# A rod which flixed in only 1 direction.

1. Jun 14, 2009

### dE_logics

Is there any sorta rod/mechanical component which only flexes in 1 or a few direction?

Or do we have any such sorta bar which is fordable only in one direction?...if you apply force in other directions it will be rigid.

2. Jun 14, 2009

### Hootenanny

Staff Emeritus
We can of course postulate such an object, for example, the term "rod" in mechanics means a one-dimensional object or a line-element (usually a rigid line-element). Obviously, such an object doesn't exist in reality and in fact there are no absolutely rigid objects in reality. So the notion of an object being absolutely rigid in one or two directions may be used as an approximation, but such an object doesn't exist in reality.

3. Jun 14, 2009

### Staff: Mentor

I-beams are made to be much more rigid in one axis than the other.

4. Jun 14, 2009

### Mapes

A bicycle chain is approximately perfectly compliant in one axis and approximately perfectly rigid in two other axes.

5. Jun 14, 2009

### dE_logics

I'm not talking about rigidity, this is a mechanical component, i.e we can assume prefect rigidity.

No I beam will not be it.

Yeah, I was wondering about chains, but is there anything which is solely made to flex in one direction and in the other its actually made to withstand large amounts of force.

Cause in chains this is comes as an obvious result...though its not actually desired.

6. Jun 18, 2009

### dE_logics

None has been made yet?

7. Jun 18, 2009

### Mapes

Can you give some context to your question? (Like the application or need.) A hinge satisfies these requirements, but it's hard to tell what you're looking for.

8. Jun 19, 2009

### dE_logics

No not a hinge, its strictly a rod/bar.

Imagine a rope which's stiff in one direction but soft in the other, such that it can be folded (and made portable) if rolled in one direction while in the other it can serve as a sort of stiff rod.

Should should have a major advantage as a construction beam...and various other applications which are concepts actually.

9. Jun 20, 2009

### Nick89

I'm thinking about some kind of protective gear I saw once for snowboarders, I believe it was for your back. It could bend forward easily, but not backward. Basically it was just a few 'plates' locking into each other such that they locked when you bend backward, and they released when you bend forward.

10. Jun 20, 2009

### dE_logics

humm...yep that will be it.

Irony is no one knows the potential of such an arrangement.

11. Jun 20, 2009

### Staff: Mentor

I-beams are used for a reason - they have a high strength to weight ratio. To understand why, you'll need to familiarize yourself with the concept of moment of inertia: http://en.wikipedia.org/wiki/Moment_of_inertia

In addition, a beam needs at least some strength in its other axes to prevent buckling.

What you are suggesting would be significantly inferior to an I-beam for structural purposes.
Including you!

I'm not seeing much a point to this thread, just a vague, ill-posed question that doesn't seem to have a purpose behind it. Are you going somewhere with it, or is this all there is?

12. Jun 24, 2009

### dE_logics

Well...I made one, it can be worked out as a very good construction material and make things 'foldable' such that when undone it give a specific shape, thus can take shape of predefined objects...the same thing which people are trying to achieve using nano tech.

I beam has to do purely with statics...this is something very different, initially, we're not talking stress here.