Bridging The Gap Between Dissimilar Road Types With Foam

February 10, 2023 by Ryan Flowers 27 Comments

When you think of driving up or down an embankment, do you ever wonder how much foam you’re currently driving on? Probably not, because it hardly seems like a suitable building material. But as explained by [Practical Engineering] in the video below the break, using an expanded material to backfill an embankment isn’t as dense as it sounds.

In many different disciplines, mating dissimilar materials can be difficult: Stretchy to Firm; Soft to Hard; Light to Heavy. It’s that last one, Light to Heavy, that is a difficult match for roadways. A bridge may be set down in bedrock, but the embankments approaching it won’t be. The result? Over time, embankment settles lower than the bridge does, causing distress for cars and motorists alike. What’s the solution?

To mitigate this, engineers have started to employ less dirty materials to build their otherwise soil based embankments. Lightweight concrete is one solution, but another is Expanded Polystyrene (EPS) foam. Its light weight makes installation simple in anything but a strong breeze, and it’s inexpensive and durable. When used properly, it can last many years and provide a stable embankment that won’t settle as far or as quickly as one made of dirt. Because as it turns out, dirt is heavy. Who knew?

Aside from roadways and bespoke aircraft, EPS foam has also been used for making home insulation. What’s your favorite use for EPS foam? Let us know in the comments below.

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Fixing A Hot Shop, With Science

September 2, 2022 by Dan Maloney 42 Comments

We know that pretty much everybody in the Northern hemisphere has had a hellish summer, and there’s little room for sympathy when someone busts out with, “Oh yeah? You think THAT’s hot? Well, lemme tell you…” But you’ve got to pity someone who lives in north Texas and has a steel Quonset hut for a shop. That’s got to be just stupidly hot.

But stupid hot can be solved — or at least mitigated — with a little smarts, which is what [Wesley Treat] brought to bear with this cleverly designed shop door heat shield. When it pushes past 42°C — sorry, that sounds nowhere near as apocalyptic as 108°F — the south-facing roll-up door of his shop becomes a giant frying pan, radiating heat into his shop that the air conditioner has trouble handling. His idea was to block that radiant heat with a folding barrier, but to make sure it would be worth the effort, he mocked up a few potential designs and took measurements of the performance of each. His experiments showed him that a layer of extruded polystyrene (XPS) foam insulation covered with reflective Mylar did better than just the foam or Mylar alone.

The finished heat shield is an enormous tri-fold plywood beast that snugs up against the door when things get toasty in the shop. There’s a huge difference in temperature between the metal door and the inside surface of the shield, which will hopefully keep the shop more comfortable. We imagine that the air between the door and the shield will still heat up, and convection could still distribute all that hot air into the shop. But at least he’s giving the AC a fighting chance.

In addition to great shop tips like this and his custom storage bins, [Wesley] is a talented signmaker. He’s pretty funny too — or maybe that’s just the heat talking.

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Foam Cutter Moves Like A Hot Knife Through Butter

July 28, 2022 by Kristina Panos 13 Comments

Make enough attempts to cut foam using whatever you’ve got — utility knife, hacksaw, serrated plastic knife — and you’ll wish hard for something that cuts cleaner, faster, and better. While there are all sorts of ways to build a hot wire foam cutter, this design from [jasonwinfieldnz] is both interesting and imitable.

If you don’t already know it, nichrome wire is nifty stuff that’s readily available in thrift store hair dryers and toasters. It stretches as it heats up, and shrinks as it cools back down.

The interesting part of this build is that instead of using a spring to keep tension on the nichrome wire, [jasonwinfieldnz] designed and 3D-printed a bow out of PLA that does the job elegantly. While [jason] was initially concerned that the bow might possibly melt, he found in practice that although the bow does get warm to the touch, it’s nowhere near hot enough to even warp.

One nice touch is the simple fence that rides along two slots and secures with wingnuts. We also like that [jason] made this foam cutter largely from scrap material, and rather than buy a spool of nichrome, he opted for a skinny heating element and pillaging the wire.

If you’re a nichrome noob, know that it doesn’t take much juice to do the job. Even though a computer power supply is what [jason] had lying around, it’s complete overkill, so you would definitely want to limit the current. Check out the build video after the break.

Still not portable enough for you? All you really need is a 18650, some nichrome, and a few bits and bobs to hold it all together.

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Surprisingly Stomp-able Soft Switches

June 2, 2022 by Kristina Panos 13 Comments

Competition sure brings out the brute in people, doesn’t it? So what do you do when you need a bunch of switches you can let people fist-pound or stomp on repeatedly without them taking damage? You could look to the guitar pedal industry and their tough latching switches, or you could simply build your own smash-resistant buttons as [wannabemadsci] has done.

The main thing about these switches is that they aren’t easily destroyed by shoes or angry fists. That’s because the shiny red push-me part of the button is made by cutting a foam ball in half.

Not easily crush-able Styrofoam, mind you — squishy, coated foam like an indoor football. This is mounted to the top of a sandwich made of hardboard and a couple pieces of easily-compressible foam from craft paintbrushes.

A brass washer is mounted to the middle of both pieces of hardboard, and these have wires soldered to them to read button presses. Then it’s just a matter of hooking it to a microcontroller like any other momentary.

There are all kinds of things you could cut in half for the top, like maybe tennis balls. Or, do what [Sprite_TM] did and use inverted plastic bowls.

Foam Surfboard From Scratch

December 29, 2021 by Matthew Carlson 5 Comments

Have you ever wanted to make your own surfboard, but felt held back by a lack of tools, materials, or the cost of it? Drawing almost entirely from what can be found at a well-known home improvement retailer, [AndrewW1997] details the steps needed to craft your board.

In his guide, he details the difference between XPS (expanded polystyrene) and EPS (extruded polystyrene) and how each product’s closed cell and open cell nature affects the final board. Starting with two pink sheets of XPS, he laminated them together with glue to form his blank. A stringer is a long piece of wood in the middle of the surfboard that provides additional flex and strength. Some flooring plywood curved with a jigsaw provides the shape needed. Unfortunately, the blank needs to be split in half to install the stringer. However, he has a trick for gluing the blank back together without it buckling, and that trick is ratchet straps.

He cuts the foam into roughly the right shape with a hot wire. Clean up is done with sanding blocks, a plane, and a level. The next step is laminating the board with epoxy and fiberglass. Next, [Andrew] details a few considerations around the process and gets to glassing. Sanding up to 2000 grit and some polishing compound make the board gorgeous. After a bit of final curing time, you’re ready to ride some waves.

There’s a handy playlist on YouTube detailing the process so you can follow along. Once you’ve finished your surfboard, perhaps your next project will be to power it up with a jet drive. Video after the break.

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Robot with star shaped wheels made of foam.

Build An Amphibious Robot Using Pool Noodles For Wheels

August 18, 2021 by Lewin Day 10 Comments

If you only think of wheels as round, you’re limiting yourself from experiencing the true wider world of whacky designs. [wadevag] has been experimenting with some such concepts, and has had success building an amphibious robot platform using star-shaped wheels built out of pool noodles.

The concept is similar to that of whegs. A portmanteau of wheel-legs, they’re in effect a form of leg that moves with a rotating motion. Essentially, the points of the stars on the wheels act like legs, pushing the robot along one by one, rather than having continuous contact with the ground as in a typical round wheel.

The flotation provided by the foam allows the robot to easily sit on top of the water’s surface, and the star shape allows them to act as viable paddles too. This is perhaps their primary advantage. A round wheel would not provide anywhere near as much forward propulsion.

[wadevag] shows off the concept’s abilities on water, concrete, and snow, and it handles them all ably. Impressively, it can both enter and exit the water under its own power. While it’s probably not a viable solution for a very heavy robot, for a lightweight design, it could work wonders. It’s not the first time we’ve seen some oddball wheel designs, either. Video after the break.

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Foam F-35 Learns To Hover

July 15, 2021 by Tom Nardi 2 Comments

With cheap RC hardware, powerful motors, and high-capacity battery packs, getting something to fly has never been easier. It also helps that, whether you’re into fixed-wing craft or multirotors, there’s plenty of information and prior art floating around online that you can use to jumpstart your own build. But when it comes to homebrew vertical take-off and landing (VTOL) planes, things are a bit trickier.

Luckily for us, [Nicholas Rehm] has made all the plans and information necessary to duplicate his incredible RC F-35 available for anyone who wants to experiment with these relatively niche fliers. Even if it was a standard park flier, the build would be worth a close look thanks to the vectored thrust motors that give it phenomenal maneuverability and a top speed in the neighboorhood of 120 KPH (80 MPH). But with the flick of a switch, the plane transitions into a tricopter-like flight mode that allows it to land and takeoff vertically.

How does it work? The downward facing motor just behind the “cockpit” lifts up the front of the foam flier and tilts left and right to provide yaw control, while the two motors on the back tilt down to lift up the rear of the aircraft. Aviation buffs in the audience may recognize this as being fairly close to how the actual F-35B hovers, although on the real jet fighter, downward thrust under the wings is generated by redirected turbine exhaust rather than dedicated motors, and yaw control is provided by swiveling the engine’s nozzle rather than the front lift fan.

Getting the plane to takeoff vertically was one thing, but being able to transition from a hover into forward flight was quite another. To make this aerial transformation possible [Nicholas] actually had to write his own flight controller software, which he calls dRehmFlight. The GPLv3 code runs on the Teensy 4.0 and uses the common GY-521 MPU6050 gyroscope/accelerometer, so you don’t need to get any custom boards spun up just to give it a test ~~drive~~ flight. In the video below he walks through configuring the software for VTOL operation by defining how each control surface and motor is to respond to control input given the currently selected flight mode.

It probably won’t surprise you to hear that this isn’t the first time [Nicholas] has experimented with unusual flying machines. Last year we covered his RC Starship, which managed to stick the “belly flop” landing even before SpaceX managed to get the real life version down in one piece.

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