This is the K'nex Ball Drop that I built based on the K'nex Ball Machine Element: No-axle Arm Drop by Thibault Art.
The 10 pictures in this section are just an overview of the project and are not part of the construction instructions.
There are 3 sections.
- The Base section which includes the ball exit ramp.
- The Middle sections, each with one drop arm.
- The Top section which includes the ball entrance ramp plus one drop arm.
I have also included images of the K'nex parts showing the colors that I use.
The wheels on the drop arms are used as counter weights, However, anything can be used in their place as long as the weight is the same.
In this model, I have used 4 different counter-weights to vary the speed that the arm drops the ball. The long grey rods as shown drop the balls at a much slower rate than the other two. You can see this in the video I created.
Step 1: Base & Exit Ramp
This is the base of the unit and includes 8 supports as well as the exit ramp for the balls. The two orange connectors and the blue rod are just there to stop the ball running off the ramp.
Step 2: Center Tower Sections
Very little to build here.
Step 3: Arm Drops
One Arm Drop is needed for each Center Section plus one extra for the Entrance Section.
My model had 3 center sections, so I needed to build 4 Arm Drops.
The counter-weight in this example consists of a yellow rod and a push-on 50mm racing wheel.
Two more examples are shown:
- Large wheel and blue rod.
- Small wheels plus connectors using a long grey rod.
Step 4: Combine Center Tower and Arm Drop
Very simple. Just connect the two white rods to the white connectors.
Do this for all the center sections you have built.
Step 5: Combine Base and Tower Sections
NOTE: When the exit ramp is facing to the right, the next section must have the counter-weight facing to the left.
After that, the counter-weights alternate (ie. right, left, right, etc.)
Step 6: Top and Entrance Ramp
This is the final piece. It includes the entrance ramp and the final drop arm.
Step 7: Finished.
Give it a try. Also play with the counter-weight rod length and weights to vary the speed that the balls fall through the Element.
The short rod counter-weights reset themselves quickly, while the long grey rods vibrate for a while after the ball has passed through. If the next ball comes through too quickly while the Drop Arm is still vibrating, then that ball might not fall as it should but could drop off to the side,