People think pulleys increase pulling power.

DaveInDenver

Expedition Leader
#76
Yes and the total pulled in by the winch would be 10 feet of rope length to move 5. If you had a single line pull you'd have pulled 5 feet of rope to move 5 feet. It's the circular equivalent of using a lever on a fulcrum that's twice a long. You have to move the side gaining advantage farther as the length grows.
 
#79
FFS...nothing...can...ever...surpass...the...global...warming...thread!
the problem we may run into increasing mechanical advantage is if we have to pull the cable longer we're going to have to run our vehicles longer so we don't kill our batteries. The extra exhaust will accelerate global warming.
 

dwh

Tail-End Charlie
#80
the problem we may run into increasing mechanical advantage is if we have to pull the cable longer we're going to have to run our vehicles longer so we don't kill our batteries. The extra exhaust will accelerate global warming.
But you're only putting half the load on the winch.
 
#84
What helps me in understanding this phenomenon of Work and Load with pulleys and in what scenario are you providing mechanical advantage.

When you have 25 feet of line going to an anchor 25 feet away. The vehicle will move forward 1 inch for every 1 inch of line pulled in by the pulley.

When you have 50 feet of line going to an pulley anchor 25 feet away, and then back again to the an anchor on the vehicle. The vehicle will move forward half an inch for every inch of line pulled by the pulley. Whenever this is the scenario there is mechanical advantage created.
 
#87
What helps me in understanding this phenomenon of Work and Load with pulleys and in what scenario are you providing mechanical advantage.

When you have 25 feet of line going to an anchor 25 feet away. The vehicle will move forward 1 inch for every 1 inch of line pulled in by the pulley.

When you have 50 feet of line going to an pulley anchor 25 feet away, and then back again to the an anchor on the vehicle. The vehicle will move forward half an inch for every inch of line pulled by the pulley. Whenever this is the scenario there is mechanical advantage created.
The problem I had was counting lines and the power coming from an external force. With the power inside, like a winch, it becomes a pulley, its line is part of the pulling force and a multiplier.
 

DaveInDenver

Expedition Leader
#89
Can you run half the engine?
Maybe half the battery or alternator. There's a minimum draw for a winch, which is it's unloaded speed. That's sometimes low enough that your engine's alternator might even keep up indefinitely. Under full load a winch is going to drain your battery pretty quick and is going to heat up very fast.

So you want to be closer to the unloaded 90A rather than the fully loaded 350A.

We could introduce the concept of duty cycle but since it took 7 pages to agree the ancient Greeks and Babylonians were right doing that might cause mental meltdown.
 

DaveInDenver

Expedition Leader
#90
Dunno offhand. My 1000lb Timken Hoist seems fairly deep ratio, probably around 20:1. (that picture is same as my hoist)
One would need to measure diameters or count teeth of its tandem chainwheel to calculate.
That's probably in the ball park. The 1 ton hoist I have seems to be 18:1 by my estimation. It's not a single chain differential like that but rather just a newer geared one with a chain loop, but I suspect ultimately the required effort would be similar anyway. Heavily loaded it still not easy to move so it's clearly rated to hold that much weight rather than move it without significant effort. But OTOH too much reduction and it takes forever to raise and lower something that isn't 2,000 lbs.
 
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