Quest Q-Jets

rockets said:

I won't be buying these until the ejection charge problem is fixed.

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Thanks, guys.
I've just removed Q-jets from my buying to-do list.

Too many teething problems.

a

I won't buy any till all the problems are fixed. Was hoping to get out some of my old Estes rockets that have been sitting for quite some time and put some Q-jets in them, but I guess they are useless.

What gets me is, how come these issues are only showing up now, when it's out in the public? Wasn't the flight testing thorough and extensive? You would think shot gun ejection charges would be obvious, right? Sheesh... Maybe there was too much of a rush to market these before extensive testing was complete.

kuririn said:

Maybe there was too much of a rush to market these before extensive testing was complete.

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Which, since we've been talking about these things in this thread alone for 10 months and in other thread for longer is pretty doggone ironic. I saw samples (which were not flown) at NSL last year.

I do wonder what, if any, real world testing was done as well. It's one thing to make sure the motor works in a test stand and it's quite another to put then into models they would likely be used in and go fly them. All three issues - the OD, the killer ejection charges and the projection which contains the ejection charge not going past the top of recent motor hooks, would have been known and could have been addressed in the redesigns that have already been done (again, look early in this very thread).

Interesting, also, that in this post from a year ago last February https://www.rocketryforum.com/showthread.php?138393-Quest-APCP-Static-Test&p=1671905#post1671905 there is no projecting hex containing the ejection charge, which would have eliminated that issue at least.

I'll get a few and fly 'em. Any excuse to fly a rocket, right?

Somewhat related, is there a requirement to actually flight-test a motor? I know all the cert process happens on test stands, not in flight rockets. I can understand the initial issues if there was no/limited flight tests done and the only motor mounts fit-tested were from tube stock you already had, which has a slightly larger ID than standard.

I doubt that there is any flight testing required for certification. It just seems pretty silly not to do so, especially when trying to put a new product into an existing market. It's not like there aren't already model rockets with 18x70mm motors already out there - for over sixty years!

I will certainly continue to fly the ones I have (my direct-from-Quest order arrived yesterday) and even make a new model or two to accommodate their peculiarities. But that doesn't really absolve them from apparently not actually trying the prototypes in likely existing applications.

heada said:

I'll get a few and fly 'em. Any excuse to fly a rocket, right?

Somewhat related, is there a requirement to actually flight-test a motor? I know all the cert process happens on test stands, not in flight rockets. I can understand the initial issues if there was no/limited flight tests done and the only motor mounts fit-tested were from tube stock you already had, which has a slightly larger ID than standard.

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Even if there was no requirement, wouldn't it be prudent to root out these problems before coming to market? Look at all the negative PR they are enduring now. It was shortsighted not to take care of these issues beforehand.

BEC said:

Interesting, also, that in this post from a year ago last February https://www.rocketryforum.com/showthread.php?138393-Quest-APCP-Static-Test&p=1671905#post1671905 there is no projecting hex containing the ejection charge, which would have eliminated that issue at least.

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Again, Aerotech already has an 18mm single use composite D motor that fits standard BT-20 tubes, has an ejection charge capped with paper INSIDE the casing, so no engine hook issues, and it's not overly energetic. At least the few times I used it, my rocket and recovery gear was not destroyed by the ejection charge. Why they couldn't have used that casing and design is beyond me. They already have the tooling, just a matter of replacing with the proper amount and kind of propellant to get the desired thrust curves, and possibly adjusting the nozzle size/aperture. See my pics in post 51.

kuririn said:

Why they couldn't have used that casing and design is beyond me.

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Not possible at this price point would be my guess. Note that they've abandoned that design for everything but the 18mm D10 and D21 AFAIK.

mikec said:

Not possible at this price point would be my guess. Note that they've abandoned that design for everything but the 18mm D10 and D21 AFAIK.

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Didn't the D21have a tendency to CATO sometimes also?
I've only flown the D10 and been happy with it's performance.

I have seen a couple of D21 CATOs though I've never had one. I have flown quite a few D10s and some D21s. In a BT-20 tube they will destroy it in one or two flights from "hibachi effect". In BT-50-based models it takes a few more flights before they get cooked. But in the right models, they are great motors and I like flying them.

Ejection charge torching is one effect I have not seen with the few Q-Jets I have flown.

I expect that the D10/D21 motors either don't lend themselves to high volume production or they are too costly to hit the desired price point, or both, which is why they are not just using those casings to create As, Bs and Cs as well. After all D10s are currently priced at 3 for $27 while the Q-Jet Bs are priced at half of that at two for $9.

Flying is not required for certification. The certification authorities simply make sure the motors perform within the constraints of NFPA 1125 for the benefit of our members. Nor is backward compatibility with any previously certified motors checked although manufacturers may want to consider it.

Thanks, Steve. That is what I’d suspected.

Well....in this case we shall have to see where the backwards compatibility issues lead....

BEC said:

Thanks, Steve. That is what I’d suspected.

Well....in this case we shall have to see where the backwards compatibility issues lead....

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.......for now as far as I'm concerned they will be in file 13 along with the RMS - EZ's and Jet Hitches. Hopefully the issues will be addressed.

Early adopters, welcome to the "Trough of Disillusionment"!

I'd post an image, but it's too labor intensive. Just google it.

General question here- if a motor mfg has to re-engineer one of their motors, what can they change before it needs to be recertfied? I'm sure changing the label is no problem, but what about changing the case thickness (to make it a smaller diameter)?

emckee said:

Early adopters, welcome to the "Trough of Disillusionment"!

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Yup.

Here's hoping we get a good way up the slope of enlightenment with these things.....

N.F.P.A. 1125
https://www.nfpa.org/codes-and-stan.../list-of-codes-and-standards/detail?code=1125
Chapter 8.

8.1.6 Any changes exceeding manufacturing tolerances made
to the physical design or chemical composition of a model
rocket motor, motor reloading kit, or component(s) by a
manufacturer after certification testing shall be reported to the
recognized testing organization that originally granted the
certification prior to sale or shipment. If the changes potentially
affect characteristics measured in the original certification
testing, that testing organization shall be permitted to require
that samples of the changed product and any supporting
changes to the user instructions be submitted for testing.

djs said:

General question here- if a motor mfg has to re-engineer one of their motors, what can they change before it needs to be recertfied? I'm sure changing the label is no problem, but what about changing the case thickness (to make it a smaller diameter)?

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BEC said:

Thanks, Steve. That is what I’d suspected.

Well....in this case we shall have to see where the backwards compatibility issues lead....

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These are 18mm motors.

tbonerocketeer said:

These are 18mm motors.

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That's the point. They're 18mm motors that don't fit in 18mm BT-20 tubes. That is one of the "backward compatibility issues".

And in reality, they are more like 19mm motors. They fit snug inside the 20mm Quest T20 tube (.747" id). Their yellow 18mm motor tube sleeve fits inside a T20. The i.d.s for the major 18mm motor tubes are:

BT-20: .710"
Quest 18mm motor tube: .712"
Centuri/Semroc ST-7: .715"

So here's what I think happened. The case manufacturer was either given the specs for a T20, or given an actual T-20 tube and told the motor should fit this, instead of using the specs from their yellow 18mm tube. Admittedly, speculation, but it explains everything.

Actually, 0.69" converts to 17.5 mm, not 18 mm.

mwtoelle said:

Actually, 0.69" converts to 17.5 mm, not 18 mm.

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????????? Did I miss something? Who mentioned .69"?

0.695 inches is the diameter of an Estes 18mm motor...so is a comfortable fit in BT-20 with an ID of 0.710 inches.

Ahh, I see. Thanks for clarifying that. Just an aside, did you ever notice that the nozzle end of an Estes engine is slightly bigger than the front end? So I guess the .695" figure might be an average?

Now you're going to make me measure a few....

kuririn said:

Ahh, I see. Thanks for clarifying that. Just an aside, did you ever notice that the nozzle end of an Estes engine is slightly bigger than the front end? So I guess the .695" figure might be an average?

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Probably has to do with the nozzle making process, the extra pressure causes the case to bulge slightly.

Saw someone fly a Q-jet for the first time yesterday. He also had to work to get the motor to fit into his 18mm mount. Nice flight, I liked the smoke. The delay seemed to be longer than advertised; ejection finally happened fairly close to the ground.

I'll definitely be interested in the Cs and Ds once the various issues are all ironed out.

0.69" (11/16") is the original standard. 18mm was just a shorthand approximation.

To BEC and anyone who experienced the aforementioned problems with their Q-Jet order:

Strongly suggest you e-mail Quest customer service and notify them. I e-mailed them a couple of days ago asking if they are giving at least a partial refund since the first batch has limited functionality.

Received a reply today from Mr. Karl Baumann, VP of R&D at RCS. He says that they are reducing the OD and recessing the front end of the newer motors to address the fit and engine hook problems. He also offered to replace the Q-Jets that I ordered with the revamped ones, when they are available.

Now that's what I call great customer service! Will be ordering the Cs and Ds when available. Keep on rock(ateer)in'!

Thanks for that. I saw your post in the YORF thread as well. I will do so.