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anhtho
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In some motorbike engines, I notice there are two springs (inner and outer) for a valve. Why do they have to make it two ?
Thanks
Thanks
In engine valves? Can you specify which bikes too?anhtho said:In some motorbike engines, I notice there are two springs (inner and outer) for a valve. Why do they have to make it two ?
Thanks
Many "classic" British motors have double valve springs. Triumph, Norton, Vincent, etc. I don't know firsthand about newer / Japanese designs. I was always told the springs rub slightly creating a damping effect, preventing valve float (as Doug says above). They don't rub much though, once they kind of polish each other. So maybe the two spring constants have an effect on the resonance other than the purported rubbing/damping.which bikes?
This written in 1948, I don't know if today's modern engines use the duplex springs. Probably metallurgy has moved along in the intervening decades and modern springs don't fracture the way they did in the 1940s. Maybe someone can comment on the current valve springs?P.E. Irving in Tuning for Speed said:After 1945 there was a change back to coils, largely because of the difficulty of enclosing hairpins without serious interruption to air-flow through the head fins, particularly on a parallel twin. Coil-spring fracture is mainly caused through "surging" or a state of rapid vibration of the centre coils; all modern coil springs are duplex with not more than six free coils in the outer. The inner spring often has one or two more coils of lighter gauge wire and it is an advantage for it to be a push fit within the outer one as this provides a certain amount of friction damping and so helps to prevent surging.
The first engine that I ever worked on (1970's small block Chevy V8) had a flat strip of steel wrapped around in a tube shape type of inner spring. I tried taking the inner spring out once and it was quite difficult to twist the inner spring in order to get it to move from within the outer spring. The strip was about twice as wide and half as thick as the outer round coil wrapped the opposite direction. I estimate that adds up to quite a lot of dampening! The last one I built about 10 years ago had larger valve diameter with a smaller stem and guide with high performance single coils, and a roller cam and rockers of course.Randy Beikmann said:I've wondered about the damping between the springs myself
A double valve spring is a type of valve spring used in internal combustion engines. It consists of two springs nested together, with one inner spring and one outer spring, to provide extra support and strength to the valve.
The main benefit of using a double valve spring is that it provides increased durability and reliability compared to a single spring. It also allows for higher engine speeds and more aggressive cam profiles, resulting in improved engine performance.
A double valve spring is typically used in high-performance engines that require extra support for their valves. This includes race cars, high-performance street cars, and heavily modified engines. It is also commonly used in engines with higher than stock lift camshafts.
Double valve springs differ from single valve springs in that they have two springs nested together, whereas single valve springs only have one spring. This provides increased strength and support for the valve, allowing for higher engine speeds and more aggressive cam profiles.
No, not all engines are compatible with double valve springs. They are typically used in high-performance engines that have been modified for increased power and speed. It is important to consult with a professional mechanic or engine builder before installing double valve springs in your engine.