[Harrison Krix’s] Marriott Chariot

Atlanta’s Mini Maker Faire had plenty of booths to keep visitors busy, but the largest spectacle by far was the racetrack smack-dab in the middle, and you’d be hard pressed to find a more eye-catching contender than [Harrison Krix’s] vehicle: the Marriott Chariot.

If [Krix’s] name looks familiar, that’s because he’s the master artisan behind Volpin Props, and is responsible for such favorites as the Futurama Holophonor replica and the Daft Punk helmet. (Actually, he made the other one, too).

The Chariot is yet another competitor in the Power Racing Series, an event that keeps popping up here on Hackaday. [Krix] drew inspiration from this Jeep build we featured earlier in the summer, and went to work sourcing an old plastic body to get started. The frame is 16 gauge square tubing, with a custom motor mount machined from 3/16 steel. After welding the chassis together, [Krix] chopped up a small bicycle to snag its head tube and headset bearings. A pair of sealed lead acid batteries fit horizontally in the frame, providing a slightly lower center of gravity.

[Krix] has a keen eye for precision and his build journal shows each step of his meticulous process. But, you ask, why “Marriott Chariot?” and why does the car look like someone threw up a kaleidoscope? Read on beyond the break, dear reader, to learn the Chariot’s origin and to see a video of it winding around the track.

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Using Excel to Watch Movies at Work

The Excel subreddit exploded earlier this week when redditor [AyrA_ch] shared his custom spreadsheet that allowed him to play video files on a locked-down work computer. How locked down? With no access to Windows Media Player and IE7 as the only browser (all plugins disabled, no HTML5), Excel became the unlikely hero to cure a 3-hour boredom stint.

Behind the cascade of rectangles and in the land of the Excel macro, [AyrA_ch] took advantage of the program’s VBA (Visual Basic for Applications) functions to circumvent the computer’s restrictions. Although VBA typically serves the more-complex-than-usual macro, it can also invoke some Windows API commands, one of which calls Windows Media Player. The Excel file includes a working playlist and some rudimentary controls: play, pause, stop, etc. as well as an inspired pie chart countdown timer.

As clever as this hack is, the best feature is much more subtle: tricking in-house big brother. [AyrA_ch]’s computer ran an application to monitor process usage, but any videos played through the spreadsheet were attributed to Excel, ensuring the process usage stayed on target. You can download it for yourself over on GitHub.

Electric Bubblegum Board

The Mini Maker Faire in Atlanta was packed with exciting builds and devices, but [Andrew’s] Electric Bubblegum Boards stood out from the rest, winning the Editor’s Choice Award. His boards first emerged on Endless Sphere earlier this summer, with the goal of hitting all the usual e-skateboard offerings of speed, range, and weight while dramatically cutting the cost of materials.

At just over 12 pounds, the boards are lightweight and fairly compact, but have enough LiFePO4’s fitted to the bottom to carry a rider 10 miles on a single charge. A Wii Nunchuck controls throttle, cruise control, and a “boost” setting for bursts of speed. The best feature of this e-skateboard, however, is the use of 3D-printed parts. The ABS components not only help facilitate the prototyping process, but also permit a range of customization options. Riders can reprint parts as necessary, or if they want to just change things up.

[Andrew’s] board is nearing the 11th hour over at his Kickstarter page, so swing by to see a production video made for potential backers, or stick around after the break for some quick progress and demo videos.

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We’re at Maker Faire Atlanta, Oct 4-5

If you live in the southeastern US, mark your calenders for next weekend—October 4th and 5th—and head out to the fourth annual Maker Faire Atlanta in downtown Decatur, GA. You can find a complete list of participants here.

I’ll be around all weekend to talk to makers about their projects and to hand out some Hackaday stickers. As [Brian] said with the HaD crew at the NY Faire, don’t be afraid to introduce yourself if you see me walking around or lurking at the Hackyard booth. See you there!

Exposed Clock is Flippin’ Cool

Some hacks are triumphs of cleverness, others…are just cool. [Super Cameraman’s] exposed retro flip clock tends toward the latter half of that spectrum—it may not be the most complex, but we’re relieved that for once there isn’t an Arduino crammed into the back of it.

You can buy pared down, exposed flip clocks at museums for an arm and a leg, or you can trudge through eBay and local thrift shops until you come across a cheapo clock radio. [Super Cameraman’s] clock cost him exactly $2, and is split into two sections: a clock side and a radio side. Prying off the knobs and popping open the case reveals all the shiny mechanisms and electronics, most of which he trashed. The radio and even the transformer were removed, leaving only the flip clock, which he re-wired directly to the plug—it seems these types of clocks run straight off 120VAC. Check out the video below.

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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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A Li-ion Battery Charging Guide

Although [pinomelean’s] Lithium-ion battery guide sounds like the topic is a bit specific, you’ll find a number of rechargeable battery basics discussed at length. Don’t know what a C-rate is? Pfffft. Roll up those sleeves and let’s dive into some theory.

As if you needed a reminder, many lithium battery types are prone to outbursts if mishandled: a proper charging technique is essential. [pinomelean] provides a detailed breakdown of the typical stages involved in a charge cycle and offers some tips on the advantages to lower voltage thresholds before turning his attention to the practical side: designing your own charger circuit from scratch.

The circuit itself is based around a handful of LM324 op-amps, creating a current and voltage-limited power supply. Voltage limits to 4.2V, and current is adjustable: from 160mA to 1600mA. This charger may take a few hours to juice up your batteries, but it does so safely, and [pinomelean’s] step-by-step description of the device helps illustrate exactly how the process works.

[Thanks mansalvo]