Originally posted by limd21
For others who've used both the nichrome bridgewire and conductive dip primer, is there a good reason to favor nichrome over the conductive primer?
I used to build my own with nichrome, but since I started using a conductive dip, I find it a lot more convenient. Strip, dip. That's all that's needed for a good black powder ignitor. For other motor types, it's strip, dip, dip.
Is one reason nichrome is to be favored is that its electrical current requirements are lower? I use a hefty battery (from my cordless drill), so I've never had any problems with enough amperage capacity.
There sure is a good reason. If one builds with nichrome wire, the current requirements will be considerably LESS than the conductive primer dipped igniters.
The article on Info Central is a really good suggestion for construction, but it leaves far too much nichrome exposed in my humbe opinion, increasing the resistance of the nichrome jumper and increasing the current requirements. What I do with mine is very similar, but I only leave perhaps 1/2" of nichrome exposed or 'unshorted' to conduct current (at most). This results in an igniter that will take much less current. I am still testing, but have not had a problem lighting the nichrome igniters with a 9 volt battery, whereas the dipped igniters don't always light with the 9 volt battery.
There was a question asked about storage. Baggies are fine, but I keep mine in a long fishing lure or small parts box to prevent mechanical stressing. It is the mechanical stressing that will cause failure over time. Make sure that they are not bent or crushed - that will lead to sure failure with the dipped units. The nichrome units are considerably more robust in this regard as well, but the pyrogen will fall off if stressed mechanically.
For nichrome, I went to eBay and purchased several small 50 - 100 foot rolls at about $3 per. Tried them all and they all work great.
For wire, I went to eBay and purchased a few rolls of twisted pair. A thousand feet of #26 twisted pair for about $9. It will last me a lifetime. I also purchased some single conductor wire-wrap #28 wire and bought 5,000 feet in red and 5,000 feet in blue for about $20. Again a lifetime supply but I haven't tried twisting it or dipping it yet. WHY did I buy so much wire? Well, for one thing, I won't have to worry about going out looking for CAT5 (or better yet, 50 pair cable, which is discarded all the time) and dissecting it. I have a lifetime supply now.... and we will use it for all of our other wiring needs in future.
Good luck with building your own igniters. If you are doing it to save money you are probably making a mistake. Unless you fly TONS of rockets or unless it is a club project. For the 20 or so igniters I use in a year it is cheaper to buy the **** things than to build them. We are building them for the fun of it and to prove to ourselves that we can master that aspect of the hobby.
Murray Lampert
. I really think the CAT 5 is a great way to go. The pairs are already twisted together, just strip 'em and dip 'em. I made my first eight this weekend using the solderless technique with 36 guage nichrome. Tried the nail polish and I'm gonna use the ping pong ball dip on a few too and see which seems to work better.
