3.5 lb alternator
 

I picked up a Permanent Magnet Alternator and regulator from a John Deere garden tractor:
http://www.dbelectrical.com/p-11869-...n-tractor.aspx
It weighs 3+ pounds, about half the weight of a Denso mini alternator.

Mark Langford's website
http://www.n56ml.com/corvair/dynamo.html
Has a page with some detail, he has a Corvair powered Kr2 based speedster.

Any constructive comments are welcome.

It's advertised in other spots as a 20 Amp alternator... if that rating is OK...

3.5 lb alternator
 

I dont have a RV but have run this Alt on a 0320 for 15 years and over 1600 hours with no issues.
Early on I did switch to a regulator from B&C that they sell for their permanent mag alt ,because it is adjustable .
I have it mounted useing a steel mount like mark landoll [?] use to sell but I reinforced the front lug as this is the only one used
Doug

Thanks on 2 counts;
1) It is suitable.
2) You gave me a mounting idea that is lighter than my original plan.
I went out to the airport with the alternator tonight after I got off work.
My Narrow Deck O-360 alternator mount is 'just wrong' to fit this PM alternator, the belt won't track right.
I'll have to modify or make a new mount.
I'm trying to make the lightest practical RV-8.

Very interested to see how you get on with this.
I'm expecting to use a B and C SD8 on my project which may or may not be adequate for a minimal electric aeroplane, this sounds like an only fractionally heavier installation with an output which would easily cover most RVs requirements.
Look forward to any updates you may have.

My son Peter has a B&C SD-8 PM alternator on his Pitts S1. He started competing with it this year, and of course has minimum radio & transponder.
Sofar the SD-8 has been satisfactory for him. His Pitts was at the Apple Cup in Ephrata WA for 4 or 5 days and two days of competition. It never saw a battery charger, yet always had a charge and started fine.
I've had the Deere 20A unit around for some time, so I want to try it on my RV-8 conversion to Lycoming power.

The one point I didn't fully consider until recently with the SD8 is that it requires a vac drive to use it. Given that the shift away from vacuum instruments to glass has reduced the need for the drive in that sense, those of us who are trying to build light probably need to consider the weight of the SD8, reg, AND vac drive, as if the drive is not used for vac or power it can be removed and replaced with a cover, which also has a weight but you get the picture!
So an apples to apples (weight only) comparison between your JD and an SD8 may well be very close if you look at the whole package each requires.
The other smaller aspect to consider is CofG. The (about) 4lb SD8 package is at the rear of the engine, the (about) 4lb JD is a foot or so forward at the front, not a great difference but still a difference.

The only issue I have ever had with the SD8 in the Bucker (very minimal electronicas - radio, some E/I gauges, and such), is if you are flying a bunch of hops, your battery can start to get drained down a bit. Too many short flights. Other than that, I think 8Amps is more than adequate. 20A for many would be just fine.
Very curious how this works out.....

True, weight & balance always;
If converting to an SD-8, the standard alternator bracket & tension arm + belt would be removed, so it's a fair offset against the vacuum pad drive housing.
In my case, the Mazda engine weight was countered with a PC680, contactor, NOVA strobe power supply and the mounting box 'in the back'. The Mazda wasn't so heavy, the CG didn't turn out forward at all.
With the lighter Lycoming engine, I plan to remove a good 6 ft of 2 ga welding wire (.488 lbs/ft) and mount a Shorai LiFePO4 battery (10.44lbs savings) + the contactor on the firewall. for13.3 lbs savings. POSSIBLY 16.8 lbs if the PM alternator works out. (Vs a DENSO mini)
The SD-8 alternator can interfere with some oil filter sets, requiring a spacer, although I think the original straight back Lycoming filter adapter is OK? I'm using the oil screen and viscosity valve to save weight.

I have the B&C 30 amp PM alternator on my little C85-powered Davis DA2A. It's coupled to the B&C regulator made specifically for this model. A great combination - it's been completely bullet-proof. B&C also makes a 20-amp rated PM alternator for small Continentals - that alternator is rumored to start out life as a John Deere unit...