Creating a sketch for building a light house made of wood

Post here for help on using FreeCAD's graphical user interface (GUI).
Forum rules
and Helpful information
IMPORTANT: Please click here and read this first, before asking for help

Also, be nice to others! Read the FreeCAD code of conduct!
User avatar
Willem
Veteran
Posts: 1852
Joined: Fri Aug 12, 2016 3:27 pm
Location: Lisse, The Netherlands

Re: Creating a sktech for building a light house made of wood

Post by Willem »

Hi Nils, when you need half a sphere it is not wrong to make a boolean cut between a sphere and a cube, but the easier way is to give the sphere an Angle3 of 180 degrees and rotate the sphere 90 degrees over the desired axis
Schermafdruk van 2017-09-30 03-49-59.png
Schermafdruk van 2017-09-30 03-49-59.png (209.83 KiB) Viewed 1643 times
chrisb
Veteran
Posts: 53922
Joined: Tue Mar 17, 2015 9:14 am

Re: Creating a sktech for building a light house made of wood

Post by chrisb »

derNiwi wrote: Fri Sep 29, 2017 5:21 pm thanks to all for helping. I have updated my "project" a little bit, focused on using the spread sheet for fast modifying the light house.
Are you interested in comments on your model? I better ask than looking like someone who always has to criticize.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
derNiwi
Posts: 40
Joined: Thu Oct 22, 2015 7:22 am

Re: Creating a sktech for building a light house made of wood

Post by derNiwi »

chrisb wrote: Sat Sep 30, 2017 4:19 amAre you interested in comments on your model? I better ask than looking like someone who always has to criticize.
Hi,

yes, of course I like to have some comments. It might help me and also other people starting with FreeCAD.
So: productive comments are always welcome :)

Nils
chrisb
Veteran
Posts: 53922
Joined: Tue Mar 17, 2015 9:14 am

Re: Creating a sktech for building a light house made of wood

Post by chrisb »

derNiwi wrote: Sat Sep 30, 2017 8:45 am yes, of course I like to have some comments.
Here you are, but let me say first, that you did a good job!

Plank lower end:
- It is overconstrained, you don't need the ortho constraint
- You can omit the construction line and apply the horizontal constraint to the endpoints
- You could calculate the angle of 112.5° in the spreadsheet and reuse it in the other sketches:
You have an octogon, thus the angle to the horizontal is half of 360/8:
112.5 = 90 + 360 / (2*8)
If you had modeled the sketch on the positive side of the Y-axis you would not need to add the additional 90°.

The same holds for Plank upper end
Something very strange happens there: When I try to do the same corrections the solver complains about redundant constraints. Deleting them leaves the sketch underconstrained - the horizontal distance is missing - but the solver recognizes it as fully constrained.

Upper base:
- one of the 135° constraints can be omitted.
- Did you know that there is a ready made octogon? I like the octogon with the symmetry constraints and I had never problems using them, but I have read here, that the solver does not like them due to possible precision issues.

Loft001
- You should not use a loft, when a pad suffices. Plank upper end001 and Plank upper end002 are identical.
- Hint aside: in FreeCAD 0.17 you could use a ShapeBinder and reuse sketch Upper base

Dome upper part:
- see Willem's comment; if you want to stay in Part Design, you can use a sketch with a quarter circle and revolve it.

Door:
- Use as little absolute measures as possible
- Use tangent constraints for circle/vertical lines
Be aware that you must not use tangent + coincident! Use tangent on the points instead
- You don't need the symmetric constraint either

Lower part:
(see comments on octogon above)
Attachments
Lighthouse03_cb.FCStd
(42.67 KiB) Downloaded 48 times
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
chrisb
Veteran
Posts: 53922
Joined: Tue Mar 17, 2015 9:14 am

Re: Creating a sktech for building a light house made of wood

Post by chrisb »

The solver issue in Plank upper end does not occur in 0.17.12222.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
derNiwi
Posts: 40
Joined: Thu Oct 22, 2015 7:22 am

Re: Creating a sktech for building a light house made of wood

Post by derNiwi »

Hi Chris,

thank ou very much. I'm using FreeCAD 0.16.6712 on my MacBook. I had about 30 or more crashes trying to use the values of the spread sheet.
chrisb wrote: Sat Sep 30, 2017 10:38 pm Here you are, but let me say first, that you did a good job!
Thank you.
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
- It is overconstrained, you don't need the ortho constraint
- You can omit the construction line and apply the horizontal constraint to the endpoints
- You could calculate the angle of 112.5° in the spreadsheet and reuse it in the other sketches:
You have an octogon, thus the angle to the horizontal is half of 360/8:
112.5 = 90 + 360 / (2*8)
If you had modeled the sketch on the positive side of the Y-axis you would not need to add the additional 90°.

The same holds for Plank upper end
Something very strange happens there: When I try to do the same corrections the solver complains about redundant constraints. Deleting them leaves the sketch underconstrained - the horizontal distance is missing - but the solver recognizes it as fully constrained.
I tried to update and use your formula for the angle. It will be calulated correctly, but after saving, closing and re-opening (or open again after a crash) the formula is changed to
=90 + 360 / 2 * 8
=> the parenthesis are removed. :(
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
Upper base:
- one of the 135° constraints can be omitted.
Ok.
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
- Did you know that there is a ready made octogon? I like the octogon with the symmetry constraints and I had never problems using them, but I have read here, that the solver does not like them due to possible precision issues.
No. It is a little bit difficult to find all the things, objects and functions.
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
Loft001
- You should not use a loft, when a pad suffices. Plank upper end001 and Plank upper end002 are identical.
- Hint aside: in FreeCAD 0.17 you could use a ShapeBinder and reuse sketch Upper base
You're right. I use the pad on several objects, but first I was not sure if the shapes should be identical or not. And I just forgot to use the pad...
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
Dome upper part:
- see Willem's comment; if you want to stay in Part Design, you can use a sketch with a quarter circle and revolve it.
Yes. I already updated my model.
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
Door:
- Use as little absolute measures as possible
- Use tangent constraints for circle/vertical lines
Be aware that you must not use tangent + coincident! Use tangent on the points instead
- You don't need the symmetric constraint either
Yes, I should be able to calculate more. But I was a little bit afraid of the many crashes.
I try to update the model.
chrisb wrote: Sat Sep 30, 2017 10:38 pmPlank lower end:
Lower part:
(see comments on octogon above)
Ok.

I also tried the v0.17. But my big problem is I can't read any measurement in the part design workbench. All the text and numbers are really tiny and I didn't find a way to change the font size.

Thank you very much.
Nils
User avatar
Willem
Veteran
Posts: 1852
Joined: Fri Aug 12, 2016 3:27 pm
Location: Lisse, The Netherlands

Re: Creating a sktech for building a light house made of wood

Post by Willem »

Hi, for a design like this V0.16 is good enough. It must be confusing for a beginner to work with 2 different versions of Freecad. My advice is continue learning on V0.16 and forget V0.17. There are a lot of differences between the 2 versions and all tutorials are written for V0.16
derNiwi
Posts: 40
Joined: Thu Oct 22, 2015 7:22 am

Re: Creating a sktech for building a light house made of wood

Post by derNiwi »

Hi Willem,

this is not my first project with FreeCAD, but I'm still a beginner, the other things were not really difficult.

I tried the 0.17 because it seems to be a little bit more stable. But you're right, there are a lot of changes.
chrisb
Veteran
Posts: 53922
Joined: Tue Mar 17, 2015 9:14 am

Re: Creating a sktech for building a light house made of wood

Post by chrisb »

derNiwi wrote: Sun Oct 01, 2017 2:19 pm thank ou very much.
You're welcome
I tried to update and use your formula for the angle. It will be calulated correctly, but after saving, closing and re-opening (or open again after a crash) the formula is changed to
=90 + 360 / 2 * 8
=> the parenthesis are removed. :(
The bug is known and I think it is removed in 0.17. For now you can write 90 + 360/16 or if you worry about precedences: 360/16 + 90
chrisb wrote: Sat Sep 30, 2017 10:38 pm - Did you know that there is a ready made octogon?
No. It is a little bit difficult to find all the things, objects and functions.
It is in the sketcher in one of the drop down icons.

Concerning the crashes I cannot speak for the Spreadsheet, but the rest of 0.16.6712 is very stable, no crashes for a very long time here! 0.17 is a bit more critical, because it is still in the middle of development. It can happen, that things don't work for a while.
A Sketcher Lecture with in-depth information is available in English, auf Deutsch, en français, en español.
derNiwi
Posts: 40
Joined: Thu Oct 22, 2015 7:22 am

Re: Creating a sktech for building a light house made of wood

Post by derNiwi »

The mathematics are not the big problem, I still solved the calculation by myself. But it is confusing if formulas are being modified (due to a bug).

The software crashes on several parts, one is the spread sheet. But also using aliases from the spread sheet in objects from part workbench or part design workbench. And sometimes I was sure I had saved the current state before I did a change to one object. After the change FC crashed and the last state was not saved... this happend sometimes which I do not really understand and this is why some object parts did not use values of the spread sheet but static values.

I'm not a programmer professional but I studied IT and also had to develop several more or less small programs. But saving should be some kind of atomar function which means during saving data no changes are possible. Until the project is saved the program should not process anything else. Today with multiple tasks and multiple threads it might be possible to save in one thread the current state to a temporary uncompressed file, after this the program may continue processing all the user inputs and parallel compress the saved file. If a crash occurs during this part several changes could be lost. Also a program should not overwrite a file, some programs like MS Office create a temporary file first, if this was successful the old file will be deleted (or first renamed?) nd the temp file will be renamed to the original file name. So a crash will not result in a big data loss but is uses more space.
Post Reply