K'nex Dragster

Here is my K'nex dragster; it is rather bulky so the acceleration is not all that impressive but there are some cool mechanics and it makes decent power.

Starting at the front, I used the smallest wheels possible to create a dragster look and minimize friction, and there is a simple steering system that locks in place for adjustments.

The body is nothing crazy, it is long and sturdy to provide the greatest distance for rubber bands. There are 4 series of bands, 2 of them power the axle (Picture and the other 2 provide power to each wheel directly (see pictures 5-8). Each group of bands travels roughly the length of the body 3 times.

The wheels have a unique ratchet system that allows the dragster to keep moving forward after the rubber bands have winded down. See the video for an example.

The axle is the length of a red rod and a grey rod; these rods are connected by white connectors and yellow rods which one rubber band series applies power to (Pictures 5-6). On one side of the axle there is a wheel with a larger radius which the other band applies power to; this one is the main source of torque (Picture 7).

The wing, in addition to looking cool, is a locking system for the axle. When pushed back it locks in 4 places along the axle, each place where power is applied. When pushed forward the wing releases the axle and lets the dragster accelerate forward. There is a simple locking mechanism to keep the wing forward when pressed as the acceleration and gravity would cause it to lock up as the axle spins.

Because of its weight, the dragster can't accelerate very fast but it makes a decent amount of power for a k'nex creation. On it's best runs it goes 3 meters in roughly 1.07 seconds, an average acceleration of 5.24 m/s squared. Weighing in at 2.32 kilos, this means the force is about 12.2 N and the work done over 3 meters is 36.5 Nm. This generates 34.1 watts of power, the equivalent of 0.0457 horsepower. This actually a lot of power for a k'nex car, and I stopped at this amount for a couple reasons: first I don't think the axle could handle much more torque; It has broken about 10 tan clips already in various trial runs. Second, I actually got a little wheel spin during a couple of my runs so I would have trouble getting any more power to the ground. I'm sure I could make a much faster car, it would just be much lighter and smaller. For now I am happy with this result, it looks awesome, has a decent amount of power and sounds cool as well!

Let me know what you guys think. I probably won't be posting instructions since the cool mechanisms such as the wheels are pretty simple to make from the pictures and video. Also, there are hundreds of ways to make dragsters using this concept, so you should experiment.

Lastly, I have to give credit to Sandroknexmaster for the wheel rim design. (He used it as a hoop in one of his ball machines) It happened to work perfectly for a ratchet system and it looks awesome on a dragster!