heating element to light model airplane timer fuse

[Alanm]

Sorry I must explain myself because a fuze lighter could be misconstrued these days.

I fly rubber powered antique model airplanes. These are free flight models flown in AMA sanctioned contests where each flight has a maximum flight time, eg 3 minutes or 5 minutes. We primarily use a punk type fuze material which we cut to length for the desired time. The fuze burns through a rubber band which holds down the horizontal stabilizer which pops up & stalls the airplane causing it to decend at the appropriate time. OK? Now, here is my question. I want to build a nichrome fuze lighter. I envision the battery pack clipped to my belt with the heating element and SPST button switch in a small container at the end of a 6 to 10 inch coiled wire.

At 6 to 12 volts (5 to 10 nicad cells), is there an existing small heating element & enclosure that would glow suffiently to light my fuze as I press the switch? I have thought to use an automobile lighter but that seems a bit large & ungainly.

Where could I find such a thing?

Thanks, Alan

[awright]

Alanm, consider using the filament out of a small, low-voltage, high current light bulb with the bulb broken off. Of course, you can't apply rated voltage to the bare filament. It would disappear in a puff of smoke. But you should be able to apply much lower than rated voltage to make the filament hot enough to ignite the fuze, but not hot enough to burn up in the oxygen of the air.

You will need a bulb made for low voltage (say, 6 volts or less) and high current to get a short, heavy filament that is tough enough to stand up to contact with the fuze. I think a bulb rated at 6 volts and several amps should be ok. The Grainger catalog shows several lamps made for emergency lighting units to operate on 6 volt lead-acid batteries.

Some of the lamps that look most suited are Tungsten-Halogens in the two-pin package. You won't be able to solder to the pins because they are made of an alloy capable of withstanding very high operating temperatures. But you can probably find female contacts out of surplus electronic connectors that will slip onto the pins. You don't need high temperature contacts because you will be operating at much lower than normal temperatures. You can also buy ceramic sockets for these bulbs, but they are expensive for the task and you don't need their high temperature capability.

CAUTION! T-H bulbs are quartz (which is very strong), under high internal pressure, and contain halogen gas, such as iodine. I know nothing about their toxicity, but I would definitely break the bulb outdoors, CAREFULLY. I'd wrap the bulb in a heavy rag, put it in a vise with a cover over it, wear gloves and a face shield, and crank down on the bulb until it breaks. Don't just hammer on it! DO THIS AT YOUR OWN RISK!

After you have a bare filament, use a low voltage power supply capable of several amps and SLOWLY bring up the voltage until you can ignite the fuze reliably. The filament should barely glow red or not glow at all. Note the current and voltage and build your battery supply. Depending upon the filament you have picked, you may find that two or three alkaline "D" cells can provide the current for the few seconds required to ignite the fuze many times.

Have fun!
awright

[Alanm]

Thanks, awright. Good idea. I'll give it a try.

Alan

[Sleepsalot]

Estes model Rocket fuses wouldwork also they use six volts.

Wayne

[GERTY]

I agree with Sleepsalot , that's the easiest..If fuses aren't available you can buy small gauge (#40) nichrome wire , do a google search for vendor. We used to wrap it around fuses of fireworks when we were kids. Just make sure the wraps don't touch each other. The larger the diameter, the higher current you will need to make it glow..

[jackrew]

Thanks for sharing helpful post... I really get lots of ideas from here..