Continue to Site

Welcome to MCAD Central

Join our MCAD Central community forums, the largest resource for MCAD (Mechanical Computer-Aided Design) professionals, including files, forums, jobs, articles, calendar, and more.

Register Log in

It is simple for sure - but not for me

Jacoolo

Jacoolo

New member
Hello every one

Lets make it short - I want to make such kind of mechanism - see video


2007-04-24_045206_MECHANIZM.zip

so first I did not really know how to bite such of stuff - I forgot everything I saw at studies;)))

so I made an assembly and to find out something about the behaviour of the mechnism I made a trace curve

View attachment 3483

but it did not say to me anything. So I thought I simplify the whole thing and I used sketcher for analysis

after some bad approaches like this one:

View attachment 3484

finaly I found correct one by the rule of : attempt - error, another attempt - error, etc

View attachment 3485

so, I brought it to mechanism, and another error appeared, analysis crushed at this moment

View attachment 3486

so while dragging it is still allowed to move the second lever which is not in my interest. It should all move as in attached mopvie

View attachment 3487

so finaly, can anyone give an advice how to handle with this? I know how to make joints, servo engines etc. Pro\e is not a problem. I want to know the rules how to build such mechanisms, what are the rules behind this? - links would be great.

In addition I attach the whole assembly in WF 2.0


2007-04-24_050910_dzwignia_no1.prt.zip
 
Hi


I have been playing with my skeleton again, if you drive the mechanisum by rotating the top link it drags the bottom link past the point of seizure!


CAD2448
 
CAD2448,


Great potential you have. I always tell my guys to first analyse the problem, apply basic principles of physics and math, and then attack the actual problem.


By the way this very problem can be solved in Wildfire 3.0 with MDO enabled.


Israr
 
Can You Israr share share the way You would use for this?

As I said - Pro\e is not a problem, I know tools. However I do not know how to bite whole thing before I start playing with Pro\e
 
Hi muadib3d


I have analysed your design and have come to the conclusion that the basic design has a flaw in it. Your current mechanism will never work as the mechanism in the video works.


Try this


View attachment 3504
 
I know it won`t work, all I did till this moment is my simple, intuitive investigation, but I feel, it is like searching something in dark. I need light, I need knowledge how to play with such situations.

I know I am close, but I still did not reach that point. I also know that I can find solution just by accident, but in the the next case I would not know how to find it again.

I want to be engineer - spend 5 days on the problem to make it next time in 5 minutes! :)))))
 
yeap Cad, you are right

I did no say this asm is good, it is only in the state I stoped. I do not how to push it further.

I know that position and shape ofthe lever you shown is critical in this design, because it is this lever to bring right function of whole device.

What I found is important here is that the point of rotation for the second lever nad third(the smallest) should line in the same line

View attachment 3508
 
Hi muadib3d


Statement 'What I found is important here is that the point of rotation for the second lever and third(the smallest) should line in the same line' is not nessesarily true the mechanisum can in some cases work better when the axis are not in vertical alignment.


I made a simple mechanisum in less than 30 minutes,it is notperfect but works alot better that your original design. This design concept was not carried ot on Proe, I used simple lever theory, and basic engineering principles. By sketching the original, and desired end positions for the levers,I was able to determine the approximate location of the joint axis required.


You made another statement 'I want to be engineer - spend 5 days on the problem to make it next time in 5 minutes' - a good idea, I will give you 5 days to solve the problem, thenI will post my 30 minute solution which still needs refinement.


CAD2448
 
well I spent some additional time on it, and - my head was almost exploding yesterday:)))) - I found solution to have exact position for the third lever. All for this moment in sketcher

so here is my new mechanism

View attachment 3516

one can say - no such a difference, but it is

and here is file for this, to play with this mechanism all dimm has to be locked apart of dim angle



2007-04-26_032633_mechanism_sketch.prt.zip

so my algorith to find this point is easy, if we first take some constraints, see below

View attachment 3517

so it can be seen the this point lays on the intersection of line provided from points of two states. To find right pint this two lines must have exact length and that is all.

What do You say?
 
hello cad

5 days passed - I am ready for Your way through this maze

so finally I gave up. I stucked in the point from last message and that was all. I do not know if You would dig it deeper - maybe so, I dont know

but if another solution exist I can not wait to find it out
 
Hi


I am very busy for the next two days i am travelling on business. I only have my laptop with me, the solution is on my main desk top back at base. when i get back i will write a short explanation of my work and send it to you





regards





richard
 
Hi


this is by no means a finished design but the mechanism does perform the intended function.


the basic principles of the design were worked out on squared paper then applied to Proe to create this model. the paper concept was derived in around 30 - 35 minutes. As yet i have not had time to scan in my original concept sketches or write an explanation of the process i used to arrive at this design. i have atattched the mechanism for you to look at and will follow up with the explanation of my design method in a few days





CAD24482007-05-11_023340_problem_4.prt.zip
 
You must log in or register to reply here.

Sponsor

Articles From 3DCAD World

Back
Top