10/04/2019

When Push Comes to Shove

Use the wrong type of damping and you’re just making matters worse…

In the war against vibration it’s often tempting to head for the most obvious solution. Springs or bobbins for example, may appear interchangeable and – once proven capable of supporting the load that the task requires – perfectly up to the job. But no two vibration challenges are the same. Spec the wrong solution and you could actually be making the problem worse.

Stop that Train

A spring will successfully compress to bring a load to rest. An example being within the chamber of a train’s buffers. A spring bears the increasing load of the slow-moving train, compresses and begins to push back, pushing back harder the more it is compressed, thereby bringing the carriage to a smooth rest. A spring always absorbs deflection and returns to a middle point – it’s resting point – once the load is removed. However, in compressing a spring you’re effectively loading it with energy, enough energy to not only return to that resting point but also to exceed it.

In our train buffer example, the springs used are perfect for the job in that the train compresses the spring but is not ‘thrown’ backwards as the spring then pushes back and expands because the weight of the train is resisting the unloading of the spring. In a coupled system – without such resistance – a spring would move forever, the energy of compression being released past the resting point before the energy of the ‘stretch’ pulls it back… and forth… forever… But gravity and other external real-world forces stop this perpetual motion. Getting your damping right is the key to success.

A damper absorbs energy from the system. Imagine a Newton’s cradle operating normally in air. The air resistance and forces of gravity that prevents the cradle from swinging forever – they are our damper. Imagine the same cradle in water. The water provides even more friction – damping – and will bring the cradle to rest even quicker.

Truck Stop

We were asked to solve a problem involving a heavy load within a moving truck. Under heavy braking the springs used compressed successfully, but when at rest they expanded setting up a vibration back and forth despite the truck no longer actually moving. The mount was causing more vibration than if it wasn’t there!

The solution was to refine the measures used and through intelligent damping absorb the precise amount of energy generated in the system. No more, no less. We used our years of experience and knowhow to spec a solution perfectly tailored to bring the load to rest in a controlled way every time the truck accelerated or braked.

Need a similar thoughtful, custom solution? Let us make it perfect for you. Why not give us a call? Tel: +44 (0) 1985 219 032