Building the Four-Wheel Rail Rider.
Do your rules require you to have “four wheels touching”? This is a process that I came up with to allow a car without a raised fourth wheel to function as a “rail rider.” The kids won many pack and council races with this method. It is the result of many hours of trial and error and track testing, and I am very confident in the effectiveness.
Important Note: This guide presumes familiarity with the workings of a “regular” Three-Wheel railrider, and the use of a tuning surface to set drift numbers.
It is important to understand how a Four-Wheel rail rider differs from a Three-Wheel car, as the ride is somewhat different. With a Three-Wheel car, you have no resistance or interference from the raised wheel. This is not the case with a Four-Wheel car.
Recessing the Front, Dominant Wheel
To begin with, you need to determine the dominant rail-rider wheel for the car. For many people, this is the front, right-side wheel. Just as with a Three-Wheel rail rider, you must recess the wood/axle-hole area about 1/16th of an inch. A convenient way to mark the size of the area that needs to be shaved is to use the width of a wheel, and add 1/8th of an inch to each side. Then shave or sand the recess to 1/16th of an inch deep.
Canting the Front Wheels
When the rules require you to have four wheels touching, finding a way to build an effective rail rider becomes less straightforward. The issue becomes finding a way to ride the rail with four wheels touching, and to do so in a fashion that you do not sacrifice speed, or violate your rules.
One issue that you’ll run into is that the front dominant wheel will need a small amount of cant and toe, in order to drift towards the rail. The more bend that you put in your axle, the more cant you will achieve. Since the cant on the front (positive) is opposite of the cant on the rears (negative), this causes the front end of the car to raise somewhat, in relation to the rear. For the non-canted front (opposite the DFW), this can cause it raise from the ground, and fall outside of the “four wheels on the floor” requirement.
One approach that some people take is to drill the front axle holes a little higher to compensate for this. This can be tricky, however. If you drill the holes too high, or too low, and you can end up with a lopsided front end, or an overly canted non-dominant wheel that either doesn’t touch the track, or rolls into the body when the car rolls forward and causes friction losses.
I am proposing a simpler and easier approach to a Four-Wheel rail rider.
The Dominant Front Wheel
The dominant front wheel on a Four-Wheel rail rider is going to need some cant and toe, but less than you use in a Three-Wheel rail rider. You often hear about using 2.5 degrees or more for a Three-Wheel rail rider. Using that much cant for a Four-Wheel rail rider will cause the non-dominant wheel to either not touch the track, or to ride the body constantly. For a Four-Wheel rail rider, you will want a smaller bend on your axle.
The obvious question to follow is “How much bend do I want?” The problem is that there isn’t a simple answer. Simply put, your car is a custom, one-of-a-kind build, as opposed to an identical model that just rolled off of an assembly line. The amount of cant that you’ll want to use is going to vary.
What I always had to do was prep additional axles. Yes, this is a bummer, but it makes it much easier than trying to adjust the bend on a single axle. I recommend producing axles in the following range for use on the dominant front wheel:
- Axle bent at 1.2 degrees
- Axle bent at 1 degree
- Axle bent at 3/4 of a degree
One method to obtain these bends is to use the Pro Rail Rider tool. It has two sizes: 1.5 degrees and 2.5 degrees. To get a varying degree of bend, you can use a lighter tap with the hammer. Another method is to add one more pieces of paper between the Axle Press and the Rail Rider tool, which will also reduce your degree of bend.
Now you have three axles with three different degrees of bend. The goal is to have your car drift with the dominant wheel. However, it will not do all of the work, only about 3/4’s.
Drift numbers will vary, depending upon track type and length, and the weight and axle placement of the car. However, 3.5 inches of drift over four feet is a safe starting place for this tutorial.
Set up your tuning surface so that you have a four-foot line going one way, and, at the end, another parallel line going across, marked with measurements. Using the bent axles you prepared, adjust your toe and cant until you get about three inches of drift from your dominant front wheel. Why 3, instead of 3.5? Recall that we only want the DFW to do about 75-80% of the work for the drift. We’ll leave the last half inch of drift to be taken care of by the non-dominant front wheel.
(Still following so far? It’s a lot to read! Sorry, folks!)
Non-Dominant Front Wheel
Recall that we produced three bent axles for our previous step. I recommend starting with the axle with the least amount of bend for the the non-dominant front wheel, in order to give it a little bit of toe-out.
In order to tune the non-dominant front wheel, you can remove the dominant front wheel and run the car down the board to achieve a drift of 1/2″ over four feet. Adjustment for the non-dominant front wheel is the same as for the dominant front wheel, twisting the axle to produce more or less toe, as needed.
If you use too much cant on either of the front wheels, you may end up with one of the wheels not touching. Because of the positive cant on the dominant front wheel, rotating the axles too far can cause the front end to lift.
Since both front axles have some degree of bend, you can try rotating them forward or backwards to get both wheels to touch.
Be sure to double check your drift numbers, and adjust accordingly.
Beware of too much toe-out on the non-dominant front wheel, as this can slow your car’s potential top speed.
By now, you should understand the concept of how a four wheel rail rider works, and how to go about building one. I did not go into rear canting, but just focused on the front end, for the purpose of this tutorial.
If you have a track and timer, you can experiment with different drift numbers, but the ones we used should give you a good standard drift that will work well for most applications.
I have found that by having the axle gap on the dominant front wheel wider than the axle gap on non-dominant front wheel, it helps to reduce problems during the track transition section. I recommend about twice as much gap in the DFW compared to the NDFW.
If your dominant front wheel and non dominant front wheel are not properly aligned, they can exert pulling forces on each other during the race, and cause the wheels to pull out somewhat. To avoid this, make certain that the axles fight tightly in their holes, or add a dab of elmer’s glue to secure them.
Perfecting four wheel rail riding will take time and practice, but you will improve with experience. Done right, this car will almost always be faster than non-four wheel rail rider!