Building An Automatic Bicycle Transmission In A Week

January 18, 2013 by Brian Benchoff 58 Comments

Every year, the ECE department of Carnigie Mellon University hosts Build18, an engineering festival intended to get students out of the classroom and into the workshop. [Andrew Toth] along with team members [Jenna MacCarley], [Peter McHale], and [Nicolas Mellis] have been busy this last week putting together an automatic bicycle transmission.

Most cyclists agree that a cadence of 80 RPM is just about right for most cycling. The team’s transmission uses Hall effect sensors to sense the cadence of the rider and will change to a higher gear if the cadence drops below 60 RPM and a lower gear if the cadence is above 100 RPM.

One of the requirements of the Build18 festival is the completed project must cost less than $250. By using an Arduino Mega and a servo to change gears, the team has a fairly low cost solution to automatically changing bicycle gears.

It’s a very cool project, and hopefully we’ll see a video once the competition is over at noon, EST today.

Retrotechtacular: The Differential

January 15, 2013 by Mike Szczys 22 Comments

Any video that starts off with two minutes of motorcycle formation riding has got to be good. If the grainy black and white video didn’t tip you off that this was made in a different time the helmetless riders standing on the seats of moving motorcycles certainly would have. But there is a purpose to this exposition. A single line of motorcycles riding shoulder to shoulder as they go around a curve illustrates why a differential is necessary and soon after you’ll find out how one works.

Two wheels mounted on one axle need to turn at different speeds as a vehicle goes around a corner or one of the wheels must slip to accommodate the speed difference. The differential is necessary to allow for these different turning rates while still letting both wheels connect to the power train. We were surprised to learn from the video after the break that early automobiles got around this issues by powering only one of the four wheels.

This instructional video is a prefect compliment to the fluid coupling video we saw in the last installment of Retrotechtacular.

Continue reading “Retrotechtacular: The Differential” →

Another Take On The Rear-window LED Marquee

January 9, 2013 by Mike Szczys 40 Comments

re-window-led-display

This rear-window LED marquee will help let the driver behind you know when you’re planing to change lanes or make a turn. But it also includes the ability to send a message like “Back Off!”. [Robert Dunn] was inspired to undertake the project after seeing the one we featured back in October. We’d say his has a better chance of being street legal since it uses all red LEDs.

The marquee is a matrix of 480 LEDs, all hand soldered to form the nearly transparent 48×10 grid shown above. This is important to preserve visibility out the back window of his truck. It makes us wonder about the feasibility of using SMD instead of through hole components. That would certainly make it even less visible when not illuminated, but the assembly process would be much more difficult. That’s because the 5mm LED packages fit nicely in the grid of holes he drilled in some plywood which served as the jig during soldering. The presence of leads also made the soldering process manageable.

Power to an Arduino board is provided from the cigarette lighter adapter. A set of six shift registers drive the columns while the rows are controlled by a 4017 decade counter and some transistors. Check out the blinker test video after the break to get a look at what this can do while on the road.

Continue reading “Another Take On The Rear-window LED Marquee” →

A Very Dash-ing IPad Mini

January 2, 2013 by Mike Szczys 22 Comments

iPad-mini-dash-install

The work which [Mark] did to mount this iPad mini in the dashboard of his Ford truck is commendable. It looks like it came from the factory this way, and the functionality matches that illusion.

He actually started the project before he had the iPad mini on hand. A PDF that mapped out the exact dimensions was used as a template for the layout and alteration. He took the stereo controls out of the original faceplate. That opening was made to fit the screen by cutting, adding putty, then sanding and finishing.

Since the bezel won’t let [Mark] get at any of the buttons on the iPad itself he picked up an external home button on eBay and mounted it just to the left of the screen. Inside the dashboard a docking connector is responsible for powering the tablet and connecting it to the sound system. There’s even a WiFi connection thanks to the MiFi system he mounted in the overhead console.

Self-balancing Unicycle Using Arduino And Sparkfun IMU

December 14, 2012 by Mike Szczys 21 Comments

Raptor-Bike-self-balancing-unicycle

Here’s proof that you can build cool stuff with simple tools. This self-balancing unicycle uses an Arduino and a five degree of freedom IMU from Sparkfun to keep the rider upright. Well, it’ll keep you upright as long as you have good side-to-side balance. But that’s true of any unicycle, right?

The Raptor was built by [Nick Thatcker] who is no stranger to self-balancing transportation. A few years back he built a Segway clone and the same type of geared motor used in that project also went into this one. I connects to the wheel with a chain, allowing him to keep the motor hidden in the saddle. He gets between 90 and 120 minutes of used on one charge with a top speed of 10 MPH. The motor could move you along faster but he has limited this in firmware to ensure it has enough power to ‘catch up’ if you lean too far forward.

Don’t miss the demo after the break. If you like this unicycle there are several others worth looking at.

Continue reading “Self-balancing Unicycle Using Arduino And Sparkfun IMU” →

Homemade Tank Joins The Battle In Syria

December 10, 2012 by Mike Szczys 107 Comments

syrian-home-made-tank

What does a hacker do when going into battle for the freedom of their country? He builds a tank from scratch, of course. It’s a little bit of a stretch calling it a tank as it lacks treads. But it’s got a high-caliber gun mounted on top and has been heavily armored.

There is room enough inside for two people. What may look low tech in this picture is a different story from the cockpit. A pair of LCD monitors display images from five different cameras. You can see the shrouds that protect three of them on the front of the vehicle with a fourth acting as the rear view. A fifth camera mounted on the gun gives the passenger a look at where he’s aiming. A PS1 controller can rotate it and we assume has a fire feature as well. Check out the demonstration video embedded after the break.

Continue reading “Homemade Tank Joins The Battle In Syria” →

Self Balancing Unicycle Built From Old Scooter

December 4, 2012 by Brian Benchoff 3 Comments

[Glenn] had an old electric scooter/motorcycle in his garage that had long ago given up the ghost. Without a working battery and motor controller this scooter wasn’t beyond repair, but [Glenn] thought he could use it to build something much, much cooler. What he came up with is a self-balancing unicycle that borrows inspiration from a Segway and other self-balancing robots.

After cutting the drive chain off his scooter, [Glenn] began work on installing a new motor controller and battery. To make this unicycle balance itself, he would need a few gyroscopes and accelerometers provided via an Arduino and Sparkfun IMU shield.

After tuning his PID loop, [Glenn] hopped on his new ride and took it for a spin with the help of a pair of ski poles. It’s much easier to ride than a traditional unicycle and [Glenn] says he’s getting better at riding it.