Yes, and now if you'd rather have a motor ejection than rely on electronics, you're screwed. You no longer have a choice. Which is exactly why I feel they shouldn't have to test every delay combination.
Probably not, if the delay is _that_ far off. But then, that exceeds the allowable variance, so the motor wouldn't be certed anyway. If that 20-second delay tested out to 22 seconds, then yes, I'd trust the 10 second delay.
I just think there has to be some other way of determining a reasonable level of reliability for delays, without burning up scores of costly motors to do it.
I'm sure there is a reasonable solution to avoid having to test a handful of each delay type for lare expensive motors. But I take it that you do agree that you need to test at elast one th see what the delay actually is.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
And back in the "good old days" when there were many more garage shop motor manufacturers, there was even greater disparity between claimed performance and tested performance. Which is yet another good reason for testing. And while most motors underperformed, some were over their claimed performance: important to know if you're close to the waiver envelope. An extra 10% IT could punch your rocket right through your FAA waiver. It's kind of hard to trust any simulation when there is no good motor performance data to feed the input side.
GIGO: Garbage In Garbage Out. Or just as often Garbage In Gospel Out.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Bingo. Someone actually understands. The greater the variance between tests, the more motors you need to test. Perhaps that would be the incentive to the manufacturer to improve delay accuracy. Test 3. If all within x% of each other AND within y% of the claimed value, then we're done. If not, more delay tests required, at the manufacturers expense.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Would you use an M motor with motor ejection if it was an untested "M" delay, and the L delay tested out to double its claimed value? And you really needed a medium?
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
So you want them tested to be sure your rocket doesn't prang.
When John tested the M1939-L and the delay was way off, he gave the manufacturer 2 choices: resubmit with more accurate delays, or to certify the delay at the value it tested to, XXL. They chose certification as XXL. Then under Toms reign of neglect, that was changed so that the L was certified as an L and the untested S, M, and XL were all certified as if they had been tested and found to be accurate.
What would YOUR response be to changing your data be Ray?
What would you say if Jerry Irvine took one of your old "fest" aerial launch photos, and doctored it to back up his attendance claims. Somehow I don't think the phrase "well, Jerry must have been right all along" would be your response. Well, that's exactly what Tom did with John's test data.
It would be nice. I'd certainly be open to suggestions. If something like "six sigma" processes were in place with all the motor vendors, it might be possible. But any solution I can see to guarantee the accuracy and consistency of the ersult would cost more than the current testing. It makes sense with a consumer product where millions are manufactured. It just doesn't work for low volume operations like we see in HPR.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
It was my suggestion, not Ray's. Maybe JBGTkicker would be even better.
The problem you would encounter going back to motor ejection is all the tests required for certification. But I agree completely with Ray that a reliable motor ejection is much simpler than electronics. But we've now self-installed an "level 3 rockets myust have dual redundant electronic ejection" mentality into our hobby.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
How do you know that's what happened? How do you know Tom didn't test them himself? Yes, the lack of test data does make it suspicious, but could also be just that -- missing data.
In any case, things have changed a lot since then.
John Cato's story sure filled in what looked like a piece of "missing data" the only place I ever saw an actual reference to an "XXL" delay was on a certification list; vendors' product listings only had "S" through "XL".
As for electronics vs. motor delay, I guess I'm at more worried about the delay system being a weak point for a potential destructive blow-through than I am about not being able to make electronics work reliably. (The old axial-seal 54mm delays in particular... I never had one blow out myself, but I have witnessed too many nasty midair "torch jobs"... especially with the long-burn "slot" motors - J90 etc...) I'm just so much less nervous with a plugged motor and electric ejection with
54mm motors & larger.
The Cesaroni and the RMS-Plus systems seem to be much more likely to be reliable, though.
I know you stated it. If one follows the thread, it is obvious you stated it.
Bob was not correct in stating that -I- attributed it to him instead of you. I did -not- modify the attributes what-so-ever. My tool inserts a '>' on the left in a reply and I quoted the whole message down to where you made that statement, at which point I inserted my comment. The confusion lies in who's tool quoted Bob's text as "Bob K. replied: >",... not to finger point,.... Ray...... ;)
Is it not a requirement of the orgs to test to NFPA 1125 including the section requiring combinations of delays? Are you certain that for a different chamber pressure(s) that the delay segment will burn at the same rate? If a state found that a certifying body was not complying with the adopted NFPA do you suppose they would continue to recognize that body as an AHJ?
Probably not, but surely a less wasteful method could be found than burning up a $$$ M motor to test a penny's worth of delay material.
Possibly not, if it was happening on a regular basis. I doubt they'd make a fuss over a few irregularities that occurred 13-14 years ago during the difficult period of getting the cert program up to speed.
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