Karen Nakamura: May 2011 Archives

From the "I wouldn't believe the physics even if I saw the youtube video" department, a sail car that can go faster downwind than the wind itself. While it's possible to go faster than the wind when tacking against it, it was long thought to be impossible to faster directly downwind. These folks prove it's not so:

Some links to enjoy:

• http://blueplanettimes.com/?page_id=4116
• http://dansdata.blogsome.com/2011/05/04/common-sense-versus-reality/
• http://www.nalsa.org/DownWind.html
• http://www.wired.com/autopia/2010/08/ddwfttw/all/1

There are a couple of free (as in beer) programs that can help you draw up wiring diagrams or schematics. Some of them will even turn them into PCB templates for you. These are the ones I've used:

Fritzing: Fritzing is designed to work with Arduino systems, but is still very much in alpha. Still, I use it for quick and simple schematics of my Arduino projects as it has most of the wiring all set to go.

Eagle: This is the program most serious people seem to be using. I find its interface to be extraordinarily complex and non-intuitive. There's a free version with just a few limitations, or pay for the real version with none. Can export to PCB templates.

Any suggestions on other alternatives? I'm a Mac user, so I only listed the Mac-compatible ones here. I know that other folks use ExpressPCB and some other programs that are Win-only.

I burnt out the original brushless motor and installed a new one, here's the new revised bill of materials (BOM) (dated 2011.5):

Base Unit	Piaggio Boxer (1971) - 50 cc 2-stroke internal combustion engine (removed)
Electric Motor	Turnigy 80-100-A 180Kv Brushless Outrunner from Hobby King - Tachs: 7700 rpm @ 43.2v nominal (6500 rpm @ 36v) - Max amps drawn: 140A @ 43V - Max watts drawn: ~ 6 kilowatts - Geared with 250A front pulley and notched V-belt - Speed: 50 kph top speed (at current gearing)
Electronic Speed Controller	Castle Creations Phoenix HV-110 (link) - 110 amps @ 50 volts limit - Force air cooled
Throttle	Magura 0-5K Potentiometer motorcycle twist grip throttle
Servo Tester (Pot to ESC)	Boman Industries Polar-Matic PC-50 (ebay) -modified for use with Magura pot and HV-110
Power Monitor	Cycle Analyst (link)
Batteries	Prius Gen 2 NiMH - 6S2P packs (12 in total) - 43.2 volts nominal @ 6.5 Ah each - 43.2 volts nominal @ 13 Ah combined - 330 watt-hours (conservative) - Range: unknown but estimated 7 km based on 45 Wh/km and 330 watt-h calculation
Power Connectors	- Anderson PowerPole 75A on main connections - link - Anderson PowerPole 30A on sub connections - link
Wiring	- 8 gauge stranded copper on main power lines and motor leads - 12 gauge stranded copper on sub power lines
Lighting	- Front lighting using 10-Watt LED (driven at 12v @ 750ma; specced at 500~600 lumens @ 6500K ) - Rear lighting using high-power red LEDs
Low Voltage (48VDC to 12/5 VDC) DC:DC Converters	Twin 12VDC @ 3A DC:DC converters using the National Semiconductor LM2576HVT-12-ND buck-converter Unit 1: Front and rear lighting, motor cooling fan Unit 2: ESC controller cooling 12 volt to 5VDC converter using MC34063 Based Switching Regulator for front lighting (currently bypassed) Quark Pro BEC 3A 5V UBEC for servo tester / RC components
Things I burned out/destroyed	E-Sky EK2-0907 Servo Tester Doc Wattson power monitor ELF 100 ESC speed controller Castle Creations Phoenix HV-110 HXT 80-100-B 130Kv Brushless Outrunner motor Right index finger on burnt out ESC Power diodes for battery tap Various burns and scrapes My pride :-)

Please leave comments and questions on this post!

Just a quick update on my Piaggio Boxer EV. I had originally thought I had burnt out a motor lead when I put it away for the winter. Taking it apart a few weeks ago, it turns out that it looks like I've shorted out the motor itself. Most likely some FOD (foreign object debris) got kicked into the motor housing, shorting out one of the stators.

I bought a replacement motor from HobbyKing but when it arrived, it turned out to be longer and larger than the original, necessitating some redesign of the motor mount. More photos to follow.

But all has been installed and my test run last night was a success. So it looks like it's back in action just in time for the summer.