Load when winching up a slope

Well my intuition is as follows - I have a car weighing about 1.5 tons or something, and it's not too much trouble for me to overcome its rolling resistance and push it along a flat road by myself. Add in a couple of mates and we could even push it up a reasonable slope.

Now consider how many blokes to lift the thing off the ground completely...?

David

Your intuition is wrong. Have a look at

The force on the boat will be "in proportion" to the slope. By my reckoning, as the force to hold the boat still on the winch goes as the angle of the slope (in your case tan**-1 1/12 or 4.76deg) from zero at 0deg to 1tonne at

Mea culpa, Chris Dixon and Wikipedia are, of course, correct. I should have been using Sine not Tangent. Not much difference at small angles but the strain figure then comes out as 83kg, not 53kg - roughly the same outcome!

Rolling resistance + 1/12th of the weight for a 1 in 12 slope. (approximately.it actually the tan of the angle whereas 1 in 12 is usually the sine but (sine)~=(tan)~=(angle in radians) for small angles)

.....................................etc., multiply this by five (say

and you need tackle with a breaking strain of 250kg. No liabilit accepted etc! [/i][/color]

Okay - I've got it now (with the qualification that it's the sine o the angle not tan) So....... I'm hauling a big bucket of water out o the well ( I'd never got round to fitting a winder, just a singl pulley). I get it to the top and say to my wife standing behind me "Just hang on to this while I grab the bucket." She takes it - halvin the angle the rope makes with the horizontal - and disappears down th well

-- MikeP

Wives should look after the sick and leave the well alone.

I'll just get my coat. :-)

You be needin' to use them sines and cosines they went on about at school. You weren't one of those who whinged "what use is this in the real world" were you?

Up a 1 in 12 slope, a 1 ton(ne) boat would exert 1 / 12 of its weight on the rope/chain, i.e 0.08333ton(ne) plus the rolling resistance. You then need additional force (ie tension on the rope) to accelerate it up the slope - minimal at winching speeds.

Bob

To calculate the rolling resistance you need to identify the road surface first, if it is a good smooth surface you take 1/25 of the total weight as the rolling resistance (40kgs in the ton) To calculate the gradient resistance take the weight of vehicle /60 multiplied by the angle of the slope in degrees, this will give you the gradient resistance, add to rolling resistance to give the total winch power required.(if angle is greater than 45degrees take total weight) I am assuming that this is on a trailer if not you would have a third set of resistance called damage resistance to factor in

Dave