Cool!
Moi (very low Poly) -->Sketchup+Lightup a very funny Render "real time" of all the 3D scene
after a little calculate you can Move, Rotate, Resize, Walkthrough... the scene, "render is always yet done" !!!

You may try to consider lofting 2 gear profiles. I think using extrude method is morphing the gear splines...

What a fantastic imagination you have, Frenchy!

Mike.

Thank you all for your suggestions and help.

I've achieved results good enough for my purpose which is 3D printing.

I choose a 12 tooth pinion and a 30 tooth gear using Module 2 meeting at 90 degrees.

I used the formulae from the info that Brian supplied to calculate angles - see below


Basically I trimmed one gear profile from the spur gear script output, extruded it to a point, laid it down on a cone and arrayed the extruded profile around the cone.

I think that it's a bit of a bodge because I couldn't find a way to extrude to the point that I wanted to extrude to which was vertically above the pitch circle I could only extrude to a point vertically above the centre of the bounding box - auto chosen (as far as I could tell) by the extrude-to-a-point function. This introduced a very slight error that I had to fudge my way around.

Images below and file attached.

Mike.

Hi Mike, re:

> I think that it's a bit of a bodge because I couldn't find a way to extrude to the point that
> I wanted to extrude to which was vertically above the pitch circle I could only extrude to a
> point vertically above the centre of the bounding box - auto chosen (as far as I could tell)
> by the extrude-to-a-point function.

If the auto chosen tracking line is not what you need, you can make extrude to point freely pick the point by pushing the "Unlock direction" button in the command options:



- Michael

Aha!
Thank you, Michael, I hadn't noticed that.
Great.

Mike.