surface flips over unwanted when moving points

Replies to This Discussion

Permalink Reply by Pieter Segeren on April 7, 2017 at 4:12pm

H(o)i Dirk,

I'd say it's caused by the SplitBrep component(s), whose output isn't sorted in a predictable manner, so what you called 'radius ring' isn't always item 0 of the list.
(wouldn't creating a profile to revolve be easier? )

Permalink Reply by Dirk Geurkink on April 9, 2017 at 1:39pm

Moi Pieter,

This is the first time I make use of this forum.

Should this be called a bug in the program and be reported as so?

I also found out that the output isn't sorted well, and tried to solve it by revolve.

To do so I tried to use the isocurves of the surfaces, but this didn't work also.

Is there a better way to make a cross section of the ring? 

Permalink Reply by Pieter Segeren on April 10, 2017 at 1:05pm

No, I don't think so, it's just an inconvenience you have to work around.
I would use a [Rectangle] plus a [Fillet], the one with as description "Fillet a curve at a parameter".
Is the ring supposed to be a separate piece from the pipe, or should it be all one solid?

Permalink Reply by Dirk Geurkink on April 10, 2017 at 3:05pm

Hallo Pieter,

- This pipe with ring is the last part of a bigger model where the pipe allways takes the right position relative to a chain running through it.

To learn Grasshopper and to build the model took quite some time, and as I see it now, the inconvenience was the problem from the beginning. I think at attempt 12 or 13, I found a way to solve this, but ran into it again with this last part.

- I'll give it a try again next friday.

- The ring has to be separate. There will be one at the other end as well, and a thin ring under an angle somewhere near the top of the pipe.

Actually it's a chainpipe for an anchor arrangement running from the winch to the chainlocker.

Permalink Reply by Dirk Geurkink on April 14, 2017 at 10:18am

Goeden avond Pieter,

Thanks for your help, it works, and the full model works to.

I'm able now to bring a chain to whatever position relative to the winch, and the pipe it runs through is positioning itself accordingly.

Permalink Reply by Pieter Segeren on April 14, 2017 at 1:42pm

Hoi Dirk, glad you got it working. Could you show what exactly you made, I really didn't understand your discriptions (vaktermen) and I'm curious about it:)

Permalink Reply by Dirk Geurkink on April 19, 2017 at 1:49pm

Hallo Pieter,

It's a little bit bussy overhere, will show you what and why I made it this weekend.

Permalink Reply by Pieter Segeren on April 19, 2017 at 2:18pm

I understand, no rush Dirk. No obligation either:)

Permalink Reply by Dirk Geurkink on April 20, 2017 at 12:36pm

Hallo Pieter,

I'm a shipbuilding engineer, and among others responsible for anchorarrangements. One of the things I run in about twice a year is the positioning of a chainpipe from the winch to the chainbox. This pipe has to force the chain exactly under the chainwheel, and in the middle of the chainbox, and every new design has the chainbox in a different position.

Doing this in Rhino takes with all the changes, moving winches several times etc, about 2.5 days per new design, so about a week work a year. An expensive pipe.

There had to be a way to do it faster, and Grasshopper seemed to be a good way to do this. First I had to learn Grasshopper, but the main problem I ran into was constructing a line tangent to two circles not in the same plane. After maybe 12 or 13 attempts I found a solution for it that is accurate up to 0.001 degrees.

It now takes minutes to make a change, and I get all the information I need: position of the pipe, endrings and closing ring. This is through iges files transported to the big Cadmatic model the ship (commercial) is in.

In the overview picture "lier met pijp en kettingbakken" you see the anchorwinch, the chainpipe and both chainboxes. I left the sb winch away.

In the picture "aanzicht kettingwiel" you can see the chainwheel that pulls the chain. The chain shackles fall in the recesses in both sides of the wheel. The red pipe represents the outside of the chain.

In the picture "vooraanzicht kettingwiel" you can see the chainpipe, or actually the ring at the end of the pipe forcing the chain (red pipe) to come straight from the chainwheel.

When the chain wouldn't  come in a straight line from the wheel, we would have a lot of wear on chain and chainwheel.

I'm able to move the top of the pipe in x and z direction, and the lower end of the pipe in x, y and z direction now.

So that was quite an excercise for a simple pipe.

But the next challenge has submitted itself allready. We now need a chainpipe consisting of 2 pieces.

The whole project is done in my own time as a study project, the hours involved do not outweigh the result.

 

Permalink Reply by Dirk Geurkink on April 21, 2017 at 3:27am

made a mistake in the end of the explanation.

It should read: I'm able to move the chain at the top of the chainpipe in x and z direction and at the bottom in the x, y and z direction now, and the pipe and rings will adjust itself accordingly.

Permalink Reply by Pieter Segeren on May 5, 2017 at 3:49pm

Hoi Dirk, thanks for your elaborate explanation and thanks for your patience. Not sure I got it all, but glad to hear you got what you wanted. (Max reply-depth reached, so I repied to this instead)