Quest QJet - underpowered ejection charges?

[Zyzzyva1000]

I had a nice successful flight of a cluster of 3x E35's yesterday (looked great) in my LOC 2.6 Phoenix, but then decided to use the remaining motor in my BT60 BBX. E12-6 has ejected the nosecone without issue in the past, but the E35 couldn't get it out. I suddenly remembered that I had the same issues with my Estes Vapor (and had stopped using the QJets). Anyone else noticed this issue? These composite motors otherwise perform well, but the ejection charges are weak sauce compared to Estes BP motors. Any reliable way to fix this? I otherwise like the motors.

 

[lakeroadster]

Sorry, but I have a side question. What ignitors did you use for the 3x E35's. In your experience, is reliable clustering an issue with these motors?

 

[Zyzzyva1000]

I just used the provided ignitors. I feel like some of the smaller (24 mm) composites have given me some issues igniting in the past. However these have a nice little piece that helps to friction fit the ignitor in. I used a clip whip which was very helpful. Definitely better than trying to wire the igniters together. I have watched lots of other clusters launch in the past and rarely do they all go. These performed great as far as the cluster aspect (and with 3 motors in a rather short/fat rocket the ejection wasn't an issue.

 

[lakeroadster]

I just used the provided ignitors. I feel like some of the smaller (24 mm) composites have given me some issues igniting in the past. However these have a nice little piece that helps to friction fit the ignitor in. I used a clip whip which was very helpful. Definitely better than trying to wire the igniters together. I have watched lots of other clusters launch in the past and rarely do they all go. These performed great as far as the cluster aspect (and with 3 motors in a rather short/fat rocket the ejection wasn't an issue.

Thank you.

 

[AeroTech]

I had a nice successful flight of a cluster of 3x E35's yesterday (looked great) in my LOC 2.6 Phoenix, but then decided to use the remaining motor in my BT60 BBX. E12-6 has ejected the nosecone without issue in the past, but the E35 couldn't get it out. I suddenly remembered that I had the same issues with my Estes Vapor (and had stopped using the QJets). Anyone else noticed this issue? These composite motors otherwise perform well, but the ejection charges are weak sauce compared to Estes BP motors. Any reliable way to fix this? I otherwise like the motors.

The Q-Jet ejection charges are sized for the average rockets they are flown in. If you have a larger rocket that needs a bigger charge, it is a simple matter to remove the retainer cap and add more BP.

There was a time when some of the 18mm charges were slightly larger but some customers complained that they were too powerful. It’s difficult to make “one size fits all”.

 

[Zyzzyva1000]

Legitimate question though, an E35 flown in place of an E12 in something like an Estes Vapor (my BBX was the same size), seems the ejection charge is considerably weaker compared to a comparable Estes BP charge? In any case, I was not aware the retainer cap could be removed and more BP added on the QJet motors, so I will just do that in the future. Like I said, I otherwise really like them.

 

[waltr]

Since the charge is accessible, it would not be a bad idea to open and measure the charge size in every Q-jet before flying.
Then one be sure of the BP amount and reliability to eject chute.

 

[lakeroadster]

Since the charge is accessible, it would not be a bad idea to open and measure the charge size in every Q-jet before flying.
Then one be sure of the BP amount and reliability to eject chute.

Only if one knows how much is enough. How would one know that? Aren't there different types of BP? How Much of Which Type of BP will produce "X" amount of force? How much force is needed?

All stuff I'd be interested in knowing from a trustworthy source.

Kind of sounds "Rocket Sciencey"

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Update.. Lots of data on these threads....

https://www.rocketryforum.com/threads/deployment-charge-pressure-volume-and-black-powder.164364/
https://www.rocketryforum.com/threads/at-single-use-ejection-charge-amount.176427/#post-2357841
And a chart I created... Tip of the hat to @Tractionengines and @afadeev

​

 

[BEC]

There was a time when some of the 18mm charges were slightly larger but some customers complained that they were too powerful. It’s difficult to make “one size fits all”.

I have to admit being one of those complainers. The very first Q-Jets in particular, when put in models that one would expect to fly with an A or B motor, had pretty violent ejection charges.

As I understand it, the shorter delays (at least in 18mm Q-Jets) now have bigger charges than the longer delays as a first approximation to sizing the charge to the sort of model that it would most commonly be flown in.

I haven’t had too many ejection charge vs. model size mismatches with Q-Jets in the last couple of years, though it occasionally happens.

OTOH, the charges in some 13mm Estes motors….WOW, what were they thinking those would be used in? It’s not universal, which makes me think that Estes, at least at some point in time, wasn’t terribly consistent with the sizes of the charges. But I don’t have enough real data to turn that into more than just an observation. We saw some big ones at the club launch today.

 

[Rocketjunkie]

Q-Jet ejection charges are 4Fg BP and burn **much** faster than Estes charges which look like 3Fa, much coarser than 4Fg. 3Fa is about as course as 2Fg. A series BP is de-dusted but not glazed with graphite like the g series.

 

[lakeroadster]

As I understand it, the shorter delays (at least in 18mm Q-Jets) now have bigger charges than the longer delays as a first approximation to sizing the charge to the sort of model that it would most commonly be flown in

 

[BEC]

Yup. That's a change that was introduced relatively recently (with respect to the release of the first Q-Jets). I had a couple of Big Bertha failures-to-deploy -4 versions of C and D Q-jets prior to that.

From a manufacturer's standpoint, trying to size the charges for both a Viking and a Big Bertha is kind of difficult.....

 

[DigBaddy]

Only if one knows how much is enough. How would one know that? Aren't there different types of BP? How Much of Which Type of BP will produce "X" amount of force? How much force is needed?

All stuff I'd be interested in knowing from a trustworthy source.

Kind of sounds "Rocket Sciencey"

______________________________________________________________________________________________________________________________________________

Update.. Lots of data on these threads....

https://www.rocketryforum.com/threads/deployment-charge-pressure-volume-and-black-powder.164364/
https://www.rocketryforum.com/threads/at-single-use-ejection-charge-amount.176427/#post-2357841
And a chart I created... Tip of the hat to @Tractionengines and @afadeev

View attachment 586895​

Nice chart! I augment the 24mm reload charges for many flights. 0.5g definitely not enough it fat/light birds.

 

[Grog6]

The calculations are a great starting point, but the key is test with the powder you're using. I usually do at least 10 tests on a new rocket before I fly it.