TOPIC: Lighting Rapiers on the Flying Field

Hi David,

this looks splendid! my only comment is the attachment of the electrode/Nichrome wire. My vote is for a couple of thin brass tubes the element can be pushed into (like the Cord Zap) . Neat and effective!

Having completed my 'proof of concept' (too grand a term, I'm afraid) I put together a 'mk 2' igniter with rather neater connections. One thing was very clear: o get a nice healthy glowing element there must be a good connection between the Nichrome wire and the electrode. I was surprised at how critical this junction is. Soi it does need to be kept clean - not easy with the dirty motor exhaust.

Having satisfied myself that it all worked, I thought, "if 4.5V is better than 3V, would 6V not be better still?" so I made a Mk 3 that incorporates a 'thread Zap', whose body has room for one AA battery. It's a bit unwieldy, but I guarantee it could cauterise an elephant or ignite the most recalcitrant motor (which we've all had).





I think I'll stop now and leave it to experts like David, but it does show that us cobblers can put something together that works, and, importantly, 6-7 volts appears to be optimum for a 28 SWG element.

Over to you, David!

I've just this minute completed the first build of the design that I will shortly be offering, documenting the construction so that I can write detailed instructions. There are always one or two little changes to make, but I'm glad to say that it went together very well.
Regarding the use of the little brass tubes to hold the element - I can't quite see in the photos how the element is secured - is it just a push fit? If so, you may be getting an erratic contact, hence my use of a terminal block with screws. I've been trying to think of a way to make use of the brass tubes that Roger has suggested, but haven't yet come up with a way of making it secure - other than crimping the tube - which would make filament replacement a bit tricky. I have wondered about filing off the top of the rear part of the tube, so that the connector block screws would hold the nichrome wire in place, but not sure about that until I get in some fine tubing. Maybe..

Roger adds:

thanks David. The Nichrome wire is a nice tight fit in the brass tubing. Usually works just fine and looks better than a screw terminal.

Perhaps we need some more ideas? Replaceable elements made up before going to the flying field perhaps, like these:



these are also a push fit into twin tubes, but the surface are is sufficient to ensue a good contact.

Using these (with our own 28 SWG elements) with your igniter would also protect your igniter pistol (and we do need a name) from the hot motor exhaust.


cheers
Dave

Before all these new igniters appeared recently, I had been refurbishing my own igniters and making a new ones so that I have plenty of options on the flying field too. The one on the far left is a converted chef's micro flame torch - the flame is turned off before attempting to ignite the motor! The white one at the bottom is a cauterizing tool adapted to take two AA batteries.
Although the instant start to full power with these is very convenient and although it is more fuss doing the prepping , I actually prefer to use fuses (when I have some that work properly that is). With fuses the slower start up time gives a moment or two to sort out the best launch grip and wait for the right moment when the thrust has built up, so often I light the fuse with my igniter! I admit though that I don't always have the patience to do it this way!!!
The one with the green tip protector tube uses brass tubes and on the clear tube one I used some heavy house wiring copper wire with the ends drilled for the ni-chrome wire which was a bit tricky.
I am also in process of making a 6 cell version to use with the lower voltage rechargeable AA's.

Hi,
phew, getting there slowly... here's a photo of the first widget (which I am thinking of naming 'Fuego') that I'll be offering to anyone. The heating element is retained by silicone tubing on a pair of 1mm copper wires (ex mains cable). I've typed up instructions for building from the component kit I'll be offering later.

I'm inclined to favour a screw terminal. These look as though they can handle the current.