Taking The Stairs
I live in what's called a "ground-level apartment". For some reason my "ground-level apartment" has a flight of stairs leading up to the front door. This usually isn't a problem, especially since stairs are equivalent to 18 calories - twice a day, say 300 days a year that's, 10,800 extra calories burned a year. Not bad. It becomes more of a problem when groceries or laundry is involved. I drudge through the routine every week. Hamper with strap slung across my back, magnetic swipey card in one hand, giant value sized bottles of detergent and softener in the other. I would skip the softener all together, but the wife is convinced socks just aren't as lovingly embracing without it.
Last week, I found myself in possession of the normal loads of whites, wadded up socks and undies on top of dusty jeans heading down to the community laundry room. While descending the stairs I became distracted thinking about malliard reactions and sides of onion rings. A slight miss step and my heel is sliding perilously off the edge of one the wooden stairs, down onto the next. The sudden acceleration caused my body to pivot sideways and obtain a slightly horizontal attitude perpendicular to the path of the stairs. The hamper full of boxer shorts and frilly girly things swung precariously over my head while my feet struggled to find solid ground between solid ledges and the oblivion of the next step. With balletic and ballistic self-preservation I swung the giant bottles of snuggly summer fresh chemicals around my body as counter weights to change both my center of gravity and act against some of the acceleration forces I was currently experiencing. I believe I completed two full pirouettes of cartoon-like boxer-blinded colorsafe swinging before finally finding terra-firma and coming to a relative stop. I say relative due to the fact that it is near impossible to stand still as you are spinning to see how many of your neighbors see you standing in the middle of what looks like a Victoria's Secret sidewalk sale at the bottom of your stairs. It's hard to look cool after sliding down your stairs with your wife's undergarments draped about you.
The important thing I took away from this was how useful the heavy bottles of detergent were in adding stability. It occurred to me that perhaps a mass damper has more use than just in racing. In previous seasons, Renault experimented with devices that actually controlled the movement of the body of the car rather than just controlling suspension movements. This seems like an obvious goal of any car dynamicist, but in reality most suspension systems on cars are designed to control wheel movement and we hope that the cars inertia will keep the body stable.
A mass damper is basically a weight mounted between two springs, connected to the body of the car. As the body moves, the weight wants to stay in the same place and the spring rate pushes the body back into place. All the force acts on the body; the suspension isn't involved at all. It sounds easy, too easy and if it were, every car would have mass dampers in both the front and rear.
Truth is, harmonic dampers have been used for years. They stop vibrations in engines and driveshafts, they aren't generally used in the body of the car. The big problem comes in tuning the entire system. A mass mounted between two springs will have a natural frequency were it resonates. Basically, it shakes back and forth and it will shake the body of the car worse than without it. You can tune it with damping and spring rates. Since we want to be able to react to different frequencies of vibrations caused by different road conditions, suspension set-ups and even tires, it would need to be an active system. Maybe something similar to electro-magnetic suspension. Or possibly using electro-active elastomers that change spring and damping rates by varying current or field.