On Board Alternator



First flown Aug. 18, 2004. Helis have been outfitted with on board alternators driven off the main gear.
This system gives output voltage at 5.6 volts at up to 3 amps continuous and 5 amps for brief periods.
This can charge up the battery while still delivering 2 amps to a full set of digital servos on a 90 size heli.
Added system weight for the alternator and regulator is about 3oz.

The On-Board-Alternator installation kit includes regulator, alternator, pinion and mounting bracket.
Ready to install - US$175 plus shipping. Battery extra.
The 4 cell KR1400AE is recommended for it's low internal resistance.
Individual prices,   Regulator = $60   Alternator = $55   Pinion = $35   Mounting brackets from $25
For more information, email Wolfgang@AirWolfRC.com


Raptor 30/50 V2 installation instructions:
Identify where the rear alternator bracket mounting holes are in the Raptor frame. Open those two holes in the Raptor frame to 3mm. The front holes are already 3mm. Undo the rear skid mounting screws, spread the frame a bit and remove the tank. Slide the alternator / pinion / bracket assembly into place. Hold it in place with the mounting screws but do not tighten. Check that the pinion fully covers the main gear teeth. If not, re-position the pinion on the alternator shaft. Replace the tank and rear skid screws.

Set the gear mesh by rolling a single thickness of copy paper between the gears and tighten the mounting bracket. Check that the paper gives little additional resistance between the gears compared to without the paper. A double thickness of paper should start to get tight. An alternate method is to lock one of the gears and rock the other back and forth. You should just be getting a bit of play between the gears. If it were any tighter, the play would be gone and that would be too tight. Check the gear mesh through one complete rotation of the main gear. Secure the regulator and route the wires.

Plug the long lead into a spare channel of your RX. When ready to fly, follow normal procedures using the on/off switch as usual.
Technical notes:
The overall effeciency comes out to about 56% +/-, which includes the alternator, rectifiers and regulator. With a 2.8A usage at 5.6V, that's 15.7W delivered. After efficiency, that's 28W used which equals 0.0375HP. That's about 85% efficiency for the alternator, 95% for the rectifier and 75% for the regulator. The new regulator at 85% will bring the overall efficiency to 65% with only 0.0324HP used for a 2.8 amp current draw. A 2.0 amp nominal current draw will require only 0.023HP

A 50 can produce as much as 1.6HP and a 90 is at 3HP. On a 50, you give up 1.4% power. On a 90, you give up only 0.75% power. By using a smaller battery, the power saved by not having to carry around that extra weight makes up for the difference.

An on-board alternator system is no different than a car system. The alternator provides the operating current and some charging current with the battery primarily as a "buffer". Don't try it without a battery. You will have the same results as your car without a battery. If you're real careful, it can work but it's not worth the risk.