This is [Lee von Kraus’] new experimental propulsion system for an underwater ROV. He developed the concept when considering how one might adapt the Bristlebot, which uses vibration to shimmy across a solid surface, for use under water.
As with its dry-land relative, this technique uses a tiny pager motor. The device is designed to vibrate when the motor spins, thanks to an off-center weight attached to the spindle. [Lee’s] first experiment was to shove the motor in a centrifuge tube and give it an underwater whirl. He could see waves emanating from the motor and travelling outward, but the thing didn’t go anywhere. What he needed were some toothbrush bristles. He started thinking about how those bristles actually work. They allow the device to move in one direction more easily than in another. The aquatic equivalent of this is an angled platform that has more drag in one direction. He grabbed a bendy straw, using the flexible portion to provide the needed surface.
Check out the demo video after the break. He hasn’t got it connected to a vessel, but there is definitely movement.
Continue reading “‘Vortex-drive’ For Underwater ROV Propulsion”
The Ranque-Hilsch vortex tube is an interesting piece of equipment. It can, without any moving parts or chemicals, separate hot and cold compressed gasses that are passed through it. Interestingly enough, you can cobble one together with very few parts for fairly cheap. [Otto Belden] tossed one together in a weekend back in 2009 just to see if he could do it. His results were fairly good and he shared some video tutorials on its construction.
His latest version, which you can see in the video below, takes compressed air at about 78degrees and spits out about 112degrees on the hot side and 8degrees on the cold side. Not too bad!
Continue reading “Building A Ranque-Hilsch Vortex Cooling Tube”
[Ben Krasnow’s] water vortex machine has been an exhibit in the lobby of the San Jose City Hall for quite some time now. Unfortuantely he recently had to perform some repair work on it due to the parts inside the water chamber rusting.
This is the same water vortex that we saw about a year ago. It uses a power drill to drive an impeller at the bottom of a water column to produce the vortex. That impeller was made from painted steel and after being submerged for eight months it began rusting, which discolored the water. [Ben’s] repair process, which you can watch after the break, replaces the shaft and the impeller. He reused a plastic PC cooling fan as the new impeller. The replacement shaft is stainless steel, as is all of the mounting hardware that will be in contact with water. But for us, the most interesting part of the repair is his explanation of the shaft gasket and bearings. Two thrust bearings and two radial bearings ensure that the shaft cannot move axially, which would cause a problem with the gasket. He had intended to swap out the oil seal for an all Teflon seal but the machined acrylic wasn’t conducive to the part swap. Instead, he replaced it with the same type of gasket, but bolstered the new one with some silicone to stave off corrosion.
Continue reading “Water Vortex Exhibit Repair Gives A Look At The Bearing And Gasket Design”