Modelling a twisted Snake Shell

[togo]

Hello,
I'm not getting anywhere trying to build a twisted snail shell.
It should be constructed like the example below.

So far my attempts were:

1. to build a helix with 3 or 4 turns and a tube with Follow me. But with the Helix Tool the spiral remains uniform and of course the tube cannot be reduced step by step.
2. With Helix-along-Curve I can successively reduce the spiral, but then how do I get a reducing sheath?

Is there a tool to place circles on the helix that would decrease with each copy and then cover them with a skin afterwards? Could that be a way?

Many thanks for tips.

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[Dave R]

I would start with an Archimedes spiral drawn with the Curve Maker extension. You might be able to get by with a circle drawn at each end of the spiral and Curviloft to connect them. I'm not at a point where I can experiment, though.

[togo]

aha, yes thanks, that is going in the right direction, great. I can change the radius of the spiral. And with Curvy Loft i can put a shell over it.
However, I can only specify the overall height of the spiral - I can't decrease the height from one round to the next.
Or how could that be possible?

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[Dave R]

You could open the helix group, explode the curve, and selectively scale parts of it. Quick and dirty example.

Or you could stack several helices on top of each other.

[togo]

good idea!
I compressed the height of the spiral by 80% after every half turn, so that it also becomes flatter and flatter towards the top. Is that what you meant?
But something is still wrong. What could it be? Maybe the way is correct, only the ratios of size and height of the spiral and start and end size of the circle are not yet right? I keep on trying.

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[Dave R]

Yeah, that's basically what I meant. I don't know what the proper scaling should be, though. Maybe the difference between first and second radius values should be closer together.

[togo]

thank you, yes i will build some and maybe i will get closer to that ...