reduced moment to the crank

[Simone Besana]

hello to all, I'm preparing the thesis with autodesk inventor. know that inventor provides, in the iproperties->physical tab, the moments of baricentric, global and main inertia. I think it is the one where in the matrix I only have the diagonal, baricentric I imagine it is the matrix of inertia calculated in the center and overall I do not understand it. In addition, the real big problem I get is to understand if inventor gives me the opportunity to calculate from him the moment of inertia reduced to the crankshaft (it's a simple manovellism centered mine) or if I have to calculate it by hand. That's because I need to size the engine to drive it. thanks in advance to all those who will answer me
simone besana

 

[Stan9411]

I don't know inventor.... but by curiosity how do you reduce the moment of inertia for example of the biella to the crankshaft? the kinematic link is not linear and is not constant because it depends on the angle that takes on the crank. to me they had taught that you make the kinematic closure, you get, for example, the angular acceleration of your biella (which will depend on the motion of the crank) the multiplication for the moment of baricentric inertia of your biella and that is the inertia generated by your biella. I don't know if I don't remember anything. .

 

[meccanicamg]

I have tried with solidworks to do similar works and clearly the moment of inertia that calculates the program will be type sinusoidal because the masses compose to the motion that is not linear but sinusoidal.
It is also true that often by simplicity a moment of equivalent inertia is calculated and multiplied by the maximum acceleration in order to determine the maximum torque of the motor, even if this is only an approximation of the real system.

 

[Stan9411]

basically then we're saying the same thing. In my case the allegation is a sinusoidal type and the moment of constant inertia baricentric, the other case (which I have never used and I do not know how to use) will have a moment of inertia that varies and considers the constant ignition.. is the same from two different perspectives. but to me a moment of inertia with sinusoidal trend is not natural to think it. the moment of inertia is a property of the body, its cinematic instead changes according to the angle of crank.

 

[Simone Besana]

Meanwhile I thank both for the answers. I do mea culpa saying that I do not remember how to calculate by hand the moment of reduced inertia (motive for which I am also looking for this thing on the internet without finding it). Meanwhile I can say that the moments of inertia made to calculate with inventor are constant. this thing comes back as it should depend only on the geometry of the system.

 

[paulpaul]

hello to all, I'm preparing the thesis with autodesk inventor. know that inventor provides, in the iproperties->physical tab, the moments of baricentric, global and main inertia. I think it is the one where in the matrix I only have the diagonal, baricentric I imagine it is the matrix of inertia calculated in the center and overall I do not understand it. In addition, the real big problem I get is to understand if inventor gives me the opportunity to calculate from him the moment of inertia reduced to the crankshaft (it's a simple manovellism centered mine) or if I have to calculate it by hand. That's because I need to size the engine to drive it. thanks in advance to all those who will answer me
simone besana

I do not know inventor, but normally to calculate the moment of inertia equivalent of a tavellism starts from energy considerations (you find them in any text of applied mechanics). the cad is useful to determine the moment of inertia and baricentro of the biella, so that you can bring it back to an equivalent system consisting of two masses (an alternating and a rotating) and from a moment of fictitious inertia, always according to the rules of the geometry of the masses (also found them written in any text of mechanics). It is obviously useful also to determine the moment of inertia of all rotary masses as well (shaft, fly, etc.). these contributions, together with those of the alternate masses as well (pink, piston, crosshead, etc.) enter the said moment of equivalent inertia: This is obviously a non-consistent size, which you need especially for the verification of the degree of irregularity and therefore of the flywheel, as well as for the calculations at the point.
I usually do these accounts in excel, parameterizing the variables above.

 

[Simone Besana]

I try to ask a more precise question. I have seen that I can make myself compute from inventor the moments of global, baricentric and main inertia. My thesis concerns, said in a very bad way, "what can and what can not be done with inventor", obviously applied in the mechanical field. for the moment we decided to start with a tactical act because I do not have very much familiarity but I know only the basics so as to simplify things. for the moment I should check if it is possible to make inventor calculate the moment reduced to the crank, the driving couple and the binding reactions to the hinges. all in two cases: constant speed of the crank (motor condition) and in the case of variable speed (motor leaving from station, comes to regimen, operation and then deceleration until stopping). I'm still thinking about the constant speed speech but I lost myself in checking if there's a way to get him to calculate the moment and the driving couple needed. for binding reactions from what I saw should be able to calculate it to me. Sorry to bother you

 

[meccanicamg]

fact is that in the biella handle all the pieces have constant mass but mass rotation centers not all geometric. If it is true that the mass is not variable, the distance from the center of rotation is not the same. the biella has its center that wanders at different distance than the center of the crank.....ergo, the moment of inertia is not constant.

 

[meccanicamg]

I think inventor as solidworld calculates a bit everything even if I think it becomes complex because first you have to do a dynamic analysis including kinematics and then apply a static or dynamic fem and determine reactions or efforts.
The systema usually has a series of examples of applications and things that you can do and the biella/handle is one of the schemes that they have always used to make tutorials around companies.

 

[Simone Besana]

Okay, thank you so much for the help, then I try to see the system a bit (which I hadn't noticed)

 

[Simone Besana]

I'm sorry, looking all over inventor I found her but now I can't find her anymore, you can suggest how to get to that systema folder please.

 

[meccanicamg]

is not a folder but an inventor resale company