Last weekend I flew two G64W-10 29/40-120 reloads in my rocket. Both motors lit and lifted the rocket about 15 - 20 feet above the pad (This tells me the igniters didn't clog the nozzles or it would have over-pressurized and never left the pad.. At that point the ejection charges went off blowing the nose cone and chute off. The rocket went unstable and spun in place for a second and when the thrust ended, it fell to the ground with a 4 ft flame coming out the BT.
The powder well was melted off the forward closures of both motors.
Disassembly showed the aft o-ring was between the nozzle and the aft closure, as it should be when assembled IAW step 13, Fig-9 of the instructions.
Removing the forward enclosure showed the o-ring was stuck to the forward closure indicating it was installed correctly IAW step 9, Fig-5 of the instructions.
The forward insulator was still attached to the Liner tube as usually happens with these reloads.
There was nothing left inside the forward closure as the delay grain, delay insulator and o-ring were all burned away.
I've assembled over a 100 of these and have never had a CATO in 11 years. I don't believe I errored in assembling the delay grain. I greased the o-ring with the other two. The o-ring was inserted into the forward closure (I pour the parts onto a tray for assembly and didn't have any parts left over.) These had 10 second delays so there was no delay spacer to insert and possible get on the wrong end of the delay. I chamfered/deburred the delay insulator with my thumbnail like I do for all the AT reloads I do. The delay grain was inserted into the delay insulator and that was inserted into the forward closure and stuck out about 1/16" IAW step 6 Fig-3 of the instructions.
Both motors were from my latest order, but both were from different batches.
Can anyone think of anything that would have caused the flame to get past the delay grains? It happened about a half second after ignition since the rocket lifted 15 - 20 ft above the 6' pad, so things held for a while. The ejection charges didn't go off until failure when the rocket was 15 - 20 feet up. I don't think it was an over pressurization because that should have blown the forward or aft closures off, but....
Anyway, any ideas would be greatly appreciated.
The powder well was melted off the forward closures of both motors.
Disassembly showed the aft o-ring was between the nozzle and the aft closure, as it should be when assembled IAW step 13, Fig-9 of the instructions.
Removing the forward enclosure showed the o-ring was stuck to the forward closure indicating it was installed correctly IAW step 9, Fig-5 of the instructions.
The forward insulator was still attached to the Liner tube as usually happens with these reloads.
There was nothing left inside the forward closure as the delay grain, delay insulator and o-ring were all burned away.
I've assembled over a 100 of these and have never had a CATO in 11 years. I don't believe I errored in assembling the delay grain. I greased the o-ring with the other two. The o-ring was inserted into the forward closure (I pour the parts onto a tray for assembly and didn't have any parts left over.) These had 10 second delays so there was no delay spacer to insert and possible get on the wrong end of the delay. I chamfered/deburred the delay insulator with my thumbnail like I do for all the AT reloads I do. The delay grain was inserted into the delay insulator and that was inserted into the forward closure and stuck out about 1/16" IAW step 6 Fig-3 of the instructions.
Both motors were from my latest order, but both were from different batches.
Can anyone think of anything that would have caused the flame to get past the delay grains? It happened about a half second after ignition since the rocket lifted 15 - 20 ft above the 6' pad, so things held for a while. The ejection charges didn't go off until failure when the rocket was 15 - 20 feet up. I don't think it was an over pressurization because that should have blown the forward or aft closures off, but....
Anyway, any ideas would be greatly appreciated.