Ground Effect Aerodynamics On An RC Car

December 21, 2021 by Zoe Skyforest 3 Comments

Ground effect aerodynamics will return to Formula 1 in a big way in the 2022 season, hopefully washing away the bad taste left in fan’s mouths after the recent controversial season decider. [Engineering After Hours] has experimented with F1 aerodynamics on RC cars before, and decided that it was time to try and implement a proper ground-effect design himself.

The aim of ground effect aerodynamics is to create a constriction for airflow between the bottom of the car and the ground underneath. This constriction accelerates the flow beneath the car, and as per Bernoulli’s principle, causes a corresponding pressure drop, sucking the car down onto the track. Viscosity also plays a role; from the car’s perspective, the road beneath the vehicle is moving backwards at some speed, pulling on the fluid thanks to the boundary layer on the ground itself. This further helps increase the strength of the effect.

A vacuum-formed undertray complete with side skirts was installed on the RC car in order to generate ground effect downforce. A quick test with a leaf blower indicates the system works, and that the side skirts are a key component.

Lateral acceleration was significantly improved by around 20% in testing with the ground effects installed, though [Engineering After Hours] admits that without a wind tunnel, the results aren’t the most scientific. However, with the undertray being relatively lightweight, we suspect the aero elements are likely providing plenty of benefit without too much of a negative effect on acceleration or handling.

Check out some of the other aero experiments [Engineering After Hours] has undertaken, too. Video after the break. Continue reading “Ground Effect Aerodynamics On An RC Car” →

The Assassin’s Teapot Is A Mischievous Design

December 20, 2021 by Zoe Skyforest 31 Comments

Many films use a similar trope when it comes to poisoning. The aspiring murderer ingests a drink poured from the same vessel as that given to their intended victim to indicate the liquid is safe to imbibe. The Assassin’s Teapot is a way one could achieve such a ruse, allowing two different liquids to be poured from what is seemingly a regular teapot, as shown by [Steve Mould]. (Video after the break.)

The trick is simple. Two separate cavities exist within the teapot, exiting via their own paths in the same spout. Each cavity also has an air hole in the top. If the hole for a given cavity is blocked by the pourer’s thumb, the liquid will not flow.

Each cavity can be filled with its own liquid. For example, one can be filled with tea, the other with poisoned tea. The murderer blocks the hole for the poison cavity when pouring their own beverage, delivering tea to their own glass. Then, when pouring for the enemy, the hole for the tea cavity is blocked, and poison is allowed to flow into the glass of one’s target.

The workings are simple; if air cannot flow into the cavity of the teapot to replace liquid flowing out, air pressure will stop the liquid flowing at all. The concept is demonstrated ably by [Steve]’s 2D recreation, letting us visualize the workings of the teapot quite easily.

It also shows a minor flaw in the design, which should be accounted for – if the spout isn’t designed carefully, sometimes flow from one cavity can dribble into the other. Between this and the chance of getting confused about which hole to cover to pour the poison, it would pay to keep some antidote on hand. Or, alternatively, just pour your guests tea instead – they’ll appreciate it!

We’ve seen [Steve] explore similarly interesting liquid vessels before too, such as this simple breakdown of the workings of the Gluggle Jug.

Continue reading “The Assassin’s Teapot Is A Mischievous Design” →

Is Cloud Seeding Good, Bad, Or Ugly?

December 20, 2021 by Zoe Skyforest 34 Comments

The Chinese Communist Party celebrated its centenary on the 1st of July, 2021. For such a celebration, clear skies and clean air would be ideal. For the capable nation-state, however, one needn’t hope against the whims of the weather. One can simply control it instead!

A recent paper released by Tsinghua University indicated that China had used cloud seeding in order to help create nicer conditions for its 100-year celebration. Weather modification techniques have been the source of some controversy, so let’s explore how they work and precisely what it was that China pulled off.

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3D Printed Parts Hold Up To Steam Heat

December 18, 2021 by Zoe Skyforest 1 Comment

Steam turbines are at the heart of all manner of industrial machinery, particularly that used for power generation. [Integza] decided he needed to better understand this technology, and decided to build one himself – using 3D printing, at that.

First, a steam source was needed, with a pressure cooker on an electric stove pressed into service. The steam was passed out via a nozzle printed in resin, which better resists heat than most FDM-printed parts. Similarly, a turbine wheel was printed in resin as well, with the steam outlet pointed directly at its vanes.

To really stress test the parts, more steam was required. To achieve this, hydrogen peroxide was pumped through a manganese dioxide catalyst impregnated into steel wool to create steam. This made an absolute mess, but the printed parts nevertheless survived.

The steam turbine didn’t do any useful work, but was able to survive the high temperatures at play. We’d love to see such a device actually used to bear some load, perhaps in some sort of 3D printed power generating turbine design.

Alternatively, if you prefer your steam turbines more classically driven, consider this build. Video after the break.

Continue reading “3D Printed Parts Hold Up To Steam Heat” →

3D Printing A Cyclonic Dust Separator

December 17, 2021 by Zoe Skyforest 20 Comments

[rctestflight] recently purchased a big CNC router, and that meant it was time to arrange for some dust extraction in the workshop. Naturally, he set about building this himself!

Using a shop vac is fine at smaller scales, but they can quickly be filled up on bigger jobs. To stop it getting filled up as quickly and wasting vacuum bags, [rctestflight] wanted to build a 3D-printed cyclonic separator to catch and dump the heavier-than-air particles from the routing process into an attached bucket.

[rctestflight] trialed a variety of designs, from a quad cyclone, to a large single cyclone and even a triple-series design. A diffuser design was also built, that aims to slow the air flow to the point where particles drop out of the air stream. At the end of the day, the large mono-cyclone design proved to be the most effective at removing particles from the airstream.

Fundamentally, if you’re making lots of dust, a cyclonic separator is a great way to go about dealing with the problem. We’ve seen similar builds scaled up to deal with the needs of a whole workshop, too. Video after the break.

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Building A Custom Branding Iron With Swappable Date Blocks

December 17, 2021 by Zoe Skyforest 6 Comments

Branding can be done on wood with just about any old bit of hot metal, but if you want to do it well, properly-crafted tooling will go a long way. [Wesley Treat] has built just that with this modular branding iron design.

The branding tooling itself is machined out of brass on an X-Carve CNC router, using [Wesley]’s own logo. The part is sanded after machining to remove tooling marks. A smaller brass slug is then machined with the numerals for various years with which [Wesley] may wish to stamp his projects.

Rather than hacking something sloppy together, the iron itself is assembled with a beautifully wood-turned handle of his own creation and a steel backing plate to hold the tooling. The date is separately removable from the main logo itself for easy changes in future. Naturally, the tool graphics are done in reverse so as to register the right way around when burned onto wood.

The tool is used with a torch to heat the brass up such that it can leave its impression on wooden surfaces. The final results are solid, if not quite perfect; getting the temperature across the tool perfectly matched would be key to getting the cleanest results. An electric heating element running in closed loop could be a way to achieve this.

Fundamentally, it’s a tidy way to mark your wooden projects in a hurry. We’ve seen wood burning reach even greater heights, too, such as with this CNC pyrography machine. Video after the break.

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Gluggle Jug Is Neat Application Of Hydrodynamics

December 17, 2021 by Zoe Skyforest 8 Comments

The Gluggle Jug is an aptly-named thing – it’s a jug that makes loud, satisfying glugging noises when poured. But how does it work? [Steve Mould] set out to investigate.

[Steve]’s first plan was to cut apart an existing Gluggle Jug to see how it worked, but cutting ceramics can be difficult and time-consuming, and the asymmetric design only made things harder. Instead, he simply smashed a jug to see what it looked like inside, and replicated the basic design in a transparent laser-cut version.

The design is simple – the glug sounds are from bubbles passing into a closed cavity within the jug as the water is poured out. Stop pouring, and air from that cavity then escapes back through the open mouth of the jug via more bubbles, making an even louder glugging sound. The frequency of the sound is determined by the height of the jug, which is essentially acting as a closed-pipe resonator.

With an understanding of the mechanisms at play, producing your own Gluggle jug is as simple as whipping up a design in your CAD software of choice and printing it in a food-safe way. Video after the break.

Continue reading “Gluggle Jug Is Neat Application Of Hydrodynamics” →