Sunday, September 11, 2011

Engine: 2 - cylinder liner

In the simplest situation cylinder liner is a tube. I'll try design something more complicated.

Start FreeCAD, open Part Design workbench. You need section sketch which will be revolved around Y axis. Start a new sketch, and try create sketch like in the screenshot. The height is 137 and inner radius is 37.5. Use poliline and horizontal, vertical, coincident constraints. If any constraint is not necessary, click on it's icon and press [del].
Note: grid is useful, set grid to 10 mm (without snapping) in TaskView. FreeCAD shows you actual position near cursor.
Use lock constraint to fix sketch certain position (inner liner radius is 37,5).

Wall thickness is variable:
Distance from top Wall thickness
0 8
7 jump from 8 to 6
105 jump from 8 to 3
137 3

Close the sketch and make a revolution around Y axis.

To achieve minimal engine length we need cut some material from liner. Select a top face of liner and start sketching.

Draw two big rectangles symmetrical to Z axis. You can use a construction line (like in the "Pin ring tutorial") as centreline. Distance between rectangles is 88.
Finish editing the sketch and use a pocket tool.

Set (in Property View-Data) Pocket length to 137.

The final effect:
Download file.

Download RAW Video.

FreeCAD 0.12 r4907 SVN.


  1. I have trouble using the pocket tool. I have followed the steps till 'Finish editing the sketch and use a pocket tool.' When I click the 'create pocket button', an error message comes out, "The sketch has to have a support for the pocket feature. Create the sketch on a face." What's wrong with it?

  2. Firstly you have to select face on the model then start sketching.

  3. I made the same mistake as 경원 전 ! As a beginner, I mixed up "creating the sketch on a face" with "on a view, such as Front view" or even "on a plan, such as XZ with offset 173 mm"...

  4. I have the trouble while using revolve option, polar pattern option

  5. very nice look your site