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TOPIC: Lighting Rapiers on the Flying Field

Lighting Rapiers on the Flying Field 3 years 5 months ago #1270

  • Terry Kidd
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Very nice.
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Lighting Rapiers on the Flying Field 3 years 4 months ago #1280

  • rogersimmonds
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The word out there is that the Tender rocket motors need a slightly hotter element to ignite reliably (i.e. a higher temperature of ignition), so 28 SWG with just the 3V of two AA batteries is not quite a guarantee of 'lift off' if the batteries in your Cord Zap are less than fresh. 4.5V gives a nice healthy glow, but modifying a cord Zap is not so easy (I know, I've tried) so, I thought, let's make one, based on a battery pack which originally saw duty as a capacitor charger.



I added a very nice push button switch supplied by the estimable Terry Kidd and butchered a defunct cautery tool, ending up with:





pressing the button gives a nice glow. The element is simple 'push in' and easily replaced.

This is very much a quick (and dirty) 'proof of concept'. But I'll refine it with a 'Mk 2'. :)

All suggestions welcome!
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Lighting Rapiers on the Flying Field 3 years 4 months ago #1281

  • DaveL
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I'm very close now to offering the kit for the pistol styled version described the other week. I decided to redesign it to make assembly much easier, with an enclosed printed body for the electronics. I had to order some bits in, but the advantage is that the pcb comes ready for use, with the microcontroller, leds, regulator all sorted. Hope to have this ready soon...
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Lighting Rapiers on the Flying Field 3 years 4 months ago #1282

  • rogersimmonds
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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!

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Lighting Rapiers on the Flying Field 3 years 4 months ago #1283

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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). :lol:





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! ;)
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Lighting Rapiers on the Flying Field 3 years 4 months ago #1284

  • DaveL
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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. :dry:


cheers
Dave
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