Potato cannon HEAT-FS tank round

The model

This model is a potato cannon projectile that is modeled after a so-called HEAT-FS round, meaning “High Explosive Anti Tank - Fin Stabilized”. 

The round has an outer diameter of 49mm. The drag made from TPU can be added for stronger sealing, so the pressure of the cannon cannot escape around it. The model itself should be scalable, though, I have not yet tested that myself.

In addition to the printed parts you will also need a rubber band or two that make the fins deploy automatically.

Assembly

Firstly, print all the pieces. You can decide if you want a hollow nose cone or a solid one, and if you want easy to print and strong, or hard to print but slightly more aerodynamic fins. I strongly recommend the normal fins however.

You will need: 

1. 1 x Nose cone (called “Head” in files)
2. (optional) 1 x drag ring made from TPU
3. 1 x Main Body
4. 6 x Fins of your choice
5. 6 x Locking pins

Only the Nose cones need support, all other parts can be printed without them.

Once all parts are printed and ready, you can beginn Assembly.
Firstly put the drag ring if you have it onto the bottom of your nose cone. There will be a small section on the nose cone with a smaller diameter to slide the ring on to.

After that, you can screw the nose cone into the main body. Depending on your print settings this might be easy, or it might not. The tolerances should suffice.

Then take your fins, put them in place like on image 3 and align the hole in the fin with the hole in the main body. The push a locking pin through both of them. To permanently lock it in place, heat the locking pin up with a lighter and quickly squish the soft plastic so that it cannot slide though the holes anymore. Do this on both sides of the locking pin and then on all remaining fins.

The last step is to install the rubber bands to engage the fins automatically. To do this, just take any rubber band and wrap it around the fins hooks as many times as you wish.