7 Motor Cluster ignition questions

[daveyfire]

Yes, thread the daveyfire leads through the motor retention screws so the leads can go up with the rocket. However, for "instant-on" ignition, Thermite (as used in the Liberty Project) is the way to go. I'm not sure if it would be kosher to post the formula, so PM or e-mail me if you're interested. This compound can be lit with a single low current daveyfire match and creates heat in excess of 6000 degrees in the top core of the motor. Wedge Oldham was trying it out this weekend in various motors, including a five cluster of K1275Rs. In the "pad cam" view of the cluster, one frame there is no flame underneath the rocket, the next one the motors are 100% up to pressure. They measured a startup time of 25 ms!

 

[Rocketjunkie]

Originally posted by jetra2
Tom,

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

Jason

I use tape.
Cat fur gets awful stinky when the motors light

 

[ClusterWiz]

I plan for the next flight of the Apocalypse will be at LDRS 23. I plan to use ALL H268s and when I dip them I will use two Daveyfires, fold one over, and dip both of them together in pyrogen. this way they will be small enuff to fit through the nozzle but I still have two igniters in each motor to ensure ignition of all motors. even though it will weigh 13lbs. loaded, if all the motors lite on the pad, it should break moch. I am gona use a horizontaly mounted camera this time so I do not have the added drag of the camera shroud which holds the miror. expected altitude if all the motors light is about 7999ft. and 9/10in. because of the low waver.

 

[marvSRG]

Sounds awesome solru...er...ClusterWiz. Heh. I can't wait to see the results of that! But just as a tip, I still would sway away from using multiple ignitors in using H motors. Although they would fit initially, after being burnt up and slammed out of a motor, they could easily bind up and clog the nozzle, and we don't want that to happen. I would reccomend a good heavy dip (as long as you have plenty of pyrogen on there, and the igniter lights, your fine...just check each one for continuity so you know they'll go). For more reliability and avoiding using another ignitor, you could also further enhance the motor by "painting" the top grain with pyrogen, and also by well securing the igniters to each motor as Tom mentioned. This allows the igniters not to pull out, and it will make plenty of punch for igntion with the extra pyrogen. Plus, even if the igniter is pulled out, the pyrogen will stay in there and let it light. All in all, though, you're doing awesome! Do you have any flight shots that weren't onboard for the recent flight? I bet that was one RED flame!

 

[daveyfire]

Uhm, on the "painting with pyrogen" thing. I got into a big discussion about this with Erik Gates (N cluster master) and he won... if you paint the grains with pyrogen, scratch the pyrogen up afterwards with a screwdriver. Yes, pyrogen is easier to light than propellant. BUT pyrogen is meant to be lit from the inside. When it dries, it forms a hard shell around the head of the igniter for protection. This shell doesn't like to light very easily. So just let it dry and hit it with a screwdriver or something scratchy to take off that outer hard coating, and let er rip!

 

[Ryan S.]

I would go with thermite, never seen it but I hear good things. I will get back with how it works I plan on flying a cluster this weekend

 

[marvSRG]

Good point, David. As Ryan said, a "horseshoe" bent piece of thermalite will work great, too. I love my thermalite

 

[ClusterWiz]

Does any one make comercial thermite igniters? that would work great for my cluster. although you couldent use it in all that big of quantities cuz you might melt the nozel away or burn a hole in your blast plate

 

[marvSRG]

Not as far as I know. I think because it's too volitile for commercial production, but it's not that hard to do it yourself.

 

[Ryan S.]

no there arent any, I beleive Darren came up with it and people have just been mixing it. Just order them chems and do it yourself, stick an ematch in a bagful and you are set

 

[marvSRG]

Thermite has actually been around a while for pyrotechnic and other use. But I know the type Darren used is slightly different...easier to light due to a different oxide, and he may have come up with that mix.

 

[ClusterWiz]

Do you just mix the copper oxide and aluminum in a powder form? I have aluminum powder for mixing with Epoxy so you can tap into it. Will that work? And is copper oxide regulated at all? I would imagine that our local crazed former chemistry teacher would have some. And if he doesn’t he’s probably one of the few people who can get it. He's on vacation now so I wont be able to make it before LDRS

 

[Elapid]

i have only heard of using Iron oxide, personally

thermite will burn a hole right through steel, i.e. the blast deflector, motor retention clip, etc.

copper is toxic, especially the water-soluble salts of copper.
Iron oxide is rust, and a tad in your diet is beneficial.

i burned the heck out of my fingers messing with thermite, or aluminum/perchlorate mixture...

BE SAFE!!!!!!

 

[daveyfire]

If you have questions regarding the thermite igniter, PM me. It is a copper oxide based mix, which has a lower activation energy and three times the delta H for the reaction of the iron oxide. As such, it basically vaporizes itself upon ignition and you aren't left with any nasty slag running anywhere. Ya gotta be careful working with any chemicals of course... don't get into it unless you know what you are doing! (that was my disclaimer)

YMMV, etc. etc.

 

[MarkABrown]

Remember, this is not the place to discuss how to make thermite or any other chemical compound.

 

[daveyfire]

Originally posted by MarkABrown
Remember, this is not the place to discuss how to make thermite or any other chemical compound.

Yup, I'm trying to avoid this very subject If you have any further questions, please PM or e-mail me.

 

[ClusterWiz]

I dipped the igniters today. I used two daveyfire 28Fs. I cant get any copper oxide before LDRS. I folded one over about an inch. And didn't fold the other one over at all. I put them next to each other, and put a piece of masking tape above it to keep them together. Then I wrapped them with some thread to keep them tight and then dipped each one. They are the ugliest igniters I have ever seen. They are all bumpy and rolled, they look like a naked 900lb. fat guy. (not that I’ve ever seen a 900lb fat guy ) but I think they will work great. They have a head on both ends of the pyrogen so they will burn twice as fast. My dad calculated that all of them together will draw 100amps!!!! I hope they all light. Do you think a few car batteries at LDRS will light them all?

 

[solrules]

100 amps? no way. You have 7 motors, 100/7 is 14.2 amps per daveyfire. No way they take that much current!

 

[ClusterWiz]

Each one is .8 ohms. 14 igniters, I don’t know what that converts into. Ohms aren’t on onlineconversion.com. Or maybe it was watts..........I’ll give ya update. But some electronics guy that’s a friend of my dads did it for him. I'm not good with electicity. But what ever it was, was alot.

 

[jflis]

well, if they are hooked up in parallel, 14 0.8 ohm ignitors will give you a load equal to 0.05722 ohms.

hope this helps in your calculations.

jim

 

[ClusterWiz]

My dad told me wrong, it is 1.2 ohms per igniter. There are 14 of them. And it does turn out to be 100amps. With only one 12 volt. all 14 igniters are sottered to 1/8in. copper rods which are shorted together for now. I will clip the alligator clips to the rods and wrap another piece of copper wire around those to ensure I have a good connection. Do you think that the launch system at LDRS will be able to handle all of this?

 

[Rocket Flier VB]

I was able to fire 7 Davy Fires by making a battery box next to the launch pad. I lost too much current going throught he long leads. Once I put the battery at the pad all 7 fired instantly. I can send pictures of the ox if needed.

Eric F.

[email protected]

 

[Rocket Flier VB]

Actually, I lost pictures of the Ox but I still have the ones of the Battery Box.

I just got laser eye surgery so my spell check is not up to par

Eric