Creating an angled curve, like a partial cone

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blakeh1
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Creating an angled curve, like a partial cone

Post by blakeh1 » Fri Mar 20, 2015 5:19 pm

Let's see if I can ask this and make sense...


Say I have the diameter of a circle. I want to place a larger circle under it, then fill in the sides with sheet styrene.

How do I calculate the curve I need for the flat sheet that will become the cone so when I cut out that shape from the flat sheet I can then just wrap it around without overhang?

For example, would I create something like the cone for the millennium falcon cockpit, but much larger diameter and much shorter

edit

i.e. something like this
http://www.korthalsaltes.com/gif1/truncated-cone.gif


Say my top circle is 10" diameter, the bottom one is 12" diameter and I want a 1.5" space between them. How would I figure out the curved side piece inner and outer radii

It will be too large to cut from one sheet and I would like to make individual sections maybe done in 8ths
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Johnnycrash
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Post by Johnnycrash » Fri Mar 20, 2015 5:40 pm

OK, this it where it get's a little complicated.

http://gekgasifier.pbworks.com/f/HowToM ... e-1000.jpg
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Sluis Van Shipyards
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Post by Sluis Van Shipyards » Fri Mar 20, 2015 7:32 pm

I used this building my Chiss fighter years ago: https://www.conelayout.com/

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Post by Andrew Gorman » Fri Mar 20, 2015 8:00 pm

Find a model rocket "shroud calculator" and you are in business.

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naoto
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Post by naoto » Fri Mar 20, 2015 8:48 pm

Andrew Gorman wrote:Find a model rocket "shroud calculator" and you are in business.
Would the following help?
http://rocketry.newcenturycomputers.net/shroudcalc.html
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blakeh1
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Post by blakeh1 » Fri Mar 20, 2015 10:37 pm

Thanks everyone, they were are all helpful but I thnk the rocketry one looks to be the easiest with the ability to generate the template

Although I did happen to come across this http://jm.davalan.org/calc/cone/index-en.html

which gave me different value than what I got here for the same inputs
http://rocketry.newcenturycomputers.net/shroudcalc.html
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Post by Chacal » Wed May 27, 2015 4:29 pm

blakeh1 wrote:Thanks everyone, they were are all helpful but I thnk the rocketry one looks to be the easiest with the ability to generate the template

Although I did happen to come across this http://jm.davalan.org/calc/cone/index-en.html

which gave me different value than what I got here for the same inputs
http://rocketry.newcenturycomputers.net/shroudcalc.html
Mind you that the two ask for different inputs. Shroudcalc asks for the diameters while the other asks for the radii.
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Post by Solomoriah » Wed Jul 15, 2015 4:42 pm

Chacal wrote:Mind you that the two ask for different inputs. Shroudcalc asks for the diameters while the other asks for the radii.
Not surprising, since model rocket body tubes are described by their diameters.

I'm the guy who wrote the Shroud Calculator, and let me say that I'm happy to see it be of use to someone besides myself!

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Post by Kylwell » Wed Jul 15, 2015 9:45 pm

We scratch builders thank you.
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Sluis Van Shipyards
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Post by Sluis Van Shipyards » Wed Jul 15, 2015 10:01 pm

Yes, thanks! I used it for the cone behind the ball cockpit on my Chiss fighter: Unfinished: http://i.imgur.com/ApUIX7P.jpg
Finished: http://i.imgur.com/mLCL0KC.jpg

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Post by Solomoriah » Thu Jul 16, 2015 8:51 am

Okay, wow. Really nice looking model. Glad I could be of some small assistance... though if you hadn't told me, I'd have never known.

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Post by CarlGo » Mon May 23, 2016 10:53 pm

I'm trying to make a similar piece, but from a non-regular cone though. I want to create the part circled in red:

http://m.imgur.com/fXvuqSm

It's the same kind of truncated cone shape, but the cone it's based on is tapered more sharply on one side, and the base is an egg shape instead of a circle. Here is the part I have so far:

http://m.imgur.com/DSMiKmj

http://m.imgur.com/6ukKusf
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Post by sbaxter » Tue May 24, 2016 5:40 am

I was trying a while back to find a formula for making a truncated cone — I wanted to make the engine cans for an X-wing fighter. Never have quite gotten to it for various reasons. However, I did learn that the word for a truncated cone shape is frustum. Just FYI.

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naoto
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Post by naoto » Tue May 24, 2016 9:56 am

CarlGo wrote:It's the same kind of truncated cone shape, but the cone it's based on is tapered more sharply on one side, and the base is an egg shape instead of a circle.
Could the article "How to Design and Build Oblique Nose Cones" be of help?
https://www.apogeerockets.com/education ... ter127.pdf

For a more general approach, look for a textbook on drafting then look up section titled something like "Developments and Patterns." Online you can try Google with combination of keywords such as "drafting development and patterns". Please note you're likely to find links that don't seem to apply (as they are about clothing), but I'd recommend that you *not* ignore those -- you may still glean some useful information from them. Think about it for a moment -- often clothing is often made up of parts cut from a flat sheet and stitched together to form relatively complex shapes. Similarly look at shoes and hats -- and ponder for a moment how those shapes are constructed (in particular how various molding techniques can be used to form rounded shape from what began as a flat sheet).

Speaking of application of techniques that doesn't seem to be related to your model-building hobby -- crochet techniques can be useful in rocketry:
https://www.youtube.com/watch?v=ETiB_V-_SGs
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Rocketeer
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Post by Rocketeer » Wed May 25, 2016 11:06 am

Or you could just eschew calculation and do it practically: Make two oval shapes out of styrene, one the shape of one end of the cone and one the shape of the other; glue a spacer between them so they're the right distance apart; then wrap the resulting "spool" shape in thin sheet.

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