Shielding / passivating incompatible mixtures (Chlorate e-match)

[deer]

First of all, currently I'm just starting by making basic rcandy rockets.

 

To achieve highly reliable ignition (mostly because I hate going up to half ignited rockets.. even 15 minutes after), I use small amount of BP in the rocket core. What worries me though is, that I have no idea what composition the store bought e-matches are (very expensive here), and most DIY recipes contain KClO3 (looking at this: http://www.berfield.com/igniters.html). What would be the best way to contain the match / BP, so that they still light up reliably, but won't contaminate each other (mainly i'm worried about sulphur to KClO3).

 

Currently the only option I can think of is storing them separately and simply install all of the parts in rocket just before launch. Since I'd prefer simple set-up, I was wondering if coating the matches with nitrocellulose lacquer could provide enough of protection?

 

Any alternate options to increase reliability? Replace BP with something sulphur-less (plain e-match sometimes burns too quickly to ignite rcandy)? Use KNO3 e-matches? How long can you store those? how well they catch fire from nichrome? Economy from doing DIY matches comes only when you make significant batches (thus the need for good shelf life).

 

TL;DR; Will dipping KClO3 e-match in nitrolacquer block sulphur from BP? What BP compatible e-matches are reliable? What KClO3 compatible secondary pyrogens are good?

 

Thanks and cheers.

Edited April 18, 2015 by deer

[Ubehage]

I would propably dip the E-match in NC lacquer, that will serve as a protective layer. As well as dipping the still-wet matchhead in a bit of Titanium.

That will ensure that you get some nice hot sparks into the Rcandy.

[nater]

I would not be comfortable dipping an ematch into titanium because it would increase the friction sensitivity of the match head.

 

I would not be concerned with the match head touching anything with sulfur in it. The chlorate / sulfur incompatibility has more to do with fully integrated mixtures rather than 2 comps next to each other. I would worry more about the friction on the match head than anything. Commercial matches come with a plastic shroud which is best to leave in place. I could not even guess how many items I have used in shows with the ematch inserted directly in the lift cups full of BP.

 

I would dip the end of a piece of quick fuse in a BP slurry and use a small piece of quick match as pigtail in between the primed fuse and ematch. This way the match head is not directly into the core of the rocket, the primed fuse burns hotter than the match and the wire leads will not impede the gasses from the burning core (more of a concern with whistles at the red line)

[schroedinger]

Also you could get some 30 NiCr wire make coil and embed this into the rcandy. Shorten the leads. This igniter works good with rcandy buf needs a power source than can supply enough amperes. A car battery is good. Most common firing system won't supply enough energy.

[deer]

Thanks for the replies.

 

I'll try dipping it in plain NC lacquer (don't have Ti anyway). I'll test how well it ignites and see if it auto-ignites if I moisturise the BP and let it drip towards the e-match and let it dry that way. The idea is to push e-match in 3..5cm long straw, fill the rest of straw with BP and plug a piece of cotton at the other end.

 

Currently I'm using AWG 40 nichrome wires. They offer reasonable strength, heat up well with 18650 Li-Ion (even AA Ni-MH), but they tend to pop - so it's either proper ignition or the wire burns and I have to approach the rocket. I tried AWG 32 - they are more difficult to heat up because they transfer more heat to solder and wire on chip, but if the battery has enough juice, can be heated continuously. Still needs e-match though, because plain rcandy sometimes burns around the wire, forming isolating charcoal layer. Then you can heat as long as you want, but the rest of it wont catch fire. I'm wondering if those matches might benefit from some current limiting.