Tales of Garage Design: Achieving Precision from Imprecise Parts

Designing parts to fit perfectly together is hard. Whether it’s the coarseness of our fabrication tools or the procedures of the vendor who makes our parts, parts are rarely the exact dimension that we wish they were. Sadly, this is the penalty that we pay by living in a real world: none of our procedures (or even our measurement tools!) are perfect. In a world of imperfect parts, imperfect procedures, and imperfect measurement techniques, how on earth are we supposed to build anything that works? Fortunately, we’re in luck! From the brooding minds of past engineers, comes a suite of design techniques that can combat the imperfections of living in an erroneous world.

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Machine Shop Soaps Are Good, Clean Learning Fun

At first glance, it’s easy to dismiss the creation of custom bath soaps as far outside the usual Hackaday subject matter, and we fully expect a torrent of “not a hack” derision in the comments. But to be able to build something from nothing, a hacker needs to be able to learn something from nothing, and there is plenty to learn from this hack.

On the face of it, [Gord] is just making kitschy custom bath soaps for branding and promotion. Cool soaps, to be sure, and the drop or two of motor oil and cutting fluid added to each batch give them a little machine shop flair. [Gord] experimented with different dyes and additives over multiple batches to come up with a soap that looked like machined aluminum; it turns out, though, that adding actual aluminum to a mixture containing lye is not a good idea. Inadvertent chemical reactions excepted, [Gord]’s soaps and custom wrappers came out great.

So where’s the hack? In stepping way outside his comfort zone of machining and metalwork, [Gord] exposed himself to new materials, new techniques, and new failure modes. He taught himself the basics of mold making and casting, how to deal with ultra-soft materials, the chemistry of the soap-making process, working out packaging and labeling issues, and how to deal with the problems that come from scaling up from prototype to production. It may have been “just soap”, but hacks favor the prepared mind.

Rehabbing an Historic Tool from Champion Blower and Forge Co.

Here’s a tale that warms our hearts. [Gord] is helping out the local living-history museum by rehabbing a historic woodworking tool that they want to add to their live demo woodshop. It’s a hundred-year-old manual drill press that has seen a ton of use.

acme-rod-tig-repairThere are three things that [Gord] has going for him. First off, the Champion Blower and Forge Co. built them to last. Second, he’s not really working on a deadline; the museum doesn’t need it back until May. And third, [Gord] has the tools he needs to do this right.

After cleaning and blasting [Gord] gets down to the really interesting repairs. First off, it wouldn’t be a drill press if someone hadn’t tried to drill through the table at some point. TIG welding filled it up and some milling brought it back. This same method was used again to make a beautiful custom replacement ACME rod. Throwing in a custom bushing replacement, turned wooden handle, and a several other fabricated parts, and [Gord] had the press working again. Check out the mechanism in the video below that shows the crank action turns the bit and a cam advances it through the work piece.

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Radial Solenoid Engine is Undeniably Cool

Radial engines are just plain cool – it’s inarguable that any tech that originated with early aviation is inherently awesome. But, what do you do when you want to build a radial engine in your dorm where a combustion engine would be inadvisable? For University of Washington students [Jeffrey Weng] and [Connor Lee] the answer was to power it with solenoids in place of the pistons.

The easiest way to approach a project like this would have been to use a microcontroller. A simple program running on an Arduino could have easily provided the timing to switch power to each solenoid in succession. [Jeffrey Weng] and [Connor Lee], however, took a much more interesting approach by controlling timing via a simple distributor. This works in the same way a spark distributor on a combustion engine would have worked, except it’s actually providing the power to actuate the solenoids instead of providing just an ignition spark.

Also impressive is what they were able to accomplish with such basic tools. Those of us who are lazy and have access to more expensive tools would have just 3D printed or CNC cut most of the parts. Either [Jeffrey Weng] and [Connor Lee] didn’t have access to these, or they wanted to increase their machining street cred, because they created all of the parts with simple tools like a band saw and drill press. We’ve seen some beautiful engine projects before, but what this build lacks in objective beauty it makes up for in ingenuity.

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3D Objects From a Laser Cutter

Actors want to be singers and singers want to be actors. The hacker equivalent to this might be that 3D printers want to be laser cutters or CNC machines and laser cutters want to be 3D printers. When [Kurt] and [Lawrence] discovered their tech shop acquired a 120 Watt Epilog Fusion laser cutter, they started thinking if they could coax it into cutting out 3D shapes. That question led them to several experiments that were ultimately successful.

The idea was to cut away material, rotate the work piece, and cut some more in a similar way to how some laser cutters handle engraving cylindrical objects. Unlike 3D printing which is additive, this process is subtractive like a traditional machining process. The developers used wood as the base material. They wanted to use acrylic, but found that the cut away pieces tended to stick, so they continued using wood. However, the wood tends to char as it is cut.

In the end, they not only had to build special jigs and electronics, they also had to port some third party control software to solve some issues with the Epilog Fusion cutter’s built in software. The final refinement was to use the laser’s raster mode to draw surface detail on the part.

The results were better than you’d expect, and fairly distinctive looking. We’ve covered a similar process that made small chess pieces out of acrylic using two passes. This seems like a natural extension of the same idea. Of course, there are very complicated industrial machines that laser cut in three dimensions (see the video below), but they are not in the same category as the typical desktop cutter.

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Custom Machined Triple Threat Slingshot

Time was when a lad in need of a ranged weapon would hack a slingshot together out of a forked tree branch and a strip of inner tube. Slingshot design has progressed considerably since [Dennis the Menace]’s day, but few commercially available slingshots can match up to the beauty and functionality of this magnificently machined multipurpose handheld weapon system.

Making it clear in his very detailed build log that this is but a prototype for a design he’s working on, [Gord] has spared little effort to come up with a unique form factor that’s not only functional as a slingshot, but also provides a few surprises: a magazine that holds nine rounds of ammo with magnets; knuckle protection on the hand grip that would deal a devastating left hook; and an interchangeable base that provides a hang loop or allows mounting a viciously sharp broadhead hunting arrow tip for somewhat mysterious purposes. There’s plenty to admire in the build process as well – lots and lots of 6061 billet aluminum chips from milling machine and lathe alike. All told, a nice piece of craftsmanship.

For a more traditional slingshot design with a twist, check out this USB-equipped slingshot that talks to Angry Birds. And when your taste in slingshots run more toward the ridiculously lethal, [Jörg Sprave]’s machete launcher never disappoints.

[Thanks Leslie!]

Miniature Cannon Packs a Punch, Shows off Manual Machining Skills

CNC machine tools are getting ever more affordable for the amateur machinist, and they’re an enabling technology for many projects. But you’ve got to respect the old school approach to turning hunks of metal into finished parts with no computer control. [Ticktock34] shows off his skills on a WWII vintage manual lathe with a photo album of his .75 caliber miniature black powder cannon build. What starts as a 3″ diameter actuator from a front end loader ends up as a beautiful replica of a full-sized cannon, along with a half-filled barrel of nicely blued scrap metal. Particularly impressive is the nicely proportioned ball end, cut by hand with no more instrumentation than a set of calipers. [Ticktock34] also shares a few tips for getting the trunnions exactly squared and aligned.

Good looking, and functional – stay tuned after the break for a video with the impressive blast from a test firing – with only a quarter charge of powder, mind you.

Want something a little safer for the kiddies and less likely to result in a visit from the police? Perhaps this PVC pirate cannon is more your speed.

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