Estes E12 design change?

[shreadvector]

Did I miss something? Nozzles for E12 motors are now larger and went from a yellow plug to a black plug. And the black plug does not seem as snug as it feels in the E9.

 

[Initiator001]

I had heard that there was to be (a) change(s) in the E12 motor to make them more reliable but I do not know the details.

 

[shreadvector]

Along those lines....We had a school group launching TARC-like rockets on Saturday with a batch of E12-4 motors from 2016. They fired somewhere between 24 and 30 motors.

Most worked fine.

At least two cato'd.

I handed them MESS forms.

Before the failures, there were numerous misfires using the Starters - most were from crossed/twisted thick wires but a few were simple bridge wire failures. This led to the questions about the plugs since we had lots of experienced people trying to help them. I was astounded that the yellow plugs fell right out so i asked for a package and confirmed they came with black plugs (did not look at the instruction sheet to see if it was updated with new plug info or a new thrust time curve).

I had heard that there was to be (a) change(s) in the E12 motor to make them more reliable but I do not know the details.

 

[ThirstyBarbarian]

If the motor is changed, wouldn't there have to be an announcement and also a recertification?

 

[samb]

I was thinking the same thing Thirsty. A change to the nozzle size/shape would imply a change to the thrust curve, no ? Wouldn't Standards&Testing want a look at that ?

Paging Bob Krech.

 

[JumpJet]

The Yellow Plug NEVER fit the E12 motor. I've tried since they came out to get the plugged changed. When the person in charge of motors retired I was able to get the plugged changed to one that actually stays in the nozzle.


John Boren

 

[samb]

The Yellow Plug NEVER fit the E12 motor. I've tried since they came out to get the plugged changed. When the person in charge of motors retired I was able to get the plugged changed to one that actually stays in the nozzle.


John Boren

So no change to nozzle geometry ?

 

[shreadvector]

I pulled out an E12 with a date code from several years ago and the pack of E12-4 motors that the teacher handed me. They had different nozzle sizes.

The black plug would not go into the older motor nozzle at all. It did go into the newer motor nozzle.

Perhaps when I get home later today I can verify the fit of the yellow plug in the older motor nozzle (with and without a Starter, since proper fit should be with a Starter). I do not think that I have any of the newer date code motors so i probably cannot check those.

Improvements are good. Higher reliability is good.

I love those motors and have not had any problems since that first batch many, many years ago.

if there is a performance change, we need to know about that for TARC since one of the biggest issues is the students using the wrong motor data (many simulation motor databases are full of horribly outdated Aerotech motor data that needs to be manually edited/updated).

Thanks.

The Yellow Plug NEVER fit the E12 motor. I've tried since they came out to get the plugged changed. When the person in charge of motors retired I was able to get the plugged changed to one that actually stays in the nozzle.


John Boren

 

[rstaff3]

I think it is great that Estes recognized an issue and acted on it.

 

[JumpJet]

Like I said before the plug change was not done because of a nozzle change. I was done because the person who was in charge of all motor production is no longer at Estes and those who wanted it changed to the correct plug size was able to get it done.

 

[Woody's Workshop]

Thanks for clearing that up Mr. Boren.
You input is always welcome.

 

[rstaff3]

Like I said before the plug change was not done because of a nozzle change. I was done because the person who was in charge of all motor production is no longer at Estes and those who wanted it changed to the correct plug size was able to get it done.

Are you also saying there was no nozzle change?

 

[shreadvector]

Confirmation:

I was hunting for a local store that had E12 motors in stock and finally found one, so I drove over there yesterday afternoon and bought a pack of E12-4 motors with the black plugs.


I compared them to a pack of E9-4 and another pack of E12-4 motors I already had.

Here are the observations:

E9-4 date code A 06 22 12:
Black plug fit tight. I used a Starter to measure the depth of the centerbore from the aft face of the nozzle in comparison to the other motors. This one was "not so deep".

E12-4 date code A 06 22 12:
Came with yellow plug. Yellow plug fell right out confirming that they "never fit". Black plug fit OK, but not as snug as the E9. Depth in comparison to the E9 was "deeper".

E12-4 date code A 07 25 16:
Came with black plugs. Black plug fit OK, but not as snug as the E9. Centerbore was deeper than the other E12 from a few years ago and much deeper than the E9. This could simply be a result of more nozzle and the actual propellant centerbore may be identical to the earlier E12 motors.

In other words, there may be no performance change. If someone has a test stand, feel free to test some old and new motors and confirm. I'll assume they are identical or very close to identical unless test results show otherwise.

The Yellow Plug NEVER fit the E12 motor. I've tried since they came out to get the plugged changed. When the person in charge of motors retired I was able to get the plugged changed to one that actually stays in the nozzle.


John Boren