I've been pondering various UL engine possibilities and one thing keeps jumping out. The generators in current use are awful heavy. A Briggs single cylinder 5A stator I have is 11Oz, the entire flywheel is a foot breaker, but likely has several ounces of magnets. anyone wanting to go direct drive and ditch the flywheel is going to be wondering how to replace the generator. While there is no shortage of mechanical skill here, the electrical and electronic side is not so well represented. So, I think I can do better, a lot better. Marketable better. I am thinking of a small, light belt driven generator, looking suspiciously like a brushless outrunner RC motor with a ribbed outrunner-pulley. It would have a separate electronics pack to regulate the output to either lead or lithium friendly voltages. Belt driven means the actual generator can be spun fast which makes it lighter. To simplify fitting to engines, the drive pulley will be a simple flat pulley. A cylinder. The generator will need to be attached to the engine by some sort of bracket that can be adjusted for tension. It would prefer to be in cool-ish air. the hotter it gets, the less current it can generate. I am thinking of building in a temp sensor to keep it alive. Some heat soak when shut down will be OK, though below 100C/212F What I particularly want to know from you lot is what kind of sizes you'd be interested in and what batteries you'd want to run. A 12V 5A generator should be << 1/4lb and << $100 and do minimal charging and ignition for bare bones aircraft. Obviously, that won't run an XP1000000 full glass panel with 360 degree synthetic vision, so bigger ones too. Likely 10A, 20A, 30A maybe 40A, though that may be into motorcycle alternator territory where I may not be able to come up with something much better. Persoanlly, I favour using lithium tool batteries. it will save me having to have a dedicated and pricey battery for my plane. But does mean that I'll have an 18V electrical system. Many devices are 12-24V and are fine with that, others can run from step down adaptors. But the separate electronics pack for the generator means that voltages and battery types can be changed fairly painlessly, possibly by setting some DIP switches. Any other comments and suggestions will be entertained.