Go to Post Everyone who has posted on this thread has brought about a lot of different ideas to the plate. Before it was just a simple 1 course meal in my mind. But when you post something on CD with tons of engineers and engineers in the making, your bound to have a feast!! - gallo26 [more]
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  #16   Spotlight this post!  
Unread 14-06-2015, 16:27
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Re: CAD for Spiral Cam

Quote:
Originally Posted by araporta View Post
Thats the first place I looked, and it doesn't really help. I can see how to enter a parametric equation, such as that in post #5 above, but I don't get how to enter Ether's equation in post #8, which is not parametric? Its probably trivial, but I just can't see how to do it.

r1 = starting radius at theta=0,

r2 = ending radius (at theta=alpha),

k=log(r2/r1)/alpha,

r = r1*exp(k*theta),

x = r*cos(theta),

y = r*sin(theta)

...

So for r1=25, r2=5, and alpha=2*pi, you would get:

x = 25*exp(-0.11124453*t)*cos(t)
and
y = 25*exp(-0.11124453*t)*sin(t)


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  #17   Spotlight this post!  
Unread 15-06-2015, 17:14
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Re: CAD for Spiral Cam


Are you sure you want a constant-slope spiral, and not a constant-torque one instead?


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  #18   Spotlight this post!  
Unread 15-06-2015, 17:34
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Re: CAD for Spiral Cam

Quote:
Originally Posted by Ether View Post
So for r1=25, r2=5, and alpha=2*pi, you would get:

x = 25*exp(-0.11124453*t)*cos(t)
and
y = 25*exp(-0.11124453*t)*sin(t)
I should have used my CAS.

x = 25*exp(-0.25615*t)*cos(t)

y = 25*exp(-0.25615*t)*sin(t)
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