Torsion Powered Vehicle

[kandrathe]

Agreed. Considering fatigue, springs are virtually guaranteed to fail in the lifetime of the car. Fatigue is a decrease in the yield strength of a material under a load over a given period of time. As the springs are held in torsion or twisted the metal will just keep getting weaker until the thing will eventually explode into twisted shrapnel. Of course increasing the number of springs will decrease the amount of energy stored in each one so failure won't be so catastrophic and replacing broken springs would be more practical.

Also keep in mind that the spring constant is not constant with deflection so this system is non-linear. A simple power calculation from 1/2*k*d^2 is not likely to be very accurate.

I was reading in one of the articles I came across that for some springs the concept of tired springs was a myth.Contrary to popular belief, springs do not appreciably "creep" or get "tired" with age. Spring steel has a very high resistance to creep under normal loads. Say, in a car engine valve spring typically undergoes about a quarter billion cycles of compression-decompression over engine's life time without noticeable change in length or loss of strength. The sag observed in some older automobiles suspension is usually due to the springs being occasionally compressed beyond their yield point, causing plastic deformation. This can happen when the vehicle hits a large bump or pothole, especially when heavily loaded. Most vehicles will accumulate a number of such impacts over their working life, leading to a lower ride height and eventual bottoming-out of the suspension.

I would think that fatigue would only be a factor in plastic deformation, not from operating within its modulus of elasticity. I imagine that the quality of the spring material itself also might be a factor though, where I could see that metals with larger granularity would fatigue faster than ones specifically crafted to be high tension springs. The design I'm thinking of would most likely fail by sheering the lever arm on either side of the spring coil resulting in the unwinding of the stored energy within a confined sleeve. It would be doubtful to result in any explosive effect other than a bang.