maximum deflection - sanity check

[dsc]

Ah yes, it's all wrong!:)

Here's the right formula (taken from http://www.clag.org.uk/beam.html):

δ = FL³ ∕ 3EI

I = πr⁴ ∕ 4 = πd⁴ ∕ 64

(for round beam)
which means that deflection at a given F and L, for a 20mm dia beam is:

δ = FL³ * 0.0002358

Assuming L = 0.18m and F=100N the maximum deflection is:

δ = 100 * 0.005832 * 0.0002358 m = 0.0001375m = 0.1375mm

Which makes much more sense than the previously calculated value.

The funny thing is that changing the dia from 20mm to 22mm gives you a maximum deflection drop from 0.1375mm to 0.094mm. That's just by making the shaft 2mm thicker. Quite amazing me thinks.

Regards,
dsc.