Gary has just announced official endorsement of the policy of drilling
delay grains on The Rocketry Forum under the 'Vendors' section.
Full information is available on the AeroTech website under the 'News'
My great appreciation and thanks to Gary for following this through in
an EXTREMELY expeditious manner!!!
Great job David.
now can you pull the same on Estes to get them to allow motors to be glued
together again ?
we did this in the 60s & 70s. It was published in the NAR model racketeer on
how to do it.
now we need Estes to say it's ok, since we have the manufacture must approve
motor mods rule.
IE tandem motors.
ohh by the way, I have a 70s NAR model racketeer reporting on removing
ejection to make delayed staging booster engines.
if we could do that yet again ;-)
I've had at least 3 different manufacturers of SU motors adjust the delays
on them for me back in the "good old days". And many SU motors are made with
long delays and then drilled down as part of the manufacturing process. It
was all done before reloads were invented. There is absolutely no technical
reason that whatever AT or CTI or any one else comes up with has to be
limited to reloadable motors.
Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD"
>>> To reply, remove the TRABoD!
Well...several decades ago I learned the hard way that drilling into an
C to increase the ignition surface available at launch was a bad idea.
CATO, though. Fifteen feet away. Wish I'd been wearing tan shorts :-)
My concern is the casual shopper at Wally-World who picks up a quick-start
set, never before having even seen an MR really shouldn't be doing mods to
motor because they don't have a clue about what the possible consequences
I agree that there is no technical reason why delay grain modification
limited to only reloadable motors. But I believe there are several
why it would be a bad idea.
Actually, if I was to want to do anything (), it would be to change
the rules that decertify certain single-use motors.
It makes no sense that I can't fly an A10-0T from the 90's, when I can
fly an A8-3 from the 60's.
Drilling a delay on a single use motor has at least one advantage: you can't
drill the wrong side of the delay. I've seen in the other thread someone
saying "Doesn't matter which side is drilled.". If I understand correctly
the way a motor works, this shouldn't be true. Side facing the combustion
chambre burns under pressure, and so probably not at the same speed than the
other side. So side does matter.
But there is also one disadvantage: you have to remove the ejection charge
and then replace it after the mod. Not easy with an estes-like motor.
Note also that, a few years ago, when apogee were still sending motor to me
(in europe) (by post), he tried to sell me 10 seconds delay motors because
other ones were not in stock, and was ready to explain me how to modify this
to have the desired delay. At this time, I refused. This seemed to me a
violation of the code.
"John Bonnett" a écrit dans le message de
The web thus burn time is same regardless of which side is drilled. Drilling
the delay grain on the chamber side is the correct method however. The
reason is better structural support of the delay grain as well as a
configuration better suited to pressure loading without deformation.
Hydrostatically test some delay grains in both configurations, especially
some that rely on O ring seals and you'll see what I mean. It also provides
better continuity in the delay train with the ejection charge.
Anthony J. Cesaroni
Cesaroni Technology/Cesaroni Aerospace
(905) 887-2370 x222 Toronto
(410) 571-8292 Annapolis
Correct. The disadvantage to drilling the top is the delay keeps burning
for a while after ejection thus cooking the inside of the rocket more.
It was probably (probably :-) ) a violation of postal rules.
It would have been legal to mod the delay had he publicly stated the mod
was a recommended procedure (similar to what Gary recently did), which
Wanna see something funny? Search rmr archives for posts from me
suggesting Gary post the delay mod permission. They go back years and
are present regularly over time.
Agreed. They just do not ever become "unsafe" or "out of performance
The only motor EVER cited as going out of range was motors by
Prodyne-Rahkonen and that was because he used radical catalysts he got
from work at Thiokol or whatever.
How many hundreds or thousands of flights (people enjoying added safety)
could have been flown with properly modified delays at certified NAR or
TRA launches if only Gary had published this 10 years ago?
I told you so.
On the record.
With the "loss of useful time" to hundreds of comsumers for over 10
I stand amused.
I advocated for consumers WITHIN THE RULES.
I told you so. ON THE RECORD.
"As for your name calling, if you don't like what I am saying thats
understandable , but if your just rude and nasty -- you probably have
a place in hell waiting for you!"
- anon from an email list
"The value was back when I said, and carefully described why, I told you