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Combined Anti-Droop Anti-Roll Spring

Promote even ride height, anti-roll and off road performance with one extra spring
  [vote for,

Almost every vehicle faster than a trotting horse is equipped with some form of suspension. Many have been developed but all share a common feature, the wheels are able to move independently of the rest of the vehicle. To achieve this trick more than once, every system so far has employed a spring. Wheel hits bump, wheel moves up, compressing spring. Wheel goes over bump, energy stored in spring returns wheel to original position. Simple.

Sadly, springs are efficient, and the above scenario isn't the full story. Wheel hits bump, wheel moves up compressing spring, spring exerts upward force on vehicle... vehicle begins to move upward, wheel passes bump and spring pushes wheel downward, while the car is moving up still. The result is a rather nasty oscillation and the vehicle bounces around for some time.

To stop the oscillations, most vehicles use dampers. Usually this is just a piston with holes in, moving through oil. This wastes energy, and the oscillation reduces in amplitude quickly. There are sophisticated ways of changing damping, lots of different valves, even oils that change their viscosity in response to a switched electomagnet.

Springs are less sophisticated, they come in two flavors, linear and progressive. A typical car will have linear coil springs* rated at something like 100kg/cm. When lowered onto its wheels, the car will sink a few cm into its suspension travel, partly compressing the springs. This is an important feature, it gives the car negative travel, so the wheels stay on the road while traveling over slight hollows or allowing the inside wheels to stay in contact with the road while cornering.

There is a problem however, imagine you are driving around the outskirts of Knutsford, Cheshire, not too far from Plumley. You find that hump-backed bridge over the railway, now, at 32mph you will get a fun roller-coaster type experience. At 58** you tend to take off***. Now, in many recently rented vehicles you may hear a "clunk" as the recently rented vehicle is carefully guided onto the correct side of the road mid air.

The "clunk" is because the spring is many times more forceful than necessary to extend the suspension.

Now, the most basic type of spring-damper shock absorber looks like this <link>. My solution is to add another spring, in this example, below the piston which is just about engaged at normal ride height. Now, the main spring IS able to fully extend the piston, but as it does so, the second spring compresses antagonizing the main spring, meaning that the effective spring rate of the main spring reduces in a non linear manner as the suspension extends in "droop" i.e. below the normal ride height. This means that the car sits at its correct ride height with the springs forming an energy hill on BOTH sides of the suspension travel, provided the car is on the ground. Should the car leave the ground, the suspension will extend with much less force while being transiently more lenient on landing.

In addition, this system will also perform a similar role to the anti roll/sway bar but without the additional components. The system will need less damping because the normal ride height is more energetically stable, the car will also have a much more stable ride height with changing loads without the horrid unloaded performance of progressive springs.

*linear coil, sew the seeds of confusion. ** National speed limit road, caught me totally by surprise officer, nothing to see here. *** Because the bridge also kinks to the right, and you can't turn in the air, the safe thing to do is take off on the wrong side of the road.

bs0u0155, Sep 20 2017

Basic shock-spring design http://www.towerhob...rad26_shock_550.jpg
[bs0u0155, Sep 20 2017]


       // outskirts of Knutsford, Cheshire, not too far from Plumley. You find that hump-backed bridge over the railway, now, at 32mph you will get a fun roller-coaster type experience. At 58** you tend to take off***. //   

       So, not the bridge at Plumley station (which is fairly forgiving), and the one on Sudlow lane is an underbridge ...   

       <peers at map>   

       The Chester-Manchester line, or the Crewe-Stockport line near Goostrey ? Our email address is in our profile.   

       The idea is interesting. How about combining leaf and coil springs ?
8th of 7, Sep 22 2017

       Ah yes - I know just the one you're referring to. The one that's name must not be named ....
normzone, Sep 22 2017


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