What gauge nichrome for DIY igniters?

Discussion in 'Low Power Rocketry (LPR)' started by SirNomad, Oct 1, 2015.

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  1. Oct 1, 2015 #1

    SirNomad

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    In case I need to make my own, and because I like the thought of building my skills, I was wanting to make some of my own igniters to start Estes engines. What guage nichrome wire would work best do y'all think? Too thick doesn't heat enough, right?
     
  2. Oct 1, 2015 #2

    GregGleason

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    You need to think in terms of systems.

    First question, is power: What power source do you plan to use? Once you know volts/amps, you can design your system so that the nichrome can heat accordingly.

    Greg
     
  3. Oct 1, 2015 #3

    SirNomad

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    I'm using the Estes Astron II powered by eight "Sunbeam" AA alkaline batteries in a Radio Shack battery holder with snap connector. :)
     
  4. Oct 1, 2015 #4

    GregGleason

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    I'm assuming the batteries are wired in series, so this would be a 12 V system (8 batteries x 1.5 V/battery), and would hold the amps to 500 mA.

    I would try a 40 gauge wire, or perhaps a 38 gauge if you wanted it to heat up a bit slower.

    Greg
     
  5. Oct 2, 2015 #5

    Micromeister

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    Greg:
    The STANDARD gauge for Estes type Igniters is and has been 30gauge for decades. I've used as long as 4" per igniter without a problem on just about any 12V launch system and most 6V AA hand held controllers.

    404-p20b_3 APCP 30ga Nichrome igniters for installation_09-18-09.JPG

    MgAp & AlAp 30ga Nichrome Igniters-c_2pic pg_01-13-07.JPG

    Estes Nichrome-pyrogen Igniters-c_2pic Pg_11-12-06.jpg
     
  6. Oct 2, 2015 #6

    GregGleason

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    John, the 30 gauge does work. But Estes Corp may have had other factors that drove picking that gauge. It's also my understanding that the igniter tip of the more recent Estes igniters is much thinner than 30 gauge, and the tip is the part that counts.

    My educated guess is that a 40 or 38 gauge will heat up faster than the 30, all other things being equal.

    Greg
     
  7. Oct 2, 2015 #7

    shreadvector

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    32

    Anything thinner will not create/radiate enough heat energy before burning in half.

    8 alkaline AA batteries will work. Believe it or not, but the biggest resistance is in the very thin launch system leads.

    8 D batteries would be better, but I often hand out 9 packs of AA batteries that I solder together. That one extra battery does the trick and produces hot molten metal.
     
  8. Oct 2, 2015 #8

    GregGleason

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    Yes ... but.

    If you are lighting AP, then 32 gauge is your friend. I think you can go to 40 gauge if you are running a sensitive pyrogen. Hope that makes sense.

    Greg
     
  9. Oct 2, 2015 #9

    SirNomad

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    So...I should have read this thread more before ordering 100' of 40 gauge. ::sighs::
     
  10. Oct 2, 2015 #10

    GregGleason

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    What motors are you planning to light? Are they primarily BP, AP, or a combination?

    Greg
     
  11. Oct 2, 2015 #11

    shreadvector

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    Yes. As well as other past threads that are easily searchable.

    40 ga is ultra thin. If used by itself, it will melt in half outside the nozzle, possibly near the micro clips before enough heat can be generated to ignite the propellant.

    it might work if you expend the absure amount of extra effort to create home-made versions of the Estes Starter: use thick wires as the main leads for the starter and use the 40 ga at the tip as a small bridge wire. Of course, you then have to make a machine like Estes has that can precisely form the tip bridge wire, hold it in place and resistance weld it to the thicker lead wires. Then you have to handle them carefully to avoid breaking them or shorting the thicker lead wires.

    Simple 32 ga nichrome wire with a loop formed at the tip is the simple way to go. Absolutely resistant to any handling damage and they can be installed in advance - even years in advance - since there is no pyrogen and nothing will heat them up except connecting them to a power source.


     
  12. Oct 2, 2015 #12

    GregGleason

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    PM me and I can send you some 32 gauge to try to see if you have better success with it.

    Greg
     
  13. Oct 3, 2015 #13

    SirNomad

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    I sent you a PM Greg. I was wondering, if I use thicker leads (I do have a soldering iron...if I can locate my solder LOL) and it's not like scrap wire is hard to come by, if the 40 guage will be salvageable. Maybe by twisting 3 or 4 strands together? I have broken telephone and USB cords that I hadn't tossed out yet, I'm sure there's usable wire in there.

    Anyway, it's fun to experiment and make the most of what we've got, right? :) But it's ALSO good to have some of what we KNOW works on hand so we don't make a trip to the park without launching anything!

    -Michael
     
  14. Oct 3, 2015 #14

    grapetang

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    While we're on the topic, is there any significant differences between nichrome-60 vs the purer nichrome-80 for igniters? Nichrome-80 seems to have a negligibly lower resistance & a higher melting point. Some sites seem to indicate that nichrome-60 has better corrosion resistance. Seems like either would work. Pros & cons of each?
     
  15. Oct 3, 2015 #15

    georgegassaway

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    Link to a post I made about homemade ignitors.

    http://www.rocketryforum.com/showthread.php?59894-Who-makes-thier-own-igniters&p=1468117#post1468117

    I used 30 gauge. But I am not using AA batteries, I'm using plenty of juice (12V 2200 mAh LiPos). Turned out they were super-reliable, only one misfire out of about 50 used so far, and that was by someone else who may have mis-prepped.

    I also got some thinner gauge, but it felt too flimsy for my needs, at least compared to the 30. if my goal had been to use AA alkalines from an Estes controller, then I'd have used the thinner nichrome.

    Thing about Estes Solars is they have a very fine bridge wire, but also have the very thick wires for most of it. So the thick wire gives plenty of stiffness and strength to hook up clips to and physically secure the ignitor without bending so easily it can short. Those Estes Solars are produced by automation that spot-welds the wires together. Nichrome itself is a PITA to solder, so for DIY ignitors, made in large numbers, it's not very practical to use a fine bridge wire that is soldered to stiffer wires.

    And if the whole ignitor is one-piece (like mine), then the thinner it is, the more problems can occur. For me the tradeoff was 30 gauge, and probably 28 gauge would be better for stiffness while the batteries I'm using would still ignite them near-instantly.

    - George Gassaway

    [​IMG]
     
    Last edited: Oct 3, 2015
  16. Oct 3, 2015 #16

    Micromeister

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    Greg:
    your educated guess would be correct for estes igniters like the solar Igniters which have a 38 Nichrome bridge wire but and I say BUT That is one of the problem areas as those super thin gauge wires are easily damage or broken if mishandled even a little. Straight 30ga with a single u-bend works perfectly with just about any pyrogen dip or for single motors just PLAIN nichrome on both current Estes 6v (4-AA) or Quest 9v hand held controllers. Straight 30gauge gives even faster ignition on any 12V controller system.

    I have used 32gauge which is OK. 34gauge in testing was more like the thinner 38 and 40gauge bridge wires in some igniters, the stuff is harder to work because of the diameter while easier to damage/break.
    As I said before 30ga has been the standard for Igniter making for decades. If someone wants to make their own igniters buying a 1/4lb roll of 30gauge .0100" dia. Nichrome is the cheapest way to go. I get mine from McMaster-Carr.
     
    Last edited: Oct 3, 2015
  17. Oct 3, 2015 #17

    GregGleason

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    One things for sure for me, I sure miss the ol' Centuri Sure-Shots! That was a cool piece of technology back in the day. At least there are some good, commercial alternatives these days.

    Greg
     
  18. Oct 3, 2015 #18

    cwbullet

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    I use 36 AWG Nichrome
     
  19. Oct 4, 2015 #19

    KevinM

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    I use 36AWG Kanthal D (similar to Nichrome) to make igniters, in my case for igniting MicroMaxx motors. I use 1.25" total length between the contact points, and I'm firing from a 2S LiPo battery. (Nominally 8V or so.) Interestingly, the wire doesn't typically burn out and I get a half dozen or more launches on a single igniter. I'm also usually only forced to replace due to mechanical damage occurring between launches, not burn-out at launch, so I don't really know what launch-induced wearout rate I'm getting. [Full disclosure on my reuse claims: I'm using these igniters in an under water launch setup so they get "quenched" pretty quickly after the rocket motor ignites and I'm firing from a microcontroller assisted launch controller which limits the fire current to a one second duration. Either of these may be driving the reusability I get from my igniters over the wire gauge I've selected, I've never tried to sort out what the contributors are to the success rate I've enjoyed.]

    There's more than just the wire gauge to consider here - as others have pointed out also you need to consider the applied voltage from your launch controller, the total resistance in your lead wires, and the length of your Nichrome bridge. Your 40AWG wire has a specific resistance per unit length, and ultimately you're trying to achieve the right circuit resistance to get the wire nice and hot without melting it. (Or at least without melting it faster than what it takes to get your motor to light.) If the Nichrome melts when you push the ignition button try bridging in a longer length between your igniter clips. If it doesn't get hot enough cut the length down. Once you've found the length that hits the right temp for your launch system go back and have a look at the length between the clips and judge if it's practical for use with your motor. If it's too short then you need to up the voltage in your launcher or try again with a finer gauge of Nichrome. If it's too long then you need to reduce the launcher's voltage, add a series resistor, or move to a heavier gauge of Nichrome.
     
  20. Oct 4, 2015 #20

    Micromeister

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    Been using Straight 30ga. up to 2" Nichrome for Micro-Maxx Igniter since 1999. Usually about 1.5" overall length. but have gone as long as 2" for models with recessed motor locations Like the Flying Ghost and others.

    I also have what I'm calling my semi-permanent MMX igniter using 24ga nichrome set in an epoxy filled holder socket. So far that single igniter has more the 120 some flights. My only objection to using it on all single motor MMX flights is it the dirty little motors make it necessary to clean off the 24ga.Nichrome with an emery board, or fine sandpaper after 3 or so flights. These are flown from a standard 12V gel-cell powered system.

    01_Motors & Nichrome Igniters.jpg

    05_Tamp into nozzle with needle or burnishing tool.jpg

    08_completed motor & Several Tamp Tools.jpg

    MM Semi-Perm Igniter-a1_ Standard & Piston System_09-07-10.JPG

    MM Semi-Perm Igniter-c1_Plug-in & base on Launcher_10-15-10.JPG

    MM Semi-Perm Igniter-Lp02c2_Igniter crud 3 burns_10-23-10.JPG

    MM Semi-Perm Igniter-Lp02j1_Unit after 13 Flights_10-23-10.JPG

    MM Semi-Perm Igniter-Lp02J2_Base&Teflon aft 13 flts_10-23-10.JPG
     
  21. Jan 5, 2020 #21

    rickster75

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    will this work for th same for 28 gauge? Just form a loop? How?
     
  22. Jan 5, 2020 #22

    rickster75

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    would you have a link the kind of battery you are using?
     

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