Vaik
Guest
Hello everyone,
I would like someone's opinion on my idea to evaluate the forces transmitted by the schematized cinematism attached.
I deliberately do not put any numerical data, because I do not care that it is resolved, but know if my reasoning can be corrected, or lacks something; and in this case understand why.
There are a lower arm on which a f force acts, which is rigidly connected to an upper arm that carries the mass bodies m1 and m2.
rotating around the axis s, for 90°, the bodies describe the trajectories highlighted in the figure: the body 1 has a constant radius to, while the body 2 has a variable radius from b to b', with b'>b; the body 2, to allow this, is fixed to a linear guide solidarity with the upper arm.
I was able to track angle charts, angle speed and acceleration depending on the time for the system path, which recalculate what I expected reported in the annex.
the force f derives from the action of a pneumatic cylinder that has the sole purpose of keeping in contact the rest of the cinematism (not visible in figure ) with a cam, from which the trend of the graph derives. the unseen part of cinematism I have not reported it because I have already "decoded" his movements and it is not fundamental now for my question.
the movement of the masses predict basically 4 phases that are repeated cyclically (following on the angle chart according to time): station; climb; rest; descent. an angle of 90° is spaced twice during a cycle (beginning and descent).
I assumed that the f force of the cylinder does not have, in the ideal case (contact helmet), no role in determining forces f1 and f2, because it only has to ensure that all cinematism moves together with the cam, being on a simple track. therefore this force is absorbed by the frame that supports cinematism.
I think the f1 and f2 forces of the rotating bodies, in the resting and staging positions, are due only to the inertia due to the rotation and then proceed with evaluating them according to this logic. in this regard right in the annexed pdf, I summarized the steps to do this: through the angular momentum due to the product of moment of inertia, j1 and j2 in the two extreme positions of the arm, and angular acceleration, equal for the two bodies, but not constant during the movement, I would evaluate the forces f1 and f2 in the moments just preceding the system "all in quiet".
I also think that during the various stages in which the bodies move, there are the following forces at stake:
station:no force, no moment (balance); but a force will be created due to inertia, opposite the bike;
ascent: couple due to force f, which is subtracted by any force of inertia;
rest:no force, no moment (balanced); but a force will be created due to the inertia that would tend to rotate the arm over 90°;
descent
air due to the f force, which is subtracted by any force of inertia;
Finally, my question isa) to evaluate the forces to which the bodies are subject in positions 1 and 2 I can, according to you, proceed through the angular momentum m1 and m2 (as attached ), considering the pair due to force f? or without the pair due to force f?b) If I traced the plot of the moment of inertia j of the bodies, and multiplied it to that of the angular acceleration, adding that of the couple due to the f force, would I do a correct thing to evaluate the forces in every moment?
I hope I've been clear enough and I haven't made mental confusion by spreading the message. if someone wants to compare they are well available.
thanks in advance.
I would like someone's opinion on my idea to evaluate the forces transmitted by the schematized cinematism attached.
I deliberately do not put any numerical data, because I do not care that it is resolved, but know if my reasoning can be corrected, or lacks something; and in this case understand why.
There are a lower arm on which a f force acts, which is rigidly connected to an upper arm that carries the mass bodies m1 and m2.
rotating around the axis s, for 90°, the bodies describe the trajectories highlighted in the figure: the body 1 has a constant radius to, while the body 2 has a variable radius from b to b', with b'>b; the body 2, to allow this, is fixed to a linear guide solidarity with the upper arm.
I was able to track angle charts, angle speed and acceleration depending on the time for the system path, which recalculate what I expected reported in the annex.
the force f derives from the action of a pneumatic cylinder that has the sole purpose of keeping in contact the rest of the cinematism (not visible in figure ) with a cam, from which the trend of the graph derives. the unseen part of cinematism I have not reported it because I have already "decoded" his movements and it is not fundamental now for my question.
the movement of the masses predict basically 4 phases that are repeated cyclically (following on the angle chart according to time): station; climb; rest; descent. an angle of 90° is spaced twice during a cycle (beginning and descent).
I assumed that the f force of the cylinder does not have, in the ideal case (contact helmet), no role in determining forces f1 and f2, because it only has to ensure that all cinematism moves together with the cam, being on a simple track. therefore this force is absorbed by the frame that supports cinematism.
I think the f1 and f2 forces of the rotating bodies, in the resting and staging positions, are due only to the inertia due to the rotation and then proceed with evaluating them according to this logic. in this regard right in the annexed pdf, I summarized the steps to do this: through the angular momentum due to the product of moment of inertia, j1 and j2 in the two extreme positions of the arm, and angular acceleration, equal for the two bodies, but not constant during the movement, I would evaluate the forces f1 and f2 in the moments just preceding the system "all in quiet".
I also think that during the various stages in which the bodies move, there are the following forces at stake:
station:no force, no moment (balance); but a force will be created due to inertia, opposite the bike;
ascent: couple due to force f, which is subtracted by any force of inertia;
rest:no force, no moment (balanced); but a force will be created due to the inertia that would tend to rotate the arm over 90°;
descent
air due to the f force, which is subtracted by any force of inertia;Finally, my question isa) to evaluate the forces to which the bodies are subject in positions 1 and 2 I can, according to you, proceed through the angular momentum m1 and m2 (as attached ), considering the pair due to force f? or without the pair due to force f?b) If I traced the plot of the moment of inertia j of the bodies, and multiplied it to that of the angular acceleration, adding that of the couple due to the f force, would I do a correct thing to evaluate the forces in every moment?
I hope I've been clear enough and I haven't made mental confusion by spreading the message. if someone wants to compare they are well available.
thanks in advance.