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Horror of the week 13/02/13....Double failure


Tony
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There has to be a design flaw with modern springs, doesn't there?

 

I don't ever remember having to replace broken springs up until the '90s but doesn't the current trend for few, widely spaced, coils and a tightly wound top (and sometimes, bottom) coil to sit in its mount mean that the spring has to move up and down that much more and hence prone to fracture from fatigue?

 

I've had to replace broken front springs on a Subaru Legacy, MK3 Golf GTi, and MX5s within the last few years but have never had to before that.

 

Anyone got any knowledge / info in this respect?

(Hoping for a detailed and highly interesting explanation on spring dynamics from Sagitar)

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Sorry, but I doubt if there is much in spring dynamics that would give a simple plausible explanation of your phenomenon.

 

The two keys to the dynamics of springs are Hookes Law (essentially, force is proportional to extension) and the fact that a freely oscillating spring follows the law of simple harmonic motion. I suspect that the problem is much more likely to be related to extending the operating envelope; using smaller safety factors in trying to lighten systems etc. It could be that attempts to improve compliance and increase the natural frequency of suspension systems gives rise to greater fatigue factors, but it is not an area in which I have worked. I read some stuff some time ago that seemed to indicate that spring breakage had increased in the UK to a greater extent than in other countries and there was a suggestion that salting roads might be contributing to the effect - some kind of embrittlement I think, but I cannot remember the details.

 

I would guess that it all comes back to trying to make all the components of cars lighter, but I don't really know much about it.

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Good point.

 

Apart from all the pot holes in my area on my trip down south on Monday they had closed the inside lane in one place on the M42 to repair the surface that was just falling apart. Also, on the M25 they had got a rolling road block whilst they did an emergency between 17 and the M40 ( fortunately on the other side ), there were two men furiously digging with forks or spades.

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I suspect the reason for springs failing is due to the fact that they are made in smaller diameters for packaging reasons. It could however be due to the use of dirty chinese / indian steel, which contains a lot of impurities such as slag and oxides. The impurities cause a locally high region of stress, which can set off fatigue cracking.

 

I'm a metallurgist by trade, but i haven't had the opportunity to examine a broken spring to see for sure.

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If they don't start really maintaining the roads properly, everyone will have no choice but to drive 4x4's and I don't mean those stupid Chelsea tractor types.

Big stinking diesel block and great knobbly tyres that will chew up everything in it's way  :angry2: That'll stuff up the climate control freaks.

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>everyone will have no choice but to drive 4x4's

Or hydraulic Citroens :-) which means you can also lower the vehicle to make cat. converters (and under-slung spare wheels) much harder to steal - 4x4s are prone to those issues.

 

I was going to go for a C5 rather than a Renault Scenic, but the 'boot' is too low to put Christophers' trike in. 

 

ttfn

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Vag group springs are know for snapping....what year was this Ibiza?  2000-2005? :thumbsdown_anim:

 

 

I usually drive around pot holes :whistle:

 

I've driven VAG group cars for the past 10 years and had 1 broken spring on the rear of the Altea, and that was at 140k miles, mainly because the wife loaded 150Kgs of marine salt in the back and drove off with all the weight on the rear axle.

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