Estes E12 now available

[Alan15578]

Good one!

What a catastrophe! (the prior post quoted)

 

[Alan15578]

Sorry, I was referring to the fillets around the ends and tops of the clay (nozzle and plug). Reports are that the CATOs are blowing out both ends prematurely. Should've made that clearer. And agreed that it probably won't help.

You should know that our motors must be designed to fail by "unloading" vertically, e.g. by blowing out the nozzle and/or forward closure. CATOs that split the casing are rare by design. If you modify the motor to prevent blowouts, you are defeating a safety design feature, and enabling a more serious failure.

 

[kuririn]

You should know that our motors must be designed to fail by "unloading" vertically, e.g. by blowing out the nozzle and/or forward closure. CATOs that split the casing are rare by design. If you modify the motor to prevent blowouts, you are defeating a safety design feature, and enabling a more serious failure.

Refer to my previous posting: OP (post #175) was advised NOT to modify any motors with epoxy.

 

[Alan15578]

Refer to my previous posting: OP was advised NOT to modify any motors with epoxy.

177, 179

 

[kuririn]

177, 179

As I said, OP (post #175) was advised NOT to modify the motor. Read the posts.

 

[beeblebrox]

Just saying...I have flown many clusters of black powder motors in the past. I ave always plugged booster motors so they wont kick out and spray motor casings all over the place. most times the motor tubes are not vented into the recovery chamber of the rocket. I think considering an epoxy plug in a booster is a stretch of the imagination calling it modifying. The nozzle will still blow out if a cato condition occurs, which we all hope won't happen. It was the NAR that complained about this practice years ago along with "Tandem" motors, (Gluing a C6-7 in the back of a D12-0 for example.) Both of these cases are not dangerous by any stretch, but do and have been documented by Doug Frost to increase Total impulse by a distinct amount which would give someone a small advantage in NAR competition. BIG DEAL, Cluster rockets are not exactly high performance anyway and not really conducive to competition anyway for the most part. (Note my only cluster rocket I currently have in flying condition is a North Coast Cluster Duck which has all the tubes vented into the recovery compartment, so I use long delay motors with ejection charges functioning there so no need for using up epoxy.

 

[shreadvector]

Tandem motors would burn through the casing wall of the lower motor, which was a safety issue.

Epoxying a C6 into the top of a D12-0 was useless for increasing total impulse since the nozzles were different sizes.

Booster nozzle needs to be the same as the upper motor nozzle. If bigger, there are losses. If smaller, there is a "failure".

 

[kuririn]

Just saying...I have flown many clusters of black powder motors in the past. I ave always plugged booster motors so they wont kick out and spray motor casings all over the place. most times the motor tubes are not vented into the recovery chamber of the rocket. I think considering an epoxy plug in a booster is a stretch of the imagination calling it modifying. The nozzle will still blow out if a cato condition occurs, which we all hope won't happen. It was the NAR that complained about this practice years ago along with "Tandem" motors, (Gluing a C6-7 in the back of a D12-0 for example.) Both of these cases are not dangerous by any stretch, but do and have been documented by Doug Frost to increase Total impulse by a distinct amount which would give someone a small advantage in NAR competition. BIG DEAL, Cluster rockets are not exactly high performance anyway and not really conducive to competition anyway for the most part. (Note my only cluster rocket I currently have in flying condition is a North Coast Cluster Duck which has all the tubes vented into the recovery compartment, so I use long delay motors with ejection charges functioning there so no need for using up epoxy.

The Cluster Duck is a great rocket. Only flew my clone once, since large fields are hard to come by around here. IIRC, aren't the booster tubes vented into the channels between the tubes and out the rear of the rocket? Also have a Semroc Hydra 7, another great kit. The booster tubes are plugged with a balsa block.
The question that was posed was not about plugging booster motors, but about filleting epoxy around the clay nozzle to prevent it from blowing out and CATOing. And my response (which could have been clearer) was that epoxy fillets around either end of a regular motor was not advised.
BTW I still have a few of these motors:

Estes D-11P. Plugged from the factory. Don't think it was discontinued due to safety concerns, but it's a small niche market. Cluster, boost glider, and oddroc applications, so the volume sold probably didn't justify it's continued production.

 

[beeblebrox]

Tandem motors would burn through the casing wall of the lower motor, which was a safety issue.

Epoxying a C6 into the top of a D12-0 was useless for increasing total impulse since the nozzles were different sizes.

Booster nozzle needs to be the same as the upper motor nozzle. If bigger, there are losses. If smaller, there is a "failure".

Your information is actually not true. Doug Frost (As I mentioned before, ran theses tandems on test equipment and got more total impulse. I have flown dozens of those decades ago and NEVER had a burnthrough. The ones that usually failed (75% failure rate were same sized motors. C6-0 to C6-7 for example. I did not do that type anyway because of the failure rate was too high. they usually come apart then act like a two stager. The upper motor accelerates some of the crud in the lower motor, thus increasing mass fraction and increasing total impulse by about 10-15% this is measurable... I never ever heard of someone filleting the nozzle end, if a motor is going to cato it is usually due to the black powder grain debonding from the case wall due to temperature cycling, epoxying the nozzle would do nothing anyway, one or both ends would still blow out. But simply plugging a booster is not unsafe.

 

[shreadvector]

Your information is actually not true. Doug Frost (As I mentioned before, ran theses tandems on test equipment and got more total impulse. I have flown dozens of those decades ago and NEVER had a burnthrough. The ones that usually failed (75% failure rate were same sized motors. C6-0 to C6-7 for example. I did not do that type anyway because of the failure rate was too high. they usually come apart then act like a two stager. The upper motor accelerates some of the crud in the lower motor, thus increasing mass fraction and increasing total impulse by about 10-15% this is measurable... I never ever heard of someone filleting the nozzle end, if a motor is going to cato it is usually due to the black powder grain debonding from the case wall due to temperature cycling, epoxying the nozzle would do nothing anyway, one or both ends would still blow out. But simply plugging a booster is not unsafe.

I ran many tandem motors on the MIT test stand. The increase in thrust is the erosion of the lower motor casing inner layers. That mass is accelerated out the lower nozzle and that greater mass results in more thrust (F=m*a).

We only saw burnthough on some of the booster motors. This was solved by using a BT-20 sleeve epoxied on the outside. This added complexity and that meant the motor mount was going to be larger. Big PITA for little gain. Composite motors were better.

I'm not sure how having the C6 exhaust run through a larger D12 nozzle does not result in losses, but if you (or Doug) have actual results, then that's fine.

 

[beeblebrox]

I am actually in the process of building a motor test stand, meesa tink more real data is beein' in the future!

 

[shreadvector]

I am actually in the process of building a motor test stand, meesa tink more real data is beein' in the future!
View attachment 373394

 

[jd2cylman]

Well this taken an eeenteresting turn it has...

 

[Ez2cDave]

Tandem motors would burn through the casing wall of the lower motor, which was a safety issue.

Epoxying a C6 into the top of a D12-0 was useless for increasing total impulse since the nozzles were different sizes.

Booster nozzle needs to be the same as the upper motor nozzle. If bigger, there are losses. If smaller, there is a "failure".

"Back in the day", there was a "secret" to it, Fred . . . Remove the nozzle of the C6 . . . Just more "fuel" for the D12 with slightly less thrust due to the smaller diameter of the fuel grain of the C6, but no "scouring" of the inside of the case, caused by a nozzle being in place.

Dave F.

 

[beeblebrox]

"Back in the day", there was a "secret" to it, Fred . . . Remove the nozzle of the C6 . . . Just more "fuel" for the D12 with slightly less thrust due to the smaller diameter of the fuel grain of the C6, but no "scouring" of the inside of the case, caused by a nozzle being in place.

Dave F.

I never removed the c6 nozzle, does not need to be done. your 'no scouring' comment is illogical. Black powder motors are low pressure, Trying to grind out the c6 nozzle would be a motor modification....Drilling it would be dangerous. Note: for shizzles and giggles...I had made a few D12-C6-B3 tandems and they all worked...like three stage without the extra weight of two more motor mounts and fins causing weather cocking. A cluster of three of those was great for cinerocs.

 

[beeblebrox]

...If one thinks a C6 would burn thru the D12 case then why would you expect an E12 to function? ...more propellant than the above tandem... If Estes had come out with the E12 in the 1970's I would not have needed the tandems...and YES, I did suggest that to Estes back then.

 

[Ez2cDave]

Not a bad idea at all. Those guys would dig it.

Chuck C.

I never removed the c6 nozzle, does not need to be done. your 'no scouring' comment is illogical. Black powder motors are low pressure, Trying to grind out the c6 nozzle would be a motor modification....Drilling it would be dangerous. Note: for shizzles and giggles...I had made a few D12-C6-B3 tandems and they all worked...like three stage without the extra weight of two more motor mounts and fins causing weather cocking. A cluster of three of those was great for cinerocs.

No, it's quite logical, I'm afraid . . . The exhaust velocity of a B6, with the nozzle in place is 2550 - 2650 ft/sec . . . That data is straight from ESTES !

https://www2.estesrockets.com/pdf/Model Rocket Engines & Igniters.pdf

With the nozzle of the C6 in place, the exhaust gases are, naturally, accelerated inside the D12 casing. The "scouring" from that accelerated flow erodes the interior wall of the casing of the D12 at a higher rate, leading to a possible burn-through of the D12 casing. It acts like a "supersonic blowtorch".

With the nozzle of the C6 removed, it just acts like an additional "propellant slug" and the motor burns longer, with lower thrust due to the smaller diameter of the C6 propellant grain. Remember that E9's & E12's burn much longer than a D12 and have identical casing wall thickness,

Yes, removing or drilling the nozzle is a motor modification, but so is epoxying them together . . . NAR no longer allows "Tandem" motors", at least not in competition.

https://forums.rocketshoppe.com/showthread.php?t=12542

Dave F.

 

[shreadvector]

...If one thinks a C6 would burn thru the D12 case then why would you expect an E12 to function? ...more propellant than the above tandem... If Estes had come out with the E12 in the 1970's I would not have needed the tandems...and YES, I did suggest that to Estes back then.

I do not "think" I "Know".

The casings in the 1970's were different and those of today are 'better'.

AVI tried making longer burning motors and they burned through the casings. They had a 20 N-s 18mm D6.1 and 40 N-s 24mm E11.8 and they would fail and burn through near the end of the long propellant burn.

Their solution was to reduce the propellant and they were no longer full D or E motors, but it got rid of the burn through problems.

Estes (under Tunick, believe it or not) did a lot of casing studies and they had two sources (hence the extra letter on the motor code). They were concerned with casing quality - most likely dimensional consistency, strength/glue.

Modern Estes casings are stronger than they were back in the 70's.

Of course, now some of you will want to go out and test this by making tandem motors with modern production motors......

 

[beeblebrox]

No, it's quite logical, I'm afraid . . . The exhaust velocity of a B6, with the nozzle in place is 2550 - 2650 ft/sec . . . That data is straight from ESTES !

https://www2.estesrockets.com/pdf/Model Rocket Engines & Igniters.pdf

With the nozzle of the C6 in place, the exhaust gases are, naturally, accelerated inside the D12 casing. The "scouring" from that accelerated flow erodes the interior wall of the casing of the D12 at a higher rate, leading to a possible burn-through of the D12 casing. It acts like a "supersonic blowtorch".

With the nozzle of the C6 removed, it just acts like an additional "propellant slug" and the motor burns longer, with lower thrust due to the smaller diameter of the C6 propellant grain. Remember that E9's & E12's burn much longer than a D12 and have identical casing wall thickness,

Yes, removing or drilling the nozzle is a motor modification, but so is epoxying them together . . . NAR no longer allows "Tandem" motors", at least not in competition.

https://forums.rocketshoppe.com/showthread.php?t=12542

Dave F.

View attachment 373598



View attachment 373601

You are missing one important point here... There is pressure in the bottom 'plenum chamber' if you wish to call it that, therefore the gas velocity of the gasses from the upper motor is not high velocity until it exits the lower motor. this un-chokes the upper nozzle. but again no-one reads...I had made many of these and so had Doug Frost extensively testing them and the failure rate is very low when motor diameters are nested. same diameter ones were not reliable and tended to blow apart. As to Shread Vector's post regarding AVI motors, they did not have as high quality casings as Estes, therefore the argument is false.

 

[Ez2cDave]

You are missing one important point here... There is pressure in the bottom 'plenum chamber' if you wish to call it that, therefore the gas velocity of the gasses from the upper motor is not high velocity until it exits the lower motor. this un-chokes the upper nozzle. but again no-one reads...

What prevents the upper nozzle from accelerating the exhaust gases from the upper motor ?

Your theory that the upper nozzle does not accelerate exhaust gases, needs some verification . . . What testing methods were employed to prove that the upper nozzle acts in the manner you suggest ?

Dave F.

 

[dhbarr]

My hunch would be the backpressure in the lower casing.

 

[beeblebrox]

Inherent knowledge of how this stuff works, this is not supposed to be a full college course on rocket propulsion, if you want that then you can meet with me privately and pay me $200/per hour...you people need to stop nit picking...I also worked for AeroTech and Industrial Solid Propulsion for 7 years, I know what the F*** im talking about...

 

[Ez2cDave]

Inherent knowledge of how this stuff works, this is not supposed to be a full college course on rocket propulsion, if you want that then you can meet with me privately and pay me $200/per hour...you people need to stop nit picking...I also worked for AeroTech and Industrial Solid Propulsion for 7 years, I know what the F*** im talking about...

beeblebrox,

Did you ever make BP motors there ?

Did they ever experiment with tandem composite motors ?

Dave F.