Stick with Ali profile or venture into plate?

[ecat]

Just to throw another spanner in the works, I'm planning on using square tube for best stiffness / cost ratio...

http://www.aluminiumwarehouse.co.uk/Aluminium-Square_Tube/c120_129/p29830/Aluminium_Square_Tube_(6082T6)_3_in_x_3_in_x_1/4_in/product_info.html

Not as convenient as profile but it should be possible to join quite accurately with a bit of drilling and tapping and a lot cheaper.

Oo, nice link. I collect them

nice one ecat... your calcs seem to good to be true... fingers crossed
the valuframe 200x40 is much more dense than the Bosch so should perform better

Too good indeed... I should check them again. Meanwhile, A quick sanity check...

The formula is: Deflection =W*L^ 3/ 3*E*I
Where W is force, L is length, E is Modulas of Elasticity in psi, and I is Second Moment of Inertia.
Moment of inertia is calculated by (width * thickness^3) / 12

So I varies with the cube of thickness.
Looking at the horizontal force the plate is 20mm thick, the profile is 40mm thick. 40^3 / 20^3 = 8. Whoops, my calcs are 10 times that...

A-ha, the Beam calc web page is for beams supported at only 1 end, the profile figure is for a beam supported at both ends. Note to self, just because the link comes from a CNC site it doesn't mean the linked page is what you think it is!

There is a spread sheet around here somewhere, I'll get back to you...