Figure out solution to bending problem

[dbenamy]

No description provided.

[dbenamy]

Possible solutions:

• 1/2" tubing
• Have blades pass each other further (if the frame doesn't continue bending. See Raise lower blade so the blades pass each other more when fully closed #5.
• Diagonal braces (3, 4, 5 triangle like we did on the backhoe).
• More plates around the blade area.

[leodearden]

So, from the discussion in the hangout, the main distortion is the box sections bending, rather than collapsing.

The machine either needs to work with less force or be stiffer.

To radically increase the bending stiffness of the ironworker beams requires using taller member(s). At present each of the four boxes bends nearly independently. If the stack of four boxes was bonded into a single structural member then it would be 4^4/4 = 64 times stiffer.

That could be achieved by:

• Welding all the boxes together along their lengths
• using a plate that covers all of both sides and a huge number of bolts
• using enough small plates on the sides that they behave like one box
• Replacing the stack of boxes with a single large I-beam, bigger box, or similar

For shearing, I think the operation could be completed with less force by cutting at a steeper angle: at the moment the blades come together almost parallel. If they crossed at an angle, so that one edge of the blade bites through before the other side has fully contacted the bar then less force would be needed. The disadvantages of this approach may include:

• more distortion of cut piece
• it's not really applicable to punching

[dbenamy]

@leodearden, This is a really helpful analysis, thanks!

Of these options, my preference would be to try a number of smaller plates along the sides and to increase the cutting angle a bit, since both of these can be done with pretty much the standard parts (http://opensourceecology.org/wiki/Warehouse) and without too much extra work.

[dbenamy]

The 1/2" tubing + a pair of extra plates on top did the trick!

I'll post pictures soon and update the assembly guide (and BOM).

We could use help updating the 3d model.

[dbenamy]

Here's a picture showing the extra plates we added (but not yet showing the final legs).

To do:

• Update the assembly guide for 1/2" tubing and the extra plate(s).
• Update the BOM from the update guides using http://ose.github.io/documentation/bom-generator/bom-generator.html
• Update the 3d model at http://opensourceecology.org/wiki/File:IronworkerI.skp