TOPIC: Lighting Rapiers on the Flying Field

Hi David,

this must be very frustrating for you!:

I have now tried 26 SWG (0.48 mm) Nichrome. I turned up the (unloaded) voltage to 4.5 volts and got a nice healthy glow which ignited a motor pretty well instantly.
So, something else for you to try!

Though the new TSP L-2 motors light quite easily with fuses, the TSP L-1 motors where the nozzle diameter is such that the fuse is a (very) tight fit and the propellant is packed in up to the end plug, were trickier, we found. The nozzle can be reamed or drilled out with a screwdriver or drill bit of 1.2mm (not more) but this did result in a drop of thrust, and my Jetex Wren only cruised around Old Warden. True, for a nice long time, but I missed seeing it high up.

So these definitely benefitted from being ignited electrically.
When I was selling modified Cord Zaps I didn't stress enough that good (read pricier then yer average) AA batteries were needed like Duracell 'Ultra'. Inferior brands scarcely heat up the 28 SWG element to skin burning temperatures (I know, I've tried it!)

David Lane, whose 'Lugeresque' 6- NiMH AA igniter did such sterling work at Peterboro Flying Aces and September's Old Warden, thinks Duracell batteries inadequate to the current an element draws, citing their high internal resistance, and recommended I investigated rhe use of. Rechargeable NiMH batteries, Which I did:



Above: my rather crude (though effective) four cell igniter. With these Duracell batteries it needed to be 'rested' after continuous use. This, says David, is due to polarisation (which NiMH cells suffer from far less).



Above: the same igniter with four 2800 mAH rechargeable cells.

In summary, comparing batteries in 2, 3 and 4 cell igniters, I get the following results:



The voltage drop under load reflects the internal resistance of the batteries and the current drawn. The NiMH batteries obviously are delivering more amps, but the difference between the two types of battery are not as great as I expected. David says that perhaps I bought the wrong NiMH batteries, in that these are more suited to toys and torches. The ones we need for our igniters are those sold by hobby outlets for electric cars and boats. I will repeat the experiments when these arrive and are charged up.

Meanwhile, David is working oh a new version of his igniter, perhaps with fewer cells that will fit in the handle.

So: watch this space

Hi guys, had a day trying to fly using old rapier today. Had a nightmare trying to ignite them, where else to come for advice but here??! After reading this thread I decided to pep up my 'cord zap' and rigged it up to a 4.8v rx pack. No more problems! As you can see I get a healthy glow and am yet to find a motor that I can't light! Not sure how long my element will last but I've ignited 20 or so motors with it and it hasn't given up yet.

That’s just the information I need. Can you give a bit more detail where and how you soldered the leads? Thanks

No problem. I butchered a servo extension lead to leave black and red wires connected to the female plug. Then I soldered the red wire to the centre tube in the head of the cord zap and soldered the black wire to the metal ring which passes under the switch. I ran the servo extension through the battery tube. I removed the spring from the bottom of the tube allowing the wire to pass through the notch when screwing the plug back in. I just have the battery taped to the tube at the minute... doesn't look the best but its very effective!

Roger adds:

the igniter elements, whether Kanthal or Nichrome, draw quite a hefty current. Are the 'servo connector leads' up to the job? Have you felt them (care!) to see how hot they get when the element is glowing?
You might need to use a heftier connector and thicker wire.

I thought the same Roger, however after some very basic testing ( switch it on and hold the wires between my fingers!) up to 30 seconds there is only a slight warming of the wires which is only noticable after 20s. Since every motor I have used it on has ignited within approximately 3 seconds I'm happy that the current wiring is up to the job.
Now back to the building board!