the cable rearward and the vehicle forward. 2 jobs. I’m sorry to write a whole chapter but I’ve seen much confusion (that included me) and arguments about this so I hope this helps someone jump past it. Funny last thought. I hope you’re not gonna tell me that you already did a whole video about it. 🤔🥴 EDIT: Counting tensions is better than counting pulleys.
Great post and yes, I have covered the "block doesn't move but you still get MA" scenario! This is complex, no two ways about it! l2sfbc.com/you-can-get-mechanical-advantage-from-a-snatch-block-that-doesnt-move/
This is honest gold. I wish you could produce some blank problem sheets to practice on like in math class. I mean this for all your pulley and redirect videos. I would buy them. There used to be (probably still is) some guy that would hold these recovery training videos for the tow industry in the USA. He would factor in inclination, vehicle weight estimates, and terrain resistance. I lost track of the guy when I left the industry.
awesome little vid. I do a use for the third set up,,, providing your load math works in a safe level. Most of my recoveries ar lighter pulls. ( usually high center on small snow drifts. ) I use a come along for most recoveries so am limited to about 3 m per set up . I may have to use this set up for some of my pulls in the future.
Thanks Robert. A good explanation except the last bit about the angle of pull. The rope has 1000kg tension and 1:1 mechanical advantage at any angle. I suggest that you revise that part of the video to show the change of load on the anchor point for various angles. 2000kg at 180 deg, 0kg at 0 degrees. Cheers.
Sorry wasn't clear - the rig shown has no MA as you said, but if it was rigged for MA eg static winch car moving casualty other end then it wouldn't be a 2:1.
i will double-check what you said at the end graph as I know is not right. the graph is fine and it is showing the load on the anchor point. But in a one-to-one simple rope line, the 1000KG on each vehicle does not change.
Thanks Robert, though I must've misunderstood - regardless of the pulley, if the recovery and casualty vehicles are both attached to the same line, then they will both move the same distance, so by my reckoning there is zero mechanical advantage - you pull a ton, you need a ton. The spreadsheet seemed to indicate that there was mechanical advantage when you alter the angles of pull - what did I miss?
The spreadsheet showed what the MA would be if the single pulley was rigged for MA at the angle given. So you can angle the two lines at say 140 degrees and the effect on the anchor will be the same as the MA depending on how you rig it.
There is no mechanical advantage between vehicles in the curve graph diagram. what changes is the load on the anchor point. it starts at 2x and, as the angle becomes smaller, the load on the anchor point also lessens. imagine a rope going around a tree- at the start the load is ripping the tree out of the ground as if both vehicles are pulling at 1000kg. As the recovery vehicle moves around to pull the casualty straight out, the rope is only skimming passed the tree = the load on the tree/anchor point is zero. in both cases and all angles in between there is no mechanical advantage to the recovery vehicle. the only thing that changes is the load on the anchor.
@@L2SFBC I'm afraid I'm as thick as two bricks Robert. I can't see how there can be mechanical advantage with one line attaching the two vehicles regardless of angle. The force on the tree will increase, I get that. But MA? I better have a look at my old Mech Eng texts....
There's no MA in the examples shown, but it could be made as such if the line was rigged back to the vehicle which was winching itself. I'm talking of the effect of the angle which is the same as for MA and anchor load, depending on rigging.
In your last example where you were talking about the load on the anchor as the angle varied, you didnt mention the winch load. I assume that that load on the winch would be the same at any angle as this is still just a redirect.
Yes the winch load was the same in all of them, 1:1 minus friction - it was the anchor load that changes. Or, if you rigged for MA, whether it was 2:1 (minus friction) or a bit less.
Speaking of winching Robert, I wonder if you could do a video on some of the other options to a bullbar mounted winch? There’s one that goes around a driven wheel and another that connects to the wheel nuts. Might be interesting for those of us that can’t afford a winch.
A lot of the added weight on the upper scales is the weight of the ropes and lower scales, can you estimate their weight Robert? As that should give the difference for the scales, helps people see why what scale has what weight on it. :-) Good video again.
Indeed, I wasn't too fussed about the exact numbers. I did mention the weight was 1.5kg but came to 1.6 with the ropes...basically I've found that the numbers in reality never match the theory exactly as there's too many variables, but they're close enough to make the point.
Would the number differ if the experiment was horizontal instead of vertical? Things like friction coefficients or line/rope sag or even pully sag would surely alter measurements such as peak load/weight.
Robert, I accidentally disliked your video because of something RUclips did (they introduced a new icon called Clip) I wanted to click the save box on the far right, for later viewing (a second time). I had to scroll that row of icons to the left to get to the Save box. This pushed Like off the left side of the screen and hid the DIS part of Dislike off the screen, making me think I was clicking Like. Do you see what I mean? You and other RUclipsrs will now, by no fault of your own, get more accidental dislikes. (by phone users anyway) I don't know if this in turn affects your earnings. Anyway I thought you should know. You've helped me, now for a change, I'm helping you - how about that!
This is very interesting and a good demo of something we don't normally think about or are taught with pulleys.
I like to think of it this way. Advantage for one end of the system must always be disadvantage for the other end. The 3rd setup produces mechanical disadvantage as described because it is the mirror of the 2nd setup whereby the moving pulley is now attached to the moving hauler as distinct from the moving load. In the 3rd setup, if the roles of the red and yellow vehicles were reversed, the MA would be restored.
I like it!
Casual StarLink box in the back
1😁
Fantastic demo and explanation. Appreciate all the effort you put in, plus the expertise. Always impressed by your videos.
Thank you very much! Please share!
Great info as always! Thanks Robert!!
Thanks, please share!
Gotta love working demonstration models. This is tricky stuff to teach because of ….three completely different sets of rules for….
A. Simple systems
B. Compound systems
C. Complex systems
Almost all recovery setups are simple systems though, so beginners don’t have to sweat it too much. There is one confusing exception in a simple system when it comes to self recovery with your own mounted winch. The optional way of figuring MA is count the number of pulleys that are moving and multiply by 2. Stationary pulleys are just redirects, not MA.
And I just created confusion for the self recovery situation, which has a redirect pulley at the anchor and no moving pulleys, but still makes 2:1 MA
because……..are ya ready for this……
The power source is “anchored” to the load. The winch is pulling the cable rearward and the vehicle forward. 2 jobs. I’m sorry to write a whole chapter but I’ve seen much confusion (that included me) and arguments about this so I hope this helps someone jump past it.
Funny last thought. I hope you’re not gonna tell me that you already did a whole video about it. 🤔🥴
EDIT: Counting tensions is better than counting pulleys.
Great post and yes, I have covered the "block doesn't move but you still get MA" scenario! This is complex, no two ways about it!
l2sfbc.com/you-can-get-mechanical-advantage-from-a-snatch-block-that-doesnt-move/
@@L2SFBC
GAAAHH!!!! 🙁 Oh well, on the plus side, you now have a redirect 😉 back to the info for anyone who needs it.
This is honest gold. I wish you could produce some blank problem sheets to practice on like in math class. I mean this for all your pulley and redirect videos. I would buy them.
There used to be (probably still is) some guy that would hold these recovery training videos for the tow industry in the USA. He would factor in inclination, vehicle weight estimates, and terrain resistance. I lost track of the guy when I left the industry.
Thanks X!!! I may do that...
@@L2SFBC
6:14
"Look for the shortening pulley line"
Could you elaborate on this please?
Very good video!
Excellent! Very useful info.
Glad it was helpful! Please share :-)
awesome little vid. I do a use for the third set up,,, providing your load math works in a safe level. Most of my recoveries ar lighter pulls. ( usually high center on small snow drifts. ) I use a come along for most recoveries so am limited to about 3 m per set up . I may have to use this set up for some of my pulls in the future.
What else can I say. Just brilliant once again. Cheers!
Thanks please share!
Thanks Robert. A good explanation except the last bit about the angle of pull. The rope has 1000kg tension and 1:1 mechanical advantage at any angle. I suggest that you revise that part of the video to show the change of load on the anchor point for various angles. 2000kg at 180 deg, 0kg at 0 degrees. Cheers.
Sorry wasn't clear - the rig shown has no MA as you said, but if it was rigged for MA eg static winch car moving casualty other end then it wouldn't be a 2:1.
Thanks
i will double-check what you said at the end graph as I know is not right. the graph is fine and it is showing the load on the anchor point. But in a one-to-one simple rope line, the 1000KG on each vehicle does not change.
Correct it doesn''t , it is the anchor load that changes
Thanks Robert, though I must've misunderstood - regardless of the pulley, if the recovery and casualty vehicles are both attached to the same line, then they will both move the same distance, so by my reckoning there is zero mechanical advantage - you pull a ton, you need a ton. The spreadsheet seemed to indicate that there was mechanical advantage when you alter the angles of pull - what did I miss?
The spreadsheet showed what the MA would be if the single pulley was rigged for MA at the angle given. So you can angle the two lines at say 140 degrees and the effect on the anchor will be the same as the MA depending on how you rig it.
There is no mechanical advantage between vehicles in the curve graph diagram. what changes is the load on the anchor point. it starts at 2x and, as the angle becomes smaller, the load on the anchor point also lessens. imagine a rope going around a tree- at the start the load is ripping the tree out of the ground as if both vehicles are pulling at 1000kg. As the recovery vehicle moves around to pull the casualty straight out, the rope is only skimming passed the tree = the load on the tree/anchor point is zero. in both cases and all angles in between there is no mechanical advantage to the recovery vehicle. the only thing that changes is the load on the anchor.
@@CoryAu Thanks Cory. That's how I understand it - oh and a good explanation too.
@@L2SFBC I'm afraid I'm as thick as two bricks Robert. I can't see how there can be mechanical advantage with one line attaching the two vehicles regardless of angle. The force on the tree will increase, I get that. But MA? I better have a look at my old Mech Eng texts....
There's no MA in the examples shown, but it could be made as such if the line was rigged back to the vehicle which was winching itself. I'm talking of the effect of the angle which is the same as for MA and anchor load, depending on rigging.
In your last example where you were talking about the load on the anchor as the angle varied, you didnt mention the winch load. I assume that that load on the winch would be the same at any angle as this is still just a redirect.
Yes the winch load was the same in all of them, 1:1 minus friction - it was the anchor load that changes. Or, if you rigged for MA, whether it was 2:1 (minus friction) or a bit less.
Speaking of winching Robert, I wonder if you could do a video on some of the other options to a bullbar mounted winch? There’s one that goes around a driven wheel and another that connects to the wheel nuts. Might be interesting for those of us that can’t afford a winch.
Already done one on the Bog Out - works and is effective at times. ruclips.net/video/SiyNvpM8f98/видео.html
A lot of the added weight on the upper scales is the weight of the ropes and lower scales, can you estimate their weight Robert? As that should give the difference for the scales, helps people see why what scale has what weight on it. :-)
Good video again.
Indeed, I wasn't too fussed about the exact numbers. I did mention the weight was 1.5kg but came to 1.6 with the ropes...basically I've found that the numbers in reality never match the theory exactly as there's too many variables, but they're close enough to make the point.
Would the number differ if the experiment was horizontal instead of vertical? Things like friction coefficients or line/rope sag or even pully sag would surely alter measurements such as peak load/weight.
Not to any significant degree
Robert, I accidentally disliked your video because of something RUclips did (they introduced a new icon called Clip) I wanted to click the save box on the far right, for later viewing (a second time). I had to scroll that row of icons to the left to get to the Save box. This pushed Like off the left side of the screen and hid the DIS part of Dislike off the screen, making me think I was clicking Like. Do you see what I mean? You and other RUclipsrs will now, by no fault of your own, get more accidental dislikes. (by phone users anyway) I don't know if this in turn affects your earnings. Anyway I thought you should know. You've helped me, now for a change, I'm helping you - how about that!
thanks will pass that on - liking/subscribing/sharing does help me too as does Patreon!
wish you could make the chart downloadable
Might make a calculator of it later
Expert presentation
Glad you think so, please share!