Hi guys,
I know that threads about resonance dampers have been done to death on here, but I have an idea which I haven't seen before in order to make them quiet.
First let's look at how I see the "rattlers" working. Yes, "centrifugal force" does not really exist but I will treat it as a real force in this as it fits well.
Let's look at a single hole in the rattler:
Here you can see the metal pin inside of it's oversized hole. As the damper spins, the "centrifugal force" forces the pin outwards in the same way that a spring would. The pin centers in the hole to rest in it's natural position.
When a change in angular velocity happens, (I.e. It speeds up or slows down.) inertia forces the pin either to the left or the right. As the "centrifugal force" still exists pushing the pin outwards, the sideways force must overcome the outwards force in order to follow the curve of the hole and move sideways. This wastes some of the sideways force, dampening it:
If we were to represent this as a spring-mass, it would look something like this:
So the first method to make it quiet would be to turn it into the spring-mass system shown above, but this would be harder to make. This is actually very simelar to the split-flywheel separated by rubber method which I've also seen on these forums.
So how can we make the pin-based rattlers quiet ? Well first of all let's look at the hole. We don't need the hole to be round as the pin, when the damper is turning, should never be pulled inwards past the half-way mark. With this in mind we can change the cutout to be this shape:
The second thing that we can do is to line the inside of the cutout with a thin piece of rubber. This can be a thin-walled tube which has been put in a cutout of the correct size.
Is this idea new or has it been done before ?
Finally, as a bit of an aside - If I were to get a 60mm diameter bar of Delrin and cut a 30mm thick chunk from it, what would be the best way to clamp it to my CNC Router ? I only have a T-Slot table on it.
Thanks,
-Andrew.