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Making an inch spool "grippy"?

  1. Aug 9, 2018 #1
    I have a winch and want to use it to assist with pulling some ropes connected to pulleys to lift some stuff. I have it setup so that it's similar to a system which I've seen in boating but unsure of the name of. It's basically using the winch to assist with the pulling but not allowing the rope to wind up on the spool, so it's basically wrapped around the spool a couple of times so it 'grips' the spool, but the other side is left hanging so that the rope doesn't actually wind up on the spool.

    does this make sense and does anyone know what this is called so I can explain myself better????

    Anyway you can see kind of what I mean in the images. Two ropes from either side wrapped around the spool about twice each. How could I make the spool a little more grippy so it actually grabs the rope to pull it, and how could I prevent the rope from sliding back down on the spool and bunching up?

    How do the mariners use this system I'm trying to very badly describe?

    Below image, the rope coming from the left side wraps around once and is left hanging on the right side.
    Rope on the right side wraps around once and is left hanging on the left side.

    I want these two ropes to be taught around the spool so that when the winch is on it will pull them and lift the load instead of just spinning and not grabbing the ropes.


    This is just the rest of the device. The two ropes of uneven length hanging down in the middle are the ropes attached to the winch. so I can hook up my load, push the button on the winch and it'll lift the entire thing evenly. IMG_7515[1].JPG
  2. jcsd
  3. Aug 9, 2018 #2
    Have you tried using more rope to make a full binding around the spool?
  4. Aug 9, 2018 #3

    jim mcnamara

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    There you want is belaying, I think. This is a clever application of it I think. The coefficient of friction depends on contact length with the pin and the type of cable/rope Wire rope may be a much better choice.

    Good question! I moved it to another forum so experts can help. I'm not expert in this field, so take my answer with a grain of salt.
  5. Aug 9, 2018 #4
    Which just means more binding. He needs to wrap it around the spool more times. The more the rope "grips" the spool, the more the spool "grips" the rope. He also might need a second spool since he's trying to use two ropes. Can't say what rope he needs since he hasn't mentioned what's the weight of the load he's trying to winch.
  6. Aug 9, 2018 #5

    jim mcnamara

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    PS: The frame is inadequate and unstable for anything but very light loads. How did you choose the pulleys and rope - working strength?
  7. Aug 9, 2018 #6
  8. Aug 9, 2018 #7


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    How heavy is your load going to be? Judging from the wooden structure and the diameter of the rope, the load will be pretty light. Why do you need a powered winch to help lift a light load? Can you just use a hand-powered winch instead?

  9. Aug 9, 2018 #8
    • Post edited by the Mentors to remove an insult
    You couldn't be further from the truth my friend. I've already tested this.

    The object that needs to be lifted is the bed of my truck weighing in at around 400lbs.

    See that trailer in the back? That's somewhere on the order of 1000+Lbs, and even without the winch I'm able to lift that trailer one side at a time.
    I've already done some basic testing with the winch and it WILL lift that trailer off the ground and not strain or wobble.
    Last edited by a moderator: Aug 10, 2018
  10. Aug 9, 2018 #9
    truck bed, about 400Lbs.

    The winch is not needed, I just happened to have one lying around and figured wth, it'll make the job that much more easy. That was pretty much a "well I've got it, might as well use it"
  11. Aug 9, 2018 #10
    So the most I can wrap around the winch is 2 times with each rope, then it fills the length of the spool and requires me pushing the "up" button and pulling on one rope to keep it taught, while my gf pulls the other rope to keep it taught.

    It really works already as it is, I was just looking for ideas about how to get a little more grip.

    When I wrap the rope around the spool twice it works ok, but the ropes "jump" over each other and get tangled...... it doesn't stay lined up as it spins...... that's the real problem here and it isn't really even much of a big problem.
  12. Aug 9, 2018 #11
    This, thank you. that's really been bugging me trying to remember the name.
  13. Aug 9, 2018 #12
    A windlass needs back tension to work. The equation, if you are interested, is ##T_1/T_2 = e^{\mu \theta}##, where e = 2.718, ##\mu## is the coefficient of friction between the rope and windlass drum, and ##\theta## is the angle of wrap. One full revolution of wrap is 2*pi = 6.283 radians. For example, if the coefficient of friction = 0.25 and you have one full wrap, then the ratio of tensions is 4.8. If you are lifting 480 lbs, you would need 100 lbs of back tension.

    The belt wrap equation assumes that the rope is flexible. A stiff rope on a small drum will need more back tension to get it to pull down onto the drum.

    And just make sure that you are not standing inside that structure when lifting a load. The most likely failure mode is the structure folding up and collapsing. I once watched a guy lifting a somewhat heavier load using a structure similar to yours. It folded up with him inside. Good thing the water was shallow or he would have drowned before I could help him get him out of there. I suggest longer angle braces at the corners.
  14. Aug 9, 2018 #13


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    That will stop slipping so it's definitely worth trying. Would it be possible to increase the diameter of the barrel with layers of strong tape? That would increase the friction without needing extra turns. The OP seems to be pretty resourceful so he may be able to dig out some alternative method of increasing the winch diameter.
    There is the problem that there is sharing of a common winch barrel and a risk of the ropes riding over each other.
    This should be avoided if the sense of the coils on the barrel takes one rope up onto one face and the other rope onto the other face.(i.e. riding in opposite directions) The outboard ends of the two ropes need to be held carefully at the correct angle to avoid problems when lowering the load. Riding turns can be embarrassing and make it awkward to lower the load - or even raise it again to clear the problem. Take it slow.....
    I can't see details of the layout but there seems a possible risk of tipping if the weight is not shared equally by all the suspension points. Could one pulley stay on the ground as the rope is taken up?
  15. Aug 9, 2018 #14

    Now I realize that in the video the frame looks to be somewhat wobbly, this is because I had to pull on the rope laterally to the frame, which naturally makes the frame wobble. Also that trailer is significantly heavier than the load that's actually being lifted.

    Since the video was posted I've added a couple extra pulleys to either side that bring the ropes over to the center of the frame to the winch. There are also pulleys at the winch location that will allow me to pull the ropes downwards on the frame instead of laterally so it doesn't wobble.

    That being said, as I mentioned above, I tested the winch with that trailer and it lifted the whole damn thing off the ground, on top of being able to actually lift it, it was completely sturdy and stable and when using the winch and not having to apply additional forces to the frame by having me pull on ropes.

    Each pulley on the frame is rated for 550lb, and each lower pulley with the hooks on them are rated for 220lbs, the rope is 3/8" nylon and rated for 340Lbs. The truck bed weighs, as far as I can find out, 387Lbs.
    but I kid you not, with the winch it lifted that trailer completely off the ground without the slightest hint of wobble, nor any sound at all.
    I feel confident that it will handle the 387Lbs of truck bed.

    Last edited by a moderator: Aug 10, 2018
  16. Aug 10, 2018 #15

    Ranger Mike

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    Water the Rope!

    Keep what you got and use a garden hose to wet down the rope.

    Rope absorbs the water, and in turn increases the elasticity of the rope. Conforms to the surface better. More grip. Techinally I have read
    water also shows hydrogen bonding, so this also increases the magnitude of net intermolecular forces in the rope. But this is over my pay grade so cant confirm.

    In the early 1500s, Bernini and Michelangelo were busy building and decorating St. Peter’s cathedral in Rome. Some years later, it was desired to re‑erect in the middle of the circular colonnade an enormous monumental pillar from antiquity that was there. The pillar, made from granite and weighing many tons, was to be brought to a vertical position and dropped into a prepared hole so that it would stand and occupy the most prominent position at the center of the most important piazza in the world.

    Elaborate preparations were made for the raising. A huge wooden structure was erected, with pulleys and ropes enabling the column to be pulled up by the combined efforts of hundreds of workers. A day was set aside. Everything was ready for the effort. As an additional guarantee of success, the Pope decreed that no one was to speak while the work was in progress, so that the instructions of the overseer could be clearly heard. The penalty for speaking is variously reported as having been death or excommunication.

    The work began. The workers toiled at the ropes, and the pillar began to rise. The hot Roman sun ascended in the sky. As the angle of the great stone obelisk increased, so did the temperature of the ropes. The energy expended by all those people pulling heated them, and the blazing sun did nothing to help. In due course they became so hot they began to smoke. If they caught fire, the obelisk would come crashing down. It might even shatter.

    It was at this time that one of the workers, a Ligurian sailor called Bresca, decided that the rule of silence was less important than the success of the project. He shouted out: “Acqua alle funi,” meaning “water to the ropes.” The astounded overseer, realizing that this was useful advice, had water fetched and poured on the ropes. The project was saved. The obelisk adorns St. Peter’s Square to this day.

    When it was reported to the Holy Father, he decided on clemency. The punishment was lifted, and the brave worker was rewarded. He and his heirs were given the privilege of a monopoly in the sale of palm leaves to pilgrims in St. Peter’s Square on Palm Sunday of each year. Apparently the family survives, and still enjoys the privilege.
  17. Aug 10, 2018 #16
    That story was a roller coaster the entire way through lmao. Honestly that was a really interesting read.

    My ropes are nylon so I'm not sure how much effect water would have being that the ropes won't absorb it like the ropes of old would have. It's still very much worth trying because hey, why not.

    I think I might even wrap some duct tape around the spool to increase it's size/grip as mentioned above.

    But really, considering the weight this was able to hold, there should be no issues with weight. I'll post the rest of the videos on the project when I'm finally able to move my truck to this spot.
  18. Aug 10, 2018 #17

    Ranger Mike

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    thank you...makes this forum fun!
    ifin it were me, i would go to Tractor Supply Company and pick up a can of Liquid Tape ( used on electric connections instead of black elec tape or use a can of liquid vinyl dip. you dip your pliers into it and it insulated the handles. i do not know the durability of the liquid tape..the vinyl coating stuff is really good.
    $6 a can at Lowes

  19. Aug 10, 2018 #18
    Just one thing. You have pulleys 'series' on the same rope. Be careful with this: this setup is not stable. On the boatlift sketch @berkeman added you can see something like this, but there is a handle between the two pulleys to fix the rope, and both end of the rope is pulled. With that handle it is possible to adjust the angle of the boat, and since the middle of the rope is actually fixed, the boat will stay stable.
  20. Aug 10, 2018 #19


    Staff: Mentor

    It's true, what you're doing is similar to a winch or windlass on a sailboat. Here's a few points, some of which may repeat what others said.
    • The rope needs to be "tailed" that means keeping tension on the loose end of the rope as it comes off the winch. Some marine winches have "self tailing" as you can see in the picture, the part at the top plus the finger hanging down. Without that, it means a person holding that end in tension.
    • There's a magic number, 3 for the number of turns around the winch. With less than 3, there is too much slippage. With more than three, the probability of the ropes getting crossed and fouled increases. See the article from my blog post The Magic Number Three .
    • The angle at which the rope enters the winch is critical. Only a small range of angles will work. In the picture, you see the sloped part of the winch at the bottom. That slope is the ideal angle. Also in the picture you can see the load end of the rope coming in from the left via a pulley that is placed to make sure it comes at just the right angle.
    • If the rope turns do cross over each other and the load can't be eased, it can be extremely difficult to untangle the mess. Avoid that at all cost.
    • The surface of the winch is roughed with a texture to increase friction. You can see that in the second picture. However, even smooth surfaces work well but only with additional "tailing" tension and only with 3 turns.
    • The winch works up to the breaking strength of the rope. For more force you use bigger diameter ropes and winches. You limitation is not the winch but the frame.


  21. Aug 10, 2018 #20


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    Thread closed temporarily for Moderation...

    UPDATE -- the OP and I are in a long PM conversation about safety issues and possible improvements. More in a bit...
    Last edited: Aug 11, 2018
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