Rolling Foam Cutter Gives Mattress A Close Shave

March 24, 2025 by Tom Nardi 18 Comments

There’s many different reasons why somebody might have to hack together their own solution to a problem. It could be to save money, or to save time. Occasionally it’s because the problem is unique enough that there might not be an accepted solution, so you’re on your own to create one. We think the situation that [Raph] recently found himself in was a combination of several of these aspects, which makes his success all the sweeter.

The problem? [Raph] had a pair of foam mattresses from his camper van that needed to be made thinner — each of the three inch (7.62 cm) pieces of foam needed to have one inch (2.5 cm) shaved off as neatly and evenly as possible. Trying to pull that off over the length of a mattress with any kind of manual tools was obviously a no-go, so he built a low-rider foam cutter.

With the mattresses laying on the ground, the idea was to have the cutter simply roll across them. The cutter uses a 45″ (115 cm) long 14 AWG nichrome wire that’s held in tension with a tension arm and bungee cords, which is juiced up with a Volteq HY2050EX 50 V 20 A variable DC power supply. [Raph] determined the current experimentally: the wire failed at 20 A, and cutting speed was too low at 12 A. In the end, 15 A seemed to be the sweet spot.

The actual cutting process was quite slow, with [Raph] finding that the best he could do was about 1/8″ (3 mm) per second on the wider of the two mattresses. While the result was a nice flat cut, he does note that at some point the mattresses started to blister, especially when the current was turned up high. We imagine this won’t be a big deal for a mattress though, as you can simply put that side on the bottom.

In the end, the real problem was the smell. As [Raph] later discovered, polyurethane foam is usually cut mechanically, as cutting it with a hot wire gives off nasty fumes. Luckily he had plenty of ventilation when he was making his cuts, but he notes that the mattresses themselves still have a stink to them a couple days later. Hopefully they’ll finish outgassing before his next camping trip.

As you can imagine, we’ve covered a great number of DIY foam cutters over the years, ranging from the very simple to computerized marvels. But even so, there’s something about the project-specific nature of this cutter that we find charming.

Building A Nerf-like Rocket Launcher With Airburst Capability

March 1, 2025 by Lewin Day 25 Comments

Nerf blasters typically fire small foam darts or little foam balls. [Michael Pick] wanted to build something altogether more devastating. To that end, he created a rocket launcher with an advanced air burst capability, intended to take out enemies behind cover.

Unlike Nerf’s own rocket launchers, this build doesn’t just launch a bigger foam dart. Instead, it launches an advanced smart projectile that releases lots of smaller foam submunitions at a set distance after firing.

The rocket launcher itself is assembled out of off-the-shelf pipe and 3D printed components. An Arduino Uno runs the show, hooked up to a Bluetooth module and a laser rangefinder. The rangefinder determines the distance to the target, and the Bluetooth module then communicates this to the rocket projectile itself so it knows when to release its foamy payload after launch. Releasing the submunitions is achieved with a small microservo in the projectile which opens a pair of doors in flight, scattering foam on anyone below. The rockets are actually fired via strong elastic bands, with an electronic servo-controlled firing mechanism.

We’ve featured some great Nerf builds over the years, like this rocket-blasting robot.

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Lost Foam Aluminium Alloy Casting

February 28, 2025 by Dave Rowntree 21 Comments

[Kelly Coffield] makes intake manifolds for old Ford throttle bodies for fun, demonstrating an excellent technique for making such things in the small shop. The mould patterns are CNC machined from a solid polystyrene block, with all the necessary gates to feed the aluminium into the mould. The principle is to introduce aluminium from a large central runner into the mould structure, which feeds the gates into the mould parts. The various foam mould components are then glued with an extra brace bar at the bottom to strengthen it.

The complete structure is then sprayed with surfactant (just plain old soapy water) and dip-coated in a refractory slurry. The surfactant adjusts the coating’s surface tension, preventing bubbles from forming and ruining the surface quality produced by this critical coating step.

Once a satisfactory coating has been applied and hardened, the structure is placed inside a moulding pan fitted with a pneumatic turbine vibrator, to allow sand to be introduced. The vibrations ease the flow of sand into all the nooks and crannies, fully supporting the delicate mould structure against the weight of the metal, and gases produced as the foam burns away. A neat offset pouring cup is then added to the top of the structure and packed in with more sand to stabilise it. It’s a simple setup that can easily be replicated in any hackerspace or backyard for those motivated enough. [Kelly] is using A356 aluminium alloy, but there’s no reason this technique won’t work for other metals.

It was amusing to see [Kelly] demould by just dumping out the whole stack onto the drive and throwing the extracted casting into a snow bank after quenching. We might as well use all that free Midwest winter cooling capacity! After returning to the shop, [Kelly] would typically perform any needed adjustments, such as improving flatness in the press, while the part was in the ‘as cast temper’ condition. We’ll gloss over the admission of cutting the gates off on the table saw! After these adjustments, the part is artificially aged to a T5-like specification, to give it its final strength and machinability properties. There are plenty more videos on this process on the channel, which is well worth a look.

Aluminium casting is nothing new here, here’s a simple way to cast using a 3D printed pattern. But beware, casting aluminum can be hazardous, it does like to burn.

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How Do We Deal With Microplastics In The Ocean?

February 6, 2025 by Lewin Day 47 Comments

Like the lead paint and asbestos of decades past, microplastics are the new awful contaminant that we really ought to do something about. They’re particularly abundant in the aquatic environment, and that’s not a good thing. While we’ve all seen heartbreaking photos of beaches strewn with water bottles and fishing nets, it’s the invisible threat that keeps environmentalists up at night. We’re talking about microplastics – those tiny fragments that are quietly infiltrating every corner of our oceans.

We’ve dumped billions of tons of plastic waste into our environment, and all that waste breaks down into increasingly smaller particles that never truly disappear. Now, scientists are turning to an unexpected solution to clean up this pollution with the aid of seashells and plants.

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Build A Super Cheap RC Trainer Plane With Foam

September 5, 2024 by Lewin Day 20 Comments

Once upon a time, RC planes were expensive models that took months to build and big money to equip with electronics. Since the 20th century though, powerful batteries have become cheap, as have servos and radio controllers. Combine them with a bit of old packing material and you can get a little RC trainer up and running for peanuts, as [Samm Sheperd] demonstrates.

[Samm] started referring to this as the “$5 trainer,” though he admits that it will cost more than that if you don’t have some bits and pieces laying around. He demonstrates how to cut cheap foamboard with a hot guitar string, and how to form it into a viable wing. That’s the most crucial part, with the fuselage and tail surfaces relatively simple by comparison. With that complete, it’s as simple as bolting on a motor, some servos, and control horns, and you’re up and running. You can even whip up a landing gear if you’re so inclined! Then, figure out your center of gravity, get it right, and then you’re pretty much ready to fly.

It’s a great primer on how to build a basic RC model, and if you do it right, it should have pretty forgiving handling, too. Plus, it’s so cheap that it should be easy to repair if you crash. Happy modelling! Video after the break.

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Is This The World’s Smallest N-Scale Train Layout?

January 23, 2024 by Kristina Panos 7 Comments

There’s just something about miniature worlds — they’re just so relaxing to look at and ponder. Think you don’t have ample room for a model train layout at your place? You may not be thinking small enough. [Peter Waldraff] knows a thing or two about hiding train layouts inside of furniture (that’s one solution), but this time, he’s built a track in plain sight that’s meant to sit on the bookshelf. The whole thing is just 5.5″ x 12″.

This N-scale layout was three years in the making, mostly because [Peter] was waiting for just the right little powered chassis to come along. For the layout, [Peter] started by creating custom flexible track by removing pieces with a sharp knife. He glued down the track to pink foam and used nails to hold it in place while the glue dried. He also built a wood frame around the base to stabilize it and hold some of the electronic components, including a switch made from an old ballpoint pen.

Then it was time to start decorating the thing, beginning with a couple of buildings made from more pink foam that are both lit up with LEDs. Eventually, [Peter] added a bunch of details like streetlights, animals, and garbage cans that really make the layout pop. As far as the engine goes, [Peter] picked up a Tomytec TM-TR02 on eBay and built a trolley out of two broken cars. [Peter]’s build is something you just have to see for yourself — fortunately for you, the build and demo video is after the break.

Like we said, [Peter]’s usual territory is hiding train layouts in end tables and coffee tables and the like, so it’s nice to see what he can do given different constraints.

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Hackaday Links: October 22, 2023

October 22, 2023 by Dan Maloney 9 Comments

The second of three major solar eclipses in a mere six-year period swept across the United States last week. We managed to catch the first one back in 2017, and still have plans for the next one in April of 2024. But we gave this one a miss, mainly because it was “just” an annular eclipse, promising a less spectacular presentation than a total eclipse.

Looks like we were wrong about that, at least judging by photographs of last week’s “Ring of Fire” eclipse. NASA managed to catch a shot of the Moon’s shadow over the middle of the US from the Deep Space Climate Observer at Lagrange Point 1. The image, which shows both the compact central umbra of the shadow and the much larger penumbra, which covers almost the entire continent, is equal parts fascinating and terrifying. Ground-based photographers were very much in the action too, turning in some lovely shots of the eclipse. We particularly like this “one-in-a-million” shot of a jet airliner photobombing the developing eclipse. Shots like these make us feel like it was a mistake to skip the 10-hour drive to the path of annularity.

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