The Geek Group is in the process of cleaning up after their fire. Their small capacitor/spark gap room sustained the most damage, with the interior nearly completely incinerated, along with some structural damage to the walls and roof. The gap room was isolated from the much larger high voltage lab by red plastic welding curtain. The curtain was fire-retardant, but when it did finally burn, it was extremely sooty. With the curtain burning, soot covered the high voltage lab. The rest of the building escaped fire damage, but nearly all of it is covered in a fine layer of soot. The group has been and are attacking the soot problem head on, with shop-vacs, rags, and elbow grease. Several of their sponsors have also promised supplies to cover the remediation.
[Chris] and [Paul] have also been doing some sleuthing as to the root cause of the fire. While the cause will never be known beyond a shadow of a doubt, they have a pretty good idea of the chain of events. Gemini, the group’s 200 kVA Tesla coil had been run about 1/2 hour before smoke was detected. The fire was concentrated in Gemini’s spark gap room. Close inspection of the rotary spark gap showed that the stationary electrodes all seemed to have sustained a mechanical impact. It appears that either while the gap was running, or as it was spinning down, one of the flying electrodes moved enough to impact the stationary electrodes. These electrodes are 3/8″ and 1/2″ tungsten, and often glowed white-hot while the gap was in operation. One set screw held each electrode in to the 12″ rotor. The set screw of one flying electrode was found to be loose, and the electrode it retained probably impacted the stationary electrodes. It’s not a far leap to guess that hot metal from these impacts could have landed in the capacitor array, smoldered, and eventually caught aflame.
A single loose screw most likely caused the entire chain of events leading up to the fire. [Chris] and [Paul] had observed the spark gap throwing out hot bits of metal even during normal operation, and had planned an encapsulation box. However, disaster struck before it was built. This is not to say that The Geek Group operates an unsafe shop. The important thing here is that no one was hurt. Everyone in the building was evacuated quickly and safely.
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