Imagining A Dune-accurate Fremen Thumper

Never underestimate the power of fandom to obsess over the smallest details of its chosen canon. We say that with all due respect, of course, as some of the builds that result are really cool, like this working Fremen thumper from the Dune universe.

If you aren’t up to speed on [Frank Herbert]’s sci-fi epic, the Fremen are a warrior race that populates the sands of the desert planet Arrakis, which is inhabited by giant sandworms. The worms are attracted to vibrations, and thumpers are supposed to be mechanical devices set into the sand to lure worms. Thumpers are only vaguely described in the text, and have been imagined to varying degrees of success in the filmed versions of the story.

[Attoparsec] decided to take a stab at a working version, with the twist of making it plausible within what’s known about the Fremen in the stories. He settled on a pneumatic drive, which seems like something the Fremen would use. Using compressed CO2 cartridges, he discovered that it’s far easier to make a high-speed pneumatic vibrator than it is to make a piston move slowly up and down. Several iterations were needed to get to a mechanism capable of the more stately movements seen in any of the film versions of the story, and even then the thumping seems a bit fast for our liking. The triggering mechanism was very cool, though, and somewhat unexpected — [Herbert] describes “lighting the candle” to trigger a thumper, which led to the use of a thermal pressure relief valve and a fuse.

The video below goes over the design and build in some detail, as well as demonstrates the thumper in action with a clever cosplay bit. Hats off to [Attoparsec] for this dive down the fandom rabbit hole, maybe a faithful version of the “pain box” will be next up on the project list.

Continue reading “Imagining A Dune-accurate Fremen Thumper”

Find And Repair A 230kV 800Amp Oil-Filled Power Cable Feels Like Mission Impossible

How do you fix a shorted cable ? Not just any cable. An underground, 3-phase, 230kV, 800 amp per phase, 10 mile long one, carrying power from a power station to a distribution centre. It costs $13,000 per hour in downtime, counting 1989 money, and takes 8 months to fix. That’s almost $75 million. The Los Angeles Department of Water and Power did this fix about 26 years ago on the cable going from the Scattergood Steam Plant in El Segundo to a distribution center near Bundy and S.M. Blvd. [Jamie Zawinski] posted details on his blog in 2002. [Jamie] a.k.a [jwz] may be familiar to many as one of the founders of Netscape and Mozilla.

To begin with, you need Liquid Nitrogen. Lots of it. As in truckloads. The cable is 16 inch diameter co-axial, filled with 100,000 gallons of oil dielectric pressurised to 200 psi. You can’t drain out all the oil for lots of very good reasons – time and cost being on top of the list. That’s where the LN2 comes in. They dig holes on both sides (20-30 feet each way) of the fault, wrap the pipe with giant blankets filled with all kind of tubes and wires, feed LN2 through the tubes, and *freeze* the oil. With the frozen oil acting as a plug, the faulty section is cut open, drained, the bad stuff removed, replaced, welded back together, topped off, and the plugs are thawed. To make sure the frozen plugs don’t blow out, the oil pressure is reduced to 80 psi during the repair process. They can’t lower it any further, again due to several compelling reasons. The cable was laid in 1972 and was designed to have a MTBF of 60 years.

Continue reading “Find And Repair A 230kV 800Amp Oil-Filled Power Cable Feels Like Mission Impossible”