Out of curiosity how much did CTI invest (molds, samples, labor) to overcome this TMT "opinion"?
I am guessing several tens of thousands of dollars.
No point if you don't even publish the results.
At TRA, certification has been treated as a wide-band go-nogo for many years. Whether that is good or bad is a matter of opinion.
It is certainly non-compliant with the very rules they insisted on authoring and adding.
Jerry
Everybody else did.
Not if they "lose" it.
Not if the manufacturer is not required to get an ATF permit by ATF, but TRA insists on one anyway.
Jerry
If, not when.
Poor Jerry. It really sucks to have to follow the same rules as everyone else when you're "Special."
-----snip----
In an ideal world, you'd want to test 7 to 9 examples of each unit to minimize the measurement uncertainty. I was inadvertently factoring in the sticker shock at how much the reloads cost :-)
Thanks for the great post Mike ! You are sure teaching me a lot about how the motor certification process works and I appreciate it !
John
-----snip-----
Which causes me to go barking mad and froth at the mouth. When a new technology is brought to the hobby, such as reloadable motors with adjustable delay grains it should be the _manufacturer's_ perogative to specify exact parameter's the device is designed to meet.
Then, when certification testing is performed, the tests should be run to validate the manufacturer's claim without bias on the part of the testing organization.
From other posts on this thread it _appears_ that CTI wasn't allowed to certify the Pro38 with unlimited delay adjustments because ONE person objected ? That should have never been allowed to happen.
John
You are quite right, ideally (cost and PITA factors notwithstanding) there would be more samples per type. But as the goal of the certification process is to not to define motor performance to the last decimal place, but rather to ensure that the products function nominally and the pertinent performance parameters are reasonably close to the manufacturer's data/claims so the consumer gets pretty much what they think they are getting, this small number of samples does the job adequately.
Luckily manufacturers don't have to pay retail for their own products... ;-)
Mike D.
Unlikely. The very few ignition failures we've had reported generally are due to the match getting folded over or caught between grains - they won't light the propellant directly. With the H143 just straighten out the leads, and when the match touches the pellet you can generally hear a little clicking sound. You can also feel it contact the hard surface of the pellet once you get a feel for it, assuming it's not mid-winter and your fingers are frozen..
Mike D.
IIRC (my brother absconded with my good statistics book) you really want a sample size of 30 or so. Which is affordable for Estes type motors, but not for HPR. 12 is probably a reasonable compromise.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
Not quite true. There's the little issue of being compliant with the safety code to deal with. Reloads required significant changes. Hybrids were also major changes. Adjustable delays required less significant changes.
I suppose TMT (or NAR) might have initially certified infinitely adjustable delays if 3 of each possibility had been submitted for testing :-)
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!
In which case if you get it right the motor will STILL work like a charm!!
Righteous ! Mid-winter here at 30.2 N means you have to wear a sweater over your Tee shirt !
John
I did that for a range of motors (ie the entire unlinked USR motor site).
No go.
As you have seen from your recent post, it is all about who asks. You simply asked re variable delays what I have been asking for many YEARS now.
Without bias? ROFL!!!!
Correct. ONE person at Tripoli!!
That cost the CTI company TENS of thousands of dollars in molds, testing, samples, labor, and paperwork. No exaggeration.
Kaplow's sig.
Jerry
Intended use is in the law, the regs and the code.
Mark Bundick even agrees!!
That's amazing.
YOU know that!!!
Not.
Relabelers do.
Not on your reload.
A couple quibbles of my own... First off, how do you know that your sim is that accurate? Is it more accurate than the motor delay? Secondly, if you really need that much accuracy, perhaps you'd be better off using a timer or altimeter for deployment.
certification
What makes you think an "independent" testing/cert authority would be more open to changing technology? I certainly don't believe that would be the case -- such an authority would have no motivation to adapt. At least when testing and certs are under the control of the rocketry orgs, we the flyers have a say in the process.
Oh great, another conspiracy theorist.
How melodramatic!
Who's stopping you from adjusting the delay? Do you fly with Kaplow's club?
Frankly, I think a better argument in favor of adjustable delays is to reduce costs, both for the consumer and for the manufacturer. Only one delay grain needs to be manufactured for each motor, and only one needs to be purchased. One of the great things about the ProXX motors is that I never have to worry about whether I have one with the correct delay or not. Even with AT motors, I always buy the longest delay available because I know it's a simple matter to adust it shorter if necessary.
a
ATF...
Really? Quoting from your own website: "ATF "knowingly and falsely" claimed PADs are not exempt..."
PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.