How to create a logarithmic spiral 4

[Theophilus]

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,



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[takedownca]

If a good curve will fix your issue, try this macro. Assuming you know what equations to use, it'll plot them for you using Cartesion, cylindrical, or spherical coordinates. For a spiral I'm guessing the cylindrical coordinates would work best. I'm not too familiar with animator, so there may or may not be a better solution using mates, but hopefully this helps.

http://members.cox.net/takedown/FuncPlot.zip

 

[Theophilus]

Thanks all, for the help! (Finally back in the office.) Good thoughts on these items I'll put into the assembly today (need to have the animation rendered by morning--yikes!).

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

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[Theophilus]

Handleman, that works! Thanks!

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

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.