Digital Stock Car Stagger Device Ryan Roberts April 2, 2013
Background • The tool I am building will be used by me on my dads stock car team. I have a tool already that I use to measure the circumference of the tires. This tool is a stand with wheels on it that the tire spins on, while the tire is spun a tape measure is run along the surface of the tire to measure the circumference of the tire. The circumference of the tire is a very crucial measurement because this measurement is used to calculate the front and rear stagger of the tires.
Stagger Explanation • Stagger is the difference between the right side tire and the left side tire. The right side tires are larger then the left side tires by about 2-3”. Stagger is very important because it can determine the handling of the car. Usually we run 2 1/4” stagger in the front and 2 3/8” in the rear. More stagger can cause the car to become loose when cornering and less stagger can cause the car to be tight when cornering so this is a very crucial measurement that is needed. These measurements are needed every time the car goes out for a session and when it comes in from a session because as the tires are run they get hotter and air pressure builds up which changes the size of the tire. So I am measuring these tires multiple times which can be very time consuming and tedious.
System Diagram • My solution to this problem is a device that automatically measures the tire with a wheel when the tire is spun on the stand and the displays the measurement on a LCD screen.
Block Diagram HCS08SH Chip LCD Display 9V to 5V Power Supply LM2674 Optical Encoder Push Buttons
Power Supply LM2674-5 • High Efficiency 90% or greater • Step down buck regulator • Input Voltage 8 – 40V • Tested with 9V input measured 4.945V output. • Basically uses battery voltage half the time and stored energy from the inductor the other half.
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