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Spring stretching

Spring stretching

Spring stretching

(OP)
Hi, below are a few pictures of 4 damaged springs, let's say the spring on the left is 1 to the spring on the right is 4. Spring 2 stretches evenly so I believe it's manufacturing quality is good but has been overloaded. However spring 3 and 4 have irregular stretch in the middle so I think the springs have quality issues. I believe possible issues are raw material and heat treatment, but I would like to read some other suggestions and recommendations on how to resolve this

Thanks

http://oi41.tinypic.com/908snl.jpg

RE: Spring stretching

Hi

Most tension springs fail usually at the ends, just like spring number 1 on your pictures.

The other springs say 3 and 4 might have heat treatment or quality issues however it looks to me as though someone as stretched them with a pair of pliers or when the springs have been fitted in service they have not been installed straight and possible bent around so obstruction that couldn't be removed.

You haven't given any information about what these springs do or service life they have already endured, all we have is your opinion but can you give any more information about these springs

RE: Spring stretching

(OP)
Actually, all springs originally have same length and spring number 1 broke in the middle, same place where the irregular stretch is.

No one uses any tools to bend or stretch them, and they are installed straight. They are intended to stretch uniaxially and must be assumed that they do, also must be assumed that the only forces applied on them are uniaxially forces at the ends of the springs (the hooks). The springs became like this after 3 months of service.

RE: Spring stretching

How do you expect us to help?
You haven't told us squat about the "service".
You haven't shown us how/where the springs are mounted, what material they're allegedly made from, or given a single pertinent dimension.
You didn't even put a ruler in the picture.

Mike Halloran
Pembroke Pines, FL, USA

RE: Spring stretching

Lacking _any_ information, I will speculate that the springs exhibit the sort of failure I'd expect if the chamber containing the spring (not in evidence) were partially filled with water (not in evidence), frozen (not in evidence), and stretched by 'the usual amount'.

Mike Halloran
Pembroke Pines, FL, USA

RE: Spring stretching

If its taken 3 months for those springs to fail in that I doubt there is any quality issue with the springs.
What are the springs used for?
Do you test the springs before they leave your company?

RE: Spring stretching

(OP)
The springs are used for trampoline, are 5.5 inches in length from the ends and take up to loads of 55 kg before overloading.

RE: Spring stretching

Now you are talking! Probably the person who used the trampoline landed directly or very close to the spring thereby bending it or overloaded the spring because he landed too close to the spring that took most of the load while the other springs did not participate in the load sharing.

RE: Spring stretching

Ah.
My high school no longer has tramps, thanks to an unfortunate incident, but I was privilieged to get tramp time in regular PE, 50+ years ago.

I recall the occasional leg going through the springs; it probably didn't do the springs any good.

I remember loose fitting pads over the springs, and I remember exposed springs. I don't know if the pads were an accessory, or if they were removed, or what.

I do remember being instructed not to step on the springs. Of course when you tell a teenage boy not to do something, guess what happens....

Mike Halloran
Pembroke Pines, FL, USA

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