kinematics/linkage 2

[markborges]

I am looking for software to solve relatively simple linkage problems. I am only really interested in load transfer through the system, but displacements and velocities would be nice. Currently, I set up traditional member analysis in MathCad and solve for the result. This works out ok; however, I have found that mathmatically there are often many solutions to these systems and sometimes it is difficult to distinguish the real world result. I have seen ProEs'motion/load solver, but I prefer to not build a 3D model just to solve a system of equations.

Thank You,

Mark

 

[ivymike]

you could use smartsketch in conjunction with mathcad, so that you can get a picture of the output (to help pick the "right" answer)

 

[MintJulep]

Kinematics problems were being solved long before the computer became common place.

Why not just do it the "old fashioned" way. You might even end up re-educating yourself in the process, and be better able to judge the adequacy of what the computer spits out the next time.

 

[markborges]

Thanks "in Hiding" I am downloading a trial copy of "smart sketch" now. I could not find it on my mathcad disk? Ok lets say that I get it and I figure out how to use it, I assume that I will need a solution for each combination of variables. Because two members need to be solved simultaneously; ie., statically indeterminant by them selves, I have one part of the linkage that has six equations and six unknowns. Is it possible to run a range variable through a solve block to get an array of solutions to plot? And to complicate things, not just one variable changes. As one member is moved, all positions of the linkage change! For each position of the loader linkage I have been solving for the loads in MathCad and ploting the data in excel. I presume that I am stuck with this methodology; however, If I could be assure that the solution that I get is correct I could move through it and save alot of time.

PS I have done the problem by hand--that is why I know that my mathcad document is funky.

Thank You

 

[ivymike]

I don't know the answers to the second volley of questions - I've done much simpler drawings in smartsketch.

I had pictured the problem from the other direction, though- use the geometric tools in smartsketch to convert input lengths, geometric constraints, etc., into a picture of your geometry, then export key angles, positions, etc., for further calcs in Mathcad. Like a fancy, parametric, free body diagram.

 

[mloew]

Mark,

Check out the FAQ Resources for Mechanism Analysis and Synthesis (faq404-804). As you are a Pro/ENGINEER user, I suggest taking a look at SyMech (

http://www.symech.com)

as it will do what you need and have the ability to actually synthesize mechanisms. I have had good luck with using a combination of the MDX functionality with the Behavioral Modeling (BMX) features for solving mechanism problems as well.

Best regards,

Matthew Ian Loew
"Luck is the residue of design."
Branch Rickey

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[markborges]

Wow, I can adjust my "skeleton" and my parts all in the same session! I have more questions for Symech regardeing force analysis; but from the website demo, symech makes PTC's Mechanism Design look like a clumsy work around--Symech must have a patent on it.

Thanks for the tip.

Mark