I mentioned before, the BT-40 body tube wall is thick!
There is also the ST-7 engine mount tube that slides into the BT-40. The BT-40 tube by itself would make a loose fitting engine without the ST-7 slid in.
To the left of the ST-7 motor mount tube is the thick Centuri style engine block.
TRIVIA: Centuri called their engine blocks "thrust rings". It is thicker than a regular Estes EB-20 engine block.
The instructions don't mention cutting a notch in the thrust ring. I'd recommend it - the Kevlar is thick and could bulge the outer ST-7 tube.
The thrust ring is recessed 1/8" in from the top of the ST-7 motor mount tube.
"Centuri called their engine blocks "thrust rings".
ReplyDeleteMakes sense. In big rockets the engines and tanks are bolted to a thrust structure.