Static Test

[Ray]

Thursday, 2 of my friends and I did a static test of some of the 54mm grains that we cast previously.

The test went well. It burned for a longer period of time that we expected so we'll need to find out why. The video can be viewed here File size is about 1.6 meg.

[Tom]

Nice stuff, and on a completley unconstructive sidenote, Stoner, now thats a last name and a half. yours?

[Ray]

Nice stuff, and on a completley unconstructive sidenote, Stoner, now thats a last name and a half. yours?

Thanks, and yes the last name is mine...I earned it when I was younger...but now, I am just a boring dad.

[Hank]

Wow, yes, congradulations. What do you use as an igniter?
Hank

[Ray]

The ignitor is home made too. We use a conductive slurry (graphite and acetone) on Cat 5 cable. The insulation is stripped back around 2mm, then dipped in the slurry. We coat with Nitrocellulose laquer made from Ping Pong balls and acetone, then we put a pyrogen on that. Another coat of Nitrocellulose laquer to keep the moisture out. They work great. This propellent lights pretty slow, but other propellents light just as fast if not faster than commercial ignitors.

[Tom]

Conductive Slurry. I love it. And I now have a use for those nice 250g bags of graphite powder my art shop sells.

Tom

[Hank]

The ignitor is home made too. We use a conductive slurry (graphite and acetone) on Cat 5 cable. The insulation is stripped back around 2mm, then dipped in the slurry. We coat with Nitrocellulose laquer made from Ping Pong balls and acetone, then we put a pyrogen on that. Another coat of Nitrocellulose laquer to keep the moisture out. They work great. This propellent lights pretty slow, but other propellents light just as fast if not faster than commercial ignitors.

Hello- I noticed what appears to be a 12 Volt battery in the test footage. (Can it actually be called footage in the digital age?) Is this the power supply for the igniter (ignitor) and what of the rest of the circuit? Hank

[Ray]

Yes the 12 V battery powers the ignitor. Its a pretty straight forward system. There is a relay box close to the motor (or the pad) and a long wire to activate the system. There is a continuity check that indicates there is no faults with the ignitor. The check it current limited to make sure the ignitor doesn't fire on accident. There are a ton of different designs, just google "rocket launch controller".

[pablo]

The ignitor is home made too. We use a conductive slurry (graphite and acetone) on Cat 5 cable. The insulation is stripped back around 2mm, then dipped in the slurry. We coat with Nitrocellulose laquer made from Ping Pong balls and acetone, then we put a pyrogen on that..

interesting, never though about that
just a question
would it work if I used the rocket fuel as the pyrogen? (for example a sugar/potassium nitrate or chorate mix)
thanks
Pablo

[Ray]

yes, you'd pby have pretty good luck with doing that. A lot of rocketeers "boost" an ignitor by cutting a small section of commercial propellent off a grain and tying it to the ignitor with some string.

You'd pby have better success if you added some metal to the potasium nitrate/sugar mix...most pyrogen mixtures use them to increase the heat output. Remember to reduce the amount of sugar in the mix, the metal will act as a fuel. Be careful that you don't use too big of chips...they burrow into the propellent and can increase burning area substantially, this leads to extremely rapid disassembly of the motor...not a good thing. Aluminum, Magnesium, Titanium would work well. -200 mesh is what you want. Don't use powdered metals with chlorates...you won't like what happens.

good luck

[pablo]

thanks ray for the fast reply

instead of using the slurry I am now using a thin wire I found yesterday and works great. Its only problem is that it takes 1 or two secs before the ignition occurs (it's not the pyrogen delay, since it is present even with explosives)

so, my current igniters are a powder mix of chlorate and sugar which sorruonds the thin wire and is covered with duct tape (this one is a sort of primer for explosives, I'll swich to nitrate for the rocket ( a sort of copy of one of R. Nakka's small motors)

Pablo

[Ray]

I want to make it very clear, that I am doing this for rocketry only. I would not have responded to the message had I known that Explosives were involved.

While many of the concepts of rocketry CAN be applied to explosives, I will NOT participate in any way in encouraging or helping those applications.

[pablo]

mi initial goal were not explosives, but while trying to make one of those "volcanos" as a test, the thing blew apart instead of throwing lights. (this happened yesterday night) - btw, I never used more than 15 gr
I've never made explosives before and I do not intend to keep working with this (making a hole is interesting, but make a rocket fly is much more challenging, it must have enough power but not as much to blow the CC)

I started using chlorate cos I felt the nitrate wasn't giving me the expected power (it burned too slow), but now it seems I'll have to switch again to nitrate.

sorry for the misunderestaning

Pablo

[MS]

Keep up the good work!

[Axt]

Ray, Im interested in the graphite igniters, but am wondering why you would place the battery so close to the engine?

For safety safe I always connect the battery well away from anything thats about to fire up. Does the graphite need more power then can be put through ~50m of cable? I cant see if your using a relay to trip the 12v battery or not.

For example, if you ran the cable from the battery ---50m---> igniter will it readily fire? what delay?

I'm currently using NC/BP/Al around nichrome, but NiCr isn't available locally and steel wool is a pain to use.