CAD for Spiral Cam

[Ether]

Originally Posted by araporta

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)

[Ether]

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

[Ether]

Originally Posted by Ether

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)