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Complexity level:
5
Project cost ($):
60
Time required:
1 hour for preparation, 1 day for science fair project
Material availability:
Easily found at a skateboard store
Safety concerns:

Basic safety requirements
 

Abstract

Why are some skateboards more expensive than others? One of the factors influencing pricing, is the quality (and consequently, the price) of its bearings. This science fair project aims to find out how the the quality of the bearings of a skateboard affects its performance. Tests will be carried out on 5different types of bearings

Hypothesis

The skateboard mounted with the most expensive bearings will travel the furthest..
 

Background

Bearings

Bearings work on the principle that an object will be easier to move by rolling than sliding. The motion of sliding is similar to skiing, where there will be a lot of friction produced. Friction will produce heat and also increase wear and tear on the surfaces. In order to slide, you will need to first overcome forces of friction. This friction can be reduced to a great extent by introducing rollers between the surfaces.

Bearings help to reduce friction and ease the movement between 2 surfaces. They make use of some metal balls that are placed between two smooth surfaces which consists of an inner ring and an outer ring. The metal balls help to carry the weight of the load and at the same time also allow the bearings to roll smoothly.

Bearings used in skateboards are subjected to a lot of abuse. This is because the skateboarders will normally push them to the extreme. Bearings will normally become weaker as their precision is improved. Therefore, when choosing the bearing for a skateboard, a balance must be sought between durability and precision.
 

Scientific Terms

Bearings, sliding motion, friction

Materials

The materials required for this science fair project are:

-    1 ramp (at least 2 meter long)
-    1 skateboard with changeable bearings
-    5 different sets of skateboard bearing (different brands and prices)
-    Tools required to change the skateboard bearings
-    1roll of measurement tape
-    1 roll of colored masking tape
-    1 long flat surface ( a flat path or basketball court)

Procedure

1.    The independent variable of this science fair project is the type of bearing used on the skate board. The dependent variable is the distance travelled by the skateboard from the ramp. This is determined  using a measuring tape. The constants (control variables) are the elevation of the ramp, the length of the ramp, the surface condition of the ramp and the floor surface.

2.    Purchase five different brands of skateboard bearings. Label them from A to E, from the  most costly to the least costly. An assumption is made that the bearing which is the most costly is manufactured with the greatest precision and is the smoothest.

3.    Fix the ramp on  the floor. Mark a horizontal line using the masking tape, 500m from the top of the ramp. This is  the starting line from which the  the skateboard shall be released.

4.    Mount bearing A on the skateboard. Place the skateboard behind the starting line on the ramp. Release it. Measure the distance travelled by the skateboard using a measuring tape. Repeat this 5 times. Record your results in the table provided below. Repeat Step 3 with the bearings labeled B to E. Record your results in the table provided below.
 

Observation

The more expensive the cost of the bearing,  the further the distance travelled by the skateboard.
 

Bearing brand used Distance traveled by the skateboard (meters) Average distance (meters)
  1 2 3 4 5
A 5.35 5.42 5.31 5.38 5.45 5.382
B 4.86 4.92 4.75 4.72 4.88 4.826
C 4.33 4.25 4.43 4.28 4.35 4.328
D 3.92 3.95 4.01 4.12 3.99 3.998
E 3.42 3.34 3.45 3.38 3.39 3.396

Plot your results into a graph, as shown below.

skateboard bearings science fair project

Conclusion

The hypothesis that the skateboard mounted with the most expensive bearings travels the furthest is proven to be true.

The more expensive bearings are normally machined to higher precision and smoothness. However, t more precise bearings are also less durable. Therefore medium priced bearings provide a good balance between smoothness and durability as they don't break as easily. Also Consider:

 

Also consider

This science fair project can be repeated using skateboards of different weights or designs.

Which ones travel the furthest? What about wheel size? How does changing the wheel size affect the distance/speed of a skateboard?
 

References

Build your own pro grade skateboard - http://skateboard.about.com/od/boardmaintenance/ss/ChoosingSkBoard_4.htm

Bearing (mechanical) - http://en.wikipedia.org/wiki/Bearing_(mechanical)

How bearings work? - http://science.howstuffworks.com/bearing1.htm
 

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