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Fusion 360 - creating boiler dome and chimney bases?





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#1 Skinnylinny

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Posted 13 January 2018 - 17:13

So I've joined a local "hackspace" (Basically a club with access to tools and materials - pay your dues and chat with like-minded people while making things) which has a CNC milling machine.

"What materials will it mill?" I asked. "Oh, aluminium, delrin (engineering grade plastic), brass..." comes the reply.
"Oooh, brass, perfect for domes for my pre-grouping engines" think I. So I buckle down and start trying to teach myself to use Autodesk Fusion 360. It's certainly a big step up from SketchUp.

Anyway, to the job in hand. Imagine, if you will, a steam locomotive boiler with a dome and a chimney on it. The chimney can be divided into three sections: the cap, a tube section (both relatively easy to make from extrusions and rotated geometry) and a base. The base is usually flared, and this is the bit I'm having trouble with. The basic idea can be seen in this image (not my own, hence linking to it) Two intersecting cylinders (one for the boiler, one for the chimney) are a good start, but I cannot seem to get the curve between the two of them to my satisfaction. I tried the Fillet tool along the joint between the two cylinders, but the curve is not quite what I'm aiming for:

ChimneyBase.png

On the prototype I'm modelling, the "filleted" curve should match up with the top surface, so the curve is not of a constant radius, neither is the angle taken up by the flare constant around the circumference of the chimney. The same geometric idea can also be found at the bottom of domes. 

Does anyone have any experience and/or advice on trying to represent this shape? My old approach in SketchUp was to hand-draw every single polygon needed to create the shape required, but that doesn't work with a) actual curves rather than collections of straight lines and b) actual solids rather than just polygon-based geometry.

Many thanks in advance!





#2 gazman424

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Posted 13 January 2018 - 22:57

Hi Skinnylinny,
I asked the same question, and the very satisfactory answers can be found about half way down the page;

http://www.rmweb.co....0-thread/page-2

Gaz.

So I've joined a local "hackspace" (Basically a club with access to tools and materials - pay your dues and chat with like-minded people while making things) which has a CNC milling machine.
"What materials will it mill?" I asked. "Oh, aluminium, delrin (engineering grade plastic), brass..." comes the reply.
"Oooh, brass, perfect for domes for my pre-grouping engines" think I. So I buckle down and start trying to teach myself to use Autodesk Fusion 360. It's certainly a big step up from SketchUp.
Anyway, to the job in hand. Imagine, if you will, a steam locomotive boiler with a dome and a chimney on it. The chimney can be divided into three sections: the cap, a tube section (both relatively easy to make from extrusions and rotated geometry) and a base. The base is usually flared, and this is the bit I'm having trouble with. The basic idea can be seen in this image (not my own, hence linking to it) Two intersecting cylinders (one for the boiler, one for the chimney) are a good start, but I cannot seem to get the curve between the two of them to my satisfaction. I tried the Fillet tool along the joint between the two cylinders, but the curve is not quite what I'm aiming for:
attachicon.gifChimneyBase.png
On the prototype I'm modelling, the "filleted" curve should match up with the top surface, so the curve is not of a constant radius, neither is the angle taken up by the flare constant around the circumference of the chimney. The same geometric idea can also be found at the bottom of domes. 
Does anyone have any experience and/or advice on trying to represent this shape? My old approach in SketchUp was to hand-draw every single polygon needed to create the shape required, but that doesn't work with a) actual curves rather than collections of straight lines and b) actual solids rather than just polygon-based geometry.
Many thanks in advance!


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#3 Quarryscapes

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Posted 14 January 2018 - 09:23

This has been answered before on here. The same principle can be used for  creating many things.

 


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#4 Skinnylinny

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Posted 14 January 2018 - 11:04

Ahhhh I didn't manage to find that with the search function, though I may have been searching with the wrong keywords. Thank you!



#5 Quarryscapes

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Posted 15 January 2018 - 07:49

No worries. Alternatively you should be able to use side and end on sketches to create guide rails rather than fiddling with the intermediate loft. I haven't tried this method yet though.