How to create a logarithmic spiral
How to create a logarithmic spiral
(OP)
Does anyone know of a way to create a logarithmic spiral? I need to generate a surface for a part to follow in an animation, and this appears to be the shape I need.
I have a hinge sort of detail. In normal SolidWorks I can accomplish what I need with a gear mate, but Animator doesn't do anything with the gear mate and lets everything flop around as if the mate didn't even exist (figures).
So here's the situation. I have two main parts (like doors), connected with an intermediate hinge piece. The intermediate piece supplies the axles for the doors. The doors rotate from folded atop one another to parallel with one another (180* of motion). However, the hinge piece rotates only 90* in this same course.
So the door rotates 180* about the other door, while the hinge piece rotates only 90*. I'd like to extrude a surface--which is starting to resemble a spiral of some sort--that I can use to control the rotation of my door when I rotate the hinge piece only 90* such that the door rotates 180* exactly. (This is quite a complicated hack for an Animator limitation--anyone know of anything simpler?)
So--is this what I'm looking for? If so, with the ratio of angle change of the door to the hinge piece being 2:1, what would the formula look like (remember, I'm an industrial designer, not an engineer--I didn't have that class [well, I probably did, but ditched the engineering career for ID at that point]). I found this, but don't know how to turn this into something useful within SolidWorks:
http://en.wikipedia.org/wiki/Logarithmic_spiral
Thanks,
I have a hinge sort of detail. In normal SolidWorks I can accomplish what I need with a gear mate, but Animator doesn't do anything with the gear mate and lets everything flop around as if the mate didn't even exist (figures).
So here's the situation. I have two main parts (like doors), connected with an intermediate hinge piece. The intermediate piece supplies the axles for the doors. The doors rotate from folded atop one another to parallel with one another (180* of motion). However, the hinge piece rotates only 90* in this same course.
So the door rotates 180* about the other door, while the hinge piece rotates only 90*. I'd like to extrude a surface--which is starting to resemble a spiral of some sort--that I can use to control the rotation of my door when I rotate the hinge piece only 90* such that the door rotates 180* exactly. (This is quite a complicated hack for an Animator limitation--anyone know of anything simpler?)
So--is this what I'm looking for? If so, with the ratio of angle change of the door to the hinge piece being 2:1, what would the formula look like (remember, I'm an industrial designer, not an engineer--I didn't have that class [well, I probably did, but ditched the engineering career for ID at that point]). I found this, but don't know how to turn this into something useful within SolidWorks:
http://en.wikipedia.org/wiki/Logarithmic_spiral
Thanks,
Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all. And awe transcends reason.






RE: How to create a logarithmic spiral
RE: How to create a logarithmic spiral
Could you use a cam to control the motion (with cam mates of course)? You can hide this cam part, but it would still be influencing the motion.
- - -Updraft
RE: How to create a logarithmic spiral
Rob Rodriguez CSWP
www.axiscadsolutions.com
www.robrodriguez.com
http://designsmarter.typepad.com/rob_rodriguez/
Eastern Region SWUGN Representative www.swugn.org www.nvtswug.com
SW 2007 SP 2.0
RE: How to create a logarithmic spiral
Theo ... could you construct one using a spline and the rectangles as shown in http://en.wikipedia.org/wiki/Golden_spiral? It would only be an approximation, but may be close enough.
Like Handleman, I'm having trouble picturing the "door" arrangement. A picture would really help.
RE: How to create a logarithmic spiral
http://www.EsoxRepublic.com-SolidWorks API VB programming help
RE: How to create a logarithmic spiral
RE: How to create a logarithmic spiral
Jeff Mirisola, CSWP
http://designsmarter.typepad.com/jeffs_blog
Dell M90, Core2 Duo
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RE: How to create a logarithmic spiral
Thanks again!
Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all. And awe transcends reason.
RE: How to create a logarithmic spiral
h
So the top door opens counter-clockwise. You can see an approximated spline drawn in, but this is far too sloppy to work by mating a point off the end of a line from the top door (maybe I can explain better later).
THANKS for your help--my mind's turned to drizzle with late nights!
Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all. And awe transcends reason.
RE: How to create a logarithmic spiral
RE: How to create a logarithmic spiral
Rob Rodriguez CSWP
www.axiscadsolutions.com
www.robrodriguez.com
http://designsmarter.typepad.com/rob_rodriguez/
Eastern Region SWUGN Representative www.swugn.org www.nvtswug.com
SW 2007 SP 2.0
RE: How to create a logarithmic spiral
I think this technique could also be used to create a rack and pinion mate in earlier versions of SW. The pinion has a helix, and the rack has a sloped line.
Eric
RE: How to create a logarithmic spiral
I'd be interested in seeing your solution as an image or file (typing from airport). Sounds like something I might get to work for me.
Animator is strange--it doesn't treat mates, etc. as SolidWorks does--so I wonder what set of rules it's following and why the SolidWorks rules don't work. It's now very common for me to expect certain parts that move just fine in SolidWorks not to function at all in Animator--or to give me the dreaded red diamond if it does (which usually hoses the rest of the animation).
Certainly this sort of thing makes it difficult to make money when bidding on animations from SolidWorks files. (Oh well, I knew what I was getting into this time.)
Thanks again, everyone, for helping out. With all these ideas, I can probably hack together a solution when I get back in the office. (Speaking of the office, the Sangres had a fresh dusting of snow on them this morning--also saw some big-horn sheep on the way through the mountain pass--I love this place!)
Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all. And awe transcends reason.
RE: How to create a logarithmic spiral
Here is what I threw together to try it out.
h
Eric
RE: How to create a logarithmic spiral
Rob Rodriguez CSWP
www.axiscadsolutions.com
www.robrodriguez.com
http://designsmarter.typepad.com/rob_rodriguez/
Eastern Region SWUGN Representative www.swugn.org www.nvtswug.com
SW 2007 SP 2.0
RE: How to create a logarithmic spiral
That's a pretty impressive thought process, but seems incredibly complex for the function desired. Perhaps I'm wrong (I can't get your assembly to move at all on my machine), but it appears that I understand the desired effect - force one component to rotate at half the speed of the other. The assembly I posted achieves that with the symmetry mate. It works for infinite rotations and drags just fine whichever component you want to drag.
RE: How to create a logarithmic spiral
Jeff, I would get out your calculus book and use those logarithmic spiral equations to define your path. You can use Excel to set this up then output the results to a CSV file then read it into SWx as 3D points. I've done this when designing gerotor pumping elements.
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RE: How to create a logarithmic spiral
I agree that the paired helixes were binding up in SolidWorks, although I was able to get them to move in the animator (with some suppressing and resuming of mates). Your file with the symmetry mate works well and gave me another idea.
The following is a 5 bar linkage similar to what Jeff has already. There are 2 extra links which form it into a polygon, and the far vertex is constrained to lie on the midplane of the hinge link. It moves correctly in both SolidWorks and the animator. It’s a lot easier on the silicon brain cells than the helixes.
http://
Eric
RE: How to create a logarithmic spiral
What about using two rotary motors in Animator, one for the hinge and one for the door set to the same direction of rotation, but twice the speed of the hinge? This would eliminate all the extra parts/constraints and the subsequent load on the SWX solver and should give you the motion described.
- - -Updraft
RE: How to create a logarithmic spiral
http://members.cox.net/takedown/FuncPlot.zip
RE: How to create a logarithmic spiral
Eric, I can now check out what you uploaded (my little laptop has no hope of running SolidWorks).
Updraft, that's something I considered--although I'm not familiar with the term of "rotary motors" you used--sounds like something in Simulator. I'll check it out. The reason I glossed over this means of moving things is that it tends to result in parts flopping all around and has difficulty when in use with limit mates (to govern the limits of motion)--but the last time I tried such a method was with SW 2006--so maybe 2007 will work fine.
Takedownca, I could get this to work fine (I think) if I can get a perfect curve--with the perfect curve I can then generate a surface on which to pierce a point from the folding door--which should properly govern everything rather simply. However, if the curve is created with a spline, I cannot see the curve being "perfect"--such that my motion won't be seized up with the slight deviations from perfection--but maybe it's no big deal.
I've got plenty of things to try out. Thanks for the suggestions, files, and ideas!
Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all. And awe transcends reason.
RE: How to create a logarithmic spiral
Eric--that was brilliant and simple. I don't think I'll have a problem making that work. That looks like the most direct way for me to arrange the assembly and should work with a limit mate to that short piece (90 - 180 degrees) without getting all stuck within Animator.
Now to do all the animation programming.
Thanks so much guys! Brilliant, simple solutions I couldn't see at all.
Jeff Mowry
www.industrialdesignhaus.com
Reason trumps all. And awe transcends reason.