- Joined
- Jun 20, 2014
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This weekend at ROC, I used the 54mm Fly-away rail guides for the first time. It did not go well...
My rocket is a 54mm, Madcow Tomach. This rocket has flown before with rail buttons. I have both diameter sets of 54 mm rail guides, the smaller one would now even "close" enough to to get the rocket onto the rail. The larger diameter one was a loose fit. Not sloppy, but the rocket would easily slide inside of the guide. I used one of the supplied rubber bands per the instructions. In a ground test, it slid nicely and popped right off.
This weekend I loaded it up with a AT K545 (DMS) for a test flight of some recovery electronics and the guide. The guide slid down the rail nicely (good job by ROC of keeping their rails clean!). The rocket was sitting on the stop at the bottom of the rail and I positioned the guide right on top of the fins (touching).
At ignition, the rocket appeared to start up the rail but jammed. It then carried the 50lb pad up into the air about 20 feet and at a significant angle before the whole shebang crashed into the playa. At this point the buttons broke off of the guide and the rocket, still under some thrust careened across the playa for about 100 yds. After the buttons broke off, the guide actually opened up, and both it and the rubber band were intact and in a normal post-flight condition. The buttons were still on the rail, but could be easily slid up and down. A post-mordem of the buttons show that there was considerable loss of nylon (nylon "strings" on the rail).
My assessment is that the fins on the Tomach, which have a shallow sweep angle, pried open the guide creating the jam on the buttons. The lack of friction between the guide and the airframe just made this bad enough to jam the buttons. Does this sound right?
Don't mis-interpret...I don't think that the guide design is necessarily at fault. It is certainly strong enough to lift a 50 lb pad off the ground! I just want to not make any mistake that I made again!
Thanks for any feedback.
My rocket is a 54mm, Madcow Tomach. This rocket has flown before with rail buttons. I have both diameter sets of 54 mm rail guides, the smaller one would now even "close" enough to to get the rocket onto the rail. The larger diameter one was a loose fit. Not sloppy, but the rocket would easily slide inside of the guide. I used one of the supplied rubber bands per the instructions. In a ground test, it slid nicely and popped right off.
This weekend I loaded it up with a AT K545 (DMS) for a test flight of some recovery electronics and the guide. The guide slid down the rail nicely (good job by ROC of keeping their rails clean!). The rocket was sitting on the stop at the bottom of the rail and I positioned the guide right on top of the fins (touching).
At ignition, the rocket appeared to start up the rail but jammed. It then carried the 50lb pad up into the air about 20 feet and at a significant angle before the whole shebang crashed into the playa. At this point the buttons broke off of the guide and the rocket, still under some thrust careened across the playa for about 100 yds. After the buttons broke off, the guide actually opened up, and both it and the rubber band were intact and in a normal post-flight condition. The buttons were still on the rail, but could be easily slid up and down. A post-mordem of the buttons show that there was considerable loss of nylon (nylon "strings" on the rail).
My assessment is that the fins on the Tomach, which have a shallow sweep angle, pried open the guide creating the jam on the buttons. The lack of friction between the guide and the airframe just made this bad enough to jam the buttons. Does this sound right?
Don't mis-interpret...I don't think that the guide design is necessarily at fault. It is certainly strong enough to lift a 50 lb pad off the ground! I just want to not make any mistake that I made again!
Thanks for any feedback.