## Calculating a specific percentage of critical damping

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Joined: Tue Jul 16, 2019 6:10 pm

### Calculating a specific percentage of critical damping

I found this equation to calculate 100% critical damping:
2*sqroot(kg*spring in N)
I'm working with a PC game that uses kg for vehicle weight, kN/m springs, and N/m/s dampers. Multiplying the 100% critical value by .55 or .6 for slow damping is giving good results, but I'm not certain if this is accurately giving 55-60% damping ratio. Can anyone confirm if it is, or if not and I need to stop being lazy and learn differential equations? Thanks!

Tim.Wright
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Joined: Fri Feb 13, 2009 5:29 am

### Re: Calculating a specific percentage of critical damping

The equation is right, but you need to use the effective spring stiffness at the wheel or the "wheel rate". To calculate this you need to know the spring motion ratio.
Not the engineer at Force India

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Joined: Tue Jul 16, 2019 6:10 pm

### Re: Calculating a specific percentage of critical damping

Like most games/consumer sims, springrate=wheelrate. LFS and probably iRacing are the only ones I know of that set spring rate within the suspension itself. The rest use dynamic alignment correction along a straight wheel path..

So.. 0.xx of 100% critical damping is accurately x% of critical damping? It's not some non-linear relationship? Differential equations are only necessary for determining the damping ratio of an existing spring/mass/damper system?

Itemfinder
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Joined: Tue Jul 16, 2019 6:10 pm

Ok, thanks!