This object was made using Tinkercad, and printed on a variety of printers from standard PLA.

 These are engine mounts for ABC engine sized model rockets specifically made for paper towel tubes. Why Paper Towel Tubes? Because this enables teachers, scout leaders, CAP cadet leaders, and other groups the ability to create model rockets without having to spend a small fortune on commercial kits. Paper towel rolls are free and come in standard sizes.  With 3D printed parts made compatible with paper towel rolls, the cost per rocket (not including the motors) is less than $1.00 per rocket. I have also included an engine mount to glue onto the top of a engine tube made from either card stock, an index card, or if you want, a commercially made engine mount tube made specifically for model rockets. Despite being made from PLA, they don't melt...even after multiple launches.  A word on safety....I have been safety testing and so far, my rocket failure rate is comparable to that of commercial kits with the vast majority of failures being those lovely igniters. The second most frequent failure is when students forget to glue in the assembled engine mount which is, again, the same issue I have had with students building commercial kits.

https://www.tinkercad.com/things/hRtHXUkxagn