Shameless update from Dale Kramer

Holding a steady voltage with a Rotax installed generator is more complex, besides, I want the generator on board when I remove the wings and Rotax so that I can drive the remaining 'motorcycle' around on the road.

Dale

LOL I like that Dale

On Thursday, March 17, 2016 at 9:53:08 AM UTC-7, DaleKramer wrote:
Holding a steady voltage with a Rotax installed generator is more complex, besides, I want the generator on board when I remove the wings and Rotax so that I can drive the remaining 'motorcycle' around on the road.

Dale

Dale, the JM1 + gas motor and some batteries sounds like a good hybrid option for a FES setup. What's the weight and output on the charging unit?

Is that Flywheel Energy Storage or Flat Earth Society?

I haven't found the gas motor I want yet for the 15kw output but I have lots of choices in the 8-10kw. Since this is needed much farther down the road, I have not put much detail design into it. I think I can build this for 25-30lbs. The JM1 only weighs 6 lbs. 10kw may be fine for me since who cares much if it takes 22 minutes to charge up during cruise versus 15 minutes.

Battery weight, you pick.

We have JM1's wound at 115 kv (I think that is RMS) but you can have change that on ordering.

On Thursday, March 17, 2016 at 10:38:42 AM UTC-7, DaleKramer wrote:
Is that Flywheel Energy Storage or Flat Earth Society?

I haven't found the gas motor I want yet for the 15kw output but I have lots of choices in the 8-10kw. Since this is needed much farther down the road, I have not put much detail design into it. I think I can build this for 25-30lbs. The JM1 only weighs 6 lbs. 10kw may be fine for me since who cares much if it takes 22 minutes to charge up during cruise versus 15 minutes.

Dale, that would be the electric glider that goes into regeneration mode when you're in thermals. Take that booming 10 knotter and dial in the regen until you can't climb. Hang in there until you've extracted the energy you want so you can skip all those wimpy thermals in between the good ones. We used to call that L/D ;-) Somewhere i came across a very technical paper on this, but haven't checked the numbers. The catch is always in underestimating the losses and overestimating the efficiency.

Hybrid glider might end up working, but what a bummer to have a gasoline motor running constantly at low output to charge batteries.

Regeneration in thermals used to be high on my list of things to try but now I just do not see being able to get much efficiency out of the process. Traction props just aren't very efficient at being a windmill blade.

Paul,

None of the rotors are directly in the propwash cone of the others, so I do not see any direct interaction between them causing a blanketing effect that reduces AOA of other other rotors.

Thanks for the comments, all welcome.

Dale

You might be assuming zero wind. Stationary hovering with no wind fits what you've said. However, when you add in wind, the downwash from the upper rotors will not be perfectly vertical and will be influenced by the wind direction and speed. It's easy to envision the downwash moving downward at an angle that would cause it to intersect with one of the lower rotors. Adding or subtracting a few knots or a few degrees could correct or exacerbate the effect. Exactly what wind speed would cause a loss of lower rotor effectiveness would be an interesting vector to work out. Perhaps that would be a design limitation that could be demonstrated and placarded.

I envision it like doing a 360 hovering turn with a good wind in a conventional helicopter. As some point, you hit a spot where the tail rotor loses effectiveness as the wind affects its angle of attack. Mentally flip it 90 degrees and imagine the wind being the downwash from an upper rotor and you'll get what I'm thinking about.

Good luck!

Paul A.