If you had connected the figure of eight to the becket of the lower pulley and then connect the lower pulley directly to the load with a carabiner,would that still be considered and function as 5:1? PS. Thanks for making these videos. They have helped me understand considerably.
I have a question that I don't think I've seen asked but maybe because it is so obvious to everybody. If I use a 15:1 setup and am using it to pull a 10,000 pound contained into place, does that mean I would have APPROXIMATELY 666 pounds on the line connected to my tractor in this case? I am just wondering how to size my rope. If I have rope that has a working load rating of 1200 pounds, it seems as though I'd be fine using it in this case if the first rope attached to the tractor is only going to see 666 pounds. Thank you very much in advance!
Aaron, in a perfect world and if the pulleys had 100% efficiency it would take 666 pounds of input force to move the load. But most pulleys are around 80-90% efficient. So without doing the math it would take around 1000 lbs of input force to move 10,000 lbs with a 15:1. Now the more important issue: minimum breaking strength for the rope. For “live loads” we usually want a 10:1 safety factor to lift or move a load(person). That means if we are moving/lifting 2 people with a combined weight of 600 lbs, we would want our minimum breaking strength of the rope to be at least 6000 lbs. most rope rated for rescue is actually rated at 8-10,000 lbs breaking strength depending on diameter and industry. So for a “non live load” you can lower the safety ratio, but you still want to keep things safe. I would use a rope that would still allow a minimum of 2:1 safety factor to move an object on the ground. Many would say it should be at least a 4:1 factor. So you will need a rope that could hold 20,000 lbs before breaking. You also need to be aware that a 15:1 is an odd system. That means a single rope would be attached to the load. All the weight of the load would be on that first strand, so it better be strong enough to hold at least twice the load. Also remember that knots in a system weaken the rope 25-50%. Therefore a rope 2x stronger than the load would be a necessity. A way to get around this would be to build a 4:1 to attach to the load, and then build another 4:1 to attach to the haul strand of the first 4:1. That would give you a 16:1, but 4 strands of rope would be sharing the load instead of a single strand on a 15:1. You also need to have pulleys and carabiners rated for at or above the load. Doubling up ropes and carabiners so the combined strength is well over the load weight is also a must. Hopefully this is clear enough to answer your question. Maybe I will make a video.
Thanks. We had (4) 16 -18" dia. oaks growing together as 1 tree cut down but we were left with a huge short stump to deal with. I can dig around it but I need serious help pulling it out. Can I build a system like yours and get it out?
Jimmy V its possible, but I cannot guarantee it will work. depends upon the strength of the gear your using, the anchor strength, number in the haul team and strength of the stump. i would recommend digging up all the roots and cutting them with an axe before you try pulling the stump. usually a stump that big takes a truck to pull it out.
You've been a big help. It's understanding how to put these pulley systems together to do what I need to do is where I think most of us have trouble. I do have a B2650 tractor to help me on the grunt end of it , but I'm afraid aluminum pulley's and parts won't hold up. I'd appreciate any input you have about that if you can. Thank you again!
@@jimmyv6310 were you able to pull the stump out? If so, what gear did you use? I’m getting ready to pull some out and been researching gear for the project. I’ve got my B3300.
Always if it is life safety. If it's just moving an object on flat ground, you might not need one. If there is risk of causing damage, dropping the load, or life safety, you should always use one. I guess just use your best judgement.
