Death Wobbles

Saul O. Ruiz

Physics is found all around us. When we walk, ride our cars, mow the lawn, in every aspect of our lives there are physics involved. Due to the resent growth of longboarding I wanted to show one of the biggest fears of many riders. Longboards are just the same as skateboards but are longer between 34-60 inches long and usually having bigger wheels almost up to 90 mm in diameter. The components of the board are reverse kingpin trucks, wheels, bearings and grip tape. The truck’s main components are the bushings, pivot cup bushing, axle, hanger and base plate. Most of the riders love going fast but there is a phenomenon that riders call speed wobbles, which takes away confidence from going faster. A speed wobble occurs when the rider is going fast usually downhill, and starts losing stability and the board starts wobbling and the board causes the rider to lose control and in most cases causes the rider to fall. Physics has a way of analyzing this phenomenon. What riders know as speed wobbles in physics it is called hunting oscillation. Hunting oscillation occurred long before skateboards where invented. Hunting oscillation occur in any system trying to find an equilibrium. That is why it is called hunting oscillation, it is an oscillation created when a system is not in equilibrium and it tries to hunt for equilibrium. One of the first recorded hunting oscillation occurred on the train tracks. Locomotive trains were reaching high velocities and started shaking side to side. It is an interesting note to mention that some locomotive trains started forming oscillations which made the locomotive shake from side to side and it would turn into a violent motion that damaged the track and the wheels of the locomotive train which caused derailment. And in later years they would create dampening suspension system that would allow the locomotive trains go faster without wobble. The actual wobble is a phenomenon called self-exciting oscillation which creates a sinusoidal wave which the amplitude grows with in reaching top velocities. What happens during longboarding at high speeds is the same as the locomotive trains it starts shifting from side to side after receiving the initial wobbles the system hunts for equilibrium and instead of being derailed you get bungeed out of the board. When riding longboards the two main reasons for wobbles are the actual rider and the lack of dampening. The way the board turns and the geometry of the trucks speed wobbles might always occur. Ways to defend against the speed wobbles is dialing up a correct setup with no bushing or pivot cup slop. Having the correct bushing hardness for your weight also helps. Even when having the “right” setup, you might still get speed wobbles. That’s when the rider comes into play; the rider is the most essential part of the problem. The usual problem with speed wobbles is the distribution of weight of the rider. Ways to correct the problem is that you want most of the rider’s weight in the front of the truck. A lower stance of the rider will also lower the center of gravity making him have more control and stability. Even when all this fails if you still get wobbles do not fight them, join them, what you want to do is relax, lean forward and ride them out creating a sine wave which returns the system to equilibrium. 

Unique Waves

Ramón Peluyera

Physics has revolutionized the world in unimaginable ways granting us the gift of knowledge throughout the ages. One of all the amazing and fascinating subjects of Physics that interest me the most is that of waves. Humanity uses it on a daily basis whether we are aware of it or not. Communications of all types are under the same category since waves are necessary for us to understand one another. Most waves have been discovered and studied by physicist and they are aware of their characteristics.  However recently, there has been news of a wave that does not travel uniformly, never seen before. This wave forms includes star shaped waves and even polygons shaped waves.

To understand how important this new discovery is one must first understand the work of a wave. Basically a wave is a flow that travels through a medium, a transportation method for example: air, water, etc. It transports energy like we have already studied in class, kinetic energy, with the exception of not transporting matter. The particles of the medium which are used to travel are moved from their original position, but then returns through equilibrium. 

Ordinarily the waves studied have been one’s who’s way of movement are linear or not uniformly linear, but this special case is rare to both cases. In the University of Nice Sophia in Nice, France Jean Rajchenbach and other colleagues were the discoverers of this new phenomenon. This new wave was made in an experiment by shaking with vibration causing frequencies that would jiggle a dish of silicone oil with a slow, but regular motion. This combination of movements would produce star-shaped waves with five or six sides. These are unusual patterns that are thought to spread out in non-linear motion between three or more separate waves. The mathematics theory behind this wave still not understood to the fullest extent. The star shaped wave appears in trays or disks of different sizes and shapes. Knowing this the wave shape is not affected by the container in which it is held, which is also a property of a wave’s shape.

Jean Rajchenbach and the team of his colleagues are developing completely new models describing this wave. According to Jean Rajchenbach the waves could be used as a relation with quasicrystals, which is an arrangement of atoms forming a structure with five fold symmetry. Further calculations suggest that the shapes of nonlinear forces are similar to that between gravity waves. Researchers hope for success in the experiment to lead to better perceptive on other nonlinear gravity waves like tsunamis. Some physicists assume that nonlinear effects could be responsible for rogue waves that are formed in the oceans. A great deal of work would go into another research for similarity between the star shaped wave with the rogue ocean waves, but thinking of the possibilities it would unimaginably effective for the entire world. Knowing the time or place a tsunami could occur due to the nonlinear similarity with the star shaped wave could save lots of lives as well. That is why expanding the knowledge from every new discovery is an important aspect of life and physics since knowing the basics is an essential part of physics.