Miniature Load Cell for measuring slipstream in speed skating
How much power can drivers actually save in the slipstream? A student project.
In fast endurance sports such as racing, hand biking and speed skating athletes often race in groups. The people behind the leading athlete can take advantage of the slipstream and thus save power. A student from Maximilian-von-Montgelas-Gymnasium in Vilsbiburg has examined this effect in more detail using one of Althen's miniature load cells.
First, the heart rates of the ice-skaters were examined in different positions, so that they can end the race with a lower load and thus, less power. Saving energy this way has proven to be quite difficult as recovery and individual skill play a major roll. The human body doesn’t work like a machine.
In order to look at the phenomena from a physical point of view and to determine the quantitative differences, force effects will be tested by using a model that consists of two cylinders that are placed on a plate on opposite sides of each other in a wind turbine. It was observed that the total force increased when the distance between the cylinders was increased. In addition, it was found that even the first driver has to spend a little less force when there is another driver directly behind him.
These results can be explained by the turbulence that’s created behind the body. Also, due to the crooked position of the cylinders, the force will increase faster with a short distance than with a longer distance between the athletes. Additionally, it was determined that the cW-value of the used cylinders was around four times that of a small car.
Structure of the Model
The load cell is mounted centrally on a flat surface in the front area. The surface has a hole in it, so that a another cylinder can be screwed on another position. The surface has wheels that roll over the rail of another equally large surface. It is constructed this way because now, the lower plate can be glued to the wind turbine while the other one is still free to move. Lifting of the top plate because of airflow is prevented by angles that make sure that the plate can only move horizontally .
Between the two plates is a force sensor "ALS251" from Althen Sensors & Controls is placed. A strain gauge, that bents when the top plate is moved by the force of the influx of air on the cylinder.