Oil-Based Sprengel Pump Really Sucks

September 17, 2025 by Tyler August 21 Comments

Have you heard of the Sprengel pump? It’s how they drew hard vacuum back before mechanical pumps were perfected — the first light bulbs had their vacuums drawn with Sprengel pumps, for example. It worked by using droplets of a particular liquid to catch air particles, and push them out a narrow tube, thereby slowly evacuating a chamber. The catch is that that liquid used to be mercury, which isn’t something many of us have on hand in kilogram quantities anymore. [Gabriel Wolffe] had the brainwave that one might substitute modern vacuum pump oil for mercury, and built a pump to test that idea.

Even better, unlike the last (mercury-based) Sprengel pump we saw, [Gabriel] set up his build so that no glassblowing is required. Yes, yes, scientific glassblowing used to be an essential skill taught in every technical college in the world. Nowadays, we’re glad to have a design that lets us solder brass fittings together. Technically you still have to cut an eyedropper, but that’s as complex as the glasswork gets. Being able to circulate oil with a plastic tube and peristaltic pump is great, too.

If you try it, you need to spring for vacuum pump oil. This type of pump is limited in the vacuum it can draw by the vapor pressure of the fluid in use, and just any oil won’t do. Most have vapor pressures far in excess of anything useful. In the old days, only mercury would cut it, but modern chemistry has come up with very stable oils that will do nearly as well.

How well? [Gabriel] isn’t sure; he bottomed out his gauge at 30 inches of Mercury (102 kPa). It may not be any lower than that, but it’s fair to say the pump draws a healthy vacuum without any unhealthy liquid metals. Enough to brew up some tubes, perhaps.

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A Steady Vacuum For The Fastest Cassette Tape Drive Ever

June 5, 2025 by Jenny List 39 Comments

If you think of a 1960s mainframe computer, it’s likely that your mental image includes alongside the cabinets with the blinkenlights, a row of reel-to-reel tape drives. These refrigerator-sized units had a superficial resemblance to an audio tape deck, but with the tape hanging down in a loop either side of the head assembly. This loop was held by a vacuum to allow faster random access speeds at the head, and this fascinates [Thorbjörn Jemander]. He’s trying to create a cassette tape drive that can load 64 kilobytes in ten seconds, so he’s starting by replicating the vacuum columns of old.

The video below is the first of a series on this project, and aside from explaining the tape drive’s operation, it’s really an in-depth exploration of centrifugal fan design. He discovers that it’s speed rather than special impeller design that matters, and in particular a closed impeller delivers the required vacuum. We like his home-made manometer in particular.

What he comes up with is a 3D printed contraption with a big 12 volt motor on the back, and a slot for a cassette on the front. It achieves the right pressure, and pulls the tape neatly down into a pair of loops. We’d be curious to know whether a faster motor such as you might find in a drone would deliver more for less drama, but we can see the genesis of a fascinating project here. Definitely a series to watch.

Meanwhile, if your interest extends to those early machine rooms, have a wallow in the past.

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Scrapyard Vacuum Dehydrator Sucks The Water From Hydraulic Oil

February 16, 2025 by Dan Maloney 23 Comments

Anyone who has ever had the misfortune of a blown head gasket knows that the old saying “oil and water don’t mix” is only partially true. When what’s coming out of the drain plug looks like a mocha latte, you know you’re about to have a very bad day.

[SpankRanch Garage] recently found himself in such a situation, and the result was this clever vacuum dehydrator, which he used to clean a huge amount of contaminated hydraulic fluid from some heavy equipment. The machine is made from a retired gas cylinder welded to a steel frame with the neck pointing down. He added a fill port to the bottom (now top) of the tank; as an aside, we had no idea the steel on those tanks was so thick. The side of the tank was drilled and threaded for things like pressure and temperature gauges as well as sight glasses to monitor the process and most importantly, a fitting for a vacuum pump. Some valves and a filter were added to the outlet, and a band heater was wrapped around the tank.

To process the contaminated oil, [Spank] glugged a bucket of forbidden milkshake into the chamber and pulled a vacuum. The low pressure lets the relatively gentle heat boil off the water without cooking the oil too badly. It took him a couple of hours to treat a 10-gallon batch, but the results were pretty stark. The treated oil looked far better than the starting material, and while it still may have some water in it, it’s probably just fine for excavator use now. The downside is that the vacuum pump oil gets contaminated with water vapor, but that’s far easier and cheaper to replace that a couple hundred gallons of hydraulic oil.

Never doubt the hacking abilities of farmers. Getting things done with what’s on hand is a big part of farm life, be it building a mower from scrap or tapping the power of the wind.

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Portable Solder Paste Station Prevents Smears With Suction

October 30, 2024 by Danie Conradie 30 Comments

Applying solder paste to a new custom PCB is always a little nerve-racking. One slip of the hand, and you have a smeared mess to clean up. To make this task a little easier, [Max Scheffler] built the Stencil Fix Portable, a compact self-contained vacuum table to hold your stencil firmly in place and pop it off cleanly every time.

The Stencil Fix V1 used a shop vac for suction, just like another stencil holder we’ve seen. The vacuum can take up precious space, makes the jig a little tricky to move, and bumping the hose can lead to the dreaded smear and colorful language. To get around this [Max] added a brushless drone motor with a 3D printed impeller, with a LiPo battery for power. The speed controller gets its PWM signal from a little RP2040 dev board connected to a potentiometer. [Max] could have used a servo tester, but he found the motor could be a little too responsive and would move the entire unit due to inertia from the impeller. The RP2040 allowed him to add a low pass filter to eliminate the issue. The adjustable speed also means the suction force can be reduced a little for easy alignment of the stencil before locking it down completely.

We love seeing tool projects like these that make future projects a little easier. Fortunately, [Max] made the designs available so you can build your own.

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On The Nature Of Electricity: Recreating The Early Experiments

October 3, 2024 by Dan Maloney No comments

Bits of material levitating against gravity, a stream of water deflected by invisible means, sparks of light appearing out of thin air; with observations like those, it’s a wonder that the early experiments into the nature of electricity progressed beyond the catch-all explanation of magic. And yet they did, but not without a lot of lamb’s bladders and sulfur globes, and not a little hand waving in the process. And urine — lots and lots of urine.

Looking into these early electrical experiments and recreating them is the unlikely space [Sam Gallagher] has staked out with the “Experimental History of Electricity,” a growing playlist on his criminally undersubscribed YouTube channel. The video linked below is his latest, describing the apparatus one Francis Hauksbee used to generate static electric charges for his early 18th-century experiments. Hauksbee’s name is nowhere near as well-known as that of Otto von Guericke or William Gilbert, who in the two centuries before Hauksbee conducted their own experiments and who both make appearances in the series. But Hauksbee’s machine, a rotating glass globe charged by the lightest touch of a leather pad, which [Sam] does a fantastic job recreating as closely as possible using period-correct materials and methods, allowed him to explore the nature of electricity in much greater depth than his predecessors.

But what about the urine? As with many of the experiments at the time, alchemists used what they had to create the reagents they needed, and it turned out that urine was a dandy source of phosphorous, which gave off a brilliant light when sufficiently heated. The faint light given off by mercury when shaken in the vacuum within a barometer seemed similar enough that it became known as the “mercurial phosphor” that likely inspired Hauksbee’s electrical experiments, which when coupled with a vacuum apparatus nearly led to the invention of the mercury discharge lamp, nearly 200 years early. The more you know. Continue reading “On The Nature Of Electricity: Recreating The Early Experiments” →

Welding Wood Is As Simple As Rubbing Two Sticks Together

July 21, 2024 by Dan Maloney 12 Comments

Can you weld wood? It seems like a silly question — if you throw a couple of pieces of oak on the welding table and whip out the TIG torch, you know nothing is going to happen. But as [Action Lab] shows us in the video below, welding wood is technically possible, if not very practical.

Since experiments like this sometimes try to stretch things a bit, it probably pays to define welding as a process that melts two materials at their interface and fuses them together as the molten material solidifies. That would seem to pose a problem for wood, which just burns when heated. But as [Action Lab] points out, it’s the volatile gases released from wood as it is heated that actually burn, and the natural polymers that are decomposed by the heat to release these gases have a glass transition temperature just like any other polymer. You just have to heat wood enough to reach that temperature without actually bursting the wood into flames.

His answer is one of the oldest technologies we have: rubbing two sticks together. By chucking a hardwood peg into a hand drill and spinning it into a slightly undersized hole in a stick of oak, he created enough heat and pressure to partially melt the polymers at the interface. When allowed to cool, the polymers fuse together, and voila! Welded wood. Cutting his welded wood along the joint reveals a thin layer of material that obviously underwent a phase change, so he dug into this phenomenon a bit and discovered research into melting and welding wood, which concludes that the melted material is primarily lignin, a phenolic biopolymer found in the cell walls of wood.

[Action Lab] follows up with an experiment where he heats bent wood in a vacuum chamber with a laser to lock the bend in place. The experiment was somewhat less convincing but got us thinking about other ways to exclude oxygen from the “weld pool,” such as flooding the area with argon. That’s exactly what’s done in TIG welding, after all. Continue reading “Welding Wood Is As Simple As Rubbing Two Sticks Together” →

Robot Seeks And Sucks Up Cigarette Butts, With Its Feet

July 20, 2024 by Donald Papp 30 Comments

It would be better if humans didn’t toss cigarette butts on the ground in the first place, but change always takes longer than we think it should. In the meantime, researchers at the Italian Institute of Technology have used the problem as an opportunity to explore what seems to be a novel approach: attaching vacuum pickups to a robot’s feet, therefore removing the need for separate effectors.

VERO (Vacuum-cleaner Equipped RObot) is a robotic dog with a vacuum cleaner “backpack” and four hoses, one going down each leg. A vision system detects a cigarette butt, then ensures the robot plants a foot next to it, sucking it up. The research paper has more details, but the video embedded below gives an excellent overview.

While VERO needs to think carefully about route planning, using the legs as effectors is very efficient. Being a legged robot, VERO can navigate all kinds of real-world environments — including stairs — which is important because cigarette butts know no bounds.

Also, using the legs as effectors means there is no need for the robot to stop and wait while a separate device (like an arm with a vacuum pickup) picks up the trash. By simply planting a foot next to a detected cigarette butt, VERO combines locomotion with pickup.

It’s fascinating to see how the Mini Cheetah design has really become mainstream to the point that these robots are available off-the-shelf, and it’s even cooler to see them put to use. After all, robots tackling trash is a good way to leverage machines that can focus on specific jobs, even if they aren’t super fast at it.

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