Mini Turbines should light a fire

[Ga6riel]

these amasing miniature gas turbine engines
could be used at the rotor tip to power a helicopter rotor

http://www.jetcatusa.com/p180.html

with an output of 45 lbs thrust @ 112,000 RPM I believe that is more than enough thrust to power a rotor of a lightweight single seat machine considering the older Gluharef engines were rated at 22-25 lbs each
there are also some lower rated engines

it will need someone smarter than me (that shouldnt be too difficult to organise), who knows the syntax to calculate a required thrust at the tip of a rotor to check this out, but Ive a feeling there are such people around here

two such engines at each blade tip would provide a torque free propulsion without the noise limitations of ram-jet engines

[karlbamforth]

Hi Ga6riel,

I have thought of this on a few occasions. Seems we are seeking the same thing. LOL.
These do appear to have enough thrust and as you say the Gluhareff was about half the thrust. They are quieter than a pulse jet but that is relative, they are still loud.
There are a few problems with this idea. Due to the turbines bearings they would need to be mounted inline with the blade spar and with approx 90 deg bend in the jet pipe. If it was mounted similar to the pulse jets the side load would destroy the bearings in a very short period of time. If it was mounted along the spar with the intake inboard then the thrust should help to offset the centrifugal load on the mounting brackets.

I can see that controlling throttle would be somewhat difficult. In fact they would almost certainly required computer control to ensure both engines produce the same amount of thrust.

EDIT, Just had a closer look at the website, they seem to have quite a low fuel consumption and self start. Maybe the turbo-prop is a better option 55lbs thrust with only 7oz per min consumption. It would be quite easy to mount it along the spar with a 90 deg gearbox at the end driving a ducted fan (watch for drag of the duct) or maybe a folding prop.

[Ga6riel]

the bearings seem to be quite high tech ceramic
however mounting at 90 degrees to thrust (or perhaps a compromised vector is more suitable given the forward speed) would present little problem. There would be losses but mostly from the intake side, and the jet exhaust would need to be ducted through suitable material such as inconel or stainless steel. Given the Harrier experience from Hawkers this shouldnt be a problem.

a computer interface is provided, further engine management and monitoring is quite possible, perhaps more is to be learned about rotors in these situations too.

I considered props too, but these may present drag issues, or another anomalies.

[Ga6riel]

Karl
whats the state of play with props in such a case ?
are there any known handling issues, additional stresses ?

Like you I got to thinking, since the tip speeds are quite high, and being aware that larger props approach 90% efficiency at 300 mph at least some of the inefficiency due to the smaller size would be recovered, and would exceed any form of jet/gas turbine/rocket propulsion.

My scheme went like this, high voltage electric motors drive the props, for this allows that wiring is kept lightweight (low amperage) and more choices of motors come to the fray. Plus there are the motor controllers etc and the thermal losses are less in the circuit. Then all thats required is an efficient lightweight gen set. That in itself might be what 12 to 20 kva. Now even aircraft apu's are around 100lbs and exceed that by a good margin. They are of course quite reliable and possibly multi fuel.

Add to that, a small battery of around 2kw wouldnt be excessively heavy and would be able to get you back onto the ground under power, or dare I say stealth mode. This battery would be constructed of metal hydride cells series connected.

Possible problems are, the availability of suitable motors, and the key here is the diameter that would need to be faired and what that and the weight does in autorotation mode. And like you point out whatever bearing issues there are, but these could easily be uprated even cooled by oil. Two bladed ground adjustable props (test phase) would be handier in smaller diameters and sourcing them would be an issue, but even custom built wouldnt be an insurmountable task.

Electric propulsion so organised would be facinatingly reliable and seems cost competitive with other forms of power at this preliminary stage. This would be appliable to a simple teeter rotor that could even be single bladed with the motor on the ballance side, nothing wasted here. and that would enable a shorter driven arm to bring the prop speed back down to around 300 mph or a tad more.

Control would be far easier on the pilot than conventional equipment without the need for a anti-torque rotor. However such a fitment would provide more instant turn reaction and better control. And need only be pitch adjustable both ways via the pedals reverting to flat pitch with the feet free and therefore becoming a tail vane in forward flight.

[karlbamforth]

I've not looked too far into this Ga6riel.

I was thinking along the lines you are. Any weight at the tip would help in autorotation as long as it was faired in to reduce drag. Props are available that fold back when not spinning. This would reduce most of the drag produced by a spinning prop.
Electric is good because it is easy to move around using slip rings etc and easier to control RPM.
A few early helis tried this with piston engines mounted about 3 feet out from the hub and had prop blades about 24 inch tip to tip. Lynch motors would be good for efficiency but have a large diameter, maybe 2 small ones back to back would reduce the cross section.

Due to the weight and size of electric motors I have also been considering air motors. Its more difficult to move air through the hub than electricity but may be a way forwards. Instead of using the air for thrust like a tipjet, we use it to drive an air motor turning a prop.

[Ga6riel]

the autorotation thing is a sleeper, for it wouldnt seem to be important untill final considerations of such a machine. As I recall it, Gluhareffs engines were checked out for autorotation, and there was a paper produced on it, I would have a pdf file of it around somewhere Im sure.

Well the upshot was the thing almost fell out of the sky like a wet brick. The engines involved were the 22lb thrust on an alluminium rotor. While the profile is large, the weight is probably less, from the top of my head around 8lbs. In the end for a rotary wing to exhibit such poor performance, it became the crunch that broke any further investment in the idea. Therefore I would take the profile drag as a critical factor.

It so happens I once saw a rather novel electric motor that looked rather like an alternator. It had a solid core with windings on the ouside that were able to be moved to alter the phase. The chap that created this motor was rather a bright young man from Iraq. His motor was up for examination for submarine propulsion, but by the time the long winded process of red tape got back to him, hed been sent back to Iraq.

His particular take on it isnt important, but it created the idea in me that you could connect the shafts of several of these motors in a modular fashion to provide the necessary power, for they were rather squat in shape. This seems conducive to your ideas as well.

[hstearnsjr]

The required thrust is easy -- you get 1 horsepower per pound of thrust
with a tip speed of 550 feet/second, so a total of 90 hp is way more than
enough.

If you mount the engines in line with the spar, you'd pick the
direction of the gyroscopic couple to be anti-coning (pushing the blades down). That could increase efficiency slightly. If there's too much
gyroscopic moment, you'd have to add a counter-rotating flywheel.

Hoyt Stearns
Scottsdale, Arizona

http://members.cox.net/hoyt-stearns

[Cobra Doc]

I know of a particular sailplane with a pair of these engines. It's a pretty decent self-launching motorglider now that the Hirth is gone.

[Ga6riel]

The required thrust is easy -- you get 1 horsepower per pound of thrust
with a tip speed of 550 feet/second, so a total of 90 hp is way more than
enough.

If you mount the engines in line with the spar, you'd pick the
direction of the gyroscopic couple to be anti-coning (pushing the blades down). That could increase efficiency slightly. If there's too much
gyroscopic moment, you'd have to add a counter-rotating flywheel.

Hoyt Stearns
Scottsdale, Arizona

http://members.cox.net/hoyt-stearns

ahh
thanks Hoyt !
so the question now is
how much thrust at 550 ft/sec
and what margin is required for other performance factors
blade between 10 and 11.5 ft

I began to calculate the drag on the blade alone
being a radius nearly drove me crazy
then I remembered the thing has to move forward too
....oh dear

[hstearnsjr]

I think the thrust would be enough. But remember that the blade ends have
thousands of G's, so the engine would weigh something like 100,000 pounds,
and the gyroscopic forces on the turbine blades would warp them + putting lots of stress on the bearings, so there's a lot of work to do :-( . Bottom line--
I don't think this is practical at all. Maybe a similar approach with electric cross flow fans in the blade tips as in my patent 4,702,437 would be a better tip jet solution.

For more interesting tip-jet history, see my Nagler website:

http://HoytStearnsJr.webhop.net

and my patent:

http://www.turbotip.webhop.net/TurboTip1.html

[Vance]

Hello Hoyt,

When I do the math I come out with less than 1,000 Gs at the tip. What am I doing wrong?

Thank you, Vance

[M. Pearce]

Vance,
Just put them on a seperate shorter propulsion type hub bar and the G's won't be so bad. They don't have to be integrated into/onto the rotor blades themselves. You just need to spin em. Mr. Hoyt I saw your previous post about one HP per pound of thrust. It's two HP per pound of thrust isn't it?

[Ga6riel]

Arrgh
Im begginning to see why Karl favours compressed air drive, for electric drives of sufficient power are looking rather wide. Air drives are also quite high rpm, and right angle drives are no issue, just look at air tools!

Other implementations of jet-air drives have been tried, I recall a turbine hooked to a tubocharger device, which allows that there be a hot and a cold side. The hot side was pushed up through the hollow mast and out through the blades to directional tip exits. This also provided a degree of de-icing because even the cold side was rather hot. The hot jet eflux was used for directional control via a conduit and directional vent at the rear of the machine. Success depends on the efficiency of the overall system, and was researched by both Voljet and Fiat, while the latter case failed due to lack of power, it would have to have been one of the ugliest looking machines you could ever see.

Mark is of course correct, a shorter hub bar would suffice in reducing G, and this was the method chosen for the propcopter (not sure it actually flew). For turbines this could actually be a problem, given that ram air is then less. Already mentioned,for props the situation would look a little different and is a workable solution. It does however add significantly to drag.

More relevant than how many HP per pound thrust, which is a question of efficiency, and that is not going to be a good picture with either turbine or prop power, given the diameters of both are rather less. There is the question of total blade drag. Where at VMax thrust = drag, just what is the blades dynamic drag? Knowing that enables me to work backwards through the drive, estimates make it seem quite feasable...

[Rotor Rooter]

Electric motors;

Plettenberg ~ Predator: (http://www.plettenberg-motoren.com/UK/Motoren/aussen/Predator/Motor.htm) Power of 11KW [14.75 hp] and a weight of 3 lbs.
A little more information (http://www.icare-rc.com/document/predator.htm)


Thrust location;

Root Turbofan Rotor (http://www.unicopter.com/0002.html)

[Ga6riel]

pretty impressive sort of motor but, 11 mins power time ?
and i take note of the position of the outlets and on that:
for props, i would like to make the speed about 280 mph, this puts them in an efficient zone at hover to slow speed, from there as it gets faster so do efficiencies get less.

I would have thought jet type compressors would be best at the tips, being that...and Ive began to outline some speeds to roll out the numbers a bit. lets say a tip speed at 550 ft sec, and vmax of around 90mph. That gives a speed at the tip of 632 ft sec on the advancing side, and 428 ft sec on the retreating side. props would clearly need to be way inboard of the tips, so a hub bar would be necessary.

Im not fond of the idea of holing the blades to provide outlets etc, not so much near the tips but def not that first half of the spar. Im not sure what reserve strength is in extrusions, but it doesnt seem wise. A blister would be ok, particularly for a motor that is short with the axis along the spar. Theres the possibility of fairing the whole shape quite a bit. But a hub bar...hmmm, its a lot of additional drag, not at all a tidy solution, puts the drive somewhat out of phase of the rotor.

and then theres this...
http://www.unicopter.com/ElectroRotor.html

[Ga6riel]

ugh ok...
the things you learn in a day eh, is it time to mention Im an industrial engineer lol
well it looks like my earlier estimations were somewhat wide of the mark
turns out, the most important criteria is to hover, everything else will be what the physics allow beyond that, so forget Vmax which is more like the speed you can manage while flying in a straight line.

so now we have a blade of 11ft, and a chord of 7 inches (no luck finding curves for reynolds numbers of this magnitude so its estimation again) the section is 0012, and I would expect the ClMax to be around 0.4 and the Cdo 0.005: slug was .00238,

Now I have no idea how ppl work the lift out, so I divided the blade into 1ft sections and calculated the speeds of each, and then assigned lift and drag values from that. I did not vary the Cl or Cd within each section. This presented a lift of 273 lbs and drag of 3.39 lbs per blade, rotating at a speed of 420 rpm. AoA was very low, so there is capacity for more lift.

Im having some trouble beleiving that this is correct because the drag is so low, but then again it is only a 6.4 sq ft wing, and the numbers are for the blade alone. The near stall case produced nearer 24 lbs of drag at .035

[Vance]

Hello Rob,

I found great value in building a spreadsheet where I could change chord, blade length, rpm, lift to drag, and figure of merit. The spreadsheet was based on information from the book Helicopter Theory by Wayne Johnson. The helicopter rotor seems easier to understand than the gyroplane rotor. The way things interact and the resulting compromises are particularly illuminating.

Thank you, Vance

[Ga6riel]

Vance
Yes I made my own tonight to compare data aquired elsewhere, and work out a logical case for this. I have a lovely complex one for fixed wing a/c from Orion AC, but Im out on a limb with this :D

[Ga6riel]

Ok short discussion on thrust generators
There are two general directions, engine driven, or electric transmission. I say electric transmission because thats how I see it. Rather than electric motor driven I prefer to see the whole system.

Engine Driven
The problem I have to face with this is the reliability of what are unknown engines. I guess if Id gone through a program of developing the engine I would have more confidence, but as that is not the case I decided to move on to electric transmission.

Electric Transmission
Now someone already mentioned the high G force at the end of the rotor, and indeed the 160 G is a foreboding force to overcome. Therefore I payed heed to other advice and began work through systems that could be with the motor shaft perpendicular to the blade axis; and an alternate that would employ a right angle drive with the engine shaft along the blade axis.

Propeller
At first glance a prop looks like an easy solution, however there are 2 difficult to broach problems. Having a prop spin at some great rate on the end of a rotor, where at 420 ft sec or some 285 mph the prop is at the beggining of peak efficient velocity. It goes without saying this is a highly dangerous situation, particularly in a small craft where the rotor is close to the ground. Add to that, in a autorotation situation the props would add inordinate drag. This can be overcome with a folding prop, an idea borrowed from the model glider community. The problem with this is it would have to be custom made, as I would envisage a prop around 24 inches diameter at this point.

Ducted Fans
A ducted fan would aleiviate this situation, the diameter is narrow enough to be less of an obstruction, and the shroud makes it a good deal safer to approach. Problem with this is axial fans are very difficult to design and produce, and one probably cant be found available for purchase. While the representative efficiencies are good, reaching that peak has been in the past quite difficult. The tollerance between blade ends and the duct is necessarily right down to thou., and would require machining to make. Variable pitch could resolve some of the design issues but, that adds considerably to development and would require the technology to keep both fans in sync.

Centrifugal Compressors
Centrifugal compressors were the forerunners of gas turbine engines. Whittles first engines were centrifugal design probably because the workings are easier to manufacture and to calculate. The compressor itself can be made from flat plate and simple working tools, and the closeness of the shroud fitment is a much more generous affair.

We dont use them as much these days because axials are of narrower profile and greater efficiency. For wing mounted engines these are critical features and in any event we have the technology. However it wont hurt so much on a rotor as we are talking an inch or so diameter at best, and the loss of efficiency would be seen in excess motor weight and watts consumed. Not altogether disabling deficiencies.

[Ga6riel]

more info, this is EMG data

[dcarr4321]

Why not use a solid rocket engine? Some of the larger model rocket engines should be able to produce quite a bit of thrust. If ignited at the maximum rpm gained from the pre rotator it may be enough of a kick to push the rpm up. Some one with physics abilities could calculate the force required to spin the rotor. Here are some links for those curious:


Force conversion
http://www.sengpielaudio.com/calculator-forceunits.htm

Rocket Motors
http://www.apogeerockets.com/rocket_motors.asp

[Ga6riel]

Dan
Too much thrust would be a problem too, and solid fuel lacks 2 components, control and sustianed flight.

Actually the thrust isnt so much of an issue as I believe it can be generated by either of several methods.

Im deceminating the data generated to come up with some reasonable equation for the thrust. Having sorted out the Cl required, the drag is derived from that. Im having to learn about the application of induced drag in a rotor, but none of these things are insurmountable

[Ga6riel]

the state of play is still evolving
researching various drives and rotor dynamics presents more information and subtly affects the hardware plans
It seems the rotor may well be better driven at around 20 ft diameter, where I had hoped that 22ft would succeed, which would be better for autorotations.
Investigating lift drag curves has at least revealed that a lot more than 5 degrees pitch is likely unnecessary.

So todays rotor is a NACA 0012 section 7" chord 20 ft diameter, rotating at 420 rpm (285 mph). Lift coefficient of .55 and drag of .014. Each blade can lift 282lbs with 7.18 lbs of drag, induced drag to be added when I learn how to calculate it :)

The drive is changing to with new information to hand, it seems there are folding props around for gliders; while they are not suitable for the rotor it demonstrates the worth of the technology. The diameter could be a good bit less than I innitially thought which makes them a more attractive option, for today at least. Certainly it would be aerodynamicly cleaner to use props, and the tip speeds are within a comfortable regime. Electric motors make it a reliable, controllable system. They would probably be pushers too.

Out on the horizon are still more drives. Such as a sideways centrifugal compressor that enables less profile drag. And magnetic bearing ducted fans to combat bearing wear, although these are probably insufficient for the high G loadings.

[Ga6riel]

some pics of the folding props, and the last an interesting jet tip, that reduces induced drag.

[Rotor Rooter]

Ga6riel,

A thought.

It is said that the higher the electric motor's RPM, the lower the weight to power ratio. In addition, they have a smaller diameter (ref. axial drag).

If the motor was brushless, a commutator could be put on the frame. This would allow the rotor to rotate in one direction and the stator to rotate in the other direction. This would allow for two propellers; one a tractor and the other a counterrotating pusher. It will also give a free 2:1 reduction in the RPM to the two props.

Dave

PS
The good: The gyroscopic force of one prop will be offset by the gyroscopic force of the other.
The bad: There will probably have to be a frame acrose the motor to isolate the motor brgs from this force.

[Ga6riel]

thats very true
however push pull has its own complications
i think i learned that first from Max Munk's discussion about biplane gap theory
because that relates well to tandem wing types of aircraft and
the ideas within relate to props that are in prop wakes
it becomes exceptionaly difficult to calculate the pitch required because you first need to figure out the stream of the wake from the preceding screw.
that said it is sorta tempting

with prop rpms currently around 6 to 8k, that would mean a motor rpm of 12 to 16k. Brushless are certainly the way to go in any event. And higher voltages are much more usefull, with less heat loss thru the wiring run, and lighter componentry all around.

The slip ring issue is going to haunt me a bit, I have no idea what is ideal for that.

[Ga6riel]

Another prop detail not to be overlooked
where a prop is fitted basicly on the wing tip, and if setup so that its direction of rotation counters the tip vortices, you win an additional increase to the aspect ratio of the wing/blade. True the air will still go around the tip, but it will now be forced to go out beyond the down blade of the prop to achieve this. This phenomena was first investigated in Voughts V-173, which used huge propellers and a wing of somewhat circular planform. The effective aspect ratio of this design proved to compare with a calculated wing plus the downblade distance on each side.

[dragonflyerthom]

Ga6riel

Some very very interesting thoughts. I'm impressed with your progressions.



Thom

[Ga6riel]

Propulsion Efficiency chart sourced from RW Hovey "Ducted Fans"

[dragonflyerthom]

Makes you wonder why ducted fans aren't in use more on gyros doesn't it.



Thom

[Ga6riel]

quite so
but only from a purely technical point of view
there is the question of the availability of the hardware
for designing/making your own ducted fan is quite beyond most ppl and small engineering facilities.

together with this they are adjustment problems and compatibility with current spec aero engines, for the shaft rpms are usually of a higher order, more compatible with auto engines.

it is indeed difficult to defeat the popularity of ground adjustable multi-blade props, and with good reason

[Ga6riel]

The requirements have been rehashed by a better method of working. Which sees an individual blade divided into foot long lengths, and the speed/lift etc are calculated on the centre of each segment. The following data is at around 5.5 degrees AoA and that fulfills the hover state condition. More power than this is required by the system, typical VTO systems require some 8 to 13% additional lift to sustain hover performance in a wide variety of conditions.

Diameter 20ft
Disk Area 314.12sq ft
Disk Loading 1.725 lbs sq ft
Radius 10 ft
Blade Length 9 ft
Chord 7"
Section 0012
Area Sq ft 5.25 sq ft
Aspect Ratio 15.43
Blade Loading 103 lbs sq ft
RPM 420
tip speed 440 ft sec
Cl 0.6
Cdo 0.0146
Cdi 0.010608954
Lift 268 lbs per blade
Drag p 6.51 lbs
Drag i 4.73 lbs
Drag 11.24 lbs
L/D Ratio 23.80

Things unaccounted for this far
still to determine max power condition, data so far is for hover state
still to determine tail rotor power, size etc
still to consolidate weights, attempts this far are working to a 540 lb lift requirement
still to select suitable hardware to fulfill spec requirements
Since this is an electrical machine, it is possible to introduce many electrical features.
constant rpm disk, where power is increased or decreased automaticly, and control is maintained via the cyclic and collective. It would be necessary to have an excess of power onboard to achieve wide synchronus control. Motor power is varied via transistor motor controller, This also ensures that a just the right amount of power is fed into the system and that the rotor is not being overdriven.
heading hold requires a fluxgate compass. This would control a tail rotor pitch control.
height control would maintain a given height

[Rotor Rooter]

Ga6riel,

Prouty's hover program was coded into my computer a number of years ago. So your data was run through the program to see what came out. Here are some of the outputs. I hope that this is of some help or interest.

Momentum Method;
Power 27.2 hp
Induced velocity; 19.0 fps
Thrust CT; 0.0034046
Power CP; 3.718E-07


Blade Element Method;
Thrust CP; 0.0033918
Profile CQo; 8.425E-05
Induced CQi; 0.000154
Torque CQ; 0.0002288
Power 30.4 hp


The collective pitch for the above is 6.3 degrees

From NVFoil;
At 6 degrees
Cl = 0.720
Cd = 0.001
Cm = -0.009

Some of the values, such as the power, come out low. I have assumed (rightly or wrongly) that this is because Prouty's program is intended for larger helicopters.


Dave

[Ga6riel]

very interesting Dave
many thanks !

when I punch in a Cl of .7, and corresponding drag from NACA of .016
I get 21.72 HP, from 27.16 lbs x 440 /550
but I get quite different lift values (312 lbs per blade)
thats like 13.5% difference in lift,
I guess theres an easy 10%+ that would be the difference between theory data and field data

Edit: Im finding some errors in my induced drag side calculations, that would explain the more significant of the difference
those figures for NVFoil look sorta whacky

[Ga6riel]

Nagler built the NR 54 V2 in response to a new set of design specifications set forth by the German Air Ministry in 1943 for a folding man-portable helicopter. They required one-hour endurance, a 50-kilometer (31 mi) operational radius, a ceiling of 500 meters (1,640 ft), and a climb rate of 2.5 meters (8 ft) per second.

The Air Ministry viewed the asymmetric engine and rotor configuration used of the NR 55 and NR 54 V1 as too unconventional, and insisted that Nagler's next design must have a symmetrical rotor system. Nagler did not abandon the rotor-mounted engine design, as it reduced the weight considerably without a drive shaft and transmission system, in addition to being torque-free. Nagler placed a small 8 hp one-cylinder, two-cycle engine at point 1.4 meters (4ft 7 in) from the axis of rotation on each of the two rotor blades. The 4.5 kg (10 lb) single-cylinder two-stroke Argus engines turned at 6000 rpm directly driving 0.6-meter (23 in) propellers, which produced 24 kg (53 lb) of thrust each. Argus had originally designed these engines as an auxiliary power source to start larger engines.

A pull rope started the engines, and starting the second engine with the first already going was likely an interesting challenge. Rotor blades were 4 meters (13 ft) in length, with a .3-meter (12 in) chord. Only those portions of the blades outboard of the engine could change pitch collectively. The blades were equipped with flapping hinges but did not incorporate any drag hinges, which, given the minimal blade size and mass, was not a significant issue. The NR 54 V2's conical fuel tank sat on top of the rotor hub, as was the case in Nagler's other wartime designs. Engine controls consisted of two handles, which projected downward from the rotor hub. One lever controlled the throttle, and the other tilted the rotor disc for directional control.

engine: 2 x 8hp, main rotor diameter: 7.92m, take-off weight: 140kg, empty weight: 36.5kg, cruising speed: 80km/h, ceiling: 457m,

[PTKay]

together with this they are adjustment problems and compatibility with current spec aero engines, for the shaft rpms are usually of a higher order, more compatible with auto engines.



What you quote as disadvantage, is exactly the opposite in case of gyroplanes.

Most of them use converted auto engines (mostly Subaru)
with a heavy, expensive and sometimes unreliable transmissions
to reduce the rpms to propeller acceptable values.

The weight of the ducted fan is also lower than prop & transmission.

And of course the diameter of ducted fan is so low,
that no drop keel or high landing gear is required to get CLT.

[Ga6riel]

Paul...no disagreement here
but you wouldnt be able to use a certified engine without a gearbox, even an auto engine requires a prop interface that is independent of the crankshaft.
And of course you would need to have aquired the fan from somewhere.
If you think making your own prop is difficult, a ducted fan is in a way different league.
Add to that, bigger is always better even in ducted fans as the Pegasus demonstrates.

[gyrofly]

I know of a particular sailplane with a pair of these engines. It's a pretty decent self-launching motorglider now that the Hirth is gone.
That's the application I was thinking about when I first saw the post. I would like to see that in action.

[gyrofly]

I couldnt believe it, this frisbee seemed to be hanging in the air and was getting bigger.........then it hit me...
Ga6riel, I like that...

[Rotor Rooter]

Google, PayPal founders fund battery-electric sports car

From July/21/ 2006 Globe and Mail newspaper


Telsa Motors Inc. (http://www.teslamotors.com/styling/body.php), a luxury auto company funded by PayPal Inc. and Google Inc. founders, plans to sell the first modern battery-electric sports car, aiming to succeed where General Motors Corp. and other car makers failed. The $100,000 (U.S.) Signature 100 roadster, with a top speed of 210 kilometres an hour, will be sold in California, Chicago, New York and Miami starting in early 2007, chief executive officer Martin Eberhard said earlier this week. The car accelerates from zero to 95 km/h in four seconds and can travel 400 kilometres before its 400 kilograms of lithium-ion batteries need recharging, he said. Closely held Tesla expects to sell "less than 1,000" of the cars in their first year, Mr. Eberhard said. Tesla, named after inventor and engineer Nikola Tesla, showed prototype models of the cars on Wednesday night and gave test rides around a hangar at the Santa Monica airport.

The car's estimated 400-km range per charge is possible, though it will drop as the battery pack is drained and recharged, said K.G. Duleep, managing director of Energy & Environmental Analysis Inc., which consults car makers and the government on new engine technologies.

The Signature's lithium-ion pack will have a five-year, 160,000-km warranty, said Elon Musk, the company's largest investor and the founder of PayPal. Other backers include Google founders Larry Page and Sergey Brin.


Telsa Motors Inc. (http://www.teslamotors.com/)

[Ga6riel]

In 1906, you could buy the Baker Electric Car, powered by its Edison wet cell batteries, and have trouble free motoring for a range of 80 miles. This in an age when cars were troublesome, problematic, hard to start, noisy and unreliable.

In 1912, Charles Kettering released the electric starter for the Ford T, sales of electric cars began to dwindle. Baker dissapeared into commercial oblivion.

In 1994, under pressure form the California Clean Air Act regulators, GM prepared the release of the Impact. The Impact could out accelerate all but the Corvette in the 1994 model lineup. After nuclear war, the electronic age, the space race and interplanetary travel...the Impact was reported variously to be capable of just 50 miles. Most of the Impacts production was sent to the desert to meet with Mr Crusher, it was designed to fail and end this nightmare for GM and others.

Now having gone full circle, it is the age of the electric car once again. For entrants to this market have no need of expensive cast technology resorting to cookie cutter like technology and available componentry. The stubborn monoliths of GM, Ford and others who have underfunded their R&D for years. Who have pushed this unsatisfactory barrow of transport to a well defined corner are set to dissapear.