Ah, but there is no H in VTOL. ;-)
And has been said, gyro's can't hover so they can't do any of the other main missions one would use a helicopter for.
Unless you go the Volocopter route, a reliable (safe) man-carrying multi-copter requires cross-shafting on the engines/motors (otherwise you will be inverted before you pop the ballistic chute). That adds a whole new level of difficulty. Then there's the stability augmentation required (thankfully the RC modelers have solved that and we can scale it up). And if it's all-electric (which I personally favor) it will have very short range due to current battery technology. Not to mention that multi-copters have limited speed capability.
Then I start thinking about tilt-rotors because of the higher speeds. They still need cross-shafting between the engines and stability augmentation. As Topaz mentioned, the transition from VTOL to airplane mode and back is a huge technical challenge. You don't see RC models of functional V-22 Ospreys because two rotor VTOL is just too hard (and RC modelers don't need the speed). I think dual tilt-rotors with cross shafting is out-of-reach for homebuilt technology.
I look to the RC and UAV world to see what might be possible in a man-carrying VTOL. In my opinion, we have to get away from the dual tilt-rotor approach for a homebuilt. One approach I like is Latitude Engineering's UAV. It looks very much like a conventional twin-boom pusher except for 4 motor driven rotors in the booms. A gas-electric hybrid works great here. Four battery powered motors in a quad-rotor configuration are used for VTOL, but the batteries only have to be sized for 5 minutes duration. The aircraft uses a single gas-powered engine for airplane mode, and to recharge the batteries after take-off. Cross shafting is still required, but we get away from the tilt-rotor aspect.
Latitude Engineering's UAV is pictured below. It's still in testing and I'm concerned about VTOL transition to airplane mode (the transition airflow will be a mess with rotors and prop running). But if it works, it might be a good candidate for a man-carrying version. Does anyone have other RC based VTOL candidates that could be scaled up to real-aircraft size?
Cross shaft failure caused the crash of the Curtis quad rotor. Don't need cross shafts if enough electric motors. With say 16 motors, any two can fail and the others can compensate.
I do agree that tilt is not simple enough.
That Latitude UAV is probably the solution, but with 8 or 16 motors.
To your point, Zee Aerospace was just granted a patent for some concepts that look similar to the Latitude UAV but with 8 rotors. This would be a man-carrying VTOL with no cross-shafting between the motors. The structure on the Zee concepts looks more complex than the Latitude UAV. It will be interesting to see if there are any patent disputes between the two companies.
The Zee concepts can be seen at the link below:
Zee is For - a Different Approach to Vertical Flight
Hard to see how the "Zee" could be patented --the exact configuration with multi lifting fans in strake extensions was featured on the front cover of Popular Mechanics some years ago ( I could locate the date if it came to it ) for a Japanese design clearly inspired by a mating of the Vari eze (or Starship) with one of the 1960s multi lifting fan designs (the Dornier Do31 perhaps) --anyway the basic concept is not new .
Philip Tperstra published his book promoting homebuilt and personal VTOL ( I have a copy) quite a few years ago and he 'selected' the Doak V 16 which had tip ducted fans as his choice but later favoured the open tilt rotor --the ducted tip fans have no downwash penalty like a tilt rotor and don't require tilting the whole wing like a tilt prop (eg XC 142/ Canadair Dynavert etc) --EAA carried a series on homebuilt VTOL as 'the way to go' in the mid sixties - about the time of most activity and the Tri service VTOL competition . One design of tailsitting contra rotating ducted props was called 'the bomb' and went from stand up in hover to belly down in flight --the Mark Moore "NASA" Puffin is a near relative in that respect . Quite a few VTOL flying cars/roadables are documented -Roadable times has a few
Without a fair margin of thrust over weight any inattention in arresting a sink rate can result in a very vertical landing especially if the rotor is stalled from overpitching --I see the "VTOL tailsitter" thread in the 'similar threads' box below -might be worth a look.
I don't get the drive-shaft. Simply put multiple motors on each prop shaft (each with a separate battery system?) and you're there. OTS motors run in the 50-80 HP category anyway, so with 5 a side you can easily stand a loss of 2 engines per side, or 4 total.
There was a concept for a freight-UAV that did VTOL, by means of a single contra-rotating prop, that hinged on the wing roots and moved towards the nose of the plane during flight. Not sure if any easier as a conventional proprotor...
Seems like the CGS Hawk should transition sets of motors separately instead of all at the same time.
Other tilt rotors, off the top of my head (sorry if these have already been mentioned):
Moller Skycar (all talk, no action... so far)
Jobi electric vtol glider (concept only, no flying prototype yet)
Rutan Scorpion Freewing (not quite VTOL and not man-carrying)
And the flight control problem still goes unsolved. You need positive flight control at all airspeeds from zero to Vne, with more control power than normal required during transition because of the strange airflows that happen during that sequence.
"Real" VTOL with wing-borne cruising flight is very hard to do.
Not sure if this counts as home built or not but the Israeli Air Mule seems promising.
An R22 is seldom as good a performer /efficient machine as a C150/152 in most respects, sure he got a couple of numbers wrong but the thrust is right.
I also have serious doubts that an R22 would "probably ourperform a Cub" in most regards, unless you're talking J3 Cub for pure performance, or 'any Cub' for ability to turn a large fortune into a small fortune, or for the poorest safety record per year in operation, even short takeoff fully loaded would be a close cut deal :roll: