BLDC Controller With The Teensy 3.1

January 13, 2015 by Brian Benchoff 18 Comments

[Will] is on the electric vehicle team at Duke, and this year they’re trying to finally beat a high school team. This year they’re going all out with a monocoque carbon fiber body, and since [Will] is on the electronics team, he’s trying his best by building a new brushless DC motor controller.

Last year, a rule change required the Duke team to build a custom controller, and this time around they’re refining their earlier controller by making it smaller and putting a more beginner-friendly microcontroller on board. Last years used an STM32, but this time around they’re using a Teensy 3.1. The driver itself is a TI DRV8301, a somewhat magical 3 phase 2A gate driver.

The most efficient strategy of driving a motor is to pulse the throttle a little bit and coast the rest of the time. It’s the strategy most of the other teams in the competition use, but this driver is over-engineered by a large margin. [Will] put up a video of the motor controller in action, you can check that out below.

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Wood-Only Kart Race Inspires Fancy Wooden Bearings

January 12, 2015 by Matt Freund 47 Comments

The mountainous Italian town of Artena holds an annual soap box derby for wood vehicles – and they mean 100% wood, not a speck of anything else. Fierce competition led [Alessio] to engineering and CNC fabricating these gorgeous wooden roller bearings for the wheels to give him an edge.

Thousands in costume attend the renaissance faire known as “Palio delle contrade di Artena”, and the popular wood-only race is called “La Carettella.” The karts are operated by a two-man team: one in front who brakes, the other in the rear who hops on and off to push as needed throughout the course. There appears to be no steering from the wheels** so turning is also a two-man effort. The wooden levers dragging on the pavement provide some steering from the “driver”, and the push-man often manhandles the entire rear end, drifting where necessary.
The course also includes full-width obstacles like hay bales. Teams are divided by community or “contrada”, and it was [Alessio]’s team captain who came to him with the special request of roller bearings. Unable to find evidence of other wooden bearings, [Alessio] knew he would have to invent them himself – so he did.

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Odd-Looking Mini EV Yard Tractor Is Made From Plywood And Bike Parts

January 12, 2015 by Rich Bremer 24 Comments

[Ian] likes to build small Electric Vehicles and his most unique project is certainly this yard tractor. During the design phase of the project [Ian] came up with a few requirements to ensure that this vehicle would be useful around the house. First, it had to be maneuverable in tight spaces. This was accomplished by the short wheel base and small diameter front-steering wheels. Next, it had to get great traction as leaving torn-up grass around the yard was not going to cut the mustard. Four mountain bike drive wheels used in the rear double the traction while at the same time distributing the friction over twice the surface area of the grass. To increase the traction even more, the rider’s seating position was intentionally put directly over the rear wheels.

The frame was kept simple by using plywood as structural members. Two 40Ah 12v batteries are set low between the front and rear axles and power the 4 DC drive motors. The motors are connected to the axle by means of sprockets and chains which results in a 36:1 reduction. That’s a large gear reduction and limits the tractor to a top speed of 12 km/h (7.5 mph). Bike tires front and rear were used because they are easily available and are super low-cost. And of course, a tractor wouldn’t be complete without a trailer hitch to tow around plants, rocks, wood or any other general yard debris.

[Ian] makes plans for his mini EV tractor available on his website. If your kid is envious of this electric tractor, maybe you can make him one of these…

Grinding A Bicycle Crank For Power Analysis

January 11, 2015 by Brian Benchoff 35 Comments

For [Mark] and [Brian]’s final project for [Bruce Land]’s ECE class at Cornell, they decided to replicate a commercial product. It’s a dashboard for a bicycle that displays distance, cadence, speed, and the power being generated by the cyclist. Computing distance, cadence and speed is pretty easy, but calculating power is another matter entirely.

The guys are using an ATMega1284 to drive an LCD, listen in on some Hall Effect sensors, and do a few calculations. That takes care of measuring everything except power. A quick search of relevant intellectual property gave then the idea of measuring torque at the pedal crank. For that, [Mark] and [Brian] are using a strain gauge on a pedal crank, carefully modified to be stiff enough to work, but flexible enough to measure.

A custom board was constructed for the pedal crank that measures a strain gauge and sends the measurements through a wireless connection to the rest of the bicycle dashboard. It works, and the measurements in the classroom show [Brian] is generating about 450 W when pedaling at 33 mph.

Video below.

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Boeing 777 From Manilla Folders, A 6+ Year Effort

January 3, 2015 by Matt Freund 67 Comments

The closer you look the more you will be in awe of this shockingly intricate 777 replica. The fully-articulating landing gear alone has over 2,000 parts and 200 hours of assembly, not even including the penny-sized tires with individually-cut lug nuts. All carved from manilla office folders by hand.

A high school ~~art~~ architecture class in 2008 inspired this build by teaching a few papercrafting techniques. When [Luca] got a hold of a precision Air India 777-300ER schematic, he started building this 5 foot long 1:60 scale model. His project has received a fair amount of media attention over the years, including some false reports that he was so focused on the build that he dropped out of college (he did, for 2 years, but for other reasons). 6.5 years in the making, [Luca] is rounding the homestretch.

The design is manually drawn in Illustrator from the schematics, then is printed directly onto the manilla folders. Wielding an X-acto knife like a watch-maker, [Luca] cuts all the segments out and places them with whispers of glue. Pistons. Axles. Clamps. Tie rods. Brackets. Even pneumatic hoses – fractions of a toothpick thin – are run to their proper locations. A mesh behind the engine was latticed manually from of hundreds of strands. If that was not enough, it all moves and works exactly as it does on the real thing.

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Offset Unicycle Built Mostly From A Single Bicycle

December 28, 2014 by Rick Osgood 32 Comments

[Lou’s] friends all said that it would be impossible to build a unicycle that had offset pedals. Moving the pedals to the front of the unicycle would throw off the balance and prevent the user from being able to ride it. [Lou] proved them wrong using mostly components from a single donor bicycle.

The donor bike gets chopped up into a much smaller version of itself. The pedals stay attached in the original location and end up being out in front of the rider. The seat is moved backwards, which is the key to this build. Having the rider’s legs out in front requires that there be a counter balance in back. Moving the seat backwards gets the job done with relative ease.

To prevent the hub from free wheeling, [Lou] lashes the sprocket directly to the wheel spokes using some baling wire. He also had to remove the derailer and shorted the chain. All of this gives the pedals a direct connection to the wheel, allowing for more control. The video does a great job explaining the build quickly and efficiently. It makes it look easy enough for anyone to try. Of course, actually riding the unicycle is a different matter. Continue reading “Offset Unicycle Built Mostly From A Single Bicycle” →

RGB Bike Rim Lights

December 26, 2014 by Marsh 8 Comments

[Yvo] sent us his latest creation, this awesome POV RGB bicycle rim light build, which features a circular interweaving of common RGB LEDs that face outward along the rim as they display constantly changing animations based on the wheel’s rpm.

Like many POV wheel builds, [Yvo]’s takes advantage of a hall effect sensor and stationary magnet to determine how fast the wheels are spinning. Unlike most POV builds, however, [Yvo’s] creation doesn’t have just one or two RGB sticks clamped onto a spoke. Instead, his wheels boast several individual RGB LED modules mounted along the rim.

Each wheel has six modules, and each module contains a scratch-build LED controller (a daisy chain of 74HC595 shift registers) that fits into a custom-made 3D-printed enclosure. The enclosures mounts onto some aluminum strips along with the RGB LEDs, and the aluminum strips mount to the wheels by straddling the rim.

At speed, the lights go into POV mode to simulate headlights / brakes with white in the front and red in the back. Check out the difference these custom circular modules make when riding and when at rest in a video below.

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