I've been looking at alternators - other than the one I'm "married" to ....... Anyways this got me to thinking that with all the tech that has changed such as led lighting, more efficient radios and such, why do we still need a 15lb alternator that puts out enough power to run a scratch-start TIG? Shouldn't someone be on the ball already, getting some STC's for a super light 30 or 40 amp alternator? I see potential to knock out some serious firewall-forward cg here, or am I missing something? I did search around some before posting - so not sure if this has been discussed.

Total your "original equipment", 337s etc and find a maximum amp potential for your type of flying. Post that number so we can get an idea of what is available as a solution.

Thanks!

B&C pretty much has this covered. 8amp 3lbs up to 30amp 4.5lbs and even bigger for Lycs.

I would be totally happy with a 25a alternator - but let's just say 30a would be great. I would ideally have a 30a spline drive alt that has a low enough profile to fit between the acc. case and the firewall Some time ago I did talk to B&C (or was it plane power - I forgot) about a lightweight option for my Franklin, but at the time there was no hope. Of course I'm not completely married to the Franklin, I could divorce it and go with a 210........or a 235. My preference is to keep what I have and improve it, but while I am down to a bare fuselage there is lots of time to plan!

I'm from the "bigger is better" school when it comes to electrical stuff--bigger battery if possible and a big alternator. The poundage saved by having a 25 amp alternator vs. a 60 amp alternator isn't enough to warrant the difference. You not only want to cover the electrical accessories, but you want to charge your battery. The more excess amperage you have available, the quicker the battery will charge after starting. Even with modern electrical items, the total can get pretty high, unless you really skimp on them.

Cary

Plane power makes an internally regulated 30amp that mounts on the vacuum pad. B&c makes a 20 amp non internally regulated and an 8 amp I believe too. That brings the cg back some.

pilot wrote:I would be totally happy with a 25a alternator - but let's just say 30a would be great. I would ideally have a 30a spline drive alt that has a low enough profile to fit between the acc. case and the firewall Some time ago I did talk to B&C (or was it plane power - I forgot) about a lightweight option for my Franklin, but at the time there was no hope. Of course I'm not completely married to the Franklin, I could divorce it and go with a 210........or a 235. My preference is to keep what I have and improve it, but while I am down to a bare fuselage there is lots of time to plan!

As others have noted, there are lots of options for lightweight and relatively low output alternators. But, if you're looking for something that'll work on a Franklin, see the thread on here about Franklin 220 engines......and bear in mind that a manufacturer has to have a reasonable expectation of recovering the money they invest in developing a product (in this case an alternator) and getting it STCd. The market for Franklins isn't very big and is getting smaller, not larger. So, good luck with that.

But, in any case, with certified aircraft, there is a formula, based upon the current draw of your airplane. If you can reduce the current demand on the alternator by installing all LED lights, modern low current draw avionics, etc, then you should be able to install a lower output and lighter alternator....IF it's been approved on your engine/airframe combination.

MTV

Look at he TCDS for some of our older airplanes. I think the original standard for the C170 was a 15A generator. I have a 35A generator on my 1953 C180 and it's more than plenty for day VFR. Re night ops, nav lights & strobes don't draw much and LED landing / taxi lights don't either.

Has anyone had any luck getting one of the small B&C alternators field approved. I have the old delco generator that weights a "ton", but I don't need the 50 amps that comes from a sky-tec. This would be installed on a Cessna 150 with 0-200.

Another issue to consider: older airplanes with generators will have very little juice available at idle, even high idle, if any at all. I can recall very distinctly many night approaches and landings in the old Skylane, which I think had a 35 amp generator, which resulted in the lights dimming just before landing and the radios blinking off line shortly thereafter, unless I shed some power-eaters right after touchdown. I got in the habit of shutting off the landing light immediately and the #2 navcom, DME, transponder, and strobes next, so that I'd have enough juice to be able to communicate on #1 and see the runway with the taxi light, especially if I had a long taxi to parking.

Conversely, with my current airplane, old but with the 60 amp alternator conversion, I can leave everything on (including the pitot heat if I wanted to) and it's still charging at normal taxi speeds, i.e., 1200 rpm or so. When my IA suggested the conversion at the time the engine was being built, I jumped at it--well worth it.

There's a big weight difference between any generator and an alternator, but the difference between a high output alternator and a low output alternator is pretty small, maybe a couple or three pounds. To my way of thinking, FWIW, if the nut behind the yoke/stick lost 5 pounds and kept the high output alternator, that'd be a better decision.

Cary

I totally understand the need for a bit of juice when you are running a decent set of avionics but my setup puts a little less stress on my electrical system. Plus I have this crazy goal of getting the empty weight of my plane as close to 900# as I can. ....it's way easier for me to turn off that landing light than put down that FBO doughnut!

delete

150STOL-ish wrote:I totally understand the need for a bit of juice when you are running a decent set of avionics but my setup puts a little less stress on my electrical system. Plus I have this crazy goal of getting the empty weight of my plane as close to 900# as I can. ....it's way easier for me to turn off that landing light than put down that FBO doughnut!

I definitely understand! Years ago when No. 1 Son and I were doing the Ride the Rockies bicycle tour, we were musing over the fancy $5,000 bikes that the vendors were displaying. The comparison of weight between my 28# bike and those 6# bikes was tempting me, but my kid brought me back to reality when he said I could save all that money if I'd just reduce the bike rider's weight by 22#.

If I'd get my weight down to just a reasonable amount again, that'd be worth 3 or 4 gallons of LL. While I'm not partial to stale FBO donuts, I sure do like to eat!

Cary

How much alternator is too much? I'm planning to use a belt driven automotive alternator because I like the design and they are easy to get if they fail. The model I want weights 10lbs and is 100amps. That's way more power than I'll ever need but is that a problem? I weighed the gear driven alternator that came with my engine and its 11lbs.

I have an automotive alternator. I think in most cases they spin backwards to airplane engines, so the cooling fans are useless. Mine hasn't overheated that I know of but appears to have failing brushes. I'm replacing it with a Plane Power alt I got from blackrock.

I plan to drive mine the same way an O470 does so it will spin the correct way. If I wasn't planing to use the automotive alternator I'd but the 30amp B&C unit that runs off the vacuum pad.

Cool thread Whee...

This may be a silly line of thought, but might it be possible to feed a tiny bit of supplemental photovoltaic-sourced electrical current into the system via a regulator and shunt? I mean say 2-3 amps of additional juice might be cool. Plus the set up could float charge/maintain a battery as well. Apparently there are some really high efficiency PV cells available as of 2015.

Here are a couple of articles. One discusses a photovoltaic that is not silicon based, but uses graphene. I wonder if a carbon fibre cowl or turtle deck with an embedded graphene photovoltaic would be possible? Maybe Courierguy can chime in since this is his element.



http://cleantechnica.com/2014/02/02/which-solar-panels-most-efficient/
Which Solar Panels Are Most Efficient?

http://www.gizmag.com/graphene-solar-cell-record-efficiency/30466/
Graphene-based solar cell hits record 15.6 percent efficiency