Uneven spiral/helix

[tloveS6H3C]

Hello, 

I am a year 11 student at a highschool in Canberra, Australia. As a part of a school assesmrnt i am trying to create a skrew in boat anchor that can hold a small boat. I am trying to create a spiral that has a different distance between revelutions as it goes up. (see photo below) this is what i am trying to achive however am unsure on how to do. 

If you have any ideas i would love to hear and it would be greatly appriciated. the closest i got was a spiral from a coil however that is not the requireed shape i was trying to achive. 

[MichaelT_123]

Hi Mr  TLoveS6H3C,

Consider looking at:

https://forums.autodesk.com/t5/fusion-design-validate-document/variable-pitch-thread-helix/m-p/84948...

Regards

MichaelT

[laughingcreek]

I think there are add-ins that will allow you to create a curve from an equation, which may produce better surface quality, but the attached is one approach you could use to do it all with just fusion-

[Warmingup1953]

An inelegant way.......It won't solve your tip needs but multiple simple coils (one rotation Each) of increasing heights will get you a "steepening" path to use in a subsequent sweep.

[HughesTooling]

To me it looks like the pitch on the parallel section of the central tube is one constant pitch and the part on the point is a finer pitch. What I also notice is the flute changes size all the way up the part. Because the flute changes shape you're going to need to use loft to make the shape, not a simple sweep with twist. I think making the helical path\paths for the loft will be quite difficult.

You can create a single path from a swept twisted surface but I'm not sure a single path is enough for the loft to work without it twisting.