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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

modelling cable and pulleys from compound bow

1588 Views, 5 Replies
03-30-2013 09:34 AM

Greetings,

I am interested in modelling a compound bow.  A glance at the pulley tool indicates that I cannot anchor a cable (bowstring) to the pulley.  Has anyone any thoughts about modelling a similar situation?

 

Thanks

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AstroJohnPE
Posts: 570
Registered: ‎08-30-2012

Re: modelling cable and pulleys from compound bow

03-31-2013 06:57 PM in reply to: tim

Hi Tim,

 

If I understand you correctly, you want one end of the cable to attach to the pulley's pivot, and then another section of the cable passes around the pulley. The documentation does not indicate that there are any restrictions on what the pivot point is connected to, so my guess is that it can be connected to any type of element.

 

So instead of doing the things that I needed to do, I did a test. I was able to attach a truss element to each of the three points of  pulley: the driver, pivot, and slack nodes. (I presume you would be using truss elements to simulate the cable, or some similar type of element.)

 

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

Simulation Mechanical user since Dec 1997
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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: modelling cable and pulleys from compound bow

04-02-2013 05:47 AM in reply to: tim

John,

thanks for your reply.  I will have a go ( as soon as I have a moment at home!).  I think it will be a good test of the MES for a complex non-linear problem.  There are a number of papers that have enough data to validate.

 

Tim

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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: modelling cable and pulleys from compound bow

04-06-2013 08:14 AM in reply to: tim

Have just started to experiment with a simple model consisting of the flexible bow limbs.  No pulleys yet.  I'm using MES to model the large strain-deflection of the bow limbs.  The numerical stresses and deflections seem ok however the graphics don't seem to update in step as they should.  The graphics go to the extreme end point in the first time step whilst the deflection/stress data increments correctly.

 

I'm using 2014 however I noticed recently with another MES run using 2013 that the graphics were not in sync with the numerical readout of the deflection?

 

Has anyone noticed this?  Prior to this MES worked well.

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AstroJohnPE
Posts: 570
Registered: ‎08-30-2012

Re: modelling cable and pulleys from compound bow

04-06-2013 09:13 PM in reply to: tim

It sounds to me that you need to set the displacement scale to an absolute factor of 1 instead of 5% (or what ever percentage it is using). "Results Contours > Displacement > Show Displaced > Displaced Options".

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

Simulation Mechanical user since Dec 1997
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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: modelling cable and pulleys from compound bow

04-08-2013 02:21 AM in reply to: AstroJohnPE

Thanks,

I finally twigged about 1/2 hour after I posted (naturally!) that I needed to set to some absolute figure and not %

 

Lots of results look right now.

 

Tim

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