Non-constant Spring Diameter

[TPMac]

I am trying to design a helical spring, using a glass fibre composite, of a single turn, that extends under load to such an extent that the outside diameter halves. All the assumptions of spring analysis (small deflections etc) no longer apply and I cannot work out any of the parameters relating load to deflection. Can anyone help?

 

[desertfox]

Hi TPMac

I have designed quite a few springs in my time of various types but I have never heard of one using a glass fibre composite let alone a single turn.
Can you be more specific in what you are trying to achieve and I may be able to help.
My first question is do you really need to make a spring in
glass fibre?
My second question is why can you not have more turns?
Third question if you succeed have you someone who can manufacture it?

regards

desertfox

 

[TPMac]

Hi DesertFox,
It's a funny one this. This is for a retractable spiral staircase that I am designing. The spring (in flat hoop form) is to be attached to the underside of a circular array of steps. As the steps move down relative to each other the spring is drawn radially inwards toward the stair centre, guided by runners. As it does so it takes the same helical form as the extending stair. Its function is to guide extension, provide some structural support and aid retraction. Metallic materials would be too heavy. If you can help....
TPMac

 

[desertfox]

Sorry TPMac

Its out of my area, although very interesting, sorry I cannot help you further here, anyway best of luck.

regards
desertfox