# Knee Speed/ Velocity Split for damper

1. May 6, 2015

### hackashack

Hey guys I'm trying to figure out the ideal knee speed or velocity split for a particular car that I'm designing. What I'm trying to do is relate the knee speed (or crossover speed) of my damper to the crossover point in the displacement transmissiblity graph so that I can achieve optimum comfort in most situations. Please refer to the .png files that I've attached. Any help would be very appreciated!

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2. May 6, 2015

### hackashack

By the way, what I mean by the crossover point of the transmissibility plot is at the square root of two for the frequency ratio.

3. May 6, 2015

4. May 6, 2015

### hackashack

That's exactly what I've just read actually. I've read the whole article but my only question out of that article is how to get that split mentioned. All the article said was "
if you’re feeling adventurous, correlate the crossover point on the transmissibility graph to a damper velocity as a split point to start from". My question is: how do you relate them??

5. May 6, 2015

### hackashack

I have basic knowledge on vibration theory as I've already taken a course on it but it didn't cover complex situations topics such as the one I'm asking. It only covered the theory aspect with the plots.

6. May 7, 2015

### jack action

Honestly, I've been looking at this many ways and can't see how you could correlate the two. The damper velocity is related $\omega A$ where $A$ is the amplitude of the damper displacement. So the same damper velocity can be achieved by a small displacement at high frequency or a large displacement at a low frequency. The displacement is a function of the road disturbance amplitude $Z$ as well as the transmissibility ratio (which is also a function of the frequency $TR(\omega)$). So you get something like $v = \omega TR(\omega)Z$. Even if you set $\omega = \sqrt{2}\omega_n$, there is still $Z$ that will affect the damper velocity.