Polymer's Guide to Knex Bobsled Tracks

Welcome to my guide on using Knex Bobsled Track components. This was a 5 month long project I decided to start on the side while I was waiting form more parts to update my ball machine Distortion Field. I created a total of 24 different files in Inventor, which were separated into 3 categories: Left Oriented, Right oriented, and Straight Oriented. Each category has 4 piece types each with a normal height and raised height. (So a total of 8 pieces for each category)

In total, there are probably 8 track types, excluding direction and height. (I contained a brief description):

• No slope - (Flat track piece)
• Straight Slope - (The standard piece)
• Curve - (Any track that veers to the Left or Right)
• Starting curve - (A transition from a Straight Track piece to a Curved piece)
• Ending Curve - (A transition from a Curved piece to a Straight Track piece)
• Direction change transition - (The S piece)
• Downward Curve - (A transition from a Flat Track piece to a Slope piece)
• Upward Curve - (A transition from a Slope piece to a Flat Track piece)

All you need for this Project is:

• Access to a 3D Printer
• Any kind of 3D Filament (Preferably one that will not shatter when bent slightly)
• Sandpaper
• A drill bit
• The Set of Bobsled Track files I have listed below for your use

When these tracks, make sure that you have supports enabled, Infill at 100% ,and print the pieces standing up like it is mounted on a frame. Apply only a thin enough layer of glue in a few areas of the build plate and do not over do it or the piece may be extremely hard to remove. Once your part is removed, carefully remove the supports and sand off any filament bumps, then test the holes to see if they fit the Knex rod. If not, sand the area slightly and repeat the process until it fits.

Note: If you are planning on having a smooth surface and you know how to use epoxy, I have an epoxy resin kit I would certainly recommend checking out:

Epoxy Resin Kit (Safe for 3D prints): https://www.amazon.com/dp/B0872SBPKD?psc=1&ref=ppx_yo2_dt_b_product_details

Silicone Epoxy Brushes: https://www.amazon.com/dp/B07TFS1DDQ?psc=1&ref=ppx_yo2_dt_b_product_details

To create the frame for a single bobsled piece, It is fairly simple, but there are multiple patterns that can be used if you don't have as much of 1 specific piece. In this example, I use two Patterns. (One with blue connectors and one with yellow connectors)

A very important thing to know about these track pieces is that there is a normal height and a (Raised) height for every piece type, and the reason is that I created the slope for the tracks to travel down 1 green rod height with every 2 red rods' distance traveled. That said, each Normal-height piece must have a Raised-height piece beside them, and the reverse. (Basically a 01010101 pattern). However this does not mean that two tracks of similar size cannot be placed beside each other as it is possible, but compensation for the structure will be needed. I have a good example of this in the later steps.

I also made an assembly clips to demonstrate how the pieces are supposed to be connected together, along with a few pictures of how the tracks should be mounted using the 4 pegs. Also to note, In the examples I did not push the pegs all the way down because it would be pretty hard to remove them from all of the pieces used in the example. Just thought I should throw that out there.

Sometimes when a track piece is made, there may be a really small gap that can be formed from bumps in the filament, or a bit of warping so when the pieces get pressed together, one may be a millimeter or two below or above the previous piece. All you need to do is apply a bit of sanding to the edge of the part on both sides, or simply press the piece down while it is sitting tightly against the second track.

Here are all of the working track combinations that I know so far.

Below are a few examples of different types of track patterns I have put together to help you out when coming up with frame designs. Each part type is included in these physical examples except for the flat track pieces and the ramps as I have not yet made any. However, the ramps do follow the same principles as the rest of the tracks: (There must be a raised track and a normal height track beside each other, or compensation for size must be created). As for the flat pieces, the same size is okay, since there is no slope.

Note: This is just an Inventor Assembly, therefore I am only accounting for the pieces used in the pictures. (Building the framework exactly like the picture will not stand on its own so it is recommended to reinforce the support below the tracks).

Parts list: Flat Track (Inventor Example) [As Seen In Picture]

---Bobsled Track Components---

Straight Upward Curve Transition: 2

Straight Downward Curve Transition: 1

Straight Slope (Raised): 1

No slope (Flat): 1

---Rods---

Red/Metallic Green 128mm rods: 17

Yellow 86mm rods: 5

Blue 54mm rods: 32

White 32mm rods: 20

Green 16mm rods: 28

---Connectors---

7-way 3D-connectors: 48

4-way 3D-connectors: 20

1-way connectors: 24

Total:  199 Pieces

Parts list: Straight Track Structure Example

---Bobsled Track Components---

Straight Slope (Raised): 2

Straight Slope: 3

---Rods---

Red/Metallic Green 128mm rods: 4

Yellow 86mm rods: 9

Blue 54mm rods: 49

Green 16mm rods: 28

---Connectors---

4-way 3D-connectors: 52

1-way connectors: 24

Total: 171 Pieces

Parts list: Spiral Track Structure Example

---Bobsled Track Components---

Left Curve (Raised): 2

Left Curve: 3

---Rods---

Red/Metallic Green 128mm rods: 49

Yellow 86mm rods: 66

Blue 54mm rods: 65

White 32mm rods: 84

Green 16mm rods: 63

---Connectors---

8-way connectors: 26

7-way 3D-connectors: 21

5-way connectors: 70

4-way 3D-connectors: 95

4-Way connectors: 1

3-way connectors: 2

1-way connectors: 29

Total: 576 Pieces

Parts list: [ Shape Track Structure Example

---Bobsled Track Components---

Straight Slope (Raised): 1

Straight Slope: 2

Left Curve: 2

Starting Left Curve Transition (Raised): 1

Ending Left Curve Transition (Raised): 1

---Rods---

Red/Metallic Green 128mm rods: 20

Yellow 86mm rods: 32

Blue 54mm rods: 82

White 32mm rods: 32

Green 16mm rods: 44

---Connectors---

8-way connectors: 8

7-way 3D-connectors: 51

5-way connectors: 8

4-way 3D-connectors: 62

4-Way connectors: 2

1-way connectors: 36

Total: 384 Pieces

Parts list: S Shape Track Structure Example

---Bobsled Track Components---

Left Curve (Raised): 2

Left Curve: 1

Right Curve (Raised): 3

Right Curve: 1

(Right to Left) Curve Transition (Raised): 1

---Rods---

Red/Metallic Green 128mm rods: 27

Yellow 86mm rods: 116

Blue 54mm rods: 111

White 32mm rods: 74

Green 16mm rods: 49

---Spacers---

Grey Spacers: 8

Light Blue spacers: 8

---Connectors---

8-way connectors: 35

7-way 3D-connectors: 33

5-way connectors: 68

4-way 3D-connectors: 75

4-Way connectors: 1

3-way connectors:  4

2-way Ladder-connectors: 4

1-way connectors: 46

Total: 667 Pieces

Parts list: Same-Height Track Structure Example (Straight)

---Bobsled Track Components---

Straight Slope: 3

---Rods---

Red/Metallic Green 128mm rods: 9

Yellow 86mm rods: 18

Blue 54mm rods: 50

White 32mm rods: 34

Green 16mm rods: 20

---Spacers---

Grey Spacers: 8

Light Blue spacers: 8

---Connectors---

8-way connectors: 4

7-way 3D-connectors: 4

5-way connectors: 27

4-way 3D-connectors: 36

3-way connectors: 6

1-way connectors: 16

Total: 243 Pieces

Parts list: Same-Height Track Structure Example (C Shape)

---Bobsled Track Components---

Right Curve Raised: 3

---Rods---

Red/Metallic Green 128mm rods: 14

Yellow 86mm rods: 52

Blue 54mm rods: 55

White 32mm rods: 26

Green 16mm rods: 30

---Spacers---

Grey Spacers: 8

Light Blue spacers: 8

---Connectors---

8-way connectors: 16

7-way 3D-connectors: 16

5-way connectors: 23

4-way 3D-connectors: 38

4-Way connectors: 1

3-way connectors: 4

1-way connectors: 16

Total: 310 Pieces

Parts list: Bridge Track Structure Example

---Bobsled Track Components---

Straight Slope (Raised): 1

Straight Slope: 1

Ending Right Curve Transition (Raised): 1

---Rods---

Red/Metallic Green 128mm rods: 4

Yellow 86mm rods: 29

Blue 54mm rods: 58

White 32mm rods: 8

Green 16mm rods: 20 

---Connectors--- 

7-way 3D-connectors: 4

5-way connectors: 4

4-way 3D-connectors: 64

1-way connectors: 12

Total: 206 Pieces

Well, I hope you enjoyed this knex guide, and if you have any questions, feel free to message me on discord at PolymerTech#9953, or if you want to join the Knex Flux Discord server, The link will be right below:

My Youtube Channel https://www.youtube.com/channel/UCs8CY8ejPZnWtg7TJnYzJow

KnexFlux Discord: https://discord.gg/wBDQvdq

r/Knex Reddit: https://www.reddit.com/r/KNEX/

Stay tuned for more upcoming guides! :D