Building a Horn Antenna for Radar

So you’ve built yourself an awesome radar system but it’s not performing as well as you had hoped. You assume this may have something to do with the tin cans you are using for antennas. The obvious next step is to design and build a horn antenna spec’d to work for your radar system. [Henrik] did exactly this as a way to improve upon his frequency modulated continuous wave radar system.

To start out, [Henrik] designed the antenna using CST software, an electromagnetic simulation program intended for this type of work. His final design consists of a horn shape with a 100mm x 85mm aperture and a length of 90mm. The software simulation showed an expected gain of 14.4dB and a beam width of 35 degrees. His old cantennas only had about 6dB with a width of around 100 degrees.

The two-dimensional components of the antenna were all cut from sheet metal. These pieces were then welded together. [Henrik] admits that his precision may be off by as much as 2mm in some cases, which will affect the performance of the antenna. A sheet of metal was also placed between the two horns in order to reduce coupling between the antennas.

[Henrik] tested his new antenna in a local football field. He found that his real life antenna did not perform quite as well as the simulation. He was able to achieve about 10dB gain with a field width of 44 degrees. It’s still a vast improvement over the cantenna design.

If you haven’t given Radar a whirl yet, check out [Greg Charvat’s] words of encouragement and then dive right in!

Stretch Bike Hauls All

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Need to haul some stuff? Got nothing to haul it with? Then fashion yourself a cargo bicycle! We’ve seen cargo bikes before, but none quite like this one. Built from a German “klapprad”, [Morgan] and his father fashioned a well constructed cargo bicycle which is sure to come in handy for many years.

They started by cutting the bike in half and welding in a 1 meter long square tubing extension. The klapprad style bicycle is made from thick metal stock, making it sturdy and easy to weld. This process also make it a true “stretch” vehicle as opposed to one that replaces the front end in order to keep the handle bar assembly near the rider.

Along with some nicely done woodwork and carbon fiber, they used parts from an old mountain bike including a front fork, front bearing and handlebar, tubing from an old steel lamp, a kickstand from a postman motorcycle, and a kitchen sink to complete the build. It should handle well so long as the weight of the cargo is not heavier than the weight of the driver.

On not getting metal fume fever with galvanized conduit

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You can find galvanized steel pipes at Home Depots and construction sites all around the world. These relatively thin-walled steel pipes would make for great structural members if it weren’t for the fact they were covered in a protective layer of zinc. This layer of galvanization lends itself to crappy welds and some terrible fumes, but badass, TV personality, and hacker extraordinaire [Hackett] shows us how to strip the galvanization off these pipes with chemicals available at any hardware store.

Since the galvanization on these pipes covers the inside and the outside, grinding the small layer of zinc off these pipes is difficult at best. To be sure he gets all the zinc off this pipe, [Hackett] decided to chemically strip the pipes with a cup full of muriatic acid.

The process is simple enough – fill a cup with acid, dunk the ends of the pipes, and clean everything up with baking soda. A great way to turn scrap pipe into a usable material, make a cool paper mache volcano, and avoid ‘ol galvie flu

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Scratch built camera tripod

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We’re used to seeing hacked camera mounts but [CroBuilder] mentioned to us that nobody is really making plain old tripods themselves. He loves to work in his shop so he spent about ten hours building this tripod for himself.

We’d say it’s built to last, but that comes at the cost of weighing a lot. He used square tubing for the legs, which are tripled up in order to allow them to telescope. Each leg has two pipes mounted to the central hub that he fabricated out of hexagonal pipe. A bolt and wing nut acts as hinge and clamp. On the bottom section of the leg there’s a tab spanning the two pieces and another clamping mechanism to hold the adjustable bottom portion of the leg in position.

He finished up the project with black paint on many of the pieces, with the legs themselves polished until shiny. Will rust be a problem if he doesn’t use a clear coat?

The nice thing about a quality tripod is that you can use them for more than just cameras. For instance, add some components to make your own laser level.

Build your own steel reinforced storm shelter

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The last few years have seen a lot of dangerous storms rip through middle section of the United States. We’re surprised to hear that many residents in that part of the country don’t have basements to take refuge in when in imminent danger. But a resourceful hacker will always be able to find a way to improve their own situation. This example is particularly useful. It’s a steel storm shelter which opens into the garage.

It all starts with a cage made of square tube. With the skeleton fully assembled it is wrapped in steel plate, adding weld joints running nearly the entire length of each of the cage’s ribs. The image at the left shows the steel door frame clamped in position. Check out the finished version on the right after the shelter has been slid into place and bolted to the concrete slab.

The Reddit discussion includes a debate on whether the door should swing in or out. Swinging out means you could be trapped if the opening is blocked by debris. But there may be scientific research that proves this is a better orientation. Either way, we hope the three dead bolts, door latch, and heavy-duty hinges will stand up to the pressure if this is ever used.

Using an angle grinder as a bench grinder

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[Saeid Momtahan] made a couple of attachments that let him use his angle grinder as a bench grinder. It may be better to refer to it as a bench motor, as he uses both a grinding wheel and a wire brush while showing off his project.

The attachments come in two parts. The first is a piece of square tube that runs parallel to the body of the grinder on the side opposite the handle. This doubles as a larger gripping area when using it as an angle grinder, as well as giving him something to clamp in his bench vise. The second attachment serves as a rest for the work piece. Above you can see him brushing some rusty stock clean with the wire attachment.

It’s nice to have the option of doubling up a tool’s tasks rather than buying yet another item that may not get used all that much. We also love the idea of building your own tools. If you don’t have a welding rig to fabricate these add-ons here’s a li-ion battery based system to get you thinking.

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Crown earns you the title King of the Junkyard

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[Greg Shikhman] wanted to use the school tools one more time before graduation. After hitting up some local motorcycle shops around town for parts he fashioned this crown for himself.

He didn’t pay ‘the iron price‘ as the motorcycle roller chain is waste material anyway. Chains do wear out and these were left over after being replaced with new ones. He first cleaned them up with a bit of WD-40 solvent, xylene, and soapy water to cut through the grime. There was also a layer of black oxide which normally keeps them from rusting which he peeled off with a dunk in some hydrochloric acid.

Chains are flexible and this would have made for a disheveled looking crown. The fix involved using an aluminum form the size of his head to keep the crown in round while he did his TIG welding. A double row of polished steel ball bearings take the place of jewels. As if the ten-pounder wasn’t painful enough he added four rings of bicycle chain as accents which he admits makes the thing unwearable because they dig into his noggin. We still don’t think that’s a good enough excuse to post about the project and not include an image of him wearing the thing during the junkyard coronation.

It would be fun to see a follow-up king-ring with similar LED features as that engagement ring but using this heavy-metal design style.