cantilever

[jdf001]

Hello all! I need to construct a cantilever to be attached to a wall to support a weight out of two sheets of 11x17 paper, glue, paper clips, and tape. I was thinking the best way to do this would to be laminating strips of the paper into triangular tubes and connect them using the paper clips to make a braced as pins and attach it to the wall with the tape. I was wondering if anyone had any thoughts on how best to determine the angle for the brace.

[DonRotolo]

Your chief material is paper, so let's focus on that.
Paper sheets are flimsy, unless their geometry is changed to make it stiff. Folding makes paper stiffer.

Paper is also strong in compression, but generally suffers from being a "slender column" (look it that definition).

It is somewhat strong in tension.

I don't know all the limitations, but paper tubes - particularly if reinforced with glue - can be quite stiff.

If you have an unlimited number of paper clips, it they are straightened, and the ends twisted into loops, they can be quite a strong tensile member.

You can also use paper clips at joints to reinforce, spreading the load out.

My advice: Buy some paper and glue make a dozen or three prototypes of the structural elements you think you need, and test - carefully, scientifically - which is strongest for your application. With data in hand, picking the winning solution becomes trivial.

Please let us know what you finally decide upon.

[GeeTwo]

I fully agree with Don's points above.

A few other configurations to consider:

• Paper tubes (especially if of several layers glued together) can hold a decent compressional load. Look at a paper towel or shipping tube for some ideas how to make this work.
• Unless it's in the rules, don't limit yourself to having one of the bars be horizontal. Also play with some acute triangles (compression at the bottom, tension on top). I suspect that for a given amount of material, something close to an equilateral triangle or a right isosceles triangle (with the right angle away from the wall) will give the best results; both members will contribute a force in the vertical direction.
• To make a tension member from paper, you don't need a large area of coverage, but you do need to ensure that tears don't propagate. A time-honored technique of making fiber materials stronger under tension is to twist - think of a rope or cable.

Out of curiosity and for my own possible tinkering someday, how far out does the cantilever point have to be, and how much weight is it expected to hold?

[jdf001]

Thank you all so much! I'll post more as I start prototyping. The goal is to support a 250 gram water bottle on the end of as long of a cantilever as possible.