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Nichrome wire as the ignition source ?

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Nichrome wire as the ignition source ?

Unread postAuthor: tatfree » Tue Mar 23, 2010 8:29 pm

I have a few differant gages of nichrome wire and have been experamenting a little with them mostly using 9 volt batteries.

I have searched nichrome on this forum and came up empty and was wondering why no one has mentioned it.

I twisted two strands of .005" nichrome wire together and after 150 times of lighting the 3/4" long wire my new 9 Volt battery went from 8.9 volts to 8.1 volts. The wire still lights with the 8.1 , but takes about 1/2 the time to do it ( Which is still under a second ).
My guess is that a single strand will do the same as above, but probably get 300 lights before dropping to 8.1 volts.
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Unread postAuthor: clemsonguy1125 » Tue Mar 23, 2010 8:33 pm

Well Ive considered trying it but you have to constantly replace the wire so in the long run I thinkk its better to use BBQ sparker or tazer but it might be worth a shot to try and see how it affects the performance if at all
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Unread postAuthor: c11man » Tue Mar 23, 2010 8:38 pm

you dont have to replace the wire, it just gets rele hot!'
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Unread postAuthor: tatfree » Tue Mar 23, 2010 8:40 pm

clemsonguy1125 wrote:Well Ive considered trying it but you have to constantly replace the wire so in the long run I thinkk its better to use BBQ sparker or tazer but it might be worth a shot to try and see how it affects the performance if at all


Replace wires ?
I don't understand why you would have to replace the wires. My wire look as good as new even after 150 lights. Think of how a toaster or Blow dryer works .
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Unread postAuthor: clemsonguy1125 » Tue Mar 23, 2010 8:43 pm

tatfree wrote:
clemsonguy1125 wrote:Well Ive considered trying it but you have to constantly replace the wire so in the long run I thinkk its better to use BBQ sparker or tazer but it might be worth a shot to try and see how it affects the performance if at all


Replace wires ?
I don't understand why you would have to replace the wires. My wire look as good as new even after 150 lights. Think of how a toaster or Blow dryer works .

I was thinking of model rocket ignitors and pieces of steel wool(I use them when I dont want to by model rocket ignitors), by the way where do you get nichrome wire
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Unread postAuthor: geardog32 » Tue Mar 23, 2010 8:43 pm

you could try a glow plug out of the little nitro hobby cars on small scale to see how it works it would screw right into some pvc.
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Unread postAuthor: MrCrowley » Tue Mar 23, 2010 9:06 pm

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Unread postAuthor: tatfree » Tue Mar 23, 2010 9:18 pm

MrCrowley wrote:
I have searched nichrome on this forum and came up empty and was wondering why no one has mentioned it.

Combustions:
http://www.spudfiles.com/forums/other-t ... t9041.html
http://www.spudfiles.com/forums/just-a- ... 10125.html
http://www.spudfiles.com/forums/ultra-e ... 10189.html
http://www.spudfiles.com/forums/glow-pl ... 14396.html
http://www.spudfiles.com/forums/glow-pl ... 16766.html
http://www.spudfiles.com/forums/rmss-ca ... rt,15.html

Hybrids:
http://www.spudfiles.com/forums/high-mi ... 20198.html
http://www.spudfiles.com/forums/ignitio ... 16096.html
http://www.spudfiles.com/forums/hybrid- ... rt,15.html

Are you using the advanced search? All I did was type in "nichrome" and selected the Combustion and Hybrid forum sections individually.

Advanced search:
http://www.spudfiles.com/forums/search.html


Ya, I came up with a lot of those and read through them but didn't seem to learn anything that I didn't already know. Hoping to learn some new ideas, but looks like I am at the end of the road and have to continue my idea from here.
I'll maybe put up some pics when I'm all done.
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Unread postAuthor: Hubb » Wed Mar 24, 2010 7:14 am

Larda's famous hybrid uses a system similar. I don't think he used nichrome, but at 200x mix, it is the only thing that will ignite the mixture.
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Unread postAuthor: jimmy101 » Fri Mar 26, 2010 7:50 pm

The reason you'll need to replace the wire is that a small gauge wire heated to a couple thousands degrees has almost zero mechanical strength. Look up the tensile strength derating for any metal when it is glowing red hot. Or, look at how fragile the filament in a light bulb is. Try smacking your nichrome filament when it is red hot.

Blast air moving at several hundred feet per second on the very hot wire and it'll tend to break.

So, the only valid test as an ignition source is to put it in a gun and see how long it lasts. I suspect a wire thick enough to survive is going to take a pretty hefty current to heat it up. Probably a lot more than a 9V battery can supply for more than a second or so.
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Unread postAuthor: tatfree » Fri Mar 26, 2010 9:15 pm

I had not thought about the fast air flow hitting the heated wire in the sanerio. I am wondering if that will effect the strength of the wire ?
All in all Nichrome wire is probably the strongest wire you can get, so at least I have that on my side. I have other gage Nichrome, but it takes more juice like you said to make it glow red and fast. I could always series to 9 volts for that wire if I had to. It would still be a smaller set up than 95% of any other ignitions mentioned on this forum.
pretty sure however that the two wires twisted together that I mentioned originally will not break ,especially when they are at the very rear of the chamber, and they are not being pulled tight, but rather lose.
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Unread postAuthor: D_Hall » Sat Mar 27, 2010 12:00 am

I've used nichrome on a gun that used a solid propellant. Worked great. But I also used some pretty heavy stuff and an automotive battery to supply the current.
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Last edited by D_Hall on Sat Mar 27, 2010 12:20 pm, edited 1 time in total.
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Unread postAuthor: tatfree » Sat Mar 27, 2010 12:29 am

I have made E-matches for yrs for Hybrid rockets and I would stuff the ignitor right up in the core of the motors and the wire is always intact and never broken afterwords, just the pyrogen is burnt up. Keep in mind this is only a single strand of the wire I mentioned in the first post and it's pulled tight.
The temp of the moters are high enough heat to pit up an Aluminum plate if placed under the motor on launch, so it's plenty hot.
As Soon as I machine out the chamber I will be able to test this ignition idea and see how it works and get back with everyone.
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Unread postAuthor: jimmy101 » Sat Mar 27, 2010 1:25 pm

tatfree wrote:IIt would still be a smaller set up than 95% of any other ignitions mentioned on this forum.

Only if you omit 95% of the guns which use piezos.

A bbq piezo is simpler, and in the long run cheaper, than anything else.

9v battery is a couple bucks
battery clip $1
suitable switch a buck or two
something to put the battery in a buck or two

wire etc. but a piezo requires that as well.

Already pretty darn close to an $12 piezo. Replace the battery once or twice, replace the nichrome a couple times and the PITA affect and the cost have exceeded a bbq piezo.

Heck for $20 total you should be able to get a stun gun (including the shipping). Its battery will last forever if it is only used to fire spud guns.
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Unread postAuthor: tatfree » Sat Mar 27, 2010 3:35 pm

jimmy101 wrote:
tatfree wrote:IIt would still be a smaller set up than 95% of any other ignitions mentioned on this forum.

Only if you omit 95% of the guns which use piezos.

A bbq piezo is simpler, and in the long run cheaper, than anything else.

9v battery is a couple bucks
battery clip $1
suitable switch a buck or two
something to put the battery in a buck or two

wire etc. but a piezo requires that as well.

Already pretty darn close to an $12 piezo. Replace the battery once or twice, replace the nichrome a couple times and the PITA affect and the cost have exceeded a bbq piezo.

Heck for $20 total you should be able to get a stun gun (including the shipping). Its battery will last forever if it is only used to fire spud guns.


I meant 95% smaller than electric ignitions out there. I would rather go this rought than a stun gun set up or electric BBQ ignitor you can get now at WalMart for $17 including battery.
I doubt I would ever have to replace the wire, and the batteries....Well if it last 200 shots + per $1.75 battery, I could care less about cost. I only will use a singel wire since my chamber is Aluminum, the rest will be the ground.
I'll build my own battery compartment,and the momentary switch will probably be right next to it completing the cercuit.
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