HandleBar model discoveries

Finally I get to see if FreeCAD is of any use.

Previously I described the problem which was to discover why Brompton bikes updated the handlebar design. I got curious to know if the top elbow would or not bend first and if the length between the two would make a great distance. All of this resorting to many assumptions and simplifications. (I am doing this for fun)

First off all I have a Brompton! I am one happy user.

Brompton handlebar
Brompton handlebar

Now The issue was the design differences, which you can checkout the new here:

2017 Brompton handlebar
2017 Brompton handlebar

And the old design here:

2015 Brompton handlebar
2015 Brompton handlebar

Our hands are positioned on the blue top zone and the handlebar is fixed on the blue bottom element.

I considered lower force justo to get an ideia, many direction could have been studied.

HandleBar model constraints
HandleBar model constraints

Then I selected my simulation package which in this case I opted for FreeCAD. And started meshing wright a way with Gmsh.

Handlebar mesh
Handlebar mesh

And now finally I got to the results part.

Handlebar bending result
Handlebar bending result for the version bellow 2017 model

From the image it seems that the lower elbow until the fixed support will take much of the stress. The bar height being bigger will increase torque which will increase the reaction force at the supports. Reducing the central bar between the lower and top elbow will increase handlebar strength. The only thing I can see that made them go for the previous geometry for the bellow 2017 model is design or manufacturing technical difficulties. Maybe it is harder to bend the single shaft with such low central support at each handlebar side.

FreeCAD works as expected… Good work open source comunity!