SD-8 Alternator

[szicree]

Anybody using the B&C SD-8 alternator as their only source of juice? If so, what sort of electrical equipment have you got? I'm building a Day-VFR plane and am thinking this approach might work real well.

Steve Zicree

[RV7ator]

Steve,

The SD-8 on my -7 backs up the 40 amp alternator on an all-electric aircraft. I've played with it to find out how it performs should I ever need it. The SD-8 is 8 amps max, and it puts out very little juice at idle rpms, even well up into cruise there's little left after a few loads and IR losses nurse off it. (I wonder if it's not really a generator; it's permanent magnet and I don't know if the regulator also contains a rectifier.) The net consequence is that your starting battery is going to gradually die for lack of recharging.

The installed cost of an SD-8 is hundreds of dollars more than an alternator, it is only ounces lighter, and a more complex installation since it needs individual regulation components. Other than back-up for dual electronic ignition, I wouldn't install one. Even then, my current project is going to be dual battery rather than SD-8.

Oh, yeah. The SD-8 interferes with the sender if you use Van's tach, thus making you buy a tach cable and finding a place to hang the sender instead of simply screwing it into the back of the accessory case.

In short, a lone SD-8 makes a wimpy, expensive, clumsy source of electricity.

John Siebold

[Air UPSer]

How about GAMI's Supplenator?

Not sure of the price, but it's self exciting and rated at 30 amps.

Brad

[gmcjetpilot]

Originally Posted by RV7ator

In short, a lone SD-8 makes a wimpy, expensive, clumsy source of electricity. John Siebold

Not to disagree I know of a RV-4 with this set up and I heard no complaint. I love the idea of a simple day VFR RV. I looked into this. For bare bone VFR cruise I got about 4-6 amps, for worst case everything (Comm. transmitting, flap motor running, boost pump on) 9.1 amps max*.

So a 8 amp PM alternator would work. Why not? You just can't go digital all electric panel and battery dependant Electronic ignition (EI). It has been done before with a basic VFR panel. With that said, a little fairly inexpensive 40 amp ND belt driven alternator can bolt to the front of the engine, or even a small 20 amp John Deer PM alternator. With the installed weight of a ND alternator at about 7lbs and low cost this may be more practical. You have the flywheel pulley there and nothing that needs to go in that space why not?


G

* You could drop almost 1 AMP of continuous load by replacing the battery contactor (relay) with a cool Kilovac (Tyco) relay that uses very little power to stay closed. It works on 12v and can handle 12-900V at 500amps continuous, weighs less than 1lb, is small and has magnetic latch relay. It is not like a latching relay that stays latched if power is removed, which could be bad. The current to keep the SPST relay closed is 0.13 amps. Typical "HOT" relay is almost 1 amp.

[szicree]

Awesome info from everybody. Thanks a million. Now my next question is where do I get a good alternator? I suppose 30 amps should be more than enough for me. I'm still on the fence regarding the OV protection/internal/external regulator thing and would appreciate advice on this as well.

Steve Zicree

[Bill Palmer]

Would someone please post an SD-8 install picture, or two? Specifically, I have an SD-8, and I'm planning to install it on my Lycoming angle-valve's vacuum-drive pad, but I'm wondering about the clearance with the tach drive. Will a tach drive 90-degree adapter clear the SD-8 okay, or do I need to use a tach cable to remote-mount a tach drive sensor?

Thank You,

Bill Palmer
RV-8A In-Work

[Russ McCutcheon]

I am solely using an SD-8 on my day/night VFR -4 with no problems, at engine overhaul I replaced it with a new SD-8 and B&C said it would actually put out about 10A at an engine speed of 2450. I run KX155 nav/com, German 396, Rnav FC-10 fuel computer, intercom with one Bose ANR head set, the old one that uses power from the plane not remote battery powered, and engine gauges. I can even fly an hour or so with the nav lights on and still start the next day but I don?t think it is quite keeping up with the lights. I normally keep the plane plugged in to a battery tender but have also made many cross country flights/trips for more then a week and never had an issue maintaining the battery with ought plugging it in. This won?t work for everybody but for a basic VFR plane it does very well and is simple and clean.

Mine is on an IO-360 angle valve and as far as the tack goes mine is an Electronics International and I don?t know where it gets its signal but the tack output on the Acss case is caped and I don?t remember if it would interfere with it or not, it must be getting its signal from a mag would be my guess.

[Geico266]

Over load protection is important. I had an "automotive" alternator fail and charged my system with 18+ volts. Cooked my EFIS stand by battery $30, and was suspect in weakening my BMA EFIS1 mother board ($900 a month later). A friend of mine had the same "auto" alternator, cost him $2,500 in fixing a Dynon, radios & transponders when his failed full power. We both replaced ours with an alternators from Plane Power.

Take a look at Plane Power. Over load protection, lite weight, and 2 year warranty from DATE of purchase.

http://www.plane-power.com/

BTW, Van's now recommends, & sells Plane Power alternators.

[Highflight]

Originally Posted by Air UPSer

How about GAMI's Supplenator?

Not sure of the price, but it's self exciting and rated at 30 amps.

Brad

The Supplenator is intriguing, but the illustration at the top is a 3D Cad drawing (evidently, there is no actual product available for a real photo to be taken), plus the last update of that page was in "1-17/02".

Does that product even exist yet?... or will it ever?

I think if push came to shove, I'd vote for 8 Amps of real power (SD-8) over 30 Amps of nothing.
The SD-8 has been around a long time and has proven to be not only a reliable back up power generator, but a good stand-alone power generator for lightly equipped day/VFR aircraft.
That said, it would be nice if the Supplinator were an actual product you could put your hands on.

[dav1111]

Bill, you can see the SD-8 installed on my engine in the following picture post:

http://img207.imageshack.us/my.php?i...onstandlz5.jpg

It is the orange item installed on the accessory case (replaces the vacumn pump) next to the 90 degree oil filter adaptor.