(Courtesy of Star Rocketry)
Adjusting New Drop Fill Stem GSE
The best way to set up your new style drop fill
stem assembly is as follows:
1. Loosen the collar so that you can slide it up
or down the fill stem.
2. Screw a fuel grain onto a motor tank.
3. Place the motor system onto the fill stem assembly so that it is firmly seated in the Kline valve.
4. Adjust collar so that the fuel grain lip is sitting on the stand-off rod.
5. Adjust and tighten collar so that the bottom of the collar is 1" above the blast plate when the fuel grain is sitting on the stand-off rod.
(Optional Double Check)
6. Take the motor system off the fill stem.
7. Place motor system back on the fill stem so that it is firmly seated in Kline valve.
8. When fuel grain is sitting on stand-off rod the bottom of the collar should be 1" from the blast plate.
The reason you have the 1" spacing is so that once the zip tie burns through the fill stem will easily fall away for a quick ignition of the N2O. With the L and M rockets that are heavy this is very important. Some people actually used to melt their fill stems for they forgot to rig their fill stem assembly to drop away. The rockets were too heavy for the internal pressure of the N2O to lift the rocket off of the fill stem.
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