Quest v. Estes Engines in LPRs

mh9162013

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When it comes to deciding what LPRs I should focus on and build, engine costs is the single most important driving factor. This is one reason why I try to focus on rocket designs and sizes that are 13mm BP engine capable, such as using an A10-3T or 1/2A3-2T. Even if it has an 18mm MMT, I'll want it to be able to fly with a 13mm engine and an adapter.

Generally speaking, the best price for these mini engines is about $2 each. But today, I was reading another thread here and discovered the Quest Q-Jet bulk packs. Yes, I've heard and seen them before, but didn't give them any serious consideration b/c they were more expensive than Estes 13mm engines.

For example, there's a 12 pack of Q-Jet A3-4s for less than $23. So now I'm reconsidering whether I should focus many of my rocket builds around the 13mm engine. Based on my research, here are the benefits of the Q-Jet A3-4s over an Estes BP rough quivalent, like the A8-3. These include:

- Price
- Cleaner burn (but is this actually true?)
- Quieter

Potential drawbacks of using a Q-Jet instead of an Estes BP:

- More finicky starting (not sure if this is true or just anecdotal)
- Might not fit in all BT-20 motor tubes due to slightly larger size (is this still true? And if it is true, some light sanding of the plastic casing should remedy this, right?)
- The ejection charge "thingy" sticking out on the top might not fit in some MMTs (probably not a major occurrence, though)

Here are my questions:

1. Am I missing any advantages or drawbacks of the Q-Jet over an Estes BP equivalent?
2. How does the ejection charge compare to the Estes BP 18mm engines? Specifically, isn't there some plastic cap that gets ejected into the rocket with the Q-Jet while the Estes BP 18mm engines just have tiny bits of clay to worry about?
 

Scott_650

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Wow, that’s a lot to unpack. I’ve been using QJets since they first hit the market and have had generally positive results - the “fat” motor thing was a non-problem that received more attention than it deserved, the fix was simply peeling the labels or, at the most, also sanding the inside of a motor tube a bit to gain some clearance (I had a 24mm motor that needed peeled last club launch, otherwise it functioned perfectly). The ejection charge well fits in every rocket I’ve used them in but there have been rare reports that it can cause fit problems - 18mm QJets fit in Estes 18/24 adapter fine. I’ve never even seen the plastic cap after a flight so in my experience it’s not a problem either. I haven’t found QJets any more or less easy or hard to start than Estes motors but that’s exclusively on 12V launch systems - both my own and at club launches. As far as the sound goes I can honestly say I’ve never paid that much attention and for me it isn’t a factor for or against - YMMV.

As far as pros/cons of QJets here’s my opinions - the D motors definitely have more “umph” than any 18mm Estes motor, the QJet C motors are about the same but you get the thrust a lot quicker which can be pretty nifty to watch. QJets also tend to be lighter than an equivalent Estes BP motor which can be a good thing with heavier rockets. As far as downsides the only thing about QJets that can be less than satisfying to me is that acceleration - BP motors with their slower acceleration and longer burn time can be a bit of a dramatic spectacle. Also, BP motors make a bigger cloud of smoke so they look a bit more realistic when launching a scale rocket like a Saturn.

I use both depending on mood or performance (Thrustcurve and OpenRocket/RocSim are your friends here!) and outside of one or the other becoming unavailable I wouldn’t be exclusive with either type of motor - but I could understand folks having a stronger preference than I do. My advice is to try both in a favorite rocket and decide what works best for you. Sounds like a fun experiment!
 
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I think the early production problems with the QJets have been resolved. I have a box of an early run QJet B4-4 bulk pack. After flying half the box (of 25) I have encountered the following:
1. Nozzle clay erosion. This resulted in an off vectored thrust which caused rockets that were known to fly stable to skywrite. Reportedly has been fixed.
2. Case deformation/burn through. A couple of my rockets have been destroyed by the propellant burning through the side of the case and destroying the motor mount and mainframe. Hopefully has been fixed.
3. Nozzle bore too small for the First Fire Micro initiators to fit through. This results in the bridge wire or pyrogen coating being broken, often without you realizing it. Again, hopefully this has been addressed.
4. Overly long ejection charge. Rockets that fly fine on the Estes B4-4 with ejection at apogee have lawn darted on the QJet B4-4, with ejection on the ground. I remember others posting this as a problem, it reportedly has been addressed IIRC.
5. Chuffing. This can occur with any composite motor. To be expected.
6. Initiator holder. Heat shrink tubing had been used to hold the initiator in place. Not very reliable or effective, as it cannot be pushed down hard to lock it in place because it's so soft. The new Q Picks are plastic and should be better.
Specifically, isn't there some plastic cap that gets ejected into the rocket with the Q-Jet while the Estes BP 18mm engines just have tiny bits of clay to worry about?
I look at the plastic cap as an advantage, since you can easily remove the ejection charge for saucers and other odd rocs that don't need it. Don't know if it may foul a baffle in time, most of my rockets use traditional wadding and everything gets ejected with the laundry
- Might not fit in all BT-20 motor tubes due to slightly larger size (is this still true?
No longer true, it's been addressed.
- The ejection charge "thingy" sticking out on the top might not fit in some MMTs (probably not a major occurrence, though)
The hex cap on the ejection charge will fit most motor mounts with an engine hook. A flat side of the cap needs to be aligned with the forward tab on the hook. On a very small percent of rockets I have not been able to get the cap past the tab. On those I use an Estes BP motor.

To Aerotech/Quests' credit they have sent me a replacement bulk pack. I have not received and flown the newer motors from the bulk pack yet.

With the recent increase in price of BP motors the QJet composites are more competitive. They also give you the option of flying a D impulse in an 18 mm motor. And they come in two flavors of propellant, one with black smoke and one with white. Choice is always a good thing.
Laters.


.
 

mh9162013

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Thanks for all the responses so far.

I read about a lot of the initial production problems, but haven't heard much lately, so I think it's safe to assume the issues have been resolved.

I do plan on using baffles in my future builds, so the ejection cap is a concern for me. I recently watched an Apogee video about how to remove ejection caps that are rattling inside a rocket (b/w the MMT and the baffle). I'm not as worried about the rattling as I am about a piece of plastic being blasted into the ejection baffle.
 

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I've had a completely different experience with Q-Jets. I bought my first packs of them after returning to the hobby almost 5 yrs ago and have had a number of issues with the motors. Everything from popping and banging on the pad with failures to ignite, failures to eject and most recently a series of burn through when the motor burns through the side of the motor about have way up the case.

I was told by a member that they updated the motors so I took a chance an picked up a pack of C12-6's. These were new stock at the local shop so presumably they were manufactured after the corrections were made. First launch the motor burned through the side of the case and the side of the rocket.

For me that was the end. I took the few Quest motors I had left and disposed of them. Not worth destroying a rocket to use those motors. Hard to believe that AT makes these as I've never had an issue with an AT branded motor.
 

neil_w

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They are not that much different. Here are the three thrust curves from Thrustcurve.org. Blue is Q-jet A3, red is Estes A3-T, green is Estes A10-T:
1655473090319.png
As you can see, the initial thrust of the Q-jet is right in between the A3T and the A10T. Therefore, it is highly likely that something built for one would work with one of the others. I'm not really sure you need to be thinking about micro-optimizing a design specifically for one of those motors.
- Cleaner burn (but is this actually true?)
- Quieter
I'm not sure those are really advantages in any meaningful sense. A motors are not exactly noisy to begin with.
 

mh9162013

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I've had a completely different experience with Q-Jets. I bought my first packs of them after returning to the hobby almost 5 yrs ago and have had a number of issues with the motors. Everything from popping and banging on the pad with failures to ignite, failures to eject and most recently a series of burn through when the motor burns through the side of the motor about have way up the case.

I was told by a member that they updated the motors so I took a chance an picked up a pack of C12-6's. These were new stock at the local shop so presumably they were manufactured after the corrections were made. First launch the motor burned through the side of the case and the side of the rocket.

For me that was the end. I took the few Quest motors I had left and disposed of them. Not worth destroying a rocket to use those motors. Hard to believe that AT makes these as I've never had an issue with an AT branded motor.

Yikes!

This post gives me pause on the Q-Jets...
 

mh9162013

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I'm not sure those are really advantages in any meaningful sense. A motors are not exactly noisy to begin with.
All else being equal, a quieter launch and a cleaner burn is advantageous to me. The biggest thing for me would be a cleaner ejection charge, but I'm assuming the Q-Jets are no cleaner than Estes BPs in that respect*.

*Except for that red cap that'll get blasted into a baffle.
 
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mh9162013

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I'm not really sure you need to be thinking about micro-optimizing a design specifically for one of those motors.

I do, depending on the engines I'm comparing.

I'm not a gram weeny, but if my rocket's sans-engine weight is 30-40 grams, using a mini engine that's about 8 grams lighter (A10-3T versus A8-3) than a regular 18mm engine is a significant difference, even if the thrust curves are comparable.
 
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Watch this video from Ronz Rocketz. He was experiencing the same issues I am but I think he is having better luck than I am.
That's my Heatseeker at 11:01 and Dark Zero at 20:00. Both were using the QJet B4-4s from an early production bulk pack. And both suffered burn throughs as I mentioned in my earlier post.
We'll see how the replacement motors are.
 

CalebJ

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For what it's worth, I've run through a few packs of Q jets and the only issue I've experienced is having to peel a label to make it fit. I'm very curious why these issues are affecting some people but not others. Lot numbers? Storage practices?
 

smstachwick

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I’m not sure that the Q-Jet failures are the result of cheap construction so much as novel manufacturing techniques. They’re a neat piece of technology that has improved significantly since launch (ba dum tsss!) and will probably continue to do so.

As far as noise, I’ve observed that volume is roughly proportionate to thrust. A G80 will really startle people on the flight line who aren’t paying attention. An H13, a lot less so. Given the higher thrust of the Q-Jets in the C class and up, I’d be prepared to dismiss any idea that they’re quieter.

Six significant things about the Q-Jets though that I haven’t seen mentioned:

Q-Jets also come with brightly colored wadding. It’s easier to see and recover than Estes wadding and will produce less litter for this reason, so that’s good if TP-type wadding is allowed. It will probably be useless if dog barf, fire blankets, a baffle, or an uninhibited ejection (for spools and such) are required/planned.

I have gotten a Q-Jet D16 into an Estes Phantom (a clear plastic Alpha III) and the motor hook got stuck in the groove between the charge cap and the forward closure. I managed to yank it out of there but I didn’t try that again.

There is no 1/2A option for the 18mm Q-Jets and there is no C option for the 24mm Q-Jets. If you’re going to under-power anything for a test flight, you’re probably better off with an Estes motor unless you need the extra thrust/total impulse of the C and D classes for a heavy rocket.

Disposal of bad Q-Jets is a bit more dicey than Estes motors. You can soak Estes motors overnight until they fall apart and then throw the soggy components away, but Q-Jets must be fired while stuck in the ground like a Roman candle. I have done this with a D16-4 where the two halves of the casing were starting to separate.

Black Max Q-Jets will leave more smoky residue in your launch equipment. Be prepared to clean igniter clips with some frequency if you fly a bunch or if the person who used the pad before you just used one.

Composites do not stage like black powder motors. You will need staging electronics if you want to fly multistage with these motors.

These may seem like drawbacks or even just non-factors, but these motors have their uses and can be a great deal of fun.
 

mh9162013

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I’m not sure that the Q-Jet failures are the result of cheap construction so much as novel manufacturing techniques. They’re a neat piece of technology that has improved significantly since launch (ba dum tsss!) and will probably continue to do so.
Nice!

There is no 1/2A option for the 18mm Q-Jets and there is no C option for the 24mm Q-Jets. If you’re going to under-power anything for a test flight, you’re probably better off with an Estes motor unless you need the extra thrust/total impulse of the C and D classes for a heavy rocket.
Good point

Disposal of bad Q-Jets is a bit more dicey than Estes motors. You can soak Estes motors overnight until they fall apart and then throw the soggy components away, but Q-Jets must be fired while stuck in the ground like a Roman candle. I have done this with a D16-4 where the two halves of the casing were starting to separate.
I didn't think of that. How do you ignite these "roman candle" Q-Jet engines? Do you have to waste a good igniter to do so? Out of curiosity, why can't you just soak these composite engines in water to destroy them? They still work when wet or something?

Black Max Q-Jets will leave more smoky residue in your launch equipment. Be prepared to clean igniter clips with some frequency if you fly a bunch or if the person who used the pad before you just used one.
Good to know. This might be the last straw that keeps me with Estes engines.
 

smstachwick

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I didn't think of that. How do you ignite these "roman candle" Q-Jet engines? Do you have to waste a good igniter to do so? Out of curiosity, why can't you just soak these composite engines in water to destroy them? They still work when wet or something?

Estes motors are almost fully water soluble. The paper casing comes unglued and unravels. I think the black powder is rendered non-flammable too, although I’m not certain of this.

The Q-Jets have plastic casings that don’t unravel. I don’t know if the propellant or any of the internals degrade, or how severely if they do, but firing them in the ground, with normal igniter hookup, is what the included instructions say to do.


Wetting a Q-Jet definitely feels like something you shouldn’t try at home. I know the nozzle is clay like the Estes motors and the loss of the nozzle may neutralize some of the pyrotechnics by denying them the pressure they need to burn vigorously, but I genuinely don’t know.

Good to know. This might be the last straw that keeps me with Estes engines.

Cleaning igniter clips isn’t that hard or time-consuming, a couple of wipes with 200 grit sandpaper will usually re-expose the metal and allow current to flow again. A few wipes on the rod will fix any binding issues.
 
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I'm not giving up on them just yet.
I should be getting the new bulk pack in a week or so.
Will report on how they perform. One thing I would like to see is extra igniters with each pack.
One igniter per motor just doesn't cut it, they're so easily damaged.
 

smstachwick

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I'm not giving up on them just yet.
I should be getting the new bulk pack in a week or so.
Will report on how they perform. One thing I would like to see is extra igniters with each pack.
One igniter per motor just doesn't cut it, they're so easily damaged.
I’ve had the same complaint about the 2- and 4-packs of Estes motors for years.

The nice thing is that since I’ve been doing a lot of multistaging, I have a bunch of extras now.
 

rharshberger

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Nice!


Good point


I didn't think of that. How do you ignite these "roman candle" Q-Jet engines? Do you have to waste a good igniter to do so? Out of curiosity, why can't you just soak these composite engines in water to destroy them? They still work when wet or something?


Good to know. This might be the last straw that keeps me with Estes engines.
Yes you have to use an igniter to dispose of them.
 

mh9162013

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Thank you all for your advice.

I'm not going to refuse to use Quest Q-Jets, and if I get an oppotunity, I'd like to try them. But I'm not going to revolve my rocket building or designs around the Quest Q-Jets. Instead, I'll stick with Estes.
 

smstachwick

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Thank you all for your advice.

I'm not going to refuse to use Quest Q-Jets, and if I get an oppotunity, I'd like to try them. But I'm not going to revolve my rocket building or designs around the Quest Q-Jets. Instead, I'll stick with Estes.
That’s probably wise. I like rockets that are versatile and can fly on anything that will fit in the mount.

Getting them back can be a challenge but that’s where flying the field comes in.
 

rharshberger

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Thank you all for your advice.

I'm not going to refuse to use Quest Q-Jets, and if I get an oppotunity, I'd like to try them. But I'm not going to revolve my rocket building or designs around the Quest Q-Jets. Instead, I'll stick with Estes.
Fly both, they both have their places, the Q-jets are great for heavy for size models, and the Estes motors are fun to fly and have options and abilities that Q-jets dont.
 

smstachwick

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If I ever get the chance to launch in a really big field and feel the need for altitude, an 18mm D Q-Jet will be a good option to have.
Better idea: Peel the label off a D20W and bring a first-timer out. Explain the motor codes and have them fly a small, quick-and-dirty rocket on a couple of 18mm 1/2A and A motors, then show them how to load up the D without mentioning what it is. Observe the look of total shock when the thing just disappears from the pad and clears 1000 ft in the blink of an eye.

“What was THAT? 😮

“D motor.”

Completely deadpan for best effect.
 

Bill S

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I've had a completely different experience with Q-Jets. I bought my first packs of them after returning to the hobby almost 5 yrs ago and have had a number of issues with the motors. Everything from popping and banging on the pad with failures to ignite, failures to eject and most recently a series of burn through when the motor burns through the side of the motor about have way up the case.

I was told by a member that they updated the motors so I took a chance an picked up a pack of C12-6's. These were new stock at the local shop so presumably they were manufactured after the corrections were made. First launch the motor burned through the side of the case and the side of the rocket.

For me that was the end. I took the few Quest motors I had left and disposed of them. Not worth destroying a rocket to use those motors. Hard to believe that AT makes these as I've never had an issue with an AT branded motor.

I have had a fair number of failures, whereas I've had exactly zero failures with Estes motors. I'm talking 400+ Estes motors, from 1/4A to E16s, zero problems. Q-Jets, at least 7 that I know of out of perhaps 25 launches or so (I'd have to check my records). I still have 40+ Q-Jets of various types, so I'm reluctant to just throw them out, but I can't in good concience sell them to someone knowing I have had problems with them in the past. I don't want to be "that guy who sold me bad motors and destroyed my rocket".

I'm slowly using them up, but its going to take a loooong time, and I'll always be nervous about using them. I don't know if the new version is better - I was told they were changing the clay nozzle materials, etc, but I have zero experience with the new ones.
 

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If I ever get the chance to launch in a really big field and feel the need for altitude, an 18mm D Q-Jet will be a good option to have.
Definitely, I fly mainly AT 18/20 reloads for that reason, occasionally I fly other motors but have yet to fly a Q-jet.
 

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I've flown several hundred Q-Jets by now. I've had a handful of failures of the sort discussed here — perhaps no more than I've had with a similar quantity of Estes motors...but the failure modes are different. I've had a couple of burn throughs and

To add my own few cents' worth on some of the discussion:

The red plug that holds in the ejection charge is a soft rubbery plastic. I fly lots of models with baffles....I've never had a baffle damaged by the plug and to get one out one just needs to shake the model a bit until it falls out — our at least that's my experience. It's also not really harder to shake out than all the clay bits from an Estes ejection cap, but there's just the one thing and you know when you've got it out (shaking the model gets real quiet...).

On A3s - Neil's overlay of the Q-Jet A3FJ, Estes A3 and A10 time-thrust curves up in post #7 tells you the story. The one advantage the Q-Jet A3FJs have is that they come to full thrust faster. Otherwise, there is no significant performance advantage. In something like an Alpha, the A3-4FJ is going to perform about the same as an Estes A8-5. They are quieter, and of course there's that cool black smoke that gets your GSE dirty....

The B4FJs are pretty much comparable in performance to their Estes counterparts (B4s and B6s), but with the quieter, smokier exhaust.

The B6Ws are still a work in progress. Early sample motors were amazing, even outperforming the Chinese-made Quest B6 black powder motors that are now long OOP. Early production motors, not so much. The last couple I have gotten are getting closer to the performance I saw in the two samples I flew at NSL in 2021. If they can make 'em that way consistently, the B6W is going to be well loved by those seeking better altitudes. They are not suitable, really, for heavier models as their maximum thrust is not greater than Estes B6s.

I think the C12FJs are kind of magical motors. They only have about 1 N-s more total impulse than an Estes C6 (9.8 vs. 8.8 N-s, per cert data). But in just about everything I've flown them in, they significantly outperform Estes C6s (or C5s), by which I mean ~20% higher maximum altitude on a fairly normal model, with the margin going higher on a model that's heavy for a C6 (the Estes 1/200 RTF Saturn V being the poster child here). Again, a quieter, smokier exhaust note coming from a rocket that just gets up and goes.

C18Ws are rip-snorting loud, but since they are higher thrust (and therefore shorter burn) they actually don't fly a given model as high as a C12 does....that extra thrust means extra speed which means extra drag (which goes up with the square of velocity). I haven't flown a lot of C18s in "heavy" models so that's an area where they might have an advantage over the C12FJs.

Be aware that both the D16FJs and D20Ws are "baby" Ds....less than 14 N-s which is less than 4 N-s over a full C. A full D is 20 N-s, Estes D12s are 16.8 N-s. As with the C18W vs C12FJ, the higher thrust means higher speed and greater drag, so models flown on them don't really outperform the same models flown on Cs (especially C12FJs) by as much as you'd expect (here again I mean mainly altitude performance). But they are cool to fly. The Ds are similar in character to the Cs. FJs are smoky and not very loud, Ws are quite loud.

On initiators: Yes, the FirstFire micros are fragile, though recent ones are much more robust (but harder to get into the As and Bs' tiny nozzles). But unless the bridge wire is broken, they will work, especially on FJ motors. @kuririn will be happy to hear that there are a few spares in the most recent C12-6FJ bulk packs I bought (but no Q-piks yet). I have had only a few misfires so far, and the FFmicros work on just about any launch controller (though ones that use a little 9V battery are marginal, as they are with Estes igniters).

On fitting in models: yes, the first A3FJs and B4FJs (back before they were labeled that way) had case diameters that were a touch large, and peeling the label (and removing the goo left behind) was the way to get them in a model. When they were redesigned the ejection charge well was also reduced in size, but in most models with an Estes motor hook one still has to take care to align one of the flat sides of the charge well with the upper end of the hook. And in some cases that upper end of the hook still projects too far in to let the charge well pass.

I would not be surprised if these low-priced packs at Belleville Hobby are old stock that have the "just a bit too large" problem. Check the shipped price, by the way....

On ejection charges:

Delays are still inconsistent, and I think, especially early on there were motors that were mislabeled. Since I fly FS Minis in many models I fly, I have the actual delay times from lots of flights, taken from the accelerometer data. The trend is generally that they're closer to the actual marked delay nowadays, but still once in awhile I get a real surprise. Estes delays (except, for some reason, for the C5-3) tend to be short of the marked value, and while I used to think this was mostly a motor age thing, I flew two made in 2021 B6-4s the day before yesterday and one had a delay of almost 3.0s and one was about 3.2s. So not getting the delay value that's on the label is a general thing. There's also a pretty big tolerance on the delay for it to be within the NFPA bounds for certification. At the moment I can't quote it, but a B6-4 with a 3.0s delay or a 5.0s delay is within certification tolerances.

The early Q-Jets had way too much ejection charge for all but the largest models. They dialed it back significantly, then dialed the short delays back up some (reasoning that the short delays would be used in larger, heavier models with more volume to pressurize, which makes sense). Every now and then I still get a really big ejection charge on a longer-delay motor. I got a real surprise flying a 24mm Q-Jet D22W not that long ago...and lost a Universal Astrocam off the rocket from the violence of it. But Estes also has "shotgun ejection charges" sometimes, and remarkably often in their 13mm motors.
 
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I have found the Quest motors to be problematic as the ejection charge is .1g smaller than the Estes ejection charge. I've had two lawn darts from failed deployments. I will only use Quest motors in clusters going forward as multiple ejection charges will compensate for the single motor deficiency.
 
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