36 replies to this topic

[BrightStar]

Thanks guys - some useful suggestions there. I'm never quite sure whether the covers are intended to provide friction protection or crush resistance. I'd considered silicone tubing or cutting up old biro cases...

Distracted from work today, I impact tested one of the chlorate primed ODA matches with a moderate blow from a steel hammer on a brick base. It snapped with a loud report, as would be expected with a commercial match. A degree of caution is clearly in order.

Edited by BrightStar, 04 May 2009 - 07:00 PM.

[phildunford]

Something like this maybe?

Rapid

[pyromaniac303]

Pyrogen mix is more sensitive and is usually chlorate based. It helps ensure ignition but if blackpowder works for you 100% of the time then you're safer just using that.

As that one is just black powder based, you could keep it as long as you want relatively safely, though its not good to store any items you've made yourself. As an added precaution, twist the bare wires together to short them out, so that it is not possible to set it off prematurely by static discharge, accidently touching them with a battery etc. This is done with most commercial ematches I've seen too.

[digger]

well made my 1st e-match and was quite pleased with the results, using all the methods iv seen i used nichrome wire around 2 wires i then place then 1" cut straw hot glued one end and using a syringe injected a standerd black powder / nc mixture into the straw.
made 10 and all 10 worked without any problems.

not sure if they would work after a couple of weeks stored so that will be my next test



worked quite good but I might use a shorter straw like 1/2 inch since once lit it lasted a few seconds longer than wanted.

Video >
2 questions if anyone know the answer

1) whats the difference with pyrogen mix and black powder mix as in the end result.
2) how long should home made e-matches last if stored.

I made a bunch of BP based ematches some time ago now. The shelf life on them was rather short as the powder attacked the nichrome wire!

[digger]

was it the copper on the wire that had corroded or the nichrome wire it self. i know when i was soldering my 1st few i noticed after a day there were signs of dry joints even with flux added before soldering which worried me since it wouldn't last 1 week at that rate, so decided to change to hot glue to see if it will seal the copper joint (no solder) before adding the black powder / nc mixture so only the nichrome wire was in the mixture this seems to make a better connection and also seems to stop risk of short circuit which helps.

I am afraid it was the nichrome that dissolved. But you may get different results to me.

[Arthur Brown]

It's one thing to have produced something but another altogether to have something that is proven to work long term. (or after long storage!)

The value of commercial igs is that they are reliable and consistent.

With DIY the bridge wire and compound are not 100% repeatable in terms of dimensions and performance, so the resultant igniters may show variability in performance. With series igs the firing current needed is the same however many igniters, BUT the ig properties must be consistent so that they all blow at the same time, because once the first has fired the circuit is broken.

Parallel igniters consume huge currents and the system may not supply the necessary sum of firing currents at the end of the wire to a safe place.

[Arthur Brown]

Electric Igniter - Resistance approx 1.6Ω
Use this figure to calculate resistance of pyro circuits and test before firing. See article on Volts,
Ohms and Amps for more.

Electric Igniter - Current required to fire approx 0.5A
Voltage is not the determining factor -

Twin cable for wiring devices -
Resistance approx 10Ω per 100m (for each wire)
Use this figure to calculate resistance of pyro circuits and test before firing. This is for cheap bell wire!

Ohms Law

I= V/R

or

V = IR

[BrightStar]

Well, I tried making some heatshrink covers... not a great success. The obvious problem is that they really do shrink when the match fires...

My favourite solution so far is this:



It's simply an M6 rawl plug with the legs chopped off a bit.

[StephF]

Did I read somewhere that Baker's flux was suitable for use in soldering nichrome wire ?

[cooperman435]

The only one I know of is plumbers flux which comes in a yellow tub from plumbers merchants and works fine for me