Low-Budget Hydroformer Puts the Squeeze on Sheet Metal Parts

Between manufacturing technologies like 3D-printing, CNC routers, lost-whatever metal casting, and laser and plasma cutters, professional quality parts are making their way into even the most modest of DIY projects. But stamping has largely eluded the home-gamer, what with the need for an enormous hydraulic press and massive machined dies. There’s more than one way to stamp parts, though, and the budget-conscious shop might want to check out this low-end hydroforming method for turning sheet metal into quality parts.

If hydroforming sounds familiar, it might be because we covered [Colin Furze]’s attempt, which used a cheap pressure washer to inflate sheet metal bubbles with high-pressure water. The video below shows a hydroformer that [Rainbow Aviation] uses (with considerably less screaming) to make stamped aluminum parts for home-brew aircraft. The kicker with this build is that there is no fluid — at least not until the 40,000-pound hydraulic press semi-liquifies the thick neoprene rubber pad placed over the sheet metal blank and die. The pressure squeezes the metal into and around the die, forming some pretty complex shapes in a single operation. We especially like the pro-tip of using Corian solid-surface countertop material offcuts to make the dies, since they’re available for a pittance from cabinet fabricators.

It’s always a treat to see hacks from the home-brew aviation world. They always seem to have plenty of tricks and tips to share, like this pressure-formed light cowling we saw a while back.

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Replicating a Victorian Era Console

[Dt99jay] lives in a historic Victorian-era district in the UK.  Most homes in the area have ornate exterior window dressings with stone consoles holding up heavy stone hood molding.

The window hood molding turned out to be wood — most likely the result of damage repaired after the blitzkrieg bombings of WWII. The 1940’s era work is now rotting away, so it was time for a repair. When the hood was pulled away from the window, disaster struck. One console completely crumbled, while the other lost large chunks of material. The They weren’t solid stone after all, but replacements most likely molded with Coade stone.

There are no ready replacements for consoles like this. [dt99jay] couldn’t just swap them out for modern looking replacements, so he set about replicating the consoles. The remaining console was much too delicate to remove from the building, so [dt99jay] glued the missing pieces back on. He then filled any missing parts and carefully scraped way all the loose paint. Then came the difficult part — making a mold while the console was still mounted on the house.

Room Temperature Vulcanizing (RTV) silicone rubber was carefully applied to the console. The RTV is thick enough to stay on while it dries. After several thick layers of RTV, the console was covered. [Dt99jay] then covered the mold with plaster of Paris bandages to support it. The finished mold was carefully removed from the house, and [dt99jay] filled all the low spots and air bubbles with RTV.

New castings were made using a mixture of cement and playground sand. Once painted, the results matched perfectly. The historic conservation committee was pleased, and the window was once again structurally sound.

Glue Your Sumo Robot to The Mat With Custom Sticky Tires

Mini Sumo seems like one of those hobbies that starts out innocently enough, and ends up with a special room in the house dedicated to it. One day you’re excitedly opening up your first Basic Stamp kit, and the next you’re milling out mini molds on a mini lathe to make mini extra sticky tires.

[Dave] started out trying to find a part from the local big box store that was just a little bigger than the wheel he wanted to rubberize. He set the wheel inside a plumbing cap and poured the urethane in. It worked, but it required a lot of time with a sharp knife to carve away the excess rubber.

In the meantime he acquired a Sherline Mini Mill and Lathe. With the new tools available to him, he made a new mold out of a bit of purple UHMW and some acrylic. This one produced much nicer results. Using a syringe he squeezed resin into the mold through a hole in the acrylic. Much less cleanup was needed.

He later applied these methods to smaller, wider wheels as his mini sumo addiction took a stronger hold on his life.

Retrotechtacular: Brunswick Shows A Bias for Tires

Somewhere between the early tires forged by wheelwrights and the modern steel-belted radial, everyone’s horseless carriage rode atop bias-ply tires. This week’s film is a dizzying tour of the Brunswick Tire Company’s factory circa 1934, where tires were built and tested by hand under what appear to be fairly dangerous conditions.

It opens on a scene that looks like something out of Brazil: the cords that form the ply stock are drawn from thousands of individual spools poking out from poles at jaunty angles. Some 1800 of these cords will converge and be coated with a rubber compound with high anti-friction properties. The resulting sheet is bias-cut into plies, each of which is placed on a drum to be whisked away to the tire room.

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Cryogenic Machining: Custom Rubber Parts

Fashioning a custom, one-off rubber part for your project isn’t usually an option, but [Ben Krasnow] has an alternative to injection molding and casting: machining frozen rubber.

As [Ben] points out, you can’t exactly pop a sheet of rubber on your mill and CNC the needed shape; the bit will push the material around rather than cut it. Freezing the rubber first, however, allows you to carve into the now-hardened material.

His initial setup consisted of a sheet of aluminum with water drizzled on top, a square of neoprene placed on the water, and a steady stream of -60 to -80C alcohol flowing directly onto the rubber. The water underneath freezes, holding the neoprene in place. This proved problematic as the ice-clamp gives way before the milling is complete. [Ben] later adds some bolts to clamp the pieces down, allowing the milling process finish as planned.

A small plastic tray sits underneath this assembly to capture the alcohol as it runs off, feeding it back with some tubing. [Ben] recommends against a submersible aquarium pump—his initial choice—because the pump stopped working after a few minutes immersed in the chilly alcohol. An external, magnetically-driven pump solved the problem although it does require manual priming.

Stick around after the jump for the video and check out some of [Ben’s] other projects, like his quest for the perfect cookie, or CT scanning a turkey.

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Building touch sensors from digital barometer chips

A couple of Harvard researchers have developed a method of using digital barometers as a touch sensor. The good news for us is that they’ve open sourced the project, including Eagle board files, firmware, and details about the materials they used.

The digital barometers were chosen for their characteristics, availability, and low-cost. The sensor uses an array of Freescale MPL115A2 chips, a MEMS Barometer designed for use in altimeters. The mass production makes them cheap (Octopart found some in single quantities for $1.71 at the time of writing). The chips are soldered onto a board which is then cast in rubber. This distributes the force while protecting the sensors. The video after the break shows them standing up to rubber hammer blows and supporting a 25 pound weight.

There are a few tricks to reading the array. The first is that the devices are designed to be used one-to-a-project so they have a fixed i2 address. A separate chip must be used to address them individually. But one it’s up and running you should be able to use it as feedback for the fingertips of that robot arm you’ve been building.

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Gently stroke this drum

The silent drum is played with your hands. It acts as a midi device by analyzing the movement of the rubbery black drum head. As you can see in the photo, one side of the body is clear and the other is white. A light shines up into it to boost the contrast and a camera picks up the black head as it moves past the white side of the shell. [Jaime Oliver] has provided an interesting look at the analysis method used with this instrument and there’s also a system of notating a composition for future performance. See and hear it played in the demo after the break.

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