Answer:

There are differing opinions on how much rear cant is enough or too much. For me, there is no need to go more that 3 degrees. I usually use the Derby Worx axle press and rail rider tool and put 2.5 degrees cant in my rear axles. Its a fast and easy process and I know the degree I’m getting.

The only things you’re trying to do is 1) allow the rear wheels to migrate away from the car body and 2) get the rear wheels to roll on the edge instead of the flat tread. 2.5 to 3 degrees is really all that’s required to achieve both of those.

The only thing I remember from my Economics class in my first year of college is the Law of Diminishing Return. The professor used the analogy of how much money can the fast food Chicken Shack afford to spend on quality control to reduce the number of fried rats per 1,000,000 pieces of fried chicken. $500,000 per year in QC may be acceptable if you only end up with 100 fried rats per 1,000,000 pieces of fried chicken. How much more can you afford to spend on QC to get the number of fried rats to 50 per 1,000,000 pieces of chicken? Eventually you will reach a point to where you cannot pay more for QC because you will eat up (no pun intended) your profit margin and your return is reduced. The point is… the more you increase QC you will eventually reach a point of diminishing return.

Now what the heck does that have to do with too much rear axle cant? …I don’t remember.

Many experts agree that its best if the wheel hubs never touch the body at all.  The only way to accomplish this is to cant both rear axles.  We want to bend both rear axles up so that the wheels migrate toward the inside of the axle head and not the car body.  It is true that this process simply shifts the wheel friction from the car body to the axle head however, the amount of friction is greatly reduced.

You can bend the rear axles using the same methods discussed above in the Rail Riding section using Derby Worx Axle Press and Rail Rider Tool.  Depending on who you talk to, the amount of rear axle canting should be from 1.5 to 2.5 degrees.  The Derby Monkey uses 1.5 to 2.00 degrees canting on its cars.

After applying lubrication to the wheels and axles, install them with the location dot of both rear axles at the 12:00 position… or position your axle head groove in the vertical position.  Look at the car from the rear and make sure that the tops of the wheels are leaning in toward the body.

Gently roll your car on a flat surface and concentrate on the rear wheel hubs. If the hubs migrate toward the body and rub against it, then slight turn the axle with pliers of an axle head screwdriver.  Continue to test and adjust until the wheels migrate out and against the axle head.  Perform this with the car rolling forward and backward.

Try to make sure that each rear wheel is parallel to the car body… at least as close as possible.

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Answer: First, I will define center of gravity (COG) as it pertains to Pinewood Derby cars. What is Center of Gravity?

The center of gravity of your pinewood derby car is the distance that the balance point of the car is in front of the rear axles. This is sometimes referred to as the center of mass, COM or COG.

Many people simply tell you to just “put the weight in the back”. While that is true, there is a lot more involved in this process. Proper placement of the COG is crucial in order to have a fast car

The exact location of the COG of your car can be determined with the use of the Derby Monkey COG Quick Ref or as follows:

1. Set a ruler on its edge on a flat and level surface.
2. Carefully lay the car across the ruler.
3. Move the car back and forth until it balances on the ruler.
4. This balance point is the COG.
5. Measure the distance from the COG to the rear axles.
6. This distance is how we express the COG location on a Pinewood Derby car.

The perfect tool for locating the COG is with the aid of the Derby Monkey’s exclusive COG Quick Ref.

Where Do You Want Your COG?

There are many different opinions regarding where the exact location of the COG should be. However, every one aggress that you want it close to the rear of the car. Most publications recommend a COG of 1″ to 1½” in front of the rear axles. A more aggressive COG (shorter) can achieve better results under very good track conditions, while a more conservative COG (longer) is more appropriate for poor conditions. Most experts agree that a COG of 1″ to 1½” is too far forward. The faster cars seem to be built with a COG of a less than 1″.

The Derby Monkey Garage builds its cars with a COG of ¾” in front of the rear axles. Some builders even go with shorter COGs.

How fast your car goes on the first flat part of the track is based on the distance that the COG of the car actually travels before it reaches the curved part of the track. The weight mass of car with the COG in front will not have traveled as far when it reaches the curved section as the weight mass of a car with the COG in the rear. The farther the weight mass travels the more speed the car picks up on the first section of track.

Your COM should also be very low in the car. The lower the COM the more stable the car will be. That’s why tungsten plates attached to the bottom of the body can help create a very fast car.

Position the weights in you car so that you have the optimum COG. Tungsten is the best weighting material because of its density. This allows you much more flexibility in controlling your COG.

Most folks simply use a drop of glue in a hold drilled to the axle.  This system is no way near fool proof.  Often, the axle comes loose from the glue or the glues never make sufficient contact with the axle in the first place.  Also, if you decide to make any last minute adjustments after the glues has set, then that presents a whole new set of problems and additional steps.

The Derby Monkey Axle Lock Set Screw Kit is perfect for locking axles and protecting your Pinewood Derby car’s alignment.  This is the system that many professional builders use instead of placing a drop of glue on the axles. Simply drill a #44 hole underneath the body directly under each axle.  Insert the4/40 x 1/8″ set screws. Align the car. Tighten the screws.  Your alignment is now locked in place.

Experts agree that controlled rail riding will produce a much faster car. Yes, that’s right; if your car consistently rubs against the rail all the way down the track it will be faster. Here’s why: since it is nearly impossible to have a track that will allow a perfectly aligned car to run straight and not hit the rail. Invariably, any car will drift into the rail causing it to bounce back toward the other side. This generates a side to side movement, causing the car to repeatedly slam into the rail. This is a huge enemy of a speedster. Therefore, knowing that you will certainly be hitting the rail (evidenced by almost every video of a fast car that you study in slow motion) you should bias the car to hit the rail on the front dominant wheel side, as opposed to the raised wheel side, which incidentally is yet another kiss of death.

Now, you must decide if you want to tackle this alignment technique. Most new builders are afraid to try this because of the time and skills required. The Derby Monkey has simplified this process by creating an easy to understand eBook and kit to help you create a rail rider. So, you should consider the following items:

Instant Download eBook: How to Build a Rail Rider
Complete Rail Riding Kit: Ultimate Rail Rider Kit