Inventor General Discussion

Inventor General Discussion

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jeffcarson
Posts: 25
Registered: ‎07-16-2013
Message 1 of 10 (909 Views)
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Motion from cable and pulley / motion constraints without contact

909 Views, 9 Replies
08-10-2013 08:51 AM

I am trying to constrain motion for the following design:

 

Object constrained to vertical motion (a counterweight).

Object constrained to horizontal motion along a track (a slider).

A cable runs from the counterweight upward, makes a 180-degree turn around a pulley, runs back down, makes a 90-degree turn around another pulley, and connects to the slider.

When the weight moves down 10 cm, the slider needs to move laterally 10 cm.

 

I don't care about modelling the cable, but I do need to have the slider move as the weight moves.

 

I will also need to model a case with a more complicated pulley, where when the weight moves down 10cm the slider moves laterally 5cm (again I don't care about the cable, just the relative motion).

 

Is there a way I can do this without creating a series of planes and cylinders and using rotation - translation constraints to link the motion of the weight to the slider?

 

I was able to get it to work by creating two motion constraints, one between the weight and a simple extruded circle, and another between the extruded circle and the slider.  I then made the extruded circle invisible and now I can move the weight and have the slider also move - perfect!

 

Contributor
jeffcarson
Posts: 25
Registered: ‎07-16-2013
Message 2 of 10 (891 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-10-2013 10:41 AM in reply to: jeffcarson

I was able to get it to work by creating two motion constraints, one between the weight and a simple extruded circle, and another between the extruded circle and the slider.  I then made the extruded circle invisible and now I can move the weight and have the slider also move - perfect!

 

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JDMather
Posts: 27,459
Registered: ‎04-20-2006
Message 3 of 10 (877 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-10-2013 02:48 PM in reply to: jeffcarson

You can also do this with a constraint Parameter (don't really need the dummy part).

Please mark this response as "Accept as Solution" if it answers your question.
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Contributor
jeffcarson
Posts: 25
Registered: ‎07-16-2013
Message 4 of 10 (862 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-11-2013 03:35 AM in reply to: jeffcarson

I'm afraid I don't understand.  The only way I know how to apply a constraint to something that moves in a straight line it to associate that object to a rotational object using a motion constraint.  Can you give me more details about how to do this without a dummy part?

 

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JDMather
Posts: 27,459
Registered: ‎04-20-2006
Message 5 of 10 (856 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-11-2013 06:08 AM in reply to: jeffcarson

Attach your assembly here.

Please mark this response as "Accept as Solution" if it answers your question.
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Certified SolidWorks Professional
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Contributor
jeffcarson
Posts: 25
Registered: ‎07-16-2013
Message 6 of 10 (853 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-11-2013 06:19 AM in reply to: JDMather

There are two straight beams forming an L

 

I would like to be able to move one and have the other move, but at a different rate (say, twice or thee times as fast).

 

Contributor
jeffcarson
Posts: 25
Registered: ‎07-16-2013
Message 7 of 10 (825 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-13-2013 11:29 PM in reply to: jeffcarson

Does anyone understand what JDMather is referring to?  How might I use a "constraint parameter" to achieve the relative motion without a dummy part?

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JDMather
Posts: 27,459
Registered: ‎04-20-2006
Message 8 of 10 (810 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-14-2013 06:35 AM in reply to: jeffcarson

The assembly you attached references a base.ipt which you did not include in the attachment.

 

Since the assembly was not complete and therefore I didn't understand your design intent - I remove extraneous stuff and made up an example.

 

In the attached find the Drive This constraint and right click on it and select Drive Constraint and then hit Play (or Reverse Play).

 

 

Please mark this response as "Accept as Solution" if it answers your question.
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Autodesk AutoCAD 2013 Certified Professional
Certified SolidWorks Professional
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Contributor
jeffcarson
Posts: 25
Registered: ‎07-16-2013
Message 9 of 10 (797 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-14-2013 08:08 AM in reply to: JDMather

Sorry I forgot the base - my bad!

 

What you sent is very helpful JDMather, thanks!!!

*Expert Elite*
JDMather
Posts: 27,459
Registered: ‎04-20-2006
Message 10 of 10 (792 Views)

Re: Motion from cable and pulley / motion constraints without contact

08-14-2013 08:24 AM in reply to: jeffcarson

I only spent 5 minutes on that right before a meeting - so not much there and not really any logic, but you will notice that I named a couple of dimension Parameters and then made one a function of the other. 

You can make any mathematical relationship you need in the constraints (or any parameters). Just watch out for units agreement (this is the most common problem posted here on the forum).

Please mark this response as "Accept as Solution" if it answers your question.
-----------------------------------------------------------------------------------------
Autodesk Inventor 2014 Certified Professional
Autodesk AutoCAD 2013 Certified Professional
Certified SolidWorks Professional
Inventor Professional 2015-SP1 64-bit
http://www.autodesk.com/edcommunity
http://home.pct.edu/~jmather/content/DSG322/inventor_surface_tutorials.htm
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