rrocket

Would NAR please publish the testing data, including thermal readings taken on casing temps.
this would also apply to all the KBA loads, that are melting my AMW hardware.

WE want full disclosure..
My motors don't melt my casings.
temp reading have been done, and they fall under the 200c requirement.
how can these new certified loads be melting casings if proper testing was done??

I thought prefered treatment was over??

Paul

billspad

I'm disappointed. It took you a week to find something to complain about. The engine data sheet hasn't made it to the website yet so I attached it to this. You'll have to ask John for the exact numbers but his test report says that the temperature was acceptable.

If you know of specific instances where casings have failed then you need to be sure they're reported here:

http://www.nar.org/NARmessform.html



But you posted this in the wrong thread because the motor your talking about must be the M3500. It also had an acceptable temperature. I'd attach the engine data sheet for that one but I'm editing my original post and I can't figure out how to do that. Never mind. I just found the right button. It's attached too.

Johnly

Paul,

The thermal testing protocol is included in the NAR S&T Motor testing manual. http://www.nar.org/SandT/docs/ST-MotorTestingManual.pdf

The relevent section is as follows:

8.6 Thermal Testing Requirements.
The external casing temperature will be measured on at least one motor of a given type during initial
certification testing, to ensure that this temperature does not exceed 2000C during or after firing, as required
by NFPA 1125.

8.6.1 Measurements will be made using a thermocouple sensor of low thermal mass, with an amplifier and
readout system capable of delivering accuracy of 10oC or better and a thermal response time of 5 seconds or
better less. Motor designs that have a history of motor casing temperatures well under 200C, the motor test
supervisor can elect to perform the temperature evaluation using a 200C color indicating sensor.

8.6.2 Thermocouples will be attached tightly and directly to the casing at two points along its length, one of
which must be at the spot corresponding to where the propellant grain and the nozzle meet and the other at the
point that is 75% of the motor casing length as measured from the nozzle end of the motor

8.6.3 The casing temperature will be recorded from the moment of motor ignition until 60 seconds after the
end of motor burn. The temperatures of all the thermocouples in use will be averaged to derive the recorded external
temperature for the test event. If this average value exceeds 200oC on the first test, two additional tests will
be conducted, and the results of all three tests will be averaged to determine whether the motor failed this
standard. If the average does not exceed the standard on the first test, additional tests are not required.

*******
The temperature testing protocol was reviewed and approved by our NFPA 1125 Committee member who was present when the 200C rule was put in place.

The temperature measurements taken during the re-firing of the M3500R were taken at both points and recorded at the time of testing. All 4 measurements (2 locations, on 2 motors) were below 200C.

John

UhClem

Something to consider is that motor testing is done in the open with nothing around the motor case but air. (I assume.)

In use the motor is installed in a motor mount tube which provides some insulation which would result in higher temperatures than in static tests. If the space between the motor mount and body tube has been foamed using urethane foam, one of the best insulators available, then the motor case could get much hotter than 200C.

billspad

Here's something else to think about. What is the significance of 200C? It's been in the NFPA codes since long before metal casings existed.

Just Jerry

You really ARE confused! It will never be over.

The AT W propellant has much more liquid metallic flow so the thermal transfer is higher. The external temperature during the firing stays under 200c, an arbitrary number inserted when NFPA codes were drafted on the presumption a "better" number would be edited later.

Later never came.

But when flown in a dynamic condition that liquid metallic flow is impinged with inertia.

Kinda like a monocopter nozzle.

What comes around goes around Paul.

Just Jerry

billspad

I knew one day you'd say something I could agree with.

So what's the better number?

Steve_Shannon

The stress-rupture strength of 6061-T6 drops off fairly significantly above 450°F (232°C), so it certainly should not be higher than 200.

billspad

So the NFPA's guess wasn't that far off?

Is there a basis for making the number lower than 200C?

rrocket

Bill

This is 'my opinion" based on many years of building quality motors, with one of the lowest failure ratios in the industry.

I see a major omission in the testing process, that can, and may be exploited.

What is to stop a manufacturer from submitting motors for testing with high quality liners, then submitting a much cheaper liner to the public??

There are NO controls, or recording of liner material, thickness etc.

As you have witnessed yourself while testing some of my motors.
Propellant grains are placed on the bench and are choses in no particular order.
You can see this in the weight variations in testing.
Liners are also placed in a pile, with extras available
Anybody is free to assemble motors, weigh grains, or request different ones.

I can remember in the early days of trying to understand the large variations in the Kosdon delays, hand picking grains, trying to get everything to within a gram, and cherry picking delays for exact similar weights.
This did NOT solve the problems.
It was later determined by X-ray what the problems were.

Maybe motor grains need to be placed in a pile, a random assembly done, LINER material, weighed, and it's color, and type noted..

In a 98mm motor, the difference between a high quality liner, and a less optimum liner can be more that $50.00 to $60.00 actual cost per load!!!

It is my opinion having observed the failures of others loads in my hardware, that there is a gross lack of consistent liner quality.

How do we address this issue, and fix it??

One other area that needs to be addressed.

how are motors fired?
In what axis?
a motor fired in a vertical position, will have different results, that one fired horizontally.
this would apply with motors of high metals, more so.
In the case of a c-slot, the motors should be fired, in the most likely mode of failure.
Common sense would ask, why are so many motors being produced to work in another mfgs. cases failing?

Now consider that those motors which take the same amount of work, materials as any other motor are priced way below normal market price.

again, in my opinion, there is a attempt to save money by taking short cuts, and using inferior materials.

As a manufacturer.
I don't want MY hardware being taken out of use, by another mfg.s failure to use quality materials.

I am not saying that this IS happening, but it is a very likely possibility, especially when there are NO controls in place to prevent it.
I have had the question asked of me, by said Mfg. in question.
"how can you make any money using that type of liner material?"

If the organizations are going to permit mfg. in other cases, then the case mfg. should have the right to spec. the materials needed to protect his hardware!!
This situation will only GET WORSE, until some positive action is taken!!

Paul

Just Jerry

The guess by Harry Stine presumed no metallic parts INCLUDING 6061-T6 aluminum.

It was an arbirtary "don't burn your finger", "don't wreck the typical Estes (Centuri) rocket." Naturally rockets back then were NOT mostly plastic. Even the Alpha III had an insulative paper motor tube and centering ring to protect the plastic from the side and top of the motor.

Sorry you are so unenlightened you agree with me so infrequently Bill.

Just Jerry

cite:

450°F (232°C)
The autoignition temperature of typical paper is 451 F. That's no coincidence.

Just Jerry

Firstly, that sounds more like a business plan than an accident. After all that would likely cause sufficient doubt in the "failed case" to encourage brand switching WITH full commercial revenue exchanging hands. You don't have to read very much RP to realize many HPR users are fairly unsophisticated on such matters. They rely on the expertise and representations of their product vendors. They are consumer rocket users, not professional rocket scientists.

And they are called Errortech. Bah Humbug!

No action by TRA is ever positive, almost. Don't encourage more!

The real solution is akin to what CTI does. Do the certs at the facility of the manufacturer, invite representatives from NAR, TRA, CAR and perform the tests if ANY of them show up, since they have treaties with each other.

That way the responsibility and authority rest in the same exact person for a certification. The manufacturer. Let the load be the determining factor and publicize warranty honor failures. NAR has an ineffective reporting program called MESS. Make the outcome quite a bit more public.

Free markets work. Make them more free.

Just Jerry

billspad

There is absolutely no defense against a dishonest manufacturer. The only solution I can think of is for the testing agencies to buy motors for recertification rather than request them from the manufacturer. This would require passing that expense on to the manufacturer. I don't see it as being a popular idea.





Everything NAR S & T fires is horizontal although we do have a stand capable of firing motors in the H to J range horizontally.




I'm sure I don't need to remind you that we weren't the ones who started this. My own personal non S & T thoughts on this were that it was going to be a giant mess for all the reasons you mention. S & T wasted a great deal of time discussing cross certification a year ago and the technical considerations lost out to the simple fact that our acceptance of reciprocal certification by CAR of CTI reloads in AT casings left us no choice. Maybe we should have challenged it when it first happened but, considering the nonsense we had to go through this year when we asked for certification documents, I'm not sure how well that would have gone.

A standardized casing would be a great thing for the hobby. However, that would require all the manufacturers to get together to agree on a standard for the casing, liner etc. and I just don't see that happening.

Just Jerry

Good point.

One possibility is rather than have one standard, have 3-4 common uses and let each manufacturer state on a S&T website if they approve that case material and liner combination for their particular propellant. It could even be specific to each diameter.

This will of course promote kit bashing of motors whether or not that practice is certified, but that might be a good thing for the industry.

It could promote lone rangers which we badly need.

Jerry

rdh8

That sounds reasonable with a bates grain motor.
What if the motor is a moon burner or c-slot?
One side would get hotter than the other.
They would need to be placed on the side with the slot/moon core to be accurate of maximum temp.

Robert

billspad

I agree but do you have some numbers to prove the point?

Steve_Shannon

About moonburners burning hotter on one side of the case:

I have never installed instrumentation on a case, but I have burned moonburners and when I clean the cases the liner is usually gone along the side with the offset core. That means that the combustion is taking place directly in contact with the aluminum. I agree with Robert that a moonburner should be placed in the test mount such that the core side is sampled for temperature. Also, I would like to see testing done such that the motor case is held in an insulated motor mount, similar to how it is held in a rocket. That could have a large effect on the case temperature.
Finally, I would argue that the type of liner with which a load is certified should be recorded as well as the weight of individual grains, so that if a dishonest manufacturer later changed a liner or grain size it could be discovered. That might also help prevent hearsay, speculation, and accusations which do nothing for our hobby.

Just Jerry

The problem is not dishonest manufacturers but dishonest test personnel. Perhaps the sensor/paint was placed opposite the core.

I have posted DOZENS of other TRA TMT irregularities, so it is certainly pattern and practice.

That is NOT an opinion.

Just Jerry

billspad

I think that's true but I think we need numbers. It's important if the difference is 50 degrees but not so important if it's 10 degrees.




The problem with that is that 1125 has a vague clause that allows a manufacturer to make changes after a motor has been certified as long as they don't significantly affect the performance. I don't remember the exact wording but it gives them a good amount of latitude.

The bigger problem is that S & T, TMT and MTC are not the motor police. We test the motors and certify that they met 1125 when they were tested and 1125 puts the burden on the manufacturer to keep the motors within limits. We can pull the certification if we're given evidence that something has changed but it would take more than second hand reports on an obscure forum to make that happen.

Steve_Shannon

I agree we need numbers. If not collected by S & T, how would you suggest such numbers be collected? My suggestion was that when the S&T testing is done, such numbers be collected. (as well as at TMT and MTC). You already have a number of motors to test and instrumentation that can be configured to collect such numbers.



If S & T, TMT, and MTC are not the motor police, who are?
I disagree that RP is obscure, but I agree completely that second hand reports should not trigger changes in certification. What would you consider second hand reports? What would you consider first hand reports? I've flown motors and had aluminum cases discolored by heat. Is that not first hand? That still might not be objective enough. That is why I suggested that liner material and more specific temperatures be noted at the time of certification testing in order to avoid such allegations. In fact my earlier post specifically said that this would help to prevent "hearsay, speculation, and accusations."
Just because you are charged with certifying motors to meet 1125 does not mean that you cannot collect data in excess of the requirements of 1125, especially when the data are just lying there waiting to be taken.

Just Jerry

I can tell you from first hand past experience that is not the case.




BATFE, DOT, USPS, FBI.

Just Jerry

ddmobley

Bill asked Robert DeHate if he had numbers. Apparently the thought is that the end users, who do not have the equipment to test for and provide the numbers, should provide the numbers to the testing committees, who do have the equipment to test for and provide the numbers. Maybe they don't want to do it?


That would be too simple. If you will provide proof of your claims, that moon burners, C-slots and the like burn hotter along the side with the thinner web thickness, then they'll think about looking into it. Common sense is not enough justification. Are you just creating more work for the volunteers?


It was an out and out dig. You should be used to it by now.


Perhaps. Until you posted it on an obscure forum.

billspad

And that may be what happens but you'd think that the manufacturers would have done this testing and would know the answer.


A MESS report or the TMT equivalent would be a first hand report.



We can collect it but we can't do much with it. The NAR Board has made it clear that S & T does what's in our manual. That's not in there but I guess it could be added. The problem I see with this is a manufacturer (and just to be perfectly clear, I am not talking about a specific manufacturer) waiving a copy at 1125 at us and asking where it says that we're supposed to do that.

billspad

Why must you be so confrontational? I've known Robert for a few years and I know he's done work for AMW so it occurred to me that maybe he knew what the target numbers were for an aluminum casing. In fact, if Paul is reading this and knows the answer I'd appreciate it if he could chime in.


I am not a metallurgical engineer and I have no idea at what temperature T6061 aluminum suffers permanent damage. Yes it makes sense that those motors will be hotter on one side but is it hot enough to do damage? And as Jerry said (oh my god I'm quoting Jerry) the 200C standard probably had more to do with the autoignition point of paper than anything else so we don't know if that temperature is relevant to casing failures.




Do not put words in my mouth. It was an honest question.




Like it or not, most of the rocketry community does not read RP or TRF or ROL or RMR.

UncleVanya

I had a vendor make a similar comment about the bank I work at repeatedly the vendor called us a "super-regional" bank. This is code for modest sized. We're in the top 10 banks in the country. Way up the list... we're in the top 10 banks in the world. The point is the vendor blew their credibility with us by not understanding our market and who were were. We didn't take them seriously from then on and we've never purchased from them.

Are you sure you want to call RP "an obscure forum"? I've seen Darrell post the hits here - this ain't exactly the back waters of the hobby.

More constructively... if MESS reports are not the answer (for one thing they only cover direct malfunctions) - what do you suggest we do? If the motor testing committees are not the motor police then what do we as fliers need to do? Should Paul be buying (at his own expense!) Aerotech reloads and test firing them himself to determine if they conform to the certification results? Should I? The purpose of motor certification (I thought) was to eliminate blind trust of the manufacturer's claims.

billspad

You'd be surprised how many people who are very active in the hobby don't read any of the forums.




MESS reports are most definitely the proper place to record a casing failure.

Certification only tells you that the motor did what it was supposed to when it was tested. It would cost a fortune to police them after that (other than recertification every 5 years). Who would pay for it? Are things that bad that we can't trust the manufacturers? There are 614 certified motors. If you're having a problem with the motors from one manufacturer I'm sure you can find another who is selling something similar. Unless you really want more regulation, let the marketplace weed out the bad guys.

UncleVanya

I know. But I also know the total number of rocket flying folks claimed isn't that large. "Obscure Forum" implies that there are non-obscure ones as well.




Thanks.




Actually Bill - I'm not saying this needs to happen. I'm just asking. The reality is that you might be right. On the other hand if there was an easy way to submit flight data to validate question motor certifications then we might be able to spot check the ongoing performance of motors over time.

I think the manufacturers mean well - but having seen first hand what "well meaning" sometimes turns out like... I ask these questions. Ask Compaq/HP what a minor change in a fan bearing can do to the uptime of a server!

If motors are not spot checked and manufacturers did turn out to be less than ethical - what keeps a manufacturer from goosing the loads from time to time?

UncleVanya

I keep seeing "market decisions" mentioned in this thread. I like market decisions - but I think HPR is such a small market that the time to influence is very slow. The word also takes a while to spread - places like this (obscure though they may be... ) help to spread those words.

So if we are going with market only solutions. Please please please file those MESS reports and post here to spread the word.

ddmobley

To the unknowing and uninformed, Rocketry Planet may be "an obscure forum", but I can promise everyone, as UncleVanya knows, the numbers of monthly visitors to the website dwarfs the entirety of the hobby rocketry community at large. In fact, in that regard, Rocketry Planet serves an obscure hobby with an obscure audience. I guess that would make the hobby itself second-hand.

ddmobley

And how many moonburners, C-slots and the like does AMW have on the certified list? I didn't think they did. Which would make your question to him valid how? Robert's question was:


Which you asked if he had numbers for. Why would Robert have information on a product AMW didn't produce?


No need to be a metalurgical engineer. During the process of the NAR S&T tests, line up the testing aparatus with the location of the area of the case with the thinnest web thickness. Results will make themselves known, with no degree required.


I did not see a question. I looked a second time and still did not see a question that should result in you making a dig at the forum you are using now. If it is obscure, why are you here? If you don't approve of the surroundings, why do you stay?


At least you got the order of use right, even if RP gets more traffic than the other three combined. Just because "most of the rocketry community" chooses not to use the Internet, can I control that? Of those that do, the numbers support where most of them spend their time. We're number one where it counts.