Gday John, 28' rotors hoping for 220+ if going electric. 5+ prerotations would be good. It is no problem to give the blades a flick before getting in. Something like the way you have controlled yours would be nice, my original thoughts were three buttons off/reset-slow ramp to 100rpm (for taxiing over rough ground)-full power, all within reach of the throttle so that once the roll has started the prerotator could be stopped at any time during the roll. For fun flying on board charging probably not necessary, but flying for work would require on board charging.What RRPM are you looking for Wolfy? What size blades do you have? How many prerotations do you need on a charge? is it important to be able to spin the blades up from a dead stop or can you give them a flip in the right direction? How do you want to control the ramp up, directly with a knob or slider or via buttons?
Probably asking a lot.
I just bought a new start battery a Lithiumax 300CCA 13 volt that only weighs 800 grams, could possibly be used in series but charged in parallel.
The home page of Lithiumax batteries, the world's best lithium engine starter batteries.
Or I will go again engine driven but with a torque limiting slip clutch, as to be able to go WOT with prespinner still engaged during the roll.