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Started By
Message
Physicists....help needed.
Posted on 6/25/12 at 12:52 pm
Posted on 6/25/12 at 12:52 pm
Will the below diagram decrease the load by 4 times or only 3? I'm insure about the horizontal rope.
8
Posted on 6/25/12 at 1:07 pm to VanRIch
If i'm understanding you correctly you're talking about a boat on a lift and how much force you would need to lift it? That would be more dependant on the ratios of the pully and the angle of the downward force, I think. My engineering degree is in making sure electrons stay in the wires and statics was not my strong point.
Posted on 6/25/12 at 1:10 pm to rustyjohnson
I understood it as however many ropes you have distributing the weight of the load, you would divide your load by that number. But I'm unsure about the horizontal as it doesn't seem like it would have the same load, but thats why i'm asking. click on the smiley face
Posted on 6/25/12 at 1:18 pm to VanRIch
Without really looking into it too hard I'd say the horizontal rope provides no support. My reasoning is torque is a sine function and the sine of 180* is 0.
Posted on 6/25/12 at 1:20 pm to rustyjohnson
cool, I was trying to determine if I was going to be lifting 23 lbs or 17 lbs, haha. I was just curious as I'll be building this tonight. Thanks.
Posted on 6/25/12 at 1:20 pm to VanRIch
You figure out hauling ratios by how many lines you have coming from the load. You have three lines coming from the load so initially I would say 3:1. But I don't think that will work as you have it drawn. You have a 2:1 system on the front of the boat and a 1:1 on the back. The yak will not raise up evenly.
Make a bridle and hook up a 2:1 if that's a yak. Should be easy enough to raise.
Make a bridle and hook up a 2:1 if that's a yak. Should be easy enough to raise.
This post was edited on 6/25/12 at 1:22 pm
Posted on 6/25/12 at 1:23 pm to VanRIch
The tension in the line stay constant. Load decreases by 3.
Posted on 6/25/12 at 1:24 pm to VanRIch
I picked B on the FE exam for all the force related questions, so I'm happy we're talking about a light load and not lifting your bay boat.
Posted on 6/25/12 at 1:26 pm to Nodust
Get rid of the ring and attach the horizontal top you have listed as 4?? to the pulley in the front. Now you have a 3:1.
Easy way to remember. If the end of the rope is tied to the load end it is odd numbered ratio. Tied to the anchor end it is even numbered ratio.
Easy way to remember. If the end of the rope is tied to the load end it is odd numbered ratio. Tied to the anchor end it is even numbered ratio.
Posted on 6/25/12 at 1:27 pm to Nodust
quote:
The yak will not raise up evenly
Thats what I thought too, but I saw a youtube video where this guy built this exact setup and it rises evenly, but I didn't have audio up so I don't know if he mentioned a ratio. Youtube "Home made kayak hoist" it's the first video 2:16.
Posted on 6/25/12 at 1:27 pm to VanRIch
Describe the last pulley, is it a single pulley with the rope wrapped around twice, or two pulleys on bearings side by side that can turn independent of each other?
eta; It's going rise evenly either way, just determines how much harder it'll be to pull.
eta; It's going rise evenly either way, just determines how much harder it'll be to pull.
This post was edited on 6/25/12 at 1:29 pm
Posted on 6/25/12 at 1:30 pm to TheDrunkenTigah
Last one is a single. The set up is two single pulleys and the one in the top right of the pic is a double.
not sure if double is the right term, i mean this.
not sure if double is the right term, i mean this.
This post was edited on 6/25/12 at 1:32 pm
Posted on 6/25/12 at 1:35 pm to VanRIch
You're dividing the load by three then.
Posted on 6/25/12 at 1:38 pm to TheDrunkenTigah
Ok thanks, not that it's a big deal, I was just curious and wanted to learn a little more. Can you tell me why it's 3 and not 4.
Posted on 6/25/12 at 1:40 pm to VanRIch
the fs12t only weighs 70lbs
Posted on 6/25/12 at 1:40 pm to VanRIch
It did work in the video. I am going to say it should be a 3:1 because the knot is tied to the load.
Let us know how it works I am curious. I deal with lots of haul systems in rescue training but never a set up quite like that with the knot tied to the load at a different point.
Let us know how it works I am curious. I deal with lots of haul systems in rescue training but never a set up quite like that with the knot tied to the load at a different point.
Posted on 6/25/12 at 1:40 pm to VanRIch
If I interpret your drawing correctly, you have a 3 to 1 system. The double sheave on the top right pulley completes your 3 to 1. I'm not sure it will raise evenly either, just depends on how much weight you have and how freely the sheaves turn on the pulleys...If you are lifting a yak, it should be fine.
Posted on 6/25/12 at 1:41 pm to VanRIch
quote:There is only 3 lines coming from the load.
Can you tell me why it's 3 and not 4.
Posted on 6/25/12 at 1:42 pm to LSURoss
Ha, I know, I know. I like building and creating things though.
Posted on 6/25/12 at 1:43 pm to Nodust
Ahhhhhhhh, gotcha, dang, I really should've realized that.
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