Electrical System: Alternator / Generator or Windmill

[sonicapollo]

I'm curious as to why I keep seeing LM recommend a total loss system or a windmill for power generation.  Great Plains seems to be the go to place for an engine, and they have setups with alternators.  Wouldn't be easiest to just buy a turnkey install like that and go with it?  Are there are particular reasons why not?  It is my understanding that the average VW needs a battery.  Great Plains also has accessory kits that allows pure no electrics via mag operation.  What am I missing here?

Would anyone consider a battery with electric start on something like a cabin eagle?

[Tom H]

DE Stubby has a GP 2180 with a bunch of accessories, including an alternator and starter.  It is a DE that has been somewhat enclosed to be a cabin.

The alternator is really a dynamo - it has stationary windings with permanent magnets that rotate around it.  Puts out AC voltage, which is then converted to DC and controlled to charge the battery, etc.  There is no field current, as in a conventional alternator.  I think this is what you mean when you say "total loss"?

The starter is real nice to have.  All this stuff adds a lot of weight to a bare-bones engine, though.

You can go with mags, no electric required.  Or with stand-alone battery which powers a standard points/coil/distributor, and you have to remember to keep the battery charged.  Or with full electric.  There are several types of electronic ignition systems that require power.  Lots of choices related to power/no power.

[Bob S.]

"Or with stand-alone battery which powers a standard points/coil/distributor, and you have to remember to keep the battery charged."

THIS is what LM means for Total Loss..... Once you use the power from the battery, it is GONE....LOST...until you charge again. Used a lot on the Legal Eagles to save weight... Others use a Magneto for ignition and don't need any batteries...as done on a LOT of LS Day Flight Only AC...

I believe if you have an electrical system (engine powered generator/alternator) in Certificated AC, you also have to have a transponder(?) along with all the nav lights....

[okdonn]

sonicapollo, my take on this is that this is experimental aviation, and you can do what you want. that having been said, i think that Leonard's goals are light, simple, and cheap. A total loss system running the stock VW ignition achieves that. A magneto with no electrical system is simpler, but more expensive. I'm personally planing on using a magneto and no electrical system.

[sonicapollo]

If your a/c is certified without an electrical system your are exempt for the transponder veil requirement.  The veil is 30nm around most class B airports. I live right under the CLE veil, so I thinks mags are in order for me.  I guess Great Plains with handstart/mags and some kind of a dual ignition system is the way to go for me.

[Dan_]

If your a/c is certified without an electrical system your are exempt for the transponder veil requirement. 

I'm pretty sure the rule reads "engine driven electrical system".  That leaves room for wind powered gen sets and solar panels...

[sonicapollo]

That's correct.  I guess I didn't really consider the stock ignition setup.  Wouldn't a mag system with a backup ignition be more reliable, though?

[Dan_]

Wouldn't a mag system with a backup ignition be more reliable, though?

... I reckon that depends on the execution of each and every setup.  Mags are points and distributor based just like the stock setup, only difference is they have the extra complication of generating their own juice.  

Simpler is usually better and lighter in airplanes...    

Leonard's way of grinding off the unused distributor cam lobes saves wear on the points and battery juice, by keeping the coil from making unused sparks...

Allowing for keeping the wires on it and well clamped against timing changes makes the stock setup hard to beat, but whatever setup you have must be well looked after.

[sonicapollo]

So, let's say I buy a Great Plains engine kit. I would then need a battery, exhaust, prop, carb, windmill, and a complete stock ignition setup. Does anyone sell the ignition setup as a kit, the number of parts seems to be mind boggling. I would imagine this would have to be relatively cheap to the mag kit Great Plains offers for 2,500, more if you want dual ignition.

[cluttonfred]

While it gives old-time A&Ps the heebie jeebies, a stock Bosch 009 distributor and coil powered by a motorcycle battery in a total loss setup (recharging on the ground only) is about as simple as it gets.  An optional wind-driven generator can keep that battery charged if you don't mind the drag and noise associated with the little turbine.  When I asked Steve Bennett of Great Plains for his recommendation on a minimalist VW installation for the Clutton FRED, that's what he recommended (see http://cluttonfred.info/post/13323368773/steve-bennett-on-fred-vw-power and http://www.ntin.net/jhardy/GenniPod.html).

One thing to keep in mind if going with any total loss or limited charging capacity system is that most of the lower maintenance, more powerful spark distributorless electronic ignitions draw much more current than a stock distributor and coil.  The GM HEI-based Davis Unified Ignition (DUI) popular in off-road and racing applications (see http://performancedistributors.com/product/vw-type-1-dui-distributor) is an interesting option, with an integral coil for easy installation and low current draw, though it's not exactly aerodynamic next to anything but a Vertex magneto.

Total loss or limited charging capacity also means you need to place little or no other electrical load on the system, since every additional amp of current draw is going to require upping the capacity of your battery.  For long battery life, you'll need to keep the total power used in amp-hours to less than half of the total battery capacity (exact fraction depends on the battery type and specs).