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## Inventor General

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Posts: 25
Registered: ‎07-16-2013
Message 1 of 10 (642 Views)

# Motion from cable and pulley / motion constraints without contact

642 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?

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Posts: 25
Registered: ‎07-16-2013
Message 2 of 10 (624 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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Posts: 24,744
Registered: ‎04-20-2006
Message 3 of 10 (610 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).

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Posts: 25
Registered: ‎07-16-2013
Message 4 of 10 (595 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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Message 5 of 10 (589 Views)

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

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

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Posts: 25
Registered: ‎07-16-2013
Message 6 of 10 (586 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).

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Posts: 25
Registered: ‎07-16-2013
Message 7 of 10 (558 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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Message 8 of 10 (543 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).

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Autodesk Inventor 2014 Certified Professional
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Posts: 25
Registered: ‎07-16-2013
Message 9 of 10 (530 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!!!

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Posts: 24,744
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Message 10 of 10 (525 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).

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