Centuri Mini-Motor Revision
 

Several years ago I was able to buy an old hobby store's supply of Centuri 1/2A 4-5M mini motors. A couple months ago we used them to fly a really fun, NAR approved, old-motor-event with my local club (JMRC). I was cleaning up today and ran across two partial boxes of the motors and as I went to consolidate them I realized they were both the long and short Centuri mini-motors. Enclosed in the box of the newer "shorties" was a notice about the "Important Revision" to the motors. I thought it might be of interest to some of you so I am posting it here, along with some photos of the motors.

Enjoy,

Steve

They used to have blue tube. :D

I think the "Important Revision" excuse of casing supplier replacement was marketing BS to mask the fact that they had closed down the motor manufacturing in Phoenix and once again were getting motors from Penrose.

There was a period when Estes sued Ball Paper to continue making convolute virgin tube for them as a sole supplier.

Jerry

I don't doubt they had a beef with their supplier (A few apparently experimental examples of Estes mini motors made with glassine covered spiral wound tubes got into stock and out on the market and I have a couple of them). I just wonder if that's the real reason Centuri went to the shorter motor.

I see only three reasons for the change:
1. Estes began making their motors again and didn't want to fool with tooling for one of the Mabels.
2. Shortened them to the "industry standard", i.e. Estes' length to be compatible with other models.
3. Decided to discontue "B" motors and shorter casings would be cheaper.

I'm with you on thinking it coincided with them outsourcing again.



.

Pictures or they don't exist! :D

I've probably posted them here or at TRF at one point or another, but I'll dig around.

Found it faster than I thought. New photos.

the date stamp says "6M171" These may have been unrelated to the casing supplier problem, but may have been when they were developing the motors in early 1971. I asked Ed Brown to confirm that they were made, but I failed to ask *when* they were made.

Of course, I don't remember how these came to me. There's a part of my memory that's trying to tell me that these were from the free packs given out at NARAM 13, but I doubt they would give out booster motors when I don't think they had a two stager in their initial kit lineup (they would convert the shorty Beta and Midget kits a few months afterward, as I recall).

The third picture shows the inner spiral gap. I only have two of these, so I must've flown the other two from the pack at some point.

4. B motor version MIGHT have had a much higher cato rate?

Not saying they did, but that is another possible reason.

IIRC the MPC B size 13mm Mini-Jets had a significantly higher cato rate than the smaller ones. Though it may have been one nororious bad batch and they didn't make that many batches of B's (or the others) before MPC bailed.

That too.

Yes, which falls under #3...stopped making B's. Once you stop making B's, there's no reason to keep the long casing. Cato issues was what I was thinking about when I listed it, but it could have been simply due poor sales numbers, or any number of other reasons involving materials and/or profitability.

Back in the early 80's, a hobby shop in Roswell was moving and was selling their rocket stuff (getting back to their RC plane basics in a smaller space) and I bought a big bag of Centuri mini-Bs for a song. I still have most of them. The few I've flown didn't cato, but had another failure mode -- weak or no ejection charges.

Bad news for the rockets of the first few flights, but at least the motors could be salvaged with a little extra powder, albeit not safety nazi approved. :rolleyes:

I'll buy them

I'm slowly flying them, not at NAR launches (though select ones I'll eventually fly under the expired motors program).

I'm also starting to fly my older (still certified) motors. The rare motors, like the D13-0, B3 (lbs)-5, the 1968 B.8-4 (with the trumpet bell nozzle), etc. I'll still keep, though even the Estes-made Rock-a-Chute motors (photo in another current thread) will get flown eventually (at least one or two).

I bought an unopened box (8 4 packs??) of B4-3s from a fellow rocketeer a couple years ago. They are -awesome- in the original scale Estes Blender, or my mini Photon Disruptor.

I have a 13mm based downscale of the Little Beth X2 that I've tried a longer delay in - but I've had poor luck staging recently - it keeps blowing out the booster motor mount. I only had 1 B4-7. Would really like a couple more -5s or -7s.

I fly them at Bong. Once the WOOSH sked is posted for the year, I apply for the Expired Motor Program permission for all the launch dates. (Yes, I note it on the flight card, too.) The staged one was flown by a friend at a TWA launch as a research flight. A 3xA+B research flight :-)

I've had no delay troubles. I've been counting them out, and they seem run about a half second long. I also notice that the smoke is thicker, yellower and distinctly more sulfury than current motors.

I have launched at least 20 of the mini B's and never had a CATO

That has happened to me with the mini B's, about one out of 15 or so.

I never had any issue with the 13mm Centuri B4 mini-motors...have always flown great without a single cato.
The 13mm MPC B3-xM minis are a totally different story....those things have been absolute trash for me with a cato rate about the same as the awful FSI E60.

The last dozen or so MPC B motors I had were taped to small dowels and 'flown' as bottle rockets. Less than half actually "flew"; most had a casing rupture with no definable upward flight. This was sometime back in the 90's. I still have a couple of them in my collection somewhere.

If you are not going to sell them after all, send me high resolution photographs of all sides of the packaging. Some day I will make a similar product. We used to buy a bunch of those packs at Claremont Rocket Society. Amazing packaging.

Jerry

01rocket@gte.net

Didn't have any packaging. Just a plastic bag of ~50 or so B4, mixed delays. Had a few envelopes of SureShot Dot igniters. Now down to about 30. Green casings (made during the problem with the casing vendor, I assume)

I only have a handful of the old Centuri 13mm B's left....wish I had a bagful.

I'm of the opinion that ONCE a motor is certified it should NEVER lose certification for age/out of production.
Motors should ONLY lose certification if for safety reasons.

Better yet, DUMP the certification process all together and ELIMINATE it's requirement.
It's as moronic as requiring blends of R/C glow fuel be 'certified'.

Exactly... I've thought the same thing for YEARS...

If you're talking about "contest certified" I can see the purpose of wanting a 'readily available" motor, but then you're talking about an "approved motor list" which is not the same thing as "safety certified".

Contest certified is really only applicable to the tiny minority of rocketeers that actually engage in contest flying... (which if that's your bag, more power to you, but the "average rocketeer" could really care less...) Like I said, that being the case, then have an "approved motor list" for contest flying, and remove motors that have been out of production or that aren't readily available for contest flying, and leave it at that.

Safety certification, once obtained for a given motor and issued, should NEVER be revoked unless it's statistically proven that a given motor is unsafe, ie prone to go "BOOM" or have some other sort of failure at a statistically unacceptable rate.

The fact that motor certifications are removed once a motor becomes "too hard to get" for contest use is really an inconvenience to the vast majority of the rocketry community not engaged in competition. If it were merely an inconvenience, it wouldn't be so bad, however, flying "uncertified" rocket motors is grounds for refusal to pay the claim should anything happen during a rocket flight causing an injury or damage on the ground, exposing the rocketeer and club/launch site to undue liability, which is why flying "uncertified" motors is usually discouraged or not allowed. It's foolish, but it's how "the system" works.

It's a system that needs to be changed.

Later! OL J R :)

As I recall, the original Safety and Contest certifications had certain performance parameters, like Safety was within 15% of stated thrust and impulse, and Contest was 5% within some amount of standard deviation.

Those went away sometime while I wasn't paying attention. Apparently, DuPont's black powder, which Estes depended on, suffered varied quality and efficiency in the 70's and 80's and Estes found it difficult to hold its motors to the same performance parameters as before.

So NAR certification simply meant they were consistent, worked properly and the company that made them could provide customer support (and a liability chain). Contest certification then became essentially the subset of motors that were commercially available to most competitors.

The liability chain is, apparently, the sticking point to making initial certification permanent.

Date codes on motor labels is probably another problem. If you say, we certify the Jones A7-5 motors made between 5-2003 and 8-2008, but no others, you've got to have the date stamped indelibly somewhere on the motor. But motor manufacturers have been inconsistent about that at best. Estes went to that 1970=A, etc system for years, then for awhile a code probably based on which Mabel it was made on, and marketing says some people think of the date as an expiry date. Aerotech had some octal system or some such, and for a long time they were printed on the ejection charge cap, so you couldn't tell anything about the motor after operation. And that's ignoring the whole reload situation.


So, what about doing away with certification totally? Well then, how do you count on anything the manufacturer tells you? You might trust Estes, but why? Why would you trust Aerotech? CTI? So you build or buy your own test stand and check them yourself, but that's usually impractical when you're talking about a K motor or larger, unless you've got money to... well, you know.

Back in the day, they needed something to distinguish model rocket motors from fire crackers. IMHO, we still do today. So we enjoy the benefit of having a certification process.

Wolf noted: "Back in the day, they needed something to distinguish model rocket motors from fire crackers. IMHO, we still do today. So we enjoy the benefit of having a certification process."

Oh Wolf, you say the nicest things. Seriously, it is what the G. Harry, the Model Missile Association, Estes and others had as an uphill battle to change or revise fireworks restrictions to allow model rockets to be flown. The MMA became the NAR and testing standards were established to certify motors to convince fire authorities to allow model rockets.
In my home state of Ohio, in my home town we had a fire marshal, Fred Long, who became a model rocketeer and advocate, supporting the NAR and the Columbus Society for the Advancement of Rocketry. I served on the NAR Standard and Testing Committee in the late '60s and early '70s (then in the Air Force much bigger motors).
Motor certification is what keeps the authorities in check along with the Safety Code. There are those who think they should be allowed to do anything they want, but we are always one "Oops" away from additional restrictions. At the least, bad press. We had a saying in the Strategic Air Command that you could have all the "Atta Boys" in the world, but it only takes one "Ah Sh*t" to wipe them all out.

Certification is what keeps the wolves away... Sorry Astrowolf...

Chas

Good points, but there could be REVISIONS to the certification process... IOW, not "decertifying" a motor simply because it goes out of production for such and such a time.

As can be seen in other threads, there can literally be thousands of them still floating around in people's personal storage, on dusty shelves in hobby shops, and in collections being swapped about in various ways. And of course there are also lots of people (on this forum and elsewhere, probably mostly elsewhere) that love to fly some of those old motors when they have the chance.

As I said, the certification process serves two purposes, or at least it should-- 1) to certify that the motor "as designed and built" is statistically safe (through verification test firings of a statistically significant number of motors to obtain the data) and 2) to verify that the performance and delay, etc. on the test stand is within an acceptable range of the specifications stated "on the label" (though strangely enough that's not usually the case-- ie the "long burn" Quest C motors, which are labeled a "C6" but actually are more like a "C3", yet are still labeled and marketed as a C6-- but anybody who's flown them knows (often through bitter experience) NOT to try them in heavy or draggy rockets, as they don't give enough "oomf" off the pad and usually ends in a lawn dart or ground kissing parachute deployments... But that's another pet peeve that I think should be addressed... perhaps NAR should assign the motor specification as part of the certification AFTER the firing tests based on the averages obtained, rather than allow the manufacturer to label it as "anything he wants so long as it's somewhere in the ballpark" just so he can market something to compete "head to head" with an established similar product by another manufacturer... but that's another story).

Of course there's a need to demonstrate to the public safety officials and regulators that there does exist a testing and verification procedure and "certification" to verify the safety and performance of the rocket motors offered for sale to the public, and to differentiate model rocket motors from their "fireworks cousins" (though of course that line has been blurred beyond belief by the love affair that a lot of folks have with sparky motors, which is basically a "firework effect" that has NO beneficial impact on the motor performance, in fact usually a deleterious effect on thrust and performance, merely for an "ooh-ahh" visual/auditory effect, IOW, FIREWORKS...) That battle is largely over-- and where it still rages on in certain "nanny state" areas it will likely never change anyway. I don't think anybody actually says that certification is a BAD thing or should necessarily go away (well, maybe GH here on the forum...)

The point is, the "safety certification" part of the motor certification should be divorced from the contest certification process... It's ridiculous that thousands of motors that have been sold to people and reside in their hands are magically "okay" to fly one day, and "not" the next based on the capricious process of deciding if it's widely available enough to be used for "contest" flying, which is a TINY portion of the model rocket hobby (and rocketry hobbyists). I get it, there exists a need to establish which motors are acceptable for flying in contests and which are not, but that process (based on the same data set) should be separate from the safety testing and performance verification part of the motor certification process-- basically it should be an "approved motor list".

Then, to top it all off, while one can sit on a collection of motors for decades that are no longer "certified" and thus cannot be flown at NAR insured launches because they went out of production and were no longer widely available enough for easy access for contest flying, not because of any statistical testing verified safety problems (like the well known catos or nozzle spitting of certain different motor types over the years), with the 'wave of a magic wand' and filling out some paperwork and genuflection to the right NAR official and receiving the "blessing", these same motors can be flown under the "old motor test flight program" (whatever it's called that the name escapes me at the moment)... IOW another capricious process that says "you cannot 'legally' fly the mass produced formerly certified motors that you own unless *we* say you can". Oy vay...

But of course, even the suggestion of change seems to not sit well in certain quarters, particularly with those who sit "at the top" in charge of such things... I'm sure my comments will be met with all sorts of criticisms and rather haughty remarks that "I just don't understand" or whatever. SO be it; I've come to expect nothing more...

Why I'm not a NAR member... I've found it to be nonresponsive and very protective of a certain small percentage of the rocketry hobbyists interests, and only changes when basically FORCED to because too many people go "off the reservation" and do what they want to do anyway, risking making NAR irrelevant... (ie the long battle over allowing HPR certification within NAR, which USED to be a "verboten" activity long ago, for those who don't remember... and remained so while NAR membership dwindled with people flocking to TRA to get HPR certified, and NAR FINALLY grudgingly accepted HPR and came up with their own reciprocal cert program). I'd suppose this "old motor testing program" (whatever it's called; can't recall the name ATM-- thinking MESS but that's the motor problem reporting program... anyway you guys know what I'm talking about...) was NAR's "grudging" way to allow people who would have flown their old "decertified" motors on their own as "mavericks" without NAR's permission or consent if they HADN'T come up with some way to do it "legally"... IOW, a band-aid on a broken process of deciding where and when motors are "certified" or "not certified" based solely on it's widespread availability for contest flying...

Later! OL J R :)