Most Common "defective" Rocket motors

Surely this topic must have come up from time to time.

Recently on another Rocketry board (on FB), a thread grew where posters were talking about their CATO experiences with A10-3 motors. (If I recall the designation correctly....)

It got me to thinking,( especially when one poster asked "Is it time for a recall on these motors"), if there has been a particular model or designation of motor that has been most likely to fail.

I don't mean to point fingers or "bad mouth" any particular manufacturer. But I am wondering if experience has proven that a particular motor has proven to be more unstable, more mis-fires, or more CATOs than any other.

In short, what are the Top FIVE most common failing motors by model number, if we can list them? Does this data exist?

Usually, if a certain motor gets a reputation for not working as it should, the manufacturer will discontinue it.

Some of these come to mind:

Estes E15 motors from the (I think) early 1990s Discontinued shortly after they were introduced.
Estes D13 motors from early 1970s. These were Estes' original D motors. Estes switched to the D12.

FSI E60 motors. These were notorious for Catos.
FSI F100 motors if they had been dropped as this would crack the large BP slug.
These 2 FSI motors were discontinued when the original FSI closed shop. Hopefully, the new FSI will bring these back… Fingers crossed as these were great motors.

User error, any motor.

Back in the 90s I remember a few bad batches of D12s. Have a Viper IV that had several of its tubes cut out and replaced over the years.

Also a bad batch of G80s from AT. Bad phenolic - cases shattered almost instantly. Have several C-slot grains from these nearly unburned around somewhere. This was also in the 90s.

I remember when quite a few AT G35W Econojets would spit their nozzles upon ignition. This was in the early 2000's - 2002, 2003 IIRC.

I had 3 of them pop, back to back. Nice motor when it worked though. Loud, long 3.5 second crackly burn.

Needless to say, AT discontinued this motor.:wink:

I've seen more than enough H410 Vmax ejection issues.

Estes E9-6


Sent from my iPad using Rocketry Forum

I've seen at least three E9's spit their nozzles at ignition... you hear a loud "PING!" as the chunk of clay bounces off the blast deflector and then you have a road flare burning for about 5-10 seconds...

Can toast a rocket pretty good if it's too close to the blast deflector...

Later! OL JR

I've had 2 incidents of an obvious failure to perform properly in all the time I've used BP motors.

1. E12-4 CATO - blew out both ends. Surprisingly little damage to the rocket due to the ejection charge blowing out the nose cone and the ceramic blast deflector actually shattering from the force of the nozzle being spit out.

2. A8-3 - For some reason, an A8-3 was so underpowered the rocket basically cleared the rod and fell to the ground. Otherwise worked normally.

I had a rocket that had flown on A10-3Ts many times, suddenly on one flight skywrite. Based on the burn pattern, the only thing I can think of is that the nozzle wasn't shaped properly and jet came out at an angle. But I'm not really sure and so I can't classify it as a true failure.

There may have been other engines that had weak or non-existent ejection charges...but again, unless the engine is plugged at the end cap, there isn't really any proof.

FC

Aerotech had a bad batch of H97's come down the line where there wasn't enough HTPB in the mix making the grains crumbly. The one I had on ignition the upper half of the upper grain crumbled into the nozzle clogging it, snuffing the motor.

...wheeee...

FastCargo said:

I've had 2 incidents of an obvious failure to perform properly in all the time I've
2. A8-3 - For some reason, an A8-3 was so underpowered the rocket basically cleared the rod and fell to the ground. Otherwise worked normally.

FC

Click to expand...

Interesting that you should mention this A8-3 here. I had a similar instance, with my Big Bertha, and we concluded that it was friction on the launch lug that had delayed much of the lift until it cleared the rod and fell over, ejecting the nosecone just prior to laying down on the grass. I also had hand primed the body tube, and it was thought that might have added a bit of weight to the thing. Launched fine on a B6-4 twice more, so i shied away from the A8-3 except for smaller rockets' first flights. (Worked fine on my Cici Glider though...)

Any old AT white lightning reloads, 2 CATO on my side and a friend land dart 1 last week, the delay was way to slow to burn , also the VMAX , delay don't burn; good thing I have altimeter backup on those one.

luke strawwalker said:

I've seen at least three E9's spit their nozzles at ignition... you hear a loud "PING!" as the chunk of clay bounces off the blast deflector and then you have a road flare burning for about 5-10 seconds...

Can toast a rocket pretty good if it's too close to the blast deflector...

Later! OL JR

Click to expand...

Been there done that-
Mine at least started to get off the pad- lol
Same deal with a Magician - but I got to watch that one burn down on the pad.