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7 Motor Cluster ignition questions

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solrules

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My friend is building a 7 motor cluster of 29mm motors. He either wants to put 1xH268R, 3xH210R, 3xH165R. This would make a brilliant red flame! Anyway, what ignitors should he use? Daveyfire? The launch system that will be used is fairly high power, and could handle plenty of current. Ive also heard that igniting composite motors by different formulations (eg. BlackJack, White Lightning, Blue Thunder, Redline) get easier to light the more "pure" the AP is. Blackjack is filled with non burning material, and is hard to light, while blue thunder and redlines are easier to light, as they have fewer additives. This would lead me to think that redlines and blue thunders would be the easiest to cluster, due to their quick lighting. Am i on the right track here? Heres where i got the info: http://www.rocstock.org/wizards/clusterwizard.pdf
They do not talk about redline propellant, as it is relatively new. I feel that redline and blue thunder are fairly equal in properties (except color, of course).

Btw, what configuration do you think would look the coolest: 7 Redlines like above, or 1xH268R, 3xH220T, 3xH128W (giving it a Red/White/Blue color for about 1 second!!!)?
 

Johnnie

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1st off I would like to say, welcome to the Forum...

can't answer your questions, but I can offer my opinion...heck we've all got one or two of those :D

as for motors, either all Red, all Blue, or all White, if you blend them, the white Lightning will all but blind out all the other motors, even though you might see a little red....buuuttt if you airstarted them Red-to-White-to-Blue, that would work great I would think.

Quick burst sells igniters that are made for clusters and airstarts...I would check them as well.

Good luck, and Oh Yeah...get used to this comment..."Pics!!" :D
 

n3tjm

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Redline is a hard propellant to light... especially if it gets old, and it ages quickly (Starts to yellow)...

If you cluster Redlines... make sure ALL of the motors are new as possible, and from the same batch... I seen redlines that took over 2 seconds to presurize... and they were only a couple years old.

I personally do not like redline... hard to light, and burns way to fast. If they could make it slower, that would be cool, but then the cases will melt down... Redline burns very hot.
 

rocwizard

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Like Doug said, redline is almost as slow to light as blackjack. At our big ROCstock lauch in Nov., a guy tried to cluster a J540 redline and 2 H210 redlines in a Magnum (I REALLY need to get one of those) all lit on the ground. What happened was, one H210 lit and pushed the rocket off the rail, as soon as it cleared the rail it angled a good 45-50 degrees because of the asymetrical thrust, then the rest of the cluster hit. MASSIVE red flame ensued, but the rocket flew a good 2 miles or so uprange. A really cool flight was when another one of our club members flew his magnum on a K1275 redline (Now THAT is a motor) and airstarted 6 H210 redlines 2 at a time. Awesome flight to 9000+.


That isn't to say that redline can't be clustered. Special preparation techniques need to be carried out though to help insure they all light. you want some HOT quick lighting ignitors. dipped e-matches would work well. Then I would recommend using more pyrogen and paint the coreof the top grain or two in each motor. This will insure that the heat and flame is transferred to the propellant surface and starts ignition. Finally, check the continuity of each of the e-matches with a meter BEFORE dipping them. Sometimes you will get a faulty match in a package.

Hope this helps!

Welcome to the forum!
 

DPatell

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I agree with Rocwizard. I guy in our club flew a modified Bruiser at LDRS 22 on a central K and 9 H268R's!!! He came back with 5 or 6 motors from the cluster that didn't light, so he sold them to club members;)

Even so, it's not stopping me from eventually trying a J420R or J315R with two H165's in my Magnum:)

Personally I would use dipped Daveyfire's from Ken Allen at www.PerformanceHobbies.com . If all of those motors light, it will be a rip roaring flight! I want to see pics of the HUGE red flame trailing that thing! Technically speaking, if it's in a 4" airframe, isn't it a minimum diameter rocket?:rolleyes: :D
 

rocwizard

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Dan, that will be really cool if it works. Again, I recommend that you get some pyrogen or borrow some from a person that has some. Ahh, heck just get it, you will be glad you did.:D and paint the motor cores with it. It WILL work then.:kill:
 

n3tjm

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Be carefull... you can put TO MUCH pyrogen in them. It is possible that the pressure inside the motor can go up so fast that it snuffs itself out. I have done this many times trying to get old D9 motors to start...
 

solrules

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Ill post pics of it as soon as i can. It is in a 4" airframe (there is a very small amount of plywood in the centering rings, so he is flodding the gap between the CR and the end of the motor tubes with epoxy+aluminium so he can tap into the rings to make motor retention and heat resistance). its using the honeycomb fin material from Giant Leap rocketry. The center 29/360 motor will have a plugged aft closure and will be tapped for an eyebolt for shock cord attachment. The nose cone is gold leafed (nose cone found in swamp in bong recreation area in wisconsin, cleaned, gold leafed). The body will have a solver/chrome sticky paper to make it really flash in the sun. Oh, yeah, the name: Apocalypse. Heres a 3d rocksim pic (does not do justice to gold leaf and chrome paper). Oh, yeah, did i mention that the Apocalypse will have an aiptek Dv2 camera in it? That means in flight video (at low fps, but its something!)

EDIT: It is not epoxy+aluminium, not epoxy+magnesium
 

Ryan S.

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All great ideas. I plan on clustering my Mission Impossible with a central K redline, either the K695 or K1275 with 2 38mm H redlines and 2 29mm H redlines (yet to be decided) I will use ematches for ignition and paint the top of the grains with pyrogen. I may do this in blue thunder form also. I have yet to decide.
 

Rocketjunkie

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I usually use the old Thermalite fuse method of airstarting motors. I flew my Motoreater on a K1100 starting 4 H268's with fast Thermalite and 4 H180's with slow Thermalite. The redlines started about as the K burned out and the H180's about when the H268's burned out. Perfect flight to 8400'

If ground starting, dipped Daveyfires and all motors the same diameter and propellant type is best.
 

daveyfire

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Painting the grains with pyrogen is good... BUT...

Pyrogen is meant to be lit from the inside. If you look at your dipped igniters, there is a hard coating around the outside of the pyrogen to protect it from moisture. Depending on the pyrogen, this can actually insulate the stuff from lighting. One trick is to paint the core, then scratch up the surface of the pyrogen. That way, you expose the easy to light center stuff of the pyrogen. But do this just before flight, to prevent it from absorbing moisture.

Learned that one from Erik Gates :)

YMMV.
 

mge55389

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Tried my own copied address and it didn't work!???

Well you could enter:

www.vataas.org/rtv
and go under lessons on the heading of the home page.
Sorry about that...
 

Rocket Flier VB

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Last summer I built a 4" 7X cluster for 29mm's. I had trouble firing all 7 at the same time because I was losing alot of current in the 75 foot leads to the igniters. I ended up using Davy Fires dipped in Pyrogen and building a battery box. The battery box put the current only 3 foot away and worked like a charm. Due to the motor shortage I only made the rocket to hold single use 29mm's so G80's are about all I can use. I put it up on 7 G80's a few months ago and she took off like a bat out of... well, you know.

My first attempt was with 6 G40's and a G80 but only 4 of the G40's lit. I think the kick of the G80 pulled the igniters out before the lit. This was before the battery box though. I haven't tried it since.

Hopefully this will be a shot of the tail end:



Eric F.
 

Rocket Flier VB

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A final shot of it taking off on 7 G80's to 4000' ( a very expensive J)



Eric F.
 

Ryan S.

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the event horizon right? I love that flame, nice rocket! The battery at the rocket is very interesting and I will need to remember that. I was wondering to myself the other day if there would be enough power.

I have one question for everyone; when you dip your ematches do you do anything special? I have heard that when you dip ematches they often get too big to fin in the nozzle
 

DPatell

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Ryan - Some people recommend doing a single fold of the ignitor, or about the top inch or so and fold it over. Some people do a double fold, whatever will fit in the nozzle. In the I357's you should have no issue with ignitors not fitting. With the K1100 you may, as it probably has all 6 Medusa holes opened up, and they are small. The K1275 has it's own nozzle that has a huge throat, so no issues there, either.

After the fold(s), dip the ignitor in your favorite pyrogen. Make sure all ignitors come from the same batch of both ematches and the batch of pyrogen, so they will all be almost identical to one another and therefore light at about the same time. This is probably overkill, but it sure will be worth it.

Also, with all the leads, you mechanically attach them to the tail end of the rocket. If one motor comes up fast and moves the rocket, the ignitors will not be pulled out of the motors. Hopefully all the ignitors will burn when current is run through them, so if they do not pull out they should all theoretically light the motors.

All good things I have picked up along the way that I hope will help:)
 

Ryan S.

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Originally posted by DPatell

Also, with all the leads, you mechanically attach them to the tail end of the rocket. If one motor comes up fast and moves the rocket, the ignitors will not be pulled out of the motors. Hopefully all the ignitors will burn when current is run through them, so if they do not pull out they should all theoretically light the motors.
thats a really good idea. Does anyone know how small the throats are in the medusa nozzle? I could dip it with very little pyrogen and then paint the top of the grain. Or, I could just inser the igniter before I put the nozzle on.
 

Rocketjunkie

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Originally posted by Ryan S.
thats a really good idea. Does anyone know how small the throats are in the medusa nozzle?
They vary by motor type but the center one is above 1/4", usually not by much.
 

JDcluster

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THough it may not be posted on my web site, I have flown a 7-29 mm cluster full up on 1-H268 on the pad to 2-H220 via G-Wiz airstart to 4-G 55 on the second G-Wiz Stage setting . Everthing lit , but it was less than vertical when the G's lit. only went about 2,200 ft altitude wise. Recovery failed when the recovery harness between the Booster & the payload section broke
. Booster was recovered , but the payload section came down in a tree to be recovered 2 years later .
 

marvSRG

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Although I'm more of a MPR clusterer, I agree w/everybody here...dipped davey's...and although the dipped pyrogen should be where the "uhhmf" comes from, I have always heard that in addition to dipping you need to use the more powerful 28F matches...why, I don't know...I just thought that as long as there was a matchhead covered in plenty of pyrogen, that should do the trick. But I have read and heard that dipped Davey 28F's are the way to go for clusters although I really think 28B's would work ok. Another good igniter to use are the Trailing Edge Technologies "Fire in the Hole" tungsten igniters. I know their owner, Jim Turner, died about a year ago, but the site is still up and from what I've heard, they're still in business. But I'd still go w/dipped Daveys for the HPR motors...cheaper and just as reliable. The Trailing Edge igniters are great for MPR clusters though b/c they light just as easily and as well as dipped daveys but they actually fit in MPR motors that can't use the dipped igniters in clusters...just a good tip for you MPR cluster freaks that can't find a fitting and reliable igniter.

Enough w/my ranting on that...I have a technique that I've been succesful with in clustering. I reccomend that you secure the igniters to the rocket by putting some small wire loops inbetween the motors, and wrapping the igniters around those. Just make sure your igniter clips can slide off easily. By doing this, you can light all the igniters on the ground but if you have late motors coming up to pressure, the igniters will stay with the rocket as it's going up. They igniters will all light at the same time, but some motors can be slow so as the rocket begins to lift on some of the quicker lighting motors, the clips will fall away but the igniters will remain in the other motors and they will finish burning and lighting them...I have video proof that igniters can be pulled out of the motors while still burning, leading to a misfire of motors due to the igniters not staying in the motors for their full duration. Hope that's a helpful tip!
 

JDcluster

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The 28F are prefered over the Br or the B's because they burn longer than the other 2. They require about 1 amp to set off & are safer because of it. I've had Davey Fire B's set off from static electricity 2 times, luckly I was not injured.
The draw back is that you have to use a high current electronics to airstart anything. You do still have to dip them though.
 

JDcluster

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I've used them once & don't like them becuase of the way they are made: 2 single stranded wires twisted together. Which can create problems especially if you are using them on longer motors
(anything over 12" or so) it could bind up at the nozzle & possibley cause the motor to Cato.

Also if you are lighting larger outbaords ; Say 38mm & above you might want to use 2 igniters in each motor to ensure ignition.

I did it on my 2x4 on a cluster of 2-I211 & 2 H124 I was able to light the 2 I's at almost the same time ( at least they were both lit by the time it left the rail .

I also help a club member ground start a K 695 along with 2 J 350's with a similar technique.: 2 igniters in the outborads & a bigger fatter igniter in the core K695.


JD
 

solrules

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Anyway, the Apocalypse flew beautifully. The motor configuration:

3xH165
3xH210
1xH268

Wow. We finally did it....it flew! We used dipped daveyfires, the 1amp type with a longer burn. These were ignited with a relay controller within 10 feet of the rocket. 5...4....3...2...1....BAM!! That sucker went up pretty quick :) It looked as if it about 20 feet off the pad, the rocket kicked into high gear (see below). Dual deployment did it's job and worked perfectly (2xPerfectFlite MAWD). They were both beeping the same altitude, a little over 3400' IIRC. We were disappointed with the altitude, but upon inspection, two H210's didnt light.

Anyway, here is what puzzles me:

The shortest motors (H165s) all lit, and should have come up to pressure faster than all the other motors. The longest motor lit (H268), but two of the medium sized ones did not! I figured that if anything would not light, it would be the longer one. What I hypothize is that the 165's lit on the pad, along with a 210 that was lucky. This was enough power to get the rocket off the pad. This pulled out all of the other ignitors out of their cores. I suspect that the H268's ignitor had lit, but the motor was still under pressurization, and finally kicked in at about 20'.

Sorry, but we did not go back to the pad to see if all the ignitors had lit :(

Any other ideas?

Onboard pics of the launch here. Note: just the onboard pics are of the Apoclypse, the rest are Kingsford High School.
 

Ryan S.

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cool, look at MDRAs liberty project, they have a formulation for ignitors that works every time
 

Rocketjunkie

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You must fasten each igniter to the motor it's igniting. This allows the slow motors to retain the burning igniters until they light.
 

jetra2

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Tom,

What is your favorite way of doing this? Tape? Rubber Band? Cat Fur? :p

Jason
 

solrules

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I thought of having the ignitors sandwiched between the motor retainer washers (3x) and the motors themselves. For some reason, this did not fly :confused:
 
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