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Details Matter: A well-built car can be slowed to a snail's pace by carelessly positioned screw eyes. Make sure they don't cause the guideline to bind on the car! More Tips |
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The items in this list are potential sources of rolling resistance. Be sure you test for each one.
- Surface friction between two surfaces moving relative to one another
– Examples include the wheels and axles, or the axles and car body. Test for spinning friction by rolling your car down a ramp and observing how far the vehicle travels. Another (perhaps less scientific) method is to spin the wheels while holding the car in an inverted position and note the time 
that has elapsed when the wheels come to a stop.
Experiment with different bearing materials or use a lubricant such as dry powder
graphite to improve performance.
- Improper wheel alignment – This happens when axle holes are not drilled straight. (Stated more precisely, straight
 means the holes should be perpendicular to the car’s longitudinal axis.) Roll the car forward on a flat smooth surface. It should go fairly straight. If the car veers drastically to the right or left, there’s a good chance the wheels are misaligned.
 Careless location of screw eyes – The guideline can actually drag on the body or wheels of the car as it moves down the track, causing a great deal of friction. Invert your car and thread an 18" length of monofilament line (fishing line) through both screw eyes. Pull the line taut, and move it back and forth. If the movement of the line is restricted, consider relocating one or both of the screw eyes.
 Wheel imperfections – Small imperfections from the molding process may be found on the rolling surface of a wheel. Examine your wheels and carefully remove any imperfections with fine-grit sandpaper.
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