Odd behavior with A8-3 motor

[Jwptrek]

I just launched a small rocket with an A8-3 while I was at lunch. Takeoff was good, but I heard several "pulses" or cutouts in the thrust. Motor was one I got with some stuff I bought at a garage sale, so who knows how it was stored. I am not sure of age. It's the Estes labeling with red and green, with code A031003. Rocksim predicted ~150 feet, but the rocket got to maybe 40-50 feet, and almost hit the ground before the ejection charge went. The rocket survived with minor zipper damage. Recovery system is undamaged. I did see tracking smoke as well. The motor is completely empty as I would normally expect with an Estes motor. I don't think it is worth a MESS report since I don't really know the motor's reliability. Thoughts?

 

[Jwptrek]

Also, I suspect this came from a bulk pack due to the packs of igniters and wadding that were included. A B6-4 from the same package gave a picture perfect launch (nearly out of sight except for tracking smoke) of the same rocket.

 

[user 35280]

2003 so pretty old motor.

 

[Jwptrek]

Definitely an old motor. However, I've read tons of posts that talk about flying old BP motors if it's warm out. I've never seen that kind of thrust variation in a BP motor. It reminded me of a chuff, but it happened during flight rather than on the pad.

 

[waltr]

It is possible a nozzle issue? Maybe got a little soft and eroded much faster during burn than a new motor. This would account for lower altitude while burning all the BP.

 

[Jwptrek]

Could be. The remains of the nozzle do look like the hole is larger than on a different spent A8-3 I had. Would the nozzle eroding account for the audible/visible chuffing, though?

 

[BEC]

That is very strange behavior for a black powder motor. I've flown Estes motors as old as 50 years and not seen that sort of behavior.

2003 is well beyond the infamous "poopy clay" nozzle time period, too, so unless this particular motor had gotten damp or something I can't imagine what would cause it to act like that.

I've seen what you described with composites but never black powder.

I'd be tempted to fly another one from that batch if you have it to see if it is similarly strange.

 

[astronwolf]

We experienced a bad A8-3 like that from a bulk pack of A8-3 motors. Barely cleared the launch rod and flopped onto the ground. I reported it on MESS.