Space frame hand calculation

[Pink Eye Pete]

Hi all!

I am not part of the formula student project, but as part of the course I have been given a project to produce a racer chassis similar to a formula student one. So I am hoping to get some help in here.

When you guys design the frame, do you do a three dimensional force/stress and moment analysis by hand before using a CAD program? Do you just use the simple free body diagram?


Thanks guys!

[Pink Eye Pete]

Hi all!

I am not part of the formula student project, but as part of the course I have been given a project to produce a racer chassis similar to a formula student one. So I am hoping to get some help in here.

When you guys design the frame, do you do a three dimensional force/stress and moment analysis by hand before using a CAD program? Do you just use the simple free body diagram?


Thanks guys!

[exFSAE]

Short answer: No.

Longer answer:

(a) The 'simple' hand calculation unfortunately isn't simple when the structure has 80+ or however many elements in it, some of which are bent, and none of which are pinned connections. Tubes are in bending as well as axial loading. Also, it's an inertial distributed load case which is a bitch.

(b) Stress generally isn't the primary issue of concern given that the structures are inherently overbuilt.

(c) Even if you determined the stress levels, determining failure criteria is non-trivial given that welding, particularly with a low-carbon filler, significantly alters the microstructure of the steel in and out of the weld pool.

(d) Deflection under load (stiffness) is the more critical parameter.