Water vortex exhibit repair gives a look at the bearing and gasket design

[Ben Krasnow's] water vortex machine has been an exhibit in the lobby of the San Jose City Hall for quite some time now. Unfortuantely he recently had to perform some repair work on it due to the parts inside the water chamber rusting.

This is the same water vortex that we saw about a year ago. It uses a power drill to drive an impeller at the bottom of a water column to produce the vortex. That impeller was made from painted steel and after being submerged for eight months it began rusting, which discolored the water. [Ben's] repair process, which you can watch after the break, replaces the shaft and the impeller. He reused a plastic PC cooling fan as the new impeller. The replacement shaft is stainless steel, as is all of the mounting hardware that will be in contact with water. But for us, the most interesting part of the repair is his explanation of the shaft gasket and bearings. Two thrust bearings and two radial bearings ensure that the shaft cannot move axially, which would cause a problem with the gasket. He had intended to swap out the oil seal for an all Teflon seal but the machined acrylic wasn’t conducive to the part swap. Instead, he replaced it with the same type of gasket, but bolstered the new one with some silicone to stave off corrosion.

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Guitar pickup winding workstation

After a bit of inspiration, [Pete] decided to build a solid body electric guitar for himself. Instead of assembling a conglomeration of off-the-shelf parts, he plans on building just about everything from scratch. This includes the guitar pickups, so he built himself a pickup winder that has measures RPM, ETA until done, and auto stop for when the pickup is complete.

Electric guitar pickups are simple devices – just a magnet for each string wrapped in thousands of turns of wire about as thin as a human hair. [Pete] began his build with a cheap sewing machine and added a tachometer and pickup mount. As an added bonus, [Pete] threw in an ohmmeter to measure the coil resistance and a Gauss meter to measure the magnetic flux and polarity of the pole pieces. It’s a very nice build that’s designed to be as functional as commercial pickup winders.

[Pete] was originally inspired to build a pickup winder by the Les Paul Google doodle, and he plans on continuing Les Paul’s tradition of guitar innovation by building his own solid body guitar. The wood has been cut already, and we can’t wait to see the final product.

Check out a video of [Pete]‘s coil winder in action after the break.

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Crazy slingshot guy at it again with a 220 lb steel ball cannon

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Good old [Jörg Sprave].

That guy just doesn’t quit building insane slingshots. If he’s not honing his machete slinging skills in preparation for the zombie apocalypse, he’s blowing out car windows with giant steel balls.

The huge cannon you see above is modeled off a small slingshot he made a while back, which fired 8mm steel bearings. In its larger form, the slingshot is said to be ten times the size of it’s smaller brother, firing 80mm steel balls with incredible force. In the video below, [Jörg] and his friends cart the slingshot out to a huge empty field where they run it through its paces on several different objects. Their first shot flies about 220 yards into a high tension tower, after which the boys aim their sights on an old car.

The power with which the slingshot fires is definitely impressive. With a few well-placed shots, the car is pretty much done for.

Now that we’ve seen [Jörg] fire off saw blades, machetes, and giant ball bearings, we can’t wait to see what comes next!

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Engine Hacks: Adding fuel injection to a riding lawnmower

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Are you tired of fiddling with the engines on your lawn equipment every spring, trying to get them to run again? [jhark] was and decided to do something about it by converting his riding lawnmower over to fuel injection. After stealing a fuel injector from his van and bolting it onto the mower’s carburetor, he sprinkled in a dash of Arduino magic. With a small amount of code tweaking he was ready to roll mow. You can find a schematic and his code if you follow the forum link to the second page.

For more fuel injection goodness, check out this project where [Steve] upgrades his Austin Healey to use the fuel injection system from a General Motors vehicle. This build log is pretty comprehensive and shows each element in the system, describes what it does, and shows where it should go. If you are a car nut, this is definitely one to check out.

Finally, if you are looking to really dig into the nuts and bolts of automotive fuel injection, take a look at the Megasquirt fuel injection computer system that allows you to finely tune things to your specific car and model.

Monitoring water levels with a Parallax Ping sensor

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When you need a mechanism to detect the water level within a container or tank, you have several different options. Most people opt for a simple float or probe that sits in the water, while others use optics to sense when the water is reaching an undesired level.

This device built by [Danilo Abbasciano] uses a Parallax Ping sensor instead. If the sensor is placed at the top of a well, cistern, or other water container, it can accurately calculate the height and volume of the fluid inside. This is done by using the Ping’s readings in conjunction with a few values already known to the user, namely the dimensions of the container.

In his implementation, the readings are relayed to a simple LCD panel for easy viewing, and a small piezo speaker is used to sound an alarm when the water level reaches a predefined threshold. This sort of measuring device can be quite useful in situations where a contact-based sensor would be subject to chemicals and corrosion, or where contamination is a concern.

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