Rebuilding A $700k Refrigerator

February 21, 2024 by Bryan Cockfield 20 Comments

When cleaning out basements, garages, or storage units we often come across things long forgotten. Old clothes, toys, maybe a piece of exercise equipment, or even an old piece of furniture. [Ben] and [Hugh] were in a similar situation cleaning out an unused lab at the University of California Santa Barbara and happened upon an old refrigerator. This wasn’t just a mini fridge left over from a college dorm, though. This is a dilution refrigerator which is capable of cooling things down to near absolute zero, and these scientists are trying to get it to its former working state.

The pair are hoping to restore the equipment to perform dark matter experiments, but the refrigerator hasn’t been in use since about 2016 (and doesn’t have an instruction manual), which is a long time for a piece of specialty scientific equipment to be collecting dust. The first step is to remove wiring and clean it of all the grime it’s accumulated in the last decade. After that, the pair work to reassemble the layers of insulation around the main cooling plate and then hook up a vacuum pump to the device which also needed some repair work.

The critical step at this point is to evacuate the refrigerant lines so they can be filled with expensive Helium-3 and Helium-4. The problem is that there’s still some of this valuable gas in the lines that needs to be recovered, but the risk is that if any air gets into the cold section of the refrigerator it will freeze and clog the whole system. After chasing some other electrical and vacuum gremlins and discovering a manual from a similar refrigerator, they eventually get it up and running and ready for new scientific experiments. While most of us won’t discover a fridge like this cleaning out our attics, this refrigerator powered by rubber bands is a little more accessible to the rest of us.

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The Wirtz Pump Spins

October 11, 2023 by Al Williams 18 Comments

Over the ages, a lot of human activity has been concerned about getting water from where we find it to where we want it. If you want to move water to a lower elevation, there’s no problem. But if you want to move water up, you need a pump. The ancients used what we call Archimedes’ screw to raise water. But a Wirtz pump as [Steve Mould] shows in the video below, is another kind of spiral pump that is also very old and uses the same basic principle as the screw pump.

In a way, the Wirtz is just an Archimedes’ screw in cross-section. Part of what makes it work, however, is air-locking. [Steve] made a small model but found it didn’t work exactly as he expected. Of course, investigating that led to some interesting observations.

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Powerful Water Pump Is Modular In Nature

June 23, 2023 by Lewin Day 28 Comments

If you’ve got one decently powerful DC motor, you could conceivably build a water pump. Gang up ten of them, however, and you could build something considerably more powerful, as [akashv44] demonstrates.

The design is straightforward, relying on simple impeller pumps driven by RS-775 DC motors. The pump housings and impellers are all 3D printed. They’re designed so that the motor integrates neatly with the pump housing, and so that multiple pumps can easily be ganged up into a single larger unit. [akashv44] demonstrates a build using ten individual pump units with a large manifold, allowing the output of all the pumps to be combined into one single outlet.

The concept is straightforward enough, and running on a 48-volt power supply, it’s clear that the pump can move a significant amount of water. Notably, though, it would be possible to improve significantly with some design changes. Currently, the water path from the pumps must make several 90-degree turns, harming efficiency. We’d love to see the pumps angled nicely into more advanced manifolds which would more smoothly combine the streams together. This would likely result in a far greater output from the system.

In any case, 3D printing pumps is an increasingly popular pastime around here.

Is This The World’s Largest Dot Matrix Printer?

June 22, 2023 by Bryan Cockfield 27 Comments

[RyderCalmDown] was watching a road painting vehicle lay down fresh stripes on the road one day and started thinking about the mechanism that lets it paint stripes in such a precise way. Effectively the system that paints the interspersed lines acts as a dot matrix printer that can only print at a single frequency. With enough of these systems on the same vehicle, and a little bit more fine control of when the solenoids activate and deactivate, [RyderCalmDown] decided to build this device on the back of his truck which can paint words on a roadway as he drives by. (Video, embedded below.)

Of course, he’s not using actual paint for this one; that might be prohibitively expensive and likely violate a few laws. Instead he’s using a water-based system which only leaves temporary lettering on the pavement. To accomplish this he’s rigged up a series of solenoids attached to a hitch-mounted cargo rack. A pump delivers water to each of the solenoids, and a series of relays wired to a Raspberry Pi controls the precise timing needed to make sure the device can print readable letters in much the same way a dot matrix printer works. There’s an algorithm running that converts the inputted text to the pattern needed for the dot matrix, and after a little bit of troubleshooting it’s ready for print.

Even though the printer works fairly well, [RyderCalmDown] had a problem thinking of things to write out on the roadways using this system, but it’s an impressive build based around a unique idea nonetheless. Dot matrix printers, despite being mostly obsolete, have a somewhat vintage aesthetic that plenty of people still find desirable and recreate them in plenty of other ways as well, like this 3D printer that was modified to produce dot matrix artwork.

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Homebrew Tire Inflator Pushes The Limits Of PVC Construction

March 22, 2023 by Dan Maloney 23 Comments

Let’s just clear something up right from the start with this one: there’s literally no reason to build your own tire inflator from scratch, especially when you can buy a perfectly serviceable one for not a lot of money. But that’s missing the point of this build entirely, and thinking that way risks passing up yet another fascinating build from PVC virtuoso [Vang Hà], which would be a shame

The chances are most of you will recall [Vang Hà]’s super-detailed working PVC model excavator, and while we’re tempted to say this simple air pump is a step toward more practical PVC builds, the fact remains that the excavator was a working model with a completely homebrew hydraulic system. As usual, PVC is the favored material, with sheet stock harvested from sections of flattened pipe. Only the simplest of tools are used, with a hand drill standing in for a lathe to make such precision components as the compressor piston. There are some great ideas here, like using Schrader tire valves as the intake and exhaust valves on the pump cylinder. And that’s not to mention the assembly tips, like making a hermetic seal between the metal valves and the PVC manifold by reaming out a hole with a heated drill bit.

We’re not sure how much abuse a plastic compressor like this will stand up to, but then again, we’ve seen some commercially available tire inflators with far, far less robust internals than this one.

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Fish Tank Dosing Pump Built Using Pi Pico

March 17, 2023 by Lewin Day 5 Comments

When you’re maintaining a fish tank, it’s actually quite important to get all your basic chemistry right. Mismanage things, and you’ll kill all the helpful bacteria in the tank, or kill your fish when things get too alkaline or too acidic. To help him get things just right, [yojoebosolo] built a custom dosing pump to maintain his fishtank.

The pumps themselves are small peristaltic pumps sourced from AliExpress. They can be had for under $10 if you look hard enough. Two of these are assembled into a PLA housing. Meanwhile, the brains of the operation is a Raspberry Pi Pico. It’s charged with running the pumps to a regular schedule, ensuring that just the right amount of chemicals are delivered when they are needed. It delivers 2 mL of Kalkwasser solution into [yojoebosolo’s] reef tank every ten minutes. The pumps are switched on and off with a simple 5V relay.

If you’ve got a delicate and complex fish tank that demands only the best, building your own dosing pump may be the way to go. Off-the-shelf versions can be expensive, after all, so sometimes it makes sense to roll your own. Video after the break.

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3D-Printed Lobe Pump Shifts Water Well

June 10, 2022 by Lewin Day 11 Comments

Lobe pumps are perhaps most popularly known for their use in Rootes-type superchargers, but they can pump water, too. [Let’s Print] demonstrates this ably with a 3D-printed design that can pump with the best of them.

The design uses two figure-eight shaped counter-rotating rotors, or lobes. As the rotors turn, they trap fluid between the rotor and the housing, forcing it towards the outlet. It’s a positive-displacement design, meaning it traps a fixed volume of fluid in each rotation, moving it from inlet to outlet.

The design requires proper timing of the two rotating lobes in order to ensure they maintain the closed volume and don’t impact each other. This is achieved with a pair of timing gears on the back of the pump. The housing, lobes, and gears are all 3D-printed, making this a build that anyone can replicate at home with their own printer.

ABS was used for the rotors for its better handling of friction without melting as easily. However, resin-printed lobes were also employed for their higher tolerances, too, with both designs working acceptably in practice.

The pump still needs more improvement; the hope is to reduce the leaks out of the rear of the pump. [Let’s Print] also intends to add a motor to the pump itself rather than using a power drill to run the device. It’s great to see these 3D-printed pump builds continuing in earnest. Video after the break.

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