Inferior bracket for recumbent seat

I designed this inferior bracket for my recumbent seat as the original one was a steel sheet and was a bit wobbly.

To get this shape I used Calculix and Beso included in FREECAD and simplified the result.

According to my calculation this bracket can withstand me (~65kg) with a good margin (>5).

Nevertheless this design comes no guarantee as many parameters can lead to failure. [Ex: number of walls used, infill, temperature, material&co]. I rode it ~40km for now including some bumps, in Paris aera.

This design use four M4 inserts for fixing the seat and two M6 insert to fix the bracket on the bike frame. I drilled one of them to 6mm as my frame use a through fixation.

On top of this I designed a TPU insert to match the flat of the bracket and the curve of the seat and for TPU shim for the same reason.

Update 08/05/2025: 

Following the breakage (last sunday) of the bracket, I release an insert made of TPU replacing the use of brass insert. The reason being I suspect that the crack initiated on a sharp edge of it. To put this insert in place you will need to:

•  drill/rectify the lower holes to 8mm and a bit more possibly (I used a M8 threading tool on my driller, first in normal direction then in reverse, several passage until no more grip)
• insert by hand, then if needed use M6 screw to make the assembly flush

The breakage was not catastrophic: the opposite side was still intact and the damage one was still holding the seat for a part. I was able to ride the last km home, including climb of montmartre on cobbles.