These days with the popularity of Pinewood Derby® racing and the information available on the internet, most racers in competitive Youth races already know the importance of wheel and axle preparation along with proper weight distribution. Therefore, to finish first in these competitive races, the Race Team needs to also focus on both Alignment and Aerodynamics (discussed in the next article).
Alignment refers to the arrangement of the wheels and axles in the car body in relation to each other and the body itself. Three areas on a Pinewood Derby® car must be aligned; failure to do so leaves speed on the track!
This chapter covers Alignment in detail; however, an animated video that presents the same information is available here:
Key Alignment #1 - Rear Wheels
The rear wheels should be set at a 3-degree angle (camber). This angle reduces friction as only a tiny portion of the wheel makes contact with the track. Plus, the angle makes the wheels migrate outward on the axle, rubbing against the axle head rather than the higher friction-prone body. Additionally, the wheel riding against the axle head stabilizes the wheel and helps prevent wiggling. The axle holes (and, therefore, the wheels) must be at the same height, and precisely aligned to each other.
The rear wheels must be parallel to each other and the car body. Additionally, the wheels must be located directly across from one another. Finally, if rules do not prohibit, the rear axle holes should be placed 5/8ths (0.625) of an inch from the car’s rear. Moving the rear wheels increases stability and maximizes speed by keeping the rear wheels on the hill of the track longer.
If the wheels are not parallel, they will be in a toe-in or toe-out orientation or a combination of these two. These orientations create a situation where the rear wheels are no longer in sync to steer in the same direction, increasing friction at the axle head and the contact point between the wheels and the track.
Key Alignment #2 - Fore/Aft
To ensure proper alignment, the front and rear of the car need to be level with each other. This is measured by comparing the distance to the track (or another flat surface) at the front and back of the car (providing the bottom of the car is flat).
However, running a three-wheel rail riding setup requires a canted front wheel; this tilts the wheel and raises the front of the car.
When the front of the car is higher than the rear, it causes a toe-out orientation on the rear wheels, increasing friction and allowing air to enter the back of the wheels, slowing the car.
Additionally, the higher front end increases the aerodynamic profile of the car, exposing a larger surface area to the airstream allowing the airflow to push against the bottom of the car, reducing the weight born by the front wheel and therefore decreasing stability.
The front axle hole needs to be placed at a precise amount higher than the rear axle holes to eliminate the problem of the front of the car being higher than the rear. This placement ensures the rear wheels are not in a toe-in or toe-out position.
Key Alignment #3 - Side to Side
The front wheel steers into the rail to stabilize the car. A stable car is much faster than one that wiggles. However, if not addressed, the rear wheel on the same side as the steer wheel will also rub the center rail creating additional friction that yields no benefit.
To eliminate this problem, the front of the car body where the wheel is attached is cut in or notched a precise amount, enabling the rear wheels to be an equal distance from the center rail. This notch ensures the rear wheels do not rub the center rail or go down the track slightly sideways, increasing friction and slowing the car.
Solving the alignment problem
Properly aligning the car can be difficult. However, Key Alignment #1 (rear wheels) can be solved using one of several drill fixtures on the market.
Key Alignments #2 (fore/aft) and #3 (side to side) are more difficult as they interact. First, to level the car front to back, you need to drill the front axle hole a precise amount higher than
the rear. Next, however, you must bend the steer axle precisely relative to the hole height to ensure the car is level. Additionally, the amount of the axle bend affects the amount you need to move the steer wheel inward toward the middle of the car by notching the body.
Here are the three elements that must be precisely calculated and implemented in order to solve Alignments # 2 and 3:
Achieving these parameters using traditional tools can be difficult. However, tools are available that address each critical area and ensure the holes are drilled in the correct locations, the body is notched the correct amount, and the axle is bent to the correct angle. They are available here and here!
PRO RACER TIP FROM DWS Racing: It is better to have the front of the car slightly lower than the rear, versus the front slightly higher than the rear. If you cannot precisely set your front hole height to achieve level condition, err on the side of caution, and place it so the front of the car is slightly lower. Lowering the front of the car is accomplished by raising the front hole height (or decreasing the bend in the front axle).
Articles in this series (click to read):
- Learn Pinewood Derby from the fastest racers in the world!
- Purpose of Pinewood Derby
- The Foundations of Pinewood Derby Speed
- The Keys to a Fast Pinewood Derby Car
- Pinewood Derby Rules
- Anatomy of a Professional Pinewood Derby Rail Riding Car
- Pinewood Derby Wheel Preparation
- Preparing Pinewood Derby Axles
- Proper Pinewood Derby Car Weighting
- Pinewood Derby Car Alignment
- Pinewood Derby Car Aerodynamics
- Pinewood Derby Car Body
- Pinewood Derby Car Lubrication
- Pinewood Derby Car Assembly
- Questionable Pinewood Derby Information
- Pinewood Derby Race Day
- Pinewood Derby League Racing
