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[DPRG] Extinguishing the FireFighting candle

Subject: [DPRG] Extinguishing the FireFighting candle
From: Sluggy slugmusk at linuxlegend.com
Date: Sun Feb 3 21:24:55 CST 2002

Oops, I meant to send this to the list, not just Clay :)


Clay Timmons wrote:
> Why am I rambling on about all this.  I just wanted to
> tap in the collective to get ideas for firefighting.

My favorite proposed method of extinquishing the candle is to utilize a 
12 gram CO2 cartridge. I have experimented with a tire inflator device 
found at a bicycle shop in which you load a cylinder and depress a lever 
on the top to release a stream of fairly high pressure CO2. There is 
enough velocity to blow out the candle, even with a fairly wide "beam", 
plus the suffocation factor of CO2 has to help. The biggest drawback in 
my implementation is the amount of force required to operate the valve. 
To operate it with an RC servo require me to add a 4 inch lever to the 
valve handle and use the servo like a cam to press it down. With this 
arrangement, it is very easy to dump quite a lot of the gas just in the 
time it takes to cycle the servo. I think a decent solenoid might serve 
better, but without a handy one, I made the assumption that a low 
current motor would be easier to control.

I have also entertained building something with my own valve, something 
that would be much more compact than the modified inflator thingy. 
Suitable hardware was difficult to locate, particularly in small sizes. 
I found lots of 500 psi electrically operated valves, but they were all 
bigger than the inflator assembly and most often required 110VAC to 

One big advantage of such an arrangement over an electric fan is that it 
is arguably easier to aim a nozzle at the end of a hose than to aim a 
motor with fanblades. In my design the CO2 device and actuator were to
at the back on the robot, with the nozzle mounted on the same pan/tilt 
servo as a camera. This way, the robot chassis needs not be aligned with 
the flame.

I saw a winning firefighter design in a Circuit Cellar Ink magazine that 
used an ozone safe camera lens duster with a servo operated lever 
attached, but you have to be careful with those. Some of them use
and that does NOT provide the desired extinguishing effect!

In about 1980, guy came by the two way radio shop where I worked. He was 
selling halon fire extinguishers. He had a demo unit which was basically 
a lens duster can full of halon. He would not sell any of these demos, 
only the real extinquishers, but if such a thing were available, that 
would likely be among the most effective of systems.


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