Comment by Jan Detlefsen on August 30, 2011 at 12:08am

awesome project, electric helicopters are just the next logic step with battery technology getting smaller and lighter. I'm sure there are a lot of projects behind closed doors in that direction. nice to see a hobbyist at the forefront of it.

 

just one advise: wear a suit when test flying just like Igor Sikorsky did.

 

curious, why don't you build a design with less but stronger motors? Do small motor have a better weight/lift ratio? would a frame based on some big bastards like this work and what are the ups and downs of bigger motors in a project like this?

 

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=...

Comment by Brian Ho on August 30, 2011 at 2:25am

Unless with well simulation and safety backup (like at least an helmet) . I won't try like this cause life don't have 2nd chance.

Comment by Jan Detlefsen on August 30, 2011 at 4:08am

i think you are wrong about the ground effect. it didn't happen here. what i think happened from the video is simple. the uplift force was high enough to lift you off the ground, then the MOSFET failure happened, the force vector of the vehicle was taken out of the vertical axis, while there was still uplift force the friction of the vehicle towards the ground was very low while the force vector was moving to the horizontal axis. so it's just logical that you vehicle was dragged over the ground backwards. there was no ground effect here.

 

ground effect only applies to flying vehicles close to the ground. a bit like when you blow under a sheet of paper and it starts moving.

Comment by Kevin Breen on August 30, 2011 at 5:15am

It's a very interesting project and I wish you success in the next attempt.  It may be too complex if you mean to put it into commercial production. Tethering the aircraft for initial testing might be a good idea as suggested elsewhere. Since you designed and built the craft I agree you're probably the most qualifed to test flight it but the FAA would probably disagree. Since it's a rotorcraft you really need a rotorcraft rating even for an experimental AC: PPSEL is for fixed wing (you didn't mention any additional ratings).

Comment by Jan Detlefsen on August 30, 2011 at 5:32am

what i don't understand, when you use an Ardupilot type of stabilization, why didn't the front rotors slow down then the aircraft when it started to roll backwards?

Comment by Brad Hughey on August 30, 2011 at 6:23am

@Jan Detlefsen: A preferred embodiment would be a 12-rotor system.  The Revelation airframe is 7-years old, and the selection of >> 1 KW motors back then was very limited.  The ground certainly stopped having an effect after pitch up of more than 30 degrees or so.  Here's a link to the patent with associated background and embodiment descriptions. 

http://tinyurl.com/eCopter-Patent

All the APM can do is change the MOSFET gate PWM duty cycle (through the ESC translator).  If the MOSFET drain is shorted-circuited to the source, the gate signal is ignored (and often becomes shorted too, toasting the driver chip).

@Kevin Breen: I am working diligently to insure that the prototype and the first production versions of the eCopter are FAR Part 103 (ultralight category) compliant.  Therefore, neither the operator nor the airframe would require any certifications, saving the FAA-type from having to form a material opinion on my qualifications.  :-P  That said, this doesn't have the classic cyclic-collective-tail rotor pitch controls of a standard helicopter, nor does it behave like a gyrocopter; eventually LSA or larger versions will likely need their own type category. 

Comment by Kevin Breen on August 30, 2011 at 1:05pm

Brad,

 

My comment wasn't meant to disparage your piloting skills. The airframe looks light enough to meet Part 103 and those licensing requirements. Without the classic rotorcraft controls it could be much easier to fly, but hasn't been certified in any category yet. What I meant to convey was "cover your butt": it's got rotors, so to the FAA it's currently a rotorcraft. Had the damage been worse any insurance companies involved (medical, liability, your own or your neighbor's) would quickly drag you into court. Good luck with the project and be safe.

Comment by Kevin Breen on August 30, 2011 at 1:32pm

I would also suggest talking with your local EAA chapter (if you haven't already) to learn how to conform to  FAA Part 103 rules and regs for your craft, insurance coverage, etc. They have a lot of practical experience and knowledge in that area.

Comment by Brad Hughey on August 30, 2011 at 2:13pm

The crash was a direct result of my cavalier disregard for the effects of power loop inductance.  I have already capitulated to using an APM system to do the actual piloting.  My creativity in that area is relegated to PID tuning now.  Experience trumps theory, so feedback or extrapolated "rules of thumb" for that are welcome.

Comment by jahur ahmed on August 30, 2011 at 10:00pm

good try but safety is first

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