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  #21  
Old 04-28-2015, 09:27 PM
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billspad billspad is offline
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Quote:
Originally Posted by ghrocketman

Back in the 'good old days' NAR even approved of one making their own BP motors with a press.
We need to get back to the 'almost NO rules' policies;


It wasn't exactly no rules:



3. If a model rocket engine is constructed by an authorized Section of the NAR as a result of a program conducted and directly supervised by an adult instructor who has (a) satisfactorily received and completed credit for 15 semester hours of college chemistry or its equivalent at a recognized, established, and competent university, and (b) has registered his name and address and has presented his credentials to NAR Headquarters for approval, said model rocket engine shall be allowed to be operated at NAR test centers and in competition. However, full data on the motor shall be presented. This data shall included (a) thrust, (b) duration, (c) specific impulse, (d) composition of propellant, (e) method of preparation and loading, (f) combustion pressure, and (g) burst pressure of the motor casing.


It will cost you $1.00 to read the whole thing .
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  #22  
Old 04-29-2015, 04:39 AM
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blackshire blackshire is offline
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Quote:
Originally Posted by billspad
I don't care if you drill your motors yourself on your own property. I do ask that when you light the house on fire you tell the fire department it was careless disposal of smoking materials. There's no better way to get an unwanted regulation that to do something stupid and have it hit the news.

Keep in mind that there have been professionals hurt and killed making motors. The process is not without risks.

And if you drill a deeper core in an E9 I'm pretty sure you can count on having it cato.
Your paternalistic and presumptive attitude ("*when* you light the house on fire..."), plus the distressing tendency of the NAR to just ignore contest ideas and other suggestions from other members I know, have made very easy a decision that I've been wrestling with of late. I know of better and more fruitful places to spend the money that I've been spending on my annual NAR membership dues all these years. The international FAI/CIAM space modeling (model rocketry) community is far more open to input from others--the NAR would do well to learn to do the same thing, especially among its own members. I've often wondered why the NAR's membership has remained small, and its "We don't really want to hear from you if you aren't part of the inner circle--just send us your dues" attitude (which certainly isn't true of all NAR officials, but there are enough to exude that cultural feeling) is a factor. Also:
Quote:
Originally Posted by billspad
It wasn't exactly no rules:



3. If a model rocket engine is constructed by an authorized Section of the NAR as a result of a program conducted and directly supervised by an adult instructor who has (a) satisfactorily received and completed credit for 15 semester hours of college chemistry or its equivalent at a recognized, established, and competent university, and (b) has registered his name and address and has presented his credentials to NAR Headquarters for approval, said model rocket engine shall be allowed to be operated at NAR test centers and in competition. However, full data on the motor shall be presented. This data shall included (a) thrust, (b) duration, (c) specific impulse, (d) composition of propellant, (e) method of preparation and loading, (f) combustion pressure, and (g) burst pressure of the motor casing.


It will cost you $1.00 to read the whole thing .
If you think that little of the value of the information it contains, why not just give it away? I'm glad that Orville Carlisle developed the model rocket motor *before* such restrictions were put in place. It was almost in spite of himself that G. Harry Stine teamed up with Carlisle to create the hobby of model rocketry, as he couldn't believe that a mere shoe salesman could possibly have developed a complete, self-contained propellant/delay/ejection charge rocket motor and airframes for them (somewhere, Thomas Edison and other such un-lettered inventors smiled indulgently...).
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  #23  
Old 04-29-2015, 04:58 AM
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Quote:
Originally Posted by ghrocketman
The ONLY ones I'm considering are B4's and not as some sort of 'experiment'.
Drilled B4's replicate original B14's. The nozzle is exactly the same and so are the motors; one has a drilled core and the other does not.
I just have to measure the right depth and core diameter of one of my old B14-0/5/6/7's

As a side note, the last produced B14's (somewhere around '79) don't have drilled cores and are exactly the same as the later B8's with a short 'pintle pressed' core. They perform noticeably different than original drilled B14's.
I cannot help but chuckle at this. Now, in fairness, *maybe* those latter-day B14s of yours (which look just like the B8 motors--I remember using B8s, and I currently have one or two B14s; I never flew a B14) meet the B14 specifications, so that it's "NAR-Kosher" to call them that, but (as your experience strongly suggests) I suspect otherwise. But, you see, it doesn't matter:

If the NAR *said* that they are B14s (by way of certifying them as such), then they *are* B14s, no matter what an instrumented static test firing's data would indicate...just like the BATFE was able to say (until a NAR [and TRA, too, if memory serves] lawsuit forced them to accept chemical data over what they claimed was true) that ammonium perchlorate, an oxidizer, is an explosive. Isn't it wonderful to be a self-proclaimed authority of power? :-)
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  #24  
Old 04-29-2015, 05:20 AM
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Quote:
Originally Posted by Jerry Irvine
I sense summoning. My tooling vendor could easily custom make such an animal and if GH and a couple others would provide me the precise diameter and depth of the core and the precise diameter and taper of the throat and exit, it would be trivial to make tools for whoever wants them. I suppose one could also modify E9's to D30's as well. I have lost all of my mod notes from the 1970's.

Jerry
A didgeridoo played in a dark room can work wonders... :-) Indeed, since you are positively disposed toward this, you deserve the credit--and the proceeds--from offering such B14-making tools. Doug Sams' posting (with his photographs of B14 motors) are a good start. Also:

Safety equipment and arrangements (eye protection, heavy-duty gloves, having water handy, etc.) would be easy for users to set up. The drill bit could be made of plastic or (for better durability combined with greater safety, especially regarding static buildup) non-ferrous metal. A "Deluxe model" could even use a hand crank and gears, so that the motor (in its vented holder sleeve or frame) would have its nozzle facing sideways, displaced completely off the line of sight, so that if it did somehow ignite, the results would just be embarrassing. In addition:

A spring-loaded drill chuck assembly (*or* having the motor spring-restricted at its front end [an aircraft-type drill bit with the set-able "depth collar" would stop the bit's forward progress at the prescribed drill depth]) would enable the exhaust gases from any accidental ignition to be vented to the atmosphere. But when used as recommended (drilling slowly on non-dry days, to avoid frictional heat and static buildup), such occurrences would be virtually unknown.
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  #25  
Old 04-29-2015, 06:12 AM
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Quote:
Originally Posted by blackshire
Also:If you think that little of the value of the information it contains, why not just give it away?



Follow the link. The dollar doesn't go to me it goes to the Heinlein archives.
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  #26  
Old 04-29-2015, 06:55 AM
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Quote:
Originally Posted by Doug Sams
Yeah, it almost looks like they were still calling them B14's for a while after going to the smaller (B8) core. One difference I did notice was that the smaller core B14 was deeper (0.75") than the later B8 (0.6"). Doug .

.


That's because they *were* still calling them B14 for awhile, the eventual shortening of the pintle notwithstanding. Though, from what I heard, the shortening wasn't entirely intentional; i.e. the pintle kept breaking off, and they would press a few hundred or thousand units before noticing. So they eventually decided that that was as deep as it needed to go, and made future pintles at the shorter length. I wonder what happened to the motors that the pintle broke off in.

Sounds good, but still doesn't explain why the C5 came out from Centuri before the B8 (the same geometry). I should ask Ed Brown, but I'm lazy.
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  #27  
Old 04-29-2015, 07:10 AM
Ltvscout Ltvscout is offline
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Quote:
Originally Posted by Royatl
Sounds good, but still doesn't explain why the C5 came out from Centuri before the B8 (the same geometry). I should ask Ed Brown, but I'm lazy.

It's easy to ask Ed. He logs in here regularly.
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  #28  
Old 04-29-2015, 07:16 AM
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Quote:
Originally Posted by Ltvscout
It's easy to ask Ed. He logs in here regularly.

I know. He's also a facebook friend. Surprising to some, I know, but modroc trivia is actually a low priority for me.
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  #29  
Old 04-29-2015, 09:00 AM
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Thanks for splitting this discussion into it's own thread.

kj
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  #30  
Old 04-29-2015, 09:06 AM
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Jerry Irvine Jerry Irvine is offline
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Blackshire (and others), I am glad you are excited about pintle drills. I am offering to manufacture one who's design has already been engineered and validated. It is possible to verify the core depth and diameter and throat diameter with cylindrical drills then fab the special tool as a properly tapered and spark free material. Then anyone with the tool could mod a commercial motor into a special purpose FX motor.

As for EX numbers, that applies to shipping, and the shape of the core is not a factor in those approvals at all. Therefore even a modified motor can be reshipped presuming you have the approvals to either mail or ship rocket motors from that vendor.

Motor modification rules are club rules not shipping rules. Before you mention NFPA, nobody enforces that until after an incident. Totally ineffective regulatory regime thank goodness.

As you know, the entire club HPR universe is a mere 4500 people worldwide. MR only a few more than that.

Tech Jerry

Last edited by Jerry Irvine : 04-29-2015 at 09:53 AM.
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