If using a snatch block and doubling the line, doesn't it equate doubling the power of your winch?
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Yep a pulley effectively doubles the capacity but it cuts the winching speed in half.If using a snatch block and doubling the line, doesn't it equate doubling the power of your winch?
Sometimes, but it depends. Smarter people than me should weigh in, since there is math involved and that's never been my strong suit. As I understand it, a snatch block can be a force multiplier or just a way to redirect. I think a basic double line pull from the winching vehicle to a fixed anchor point with a snatch block and back to the winching vehicle will give you that 2:1 multiplier. Then again, if you are winching from a stuck vehicle, to a snatch block on a fixed anchor point and then running it another fixed anchor, you are doing a redirect (and not getting the 2:1 force multiplier). There's a whole other forum on mud for this if you want good info from experts - people that have done this forever or are professional riggers.If using a snatch block and doubling the line, doesn't it equate doubling the power of your winch?
Not quite sure that I agree. If you put a snatch block on a tree and the line goes from the truck, through the block and attaches to the truck I don’t think there is any mechanical advantage. I think that you would have to have two blocks and go from truck to tree to truck and back to tree to gain a mechanical advantage. It’s no different than a pulley on a branch lifting a pail.Yep a pulley effectively doubles the capacity but it cuts the winching speed in half.
This is correct.Sometimes, but it depends. Smarter people than me should weigh in, since there is math involved and that's never been my strong suit. As I understand it, a snatch block can be a force multiplier or just a way to redirect. The force multiplication varies by the angle of the pull as well as what you're anchoring to. I think a basic double line pull from the winching vehicle to a fixed anchor point with a snatch block and back to the winching vehicle will give you that 2:1 multiplier. Then again, if you are winching from a stuck vehicle, to a snatch block on a fixed anchor point and then running it another fixed anchor, you are doing a redirect (and not getting the 2.1 force multiplier). There's a whole other forum on mud for this if you want good info from experts - people that have done this forever or are professional riggers.
Pulling a rope through a pulley on a branch to a pail is a 1:1 (redirect), with no mechanical advantage.Not quite sure that I agree. If you put a snatch block on a tree and the line goes from the truck, through the block and attaches to the truck I don’t think there is any mechanical advantage. I think that you would have to have two blocks and go from truck to tree to truck and back to tree to gain a mechanical advantage. It’s no different than a pulley on a branch lifting a pail.
You don't have to agree, but the laws of physics say I'm right (for once!)Not quite sure that I agree. If you put a snatch block on a tree and the line goes from the truck, through the block and attaches to the truck I don’t think there is any mechanical advantage. I think that you would have to have two blocks and go from truck to tree to truck and back to tree to gain a mechanical advantage. It’s no different than a pulley on a branch lifting a pail.
One day I’ll be a big boy and do stuff like this. A multi vehicle pulley rescue would be cool as f to see.Heh. You with eight pulleys and enough rope you could winch an empty 737, assuming you're willing to wait that long...
No. Well, really it depends.Better to always get higher rated stuff I guess?
We were taught that each wheel reduces mechanical advantage by 10% because of friction. Obviously a general rule of thumb but there is still loss of efficiency.Heh. You with eight pulleys and enough rope you could winch an empty 737, assuming you're willing to wait that long...
9 pulleys then? Or 8 pulleys and a massive tube of graphite?We were taught that each wheel reduces mechanical advantage by 10% because of friction. Obviously a general rule of thumb but there is still loss of efficiency.
The math is easy, I just googled "pulley force calculator". First link:That'd be some pain in the neck math for someone like me - you can't say 10 pulleys each reduces by 10% so it reduces by 100%. It must be "of the load applied to that pullley", so some goofy math I forgot or never learned how to do. I don't think it probably matters all that much in the kind of vehicle winching we do, at least for practical purposes. Stuff like number of stuck wheels, angle of incline, whether it is assisted or non-assisted, probably matter a lot more, and most also have some good rules of thumb for use in the field.
I really like @linuxgod s reminders about keeping in mind the forces involved and weak links. If you are winching from a vehicle and hooking back to that vehicle for a multi-line pull, you are potentially adding a huge force multiplier and the winching vehicle is feeling all of that force. I try to keep this in mind - flying winch lines, bumper parts and tackle are bad bad bad.
No. Well, really it depends.
If $ is no object it's better to get a winch with more pulling power. There's more to a winch than just the weight rating - you have to consider duty cycle, pulling speed, etc. Realistically you're trading off $ for winch capacity though, and you might be better off investing some of those $ into other gear or mods.
For other gear you want stuff that is properly rated for the working load and that has a sufficient breaking strength. That said if you're trying to pull a 737 (or just get yourself out of a really sticky mud hole) you need to consider where you want your failure point to be. Consider:
I read a story once about how Kitchenaid mixers have a plastic gear in them that's designed to break if they get stuck when cranking. Better to break a plastic gear that's readily serviceable than to bust the motor. Similarly recovery gear should be rated for the load you need, but you should intentionally consider where you want your weak link to be in the event of a problem and then when that weak link gives out what the impact will be (flying projectiles, ability to fix/replace what breaks and continue the recovery, etc).
- If your shackles or snatch blocks are the weak point and they break you could have hunks of steel flying around
- If your winch line, kinetic recovery straps, tree saver, etc are the weak link they could go flying as well. Having something to dampen and absorb the energy (like a blanket tied to the winch line) helps here, but even still things can go sideways quickly
- As discussed in a recent thread some equipment like kinetic ropes are designed to stretch and then release their energy to help in the recovery. Too little rating and they will break; too much rating and they won't stretch
- If everything you buy has a 1,000,000# load rating and will never break, when you try to pull that 737 (or your buddy stuck on a rock) the weak point is going to be your vehicle frame (or the bumper mounts).
Disclaimer: I'm not a winching expert. I've watched a bunch of videos and I've done a couple recoveries. There's a subsection of the forum with people far more experienced than I am.
Lol.. It was a ”rule of thumb” because size of wheel, quality of bearings etc. come into play and we never used more than 6 part blocks before we moved to come alongs and chain hoists.9 pulleys then? Or 8 pulleys and a massive tube of graphite?
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