springs - ratchet and pawl?

[sbutau]

Hi Guys

This is for a high school project. I have a basic ratchet and pawl system.  I have used the contact set functions so that the pawl lifts up when the ratchet turns. 

 Is there anyway to allow it to lift up and then drop back down again as i drive the constraint? (ratchet turning)

  I put in a torsion spring just to see what it would do, but it won't work quite like i want it to..

any help or other ideas?

 

[JDMather]

You will need to use Dynamic Simulation to do that (Environments>Dynamic Simulation). 
A bit advanced for most HS students.
Can you attach your assembly here?

[sbutau]

Thanks for the reply.  Part of the assembly is attached..

At school we have jumped from Inventor 2008 to 2011 so nobody has used the dynamic simulation environment before.. I'll have a look at the tutorial files for it and see if i can get something working..

All I really want, is for the pawl to drop down on the ratchet when i turn the crank.. if there is an easier way to do this i'd love to hear it.

Thanks again..

[JDMather]

While I work on this a bit - you might want to read this document - I noticed that your sketches aren't constrained.  You should probably master this before going on to assemblies and Dynamic Simulation - pretty basic stuff.

http://home.pct.edu/~jmather/skillsusa%20university.pdf

[Loren_J]

Have you tried a tangent constraint with limits and a contact set? Constraint limits where added to Inventor in 2011, and it simplifies basic assembly motion. Once you get it working, you should also learn how to set this up in DS.

If you were trying to get your job done I would provide steps, but since you are a student it is a good opportunity for you to dig in and figure out how these things work. If the help and tutorials aren't helpful, then ask your instructor. If s/he can't figure it out, then they should post here for further instructions.

[JDMather · Accepted solution]

It works with a 2D Contact joint and a Spring/Damper/Jack joint - but I haven't had time to document the steps.
You might check this book. http://vrblog.info/

[sbutau]

thanks guys.. I had a look at the tutorials and managed to get there using the 2D contact and spring joint as suggested.

this is basically what I was trying to achieve:

[Loren_J]

That looks nice. Now that you have it working, you should try it in Dynamic Simulation. Driving constraints in Inventor gives you the animation, but you don't get any information on the forces, etc. This should be relatively easy to set up since there aren't very many moving parts. It is always a good idea to expand your knowledge of other functionality.

LorenJ

[JDMather]

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@Loren_J wrote:

... you should try it in Dynamic Simulation.

LorenJ

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Using 2D Contact and Spring joints are done in Dynamic Simulation.  (not to be confused with Contact Sets - which would not give the desired behavior of the Pawl dropping back).

"managed to get there using the 2D contact and spring joint as suggested."

This student figured it out on his(her?) own from two tips.

[Loren_J]

I had a brutal commute this morning and I ran out of coffee halfway to work. I was cruising the newsgroup to improve my frame of mind, and I was pleased to see the animation. I had knocked together a ratchet and pawl using constraint limits, which was trivial, and given his previous issues I jumped to the conclusion he had done it the same way. I'm going to chalk it up to my thought processes being clouded by a combination of frustration and caffeine deficiency. It is probably a good thing I wasn't doing real work.

LorenJ

[Anonymous]

my name is vamsi,as i m doing rachet and pawl mechanism ppt.I m not able to open urs attachement file(winch.zip) in my system,could any one tell me how can i open those files.