The table case and the open source quest

On a previous post http://numerica.pt/2017/07/31/chair-legs-and-ikea/ I introduced the table/chair dilemma, a thing I looked at on a  trip did,  I found a very nice table that I wondered if I could use it as a decorative seat (http://numerica.pt/2017/07/21/tilted-leg-table-curiosity/). I showed that there  are a big variety of leg supporting types (leg configuration) for seats and that this arrangement was just one of many.

4 Straight Leg Chair Design
4 Straight Leg Chair Design
Side Legs Chair
Side Legs Chair

My initial target design was as follows:

Tilted table
Tilted table

I modelled the behaviour of this table to understand possible weaknesses. The model was as simplified as possible. Also material properties used were very far from the real behaviour of my target subject.

Table with tilted legs
Table with tilted legs

The weight support on this design is concentrated on the center. However I can imagine if we lean forward the bulk of our weight shift to the front and produces a bending effect on the table this in turn will stress highly the leg to table connective zone since it has liberty to rotate in that direction. For this design the top location of the legs are more stressed due to their angled design.

My conclusions: To use this table as a seat the material used in the legs should be very strong specially to deal with the bending moment generated due to the tilted angle and centered position of the connection table to leg. The connection interface between legs and table is a critical interface for this design since it will have to deal with the torsional moment that we generate when we lean front, back, left and right.

Remarks: This analysis was performed with FreeCAD and images were retouched with imaging software like gimp. Although these open source tools don’t allow for major analysis we can still learn something. If I were to study this in detail, commercial software would be much easier and powerful to use and understand exactly what was going on with the design.