[Richard] does say making larger rocket engines out of 2 or 3-inch PVC may not make much sense due to the increased chamber pressures. There is a fairly clever reinforcement method for these PVC ...

All those 60s, 70s, 80s and 90s kids out there may remember the classes of model rocket engines – generally A, B, C, and D sized engines used to push your cardboard tube with balsa fins skyward.