Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

** Community Tip** - You can Bookmark boards, posts or articles that you'd like to access again easily!
X

- Community
- Creo (Previous to May 2018)
- Creo Modeling Questions
- Modelling a Reef Knot

Options

- Subscribe to RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

May 29, 2014
10:53 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 29, 2014
10:53 AM

Modelling a Reef Knot

Hello,

I have, unfortunately, a requirement to model a Reef Knot (or Square Knot, as you might know it) again.

In the past, I have made a couple of wiggly curves orthogonal to each other and intersected them and run a VSS along them to create each half loop. A few mirrors and you have a passable looking knot. It takes a lot of tweaking and fiddling to get it looking presentable, though. Then there was the added complication that I was required to model a Slip-Reef Knot - one with a loop on one side that you could pull to undo the knot, a bit like a shoelace.

Is there an equation (or equations) to define such a knot? The nice thing about the equation approach would be that it took less work to make it look good and it would also scale nicely. That way, it would be done once and for all and I wouldn't have to repeat all the tweaking every time.

I'm sure someone out there has sorted this out.

Currently using WF4, M220, but I would imagine the principle applies equally well to any version. Bear in mind that I won't be able to open your solutions created in Creo 2.0, though...

Cheers,

John

Solved! Go to Solution.

1 ACCEPTED SOLUTION

Accepted Solutions

May 30, 2014
08:48 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
08:48 AM

I made it.

X=.45*cos(t)+.25*cos(-t)-.45*cos(-3*t)

y=.45*sin(t)+.25*sin(-t)-.45*sin(-3*t)

z=0.2*sin(5*t)

11 REPLIES 11

May 29, 2014
11:38 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 29, 2014
11:38 AM

If anyone would have it, it would be http://mathworld.wolfram.com/SquareKnot.html

It doesn't look like anything useful for modeling, though the topology is OK.

May 29, 2014
02:36 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 29, 2014
02:36 PM

Fun problem. It should be just a matter of parameterizing the knot and plugging the equations into a datum curve by equation.

That being said, I have no idea how one might go about parameterizing a knot.

The guy who made this website does. He has parametric equations for a granny knot which is similar to a reef knot.

http://paulbourke.net/geometry/knots/

I plugged the following into a datum curve:

x = -22*cos(t) - 128*sin(t) - 44*cos(3*t) - 78*sin(3*t)

y = -10*cos(2*t) - 27*sin(2*t) + 38*cos(4*t) + 46*sin(4*t)

z = 70*cos(3*t) - 40*sin(3*t)

And with a sweep I got this:

Maybe you can tweak these equations to form a reef knot. I might work on this later.

May 29, 2014
07:37 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 29, 2014
07:37 PM

May 30, 2014
08:48 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
08:48 AM

I made it.

X=.45*cos(t)+.25*cos(-t)-.45*cos(-3*t)

y=.45*sin(t)+.25*sin(-t)-.45*sin(-3*t)

z=0.2*sin(5*t)

May 30, 2014
11:22 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
11:22 AM

Whoa, cool!

Done by "curve by equation" I take it?

May 30, 2014
01:49 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
01:49 PM

Frank, yes curve by equation.

It's not a big thing, I think I just had more successful google searching.

May 30, 2014
03:00 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
03:00 PM

Figured. I thought this would be cool to use for a coiled wire rope model.....

May 30, 2014
04:06 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
04:06 PM

yeah it would, hopefully someone will work on that, I dont really have the time at the moment.

May 30, 2014
11:24 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
11:24 AM

Nice work Matt!

May 29, 2014
10:49 PM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 29, 2014
10:49 PM

Search for "Instructional Knot Tying Animations (Blender)" and view in wonder.

No doubt it's not trivial work, but still amazing.

May 30, 2014
03:49 AM

- Mark as New
- Bookmark
- Subscribe
- Mute
- Subscribe to RSS Feed
- Permalink
- Notify Moderator

May 30, 2014
03:49 AM

Amazing, indeed.