Bodging: 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

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!