LOC Warlock - Any worries about Engine Eject not pressurizing 8" dia tube?

JSW

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Launching a LOC Warlock for my L2 cert,...

The nose cone is a little tight. I've done what I can to get a looser fit. I can hold it vertically and the body will drop off. Is that loose enough?

Any worries about engine eject not pressurizing the 8" dia tube enough to pop the nose cone?

Wondering if I should extend the motor mount and put in a new bulkhead to reduce the volume that needs to be pressurized?

Any insights appreciated.
 

DAllen

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You mean centering ring?

I think those are referred to as "stuffer" tubes and frankly it isn't a bad idea. I'd do it for sure just so long as you're not making it impossible to put the recovery gear in...
 

Steve Shannon

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You have two things to worry about.
Yes, there’s the possibility that the factory ejection charge will not adequately eject a heavy nosecone from a tube with that volume.
You also have a possibility that your nosecone will slip out of the rocket when the motor thrust ends. Typically you do not want a nosecone that falls free of its own weight, or when the rocket is picket up by the nosecone.
You need to ground test to determine if the ejection charge is enough.
 

ThirstyBarbarian

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I add another 1.5 grams of black powder, for a total of about 3 grams. That will pop it open nicely.

And as @Steve Shannon said, you don’t want the nosecone too loose either. Mine is typically a bit loose, and I put two tabs of 1” masking tape a couple inches long on either side of the rocket to tape the nosecone to the body tube. That keeps it from drag separating, but the ejection charge easily breaks the tape.
 

crossfire

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I ordered a LOC Bruiser and am thinking of going with a longer MMT to take up some of the tube space to help with ejection of the chute.
 

H_Rocket

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I’ve ground tested with the amount of BP that comes with a 38mm AT reload. It worked okay but I normally add another 1/2 gram or so for a belt-n-suspenders level of confidence.
 

ThirstyBarbarian

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I’ve watched more than one Warlock fail to eject the nosecone and crash. Not pretty.

The first one, the nosecone had fit fine with a wrap or two of tape around the shoulder in the owner’s garage according to the owner. But the launch was extremely hot, and the rocket sat in the sun, and the nosecone expanded and got tight. So you want to be aware of that. Check the fit each time before flight. The owner also did not supplement the ejection charge, so that probably contributed too. That one came in ballistic and completely disintegrated on impact. It made a BOOM when it hit.

The second one, the fit was probably fine, but the owner did not supplement the charge. The nosecone partially ejected, but not all the way, and the recovery gear stayed in the body. It came down on its side, and was pretty much destroyed.

I think there’s little risk of a too-energetic ejection charge, so put in an extra gram, gram and a half, or two.
 

Back_at_it

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I just flew a Warlock for my level 1. You absolutely need to add additional powder for the ejection.

For my Cert flight, I added black powder to ejection for a total of approx. 3.0 - 3.1 grams. Ejection was perfect. At the time of launch, I checked my nose cone. The rocket body would slowly slide off the nosecone if I picked it up by the cone.
 

mikec

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I've never flown a Warlock but I feel like there's a lot of variation here. Has the pressurized volume of the kit changed over time or do people build with the upper centering ring in different locations? https://rocketrycalculator.com/rocketry-calculator/bp-estimator/ says 4g per 12 inches of length for a 7.5" tube, but freely admits that this is probably an overestimate. Obviously there could be a lot of variation in nose cone fit. IIRC an AT reload has 1.7g of BP or thereabouts.
 

green dragon

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Wiped out my Warloc on a Pro 38 motor without added powder... you need to add some to the charge.just to be safe. agree on 2.5-3 gms total sounding about right.
 

pathtouch

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Might as well pile on a data point. I have a 7.5” Doorknob but it splits in half with an AV bay so my volumes are probably close to yours. I run 3g primary charges.
 

ThirstyBarbarian

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Everyone agrees add powder, and the consensus is you probably want to have around 3 grams total, so how do you do that?

I fly Aerotech DMS motors and CTI motors. The DMS motors come with the pre-measured ejection charge packaged in a small plastic vial with volume markings on the side. (I assume Aerotech reloads are the same.) I thought they usually come with 1.4 grams, but someone upthread just said 1.7, which may well be true. I don’t really remember. You can use those vials to measure your supplemental charges. I’ve saved up a bunch of them and keep a few in my range boxes.

For DMS, the full 3 grams won’t fit in the charge well and allow you to use the usual red cap to seal the charge well. What I do is put a wrap of masking tape around the top of the charge well to make a little tape cup to extend the rim of the charge another half inch or so. After you drill your delay, dump the pre-measured charge into the charge well. Then pour some ffffg black powder into the vial until it reaches the volume mark for your supplemental charge. I fill it up to the 1.5 mark. Then pour that into the tape cup/well on top of the BP you already added for the standard charge. Then fold or twist the tape shut to seal up the whole 3-gram charge. You don’t want any extra space in there, so if the BP doesn’t come all the way up to the rim of the charge well, pack a little dog barf or wadding in on top before you seal up the tape so that everything is nice and tight. Add some extra tape if needed to keep it all secure.

For CTI, it‘s the same basic idea, except the factory ejection charge is already sealed. Just leave it like that and assemble the motor in the case as usual. Measure out your 1.5 grams supplemental charge. I use an old spare DMS vial just like I do for DMS motors. You can make a tape cup for the extra charge right on the end of the case, which is what I’ve mostly done. You have to be careful because wrapping the tape around the end of the motor case can add enough diameter to the case it can be more difficult to slide into the motor tube. And if you have to pull the motor out before flight for any reason, be sure the tape cup doesn’t peel away from the case and dump the supplemental charge. Another option is to pour the supplemental charge into a small square of wadding, fold that up, and then tape that to the end of the case right above the factory charge. The factory charge will blow right through the wadding and light the supplemental charge. I’ve been using that method the last few times.

I’m sure the method for Aerotech reloads is pretty similar.
 

JSW

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Everyone agrees add powder, and the consensus is you probably want to have around 3 grams total, so how do you do that?

I fly Aerotech DMS motors and CTI motors. The DMS motors come with the pre-measured ejection charge packaged in a small plastic vial with volume markings on the side. (I assume Aerotech reloads are the same.) I thought they usually come with 1.4 grams, but someone upthread just said 1.7, which may well be true. I don’t really remember. You can use those vials to measure your supplemental charges. I’ve saved up a bunch of them and keep a few in my range boxes.

For DMS, the full 3 grams won’t fit in the charge well and allow you to use the usual red cap to seal the charge well. What I do is put a wrap of masking tape around the top of the charge well to make a little tape cup to extend the rim of the charge another half inch or so. After you drill your delay, dump the pre-measured charge into the charge well. Then pour some ffffg black powder into the vial until it reaches the volume mark for your supplemental charge. I fill it up to the 1.5 mark. Then pour that into the tape cup/well on top of the BP you already added for the standard charge. Then fold or twist the tape shut to seal up the whole 3-gram charge. You don’t want any extra space in there, so if the BP doesn’t come all the way up to the rim of the charge well, pack a little dog barf or wadding in on top before you seal up the tape so that everything is nice and tight. Add some extra tape if needed to keep it all secure.

For CTI, it‘s the same basic idea, except the factory ejection charge is already sealed. Just leave it like that and assemble the motor in the case as usual. Measure out your 1.5 grams supplemental charge. I use an old spare DMS vial just like I do for DMS motors. You can make a tape cup for the extra charge right on the end of the case, which is what I’ve mostly done. You have to be careful because wrapping the tape around the end of the motor case can add enough diameter to the case it can be more difficult to slide into the motor tube. And if you have to pull the motor out before flight for any reason, be sure the tape cup doesn’t peel away from the case and dump the supplemental charge. Another option is to pour the supplemental charge into a small square of wadding, fold that up, and then tape that to the end of the case right above the factory charge. The factory charge will blow right through the wadding and light the supplemental charge. I’ve been using that method the last few times.

I’m sure the method for Aerotech reloads is pretty similar.
Thanks for the details!

I’m using the AEROTECH DMS.

I’ll have to see if I can track down some black powder.

Also, good suggestion to use the BP calc. I hadn’t considered - given I was using engine eject.
 

DarthDaddy762

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I used stiffer tubes on my LOC 7.5 DoorKnob with nose cone ejection. Will a J360 ejection charge be enough? BTW the nose cone has a RNWS system and two pounds of lead shot.
 

JSW

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Really good point about estimating using the BP calc. I hadn’t considered being able to adjust a “factory engine eject”.

I also realized that LOC instructs you to drill two 1/2” holes in the base of the Warlock nose cone for securing the shock cord. So the volume of the nose cone would also need to be pressurized. Might equate to another foot of body tube?

Does anyone know if Estes igniters could be used to ground test with BP? If not,… probably won’t be able to get e-matches in time to ground test. Hoping to attend the Nashville launch (http://www.mc2rocketry.com/) this coming weekend.

Thanks again to all.
 

ThirstyBarbarian

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Ground testing would be ideal, but using an Estes igniter probably would not be very convenient.

Also, doing the BP calc would be ideal, but also probably not necessary. Things like the nosecone holes are kind of difficult to know how to handle. Generally, the pressure builds so quickly when the charge goes off, you don’t really need to consider smallish holes, and I don’t think a couple of 1/2” holes in the nosecone mean you need to account for the volume of the cone. The pressure wave will hit the bottom of the cone and eject it from the rocket before enough gas and pressure enter the cone through those hole to make much difference.

If pressed for time, you can probably skip those calcs and tests for now and just go with the recommendations in the thread. I add about 1.5 grams to the standard charge, so about 3 grams total. For some kinds of rockets, you should be more precise, like if you are using shear pins. Some situations need to be dialed in precisely and being half a gram off could be a problem. But this is not like that. This is a robust rocket, and the main issue is its large volume, so I think it’s ok to be a bit loose with the amount. Probably anything over 2.5 grams total would be big enough to eject the cone reliably, and anything under 3.5 would be small enough not to damage the rocket. There’s wiggle room. A total of 3 grams is probably enough and not too much, and it sounds like most people use about that much.

I think it would be great to circle back and do the BP calculations and do your ground tests, but if you can’t get to those before the launch, just supplement the charge with 1-2 grams.
 

ThirstyBarbarian

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A few other tips on the Warlock:

I don’t know if the directions call for it, but you should drill a few small holes in the body of the rocket to vent the main compartment with the chute in it. I think I have 3 holes in mine, each about 1/8”. Any rocket that goes above 2,000 feet or so should have vent holes, especially if it’s going to be fast. I put vent holes in all my rockets, even the ones that I don’t plan to fly that high or fast. Without vent holes, the rapid change of pressure during the flight can force the nosecone out. The holes allow the pressure to equalize during the flight. But the holes are not big enough to interfere with the ejection charge, so don’t worry about that.

The supplemental charge means the ejection is going to be pretty hot and strong. That means it can be more of a danger to recovery gear. Even though I use nomex chute protectors and harness sleeves, I still dump in a good load of dog barf. Nomex is good protection for heat and flame, but blast is a different concern, and the blast from a 3 gram ejection charge can penetrate nomex and damage a chute. So a layer of dog barf is a good option.
 

rfjustin

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Good advise and something I'd like to try someday. How would I go about ground testing with motor ejection?
Put the smallest piece of motor hardware you have in the bird (with forward and rear closures installed) , seal the after end with tape, build an ejection charge "into" the forward closure, make sure its sealed in some capacity, route a small set of wires out the vent hole. Ignite an e-match or comparable Chinese firework igniter from a distance off a 9V battery.

Now go wake the neighbors... :)
 

Sooner Boomer

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