A graphical analysis of lever arms is easy, product of the distance from the axis to the actual force line by the exact force, weight plus reaction force.
The more the weight of the log is stronger the stronger the lever arm and therefore the tightening is increased in this system which hangs without being able to crack because the line of force approaches the axis of rotation !!!
The parallelogram does not change much, apart from shifting the axis of rotation towards the log, which increases the support force which tightens, because its line of force passes through the axis and more horizontal the tightening reaction increases ( draw the forces), which is useful for lifting by hand while tightening better, without penetrating into the wood with a weak force for a not very heavy log which can be manipulated with the hands.
A small question of agricultural mechanics ...
I'm also going to try it to pick up big stones
the problem is that the pebbles are not beautiful cylinders but of any shape and the clamps will slide most often on non-vertical faces, which moreover do not yield under the pressure of the metal to hang.
So it will be much more difficult and less safe not to receive the stones on the feet !!
Straps are safer for large stones but less easy to pass.
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- Obamot
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Easy? Yes and no. Yes because we will not perceive much since the "worker" only feels in his arms the lifting force (which will remain the same => weight of the log). No, because it makes the calculation formula much more complicated for two resulting moments which multiply. Here is already the calculation of a resulting moment:dedeleco wrote:A graphical analysis of lever arms is easy, product of the distance from the axis to the actual force line by the exact force, weight plus reaction force.
The more the weight of the log is stronger the stronger the lever arm and therefore the tightening is increased in this system which hangs without being able to crack because the line of force approaches the axis of rotation !!!
The parallelogram does not change much, apart from shifting the axis of rotation towards the log, which increases the support force which tightens, because its line of force passes through the axis and more horizontal the tightening reaction increases (draw the forces), which is useful for lifting by hand while tightening better, without penetrating into the wood with a weak force for a not very heavy log which can be manipulated with the hands.
whereas initially (with a zero rotational force) the formula would seem so "simple":
"Strength" ou "log weight" (x) "lever arm" (=) "the moment" ...
Without the need to do the calculation (not push ... ) we can easily say that theoretically the new ones are a little better than that of Grelinette, by the simple fact that the double lever arm is longer, therefore it exerts a resulting moment more important (which would be especially useful to better penetrate the hooks in the wood before lifting, but by jerking, I'm not sure the result is terribly noticeable).
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- chatelot16
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to lift stones you would need very different proportions
the main characteristic of this kind of pliers, and the ratio between the elongation in height of the pliers and the clamping in width: if the ratio was 1, the force which plants the teeth would be equal to the weight of the log: it would be too : the teeth would be planted too deep ... I think that a 1/2 ratio is enough: clamping effort equal to half the point of the log
to lift a pebble there will be no point that crashes: you would need a clamping force 2 or 4 times greater than the weight of the pebble: it will mean a stroke in height of the mechanism 2 or 4 times greater than the stroke clamping width: problem, for manual use! it will have to be lifted high enough for it to tighten ... not practical at all ... it would therefore need a ratchet system so that this tightening amplification does not lose too much height
there are pliers to lift sheet metal: the height stroke is at least 20 times greater than the clamping of the clamp: it allows smooth pliers to lift the sheet in complete safety
the main characteristic of this kind of pliers, and the ratio between the elongation in height of the pliers and the clamping in width: if the ratio was 1, the force which plants the teeth would be equal to the weight of the log: it would be too : the teeth would be planted too deep ... I think that a 1/2 ratio is enough: clamping effort equal to half the point of the log
to lift a pebble there will be no point that crashes: you would need a clamping force 2 or 4 times greater than the weight of the pebble: it will mean a stroke in height of the mechanism 2 or 4 times greater than the stroke clamping width: problem, for manual use! it will have to be lifted high enough for it to tighten ... not practical at all ... it would therefore need a ratchet system so that this tightening amplification does not lose too much height
there are pliers to lift sheet metal: the height stroke is at least 20 times greater than the clamping of the clamp: it allows smooth pliers to lift the sheet in complete safety
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- chatelot16
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This ingenious tool is designed analogously
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Reason is the madness of the strongest. The reason for the less strong it is madness.
[Eugène Ionesco]
http://www.editions-harmattan.fr/index. ... te&no=4132
[Eugène Ionesco]
http://www.editions-harmattan.fr/index. ... te&no=4132
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