After successfully launching a multitude of my 3D printed Bounty Towel rockets, my kids and I decided we needed a more badass rocket launcher than the bland and generic store bought mass manufactured versions. My biggest complaint with the generic store bought models is when you press the switch you get very little feedback on what is happening. This is especially concerning when the rocket doesn’t immediately launch. There is also ample opportunity for improvement in the aesthetics department on these devices.
If we wanted an awesome rocket launcher we were going to have to print, build, wire, and assemble it ourselves!
For the second iteration of the bounty towel rocket I made the fins much bigger and I made the nose cone more aerodynamic looking. In an effort to get better flight telemetry we taped two nickels to the inner nose cone in order to get the center of pressure (CP) behind the center of gravity (CG). In our case two nickels was enough for a perfectly straight flight of our 3D printed rocket into the heavens.
For the second iteration of the 3D printed Bounty paper towel rockets I’m now pushing the envelope when it comes to minimum wall thickness of the printed assembly to save weight and material as well as optimizing the print time. I cut down the size of the tapered piece for the nose cone and base that slide into the power towel roll ends. The diameter for the model engine is better but still too much of a tight interference fit for my liking. That will also require some more “dialing in”.
The 3D printed rockets are not satisfactorily stable and have a tendency to flip ass over teacup in midair. After further research I have been most recently enlightened that we need to modify the design parameters such that the center of pressure (CP) is behind the center of gravity (CG) for suitable stability. A destabilizing force is created when the CP is above the CG. the next design is going to have much bigger fins and the nose cone will have internal threads to accept a 1/4 UNC bolt (and nuts if needed) to push the model rocket’s CG forward to obtain better stability.
I always enjoyed building model rockets with my dad and sister as a kid but always found the construction process of cutting, sanding, aligning, and gluing the balsa wood fins to be tedious and take a lot of fun out of the process. Back then the hot glue gun fixed a number of model rocket fabrication shortcomings for me.
Paper Towel Roll Concept
For a good while now every time I see an empty paper towel roll I see a model rocket body. I’ve been mulling a concept in my head for some time now to design and 3D print a model rocket nose cone and model rocket fins that could attach seamlessly to a paper towel roll to serve as the model rocket body. We had some empty bounty paper towels in the house so this weekend we fired up the CAD and the 3D printer and gave it a shot. The final results came out better than I could have expected!
It works! Our only problem was that we only had wimpy “A” rated model rocket engines on hand. Due to the weight of the assembly combined with the underpowered rocket engine the first two 3D. Printer paper towel roll prototypes went less than 100 feet into the air. Other than that everything worked splendidly.
My goal for the next iteration is to take the design down to the minimum 3d printer wall thickness (the internet is telling me the minimum is about 1.5 to 0.8 mm for the absolute minimum) and see how well the structural integrity of the design holds up. That combined with some “C” rated model engines should add some serious kick to our rocket power of these 3D printed “bounty towel” rockets. This isn’t rocket science (or is it?)
I’ve been wanting to add multi color printing capability to my 3D printing repertoire and pulled the trigger on ordering a Prusa MMU2S. My son has increasingly become more interested in 3d printing and helped me execute the majority of the build. I was grateful for his help. The whole build took us two long (and I mean L-O-N-G) afternoons to complete the build.
Prusa Mk3s+ upgrade
The website says you need to upgrade from the MK3S to the MK3S+ before performing the MMU2S upgrade. I didn’t mind the fact the MK3S to MK3S+ was only $49.99.