Wire With Greatest Bending Fatigue Resistance

[itsdonny]

I need to add flexibility to this joint (where the arrow is pointing) and I was thinking about using a method I saw on this flexible clamp. I ripped it apart and it looks like they used copper wire as the flex material. What would be the best wire to use? I'm worried that perhaps it could only be flexed so many times before breaking. The design I'm making won't require continual flexing but some users may flex the joint 2-3 times per day at the most.

Also I'm open to other ideas to add flexibility to this joint if you have any ideas.

Thanks!
Don

http://laphotopro.com/public/hinge-flex.jpg
http://laphotopro.com/public/flex-wire-05-sm.jpg
http://laphotopro.com/public/flex-wire-04-sm.jpg
http://laphotopro.com/public/flex-wire-03-sm.jpg
http://laphotopro.com/public/flex-wire-02-sm.jpg
http://laphotopro.com/public/flex-wire-01-sm.jpg

 

[nsaspook]

I've used this type of cable in robotic wafer handling systems. Maybe a bit of overkill for your application. http://www.newark.com/pdfs/techarticles/belden/ProductBulletin_InfinityCables.pdf

 

[Danger]

Do you need something that acts as a spring, or simply is durable under flexation? That might limit the options. In either case, though, phosphor bronze is always a reliable choice.

 

[itsdonny]

Thanks guys. I don't want it to spring back. I want the user to be able to adjust it to the position of their liking and have it stay there. I just want to make sure I'm using a material that can be flexed thousands of times and not snap. Phosphor bronze will do this?

 

[Danger]

I just want to make sure I'm using a material that can be flexed thousands of times and not snap. Phosphor bronze will do this?

Absolutely, but I'm not sure about it holding a new shape. It's pretty versatile, though, so I expect that some version of it will do so. It's used in everything from the springs in the pin cells of locks to dental appliances such as braces. Ship propellers are often made from it as well, since it has terrific corrosion resistance.

edit: Something else just came to mind, but it probably won't be appropriate for you. I had a wee flashback to this snaky thing that let's me use my screwdriver around corners. Would it be to your advantage to use one or more tight-fitting U-joints rather than a single piece of flex metal? It would be something like the armatures that model-makers use for the positioning of characters in stop-motion animation films.

 

[itsdonny]

I think you're right Danger. A tight fitting joint may be the best way.

Thanks

 

[Danger]

You're more than welcome. I hope that it works for you. Remember to design in some sort of adjustment screw or other system to compensate for loosening due to wear.
Please post your results when you get done; I'm interested to see how it turns out.