I once had an old LandRover that had an optional extra bolt-on flywheel mounted on the gearbox output shaft, consisting of a heavy iron ring rubber bonded onto the mounting flange. It's purpose was to absorb vibration, and to prevent take-up snatch in the long drive train. The improvement on fitting it was incredible.
I also had a car with a harmonic balancer mounted on the pulley end. This was of similar construction, and likewise damped vibrations.
So it's fundamentally an old idea, just not made very reliably.
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>>So it's fundamentally an old idea, just not made very reliably.
The big difference Cliff is that in the case of the DMF, the compliant element is part of the power transmission path. The devices you mention work as tuned mass absorbers, they absorb vibration stongly at one frequency, but there's no direct power transmission path across the rubber - the rubber's only driving a small metal ring, not the whole car!
It is that all the power must pass through the compliant element that causes all the trouble with DMFs. It's difficult to design parts which deform enough to absorb vibration and also have a decent fatigue life while handling full engine torque.
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The youtube animation is indeed brilliant.
Cars used to run smoothly without them though. Why is it thought that they no longer do?
It's true that modern cars are amazingly refined in feel. But isn't this expensive Heath Robinson way of making them so a step too far?
I don't like it as a general idea. It brings out the puritan in me, unlike most things.
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