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I'm making a prototype that will have some load cells mounted approximately where the arrows are pointed in the image. The prototype will hold up to 100kg of load/force in the marked location thus I need to fabricate a frame with the correct strength to not bend or flex too much under load. I want to achieve this without welding and only bending 90-degree angles out of a sheet of metal to make the frame to the right in the attached image. The frame will be mounted to a wall, so the load is applied approximately 50mm or 2 inches out from the wall itself.

What grade of steel/metal and thickness do I need to achive this? Or how can I calculate this? Or maybe you guys know of a software I can use to calculate or simulate it?

Finished frame to the right

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Let's say that the loads are going to have at least 1cm radius at footprint, the stress of which will have a spread by the time it reaches the end of the steel bracket lip, adding to a total of 15cm stress width at the contact with vertical surface at wall.

section modulus of a rectangular steel sheet is with 15 cm base and T ticknes $ S= BT^2/6 \quad$, and steel allowable stress is 2500kgf/cm2 = 25kgf /mm2

$$ M= \sigma\cdot S \\ M= 100kg\cdot 2.5cm = 100*25mm_{load\ distance}=2500kg.mm \\2500 =25*150\cdot T^2/6 \\ T^2/6 = 0.66, \quad T^2=4 \\ T =2 mm $$ Your sheet has to be at least 2mm thick.

This is a very rough analysis for a concentrated load at 25mm away from the wall. The more detail the better answer will be.

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Could you add some more information about how you are going to attach the housing to the wall? I'm asking because the bottom might be the weakest part of your project. You might want to reconsider your design and overlap some of the metal so that you can use rivets, screws or something like that, to reduce deformation under load.

Oh and I could help you out with a quick FEM analysis if needed.

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  • $\begingroup$ This seems more like a comment then an answer. Please use the "add a comment" link when you need clarifying information. $\endgroup$ – Eric S Apr 7 at 14:00

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