I wouldn't trust Moller as far as I could throw him.

Keep in mind that most general aviation engines turn the prop at < 2400rpm. At ~2400 RPM (or 2700, depending on the prop), the tips of the blades start going transonic -- which makes and aweful racket and ruins the efficiency of the prop. You might hear the "prop crack sound" on an old warbird or on some high performance singles -- that's what's happening.

Also, keep in mind that the smallest general aviation aircraft that you find at most airports is the Cessna 150. The smallest engine that you can find in one of those is just over 100hp. And, it has to deliver that 100hp at 2300RPM or so.

Some airplane engines (Rotax, auto conversions, etc) use a reduction drive (gearbox, giant belt with pulleys, etc) - so that the prop can spin around 2k RPMs, and the engine can spin at 4500+ (depending on the ratio you picked when you bought the gearbox). But, that's a heavy piece that bolts onto the engine block, and opens up a wholenother dimension of engineering tradeoffs.

So, in short, a 22hp engine that runs at 4500rpm isn't appropriate for the kind of aircraft that I've flown. Maybe it would be appropriate for a UAV (less HP required, and a smaller-diameter prop that can spin at more rpms without the tip going transonic (the speed of the tip of the prop is rpm*pi*r^2). But, it would not be appropriate for anything that could haul my chubby self off of the runway.

Dr. Moller,

Unless you know something that the rest of the world don't, including Madza, NSU Wankel, Cummin, Detroit, etc...the Wankel rotary has been tested and retested ad nauseum, and has been repeatedly shown to be far inferior to a piston gasoline engine in term of thermal efficiency, combustion efficiency, and exhaust emission. This is due to the wedge-shape combustion chamber that makes for less efficient combustion, and large combustion chamber surface area that increases heat loss.
The Mazda Rx7 and Rx8 are cases in point, which show horrible fuel efficiency, worse than the much heavier and far more powerful Corvette. Reliability record for the Rx7 has not been good, either. The Mazda 13-B engine when adapted for aviation use has not shown any efficiency advantage nor any gain in power-to-weight ratio over the antiquated Lycoming or Continental aircraft engines, except for cost, when the 13B came from used Rx7 cars in Japan that must have its engines replaced by law after 30,000 miles.

How can Dr. Moller say that a turbocharged otto-cycle engine with effective compression ratio of 12 (geometric ratio even less) can compare efficiency-wise with a turbocharged diesel engine with compression ratio of >18 and expect people to believe it? If this is true, Dr. Moller, the whole world will start driving your "Rotapower" rotary engines in a heart beat.

My bad about the formula... That was dumb!

Never seen a 40" prop on a C150, though -- they're usually around 69 inches or so.

Andrey:

I fully agree with you. The ICE driven on- board generator (and the vehicle body and accessories) should be as light as possible to maximize the PHEV electric mode range.

Assuming that the PHEV range extender ICE driven generator would operate about 15% of the time, a 30,000 miles generator endurance would last about 200 000 total miles. That should be sufficient for most private vehicles.

I read some times ago, that an Indian firm has produced a very light weight (24 lbs.) 24-HP diesel that could compete with the weight/power ratio of the rotaries. Any more on this motor? Is it another fantasy?

Luke, I believe the Skycar would have 8 150hp engines mounted in pairs in 4 ducts not a single 22hp motor. or am i missing something from your post?

The rotary engine may well be the norm in most new vehicles within the next decade. Their positive characteristics outweigh their short comings. There are dozens of companies all over the planet currently testing rotary engines for hybrids. Because rotary engines have separate chambers for intake and combustion, they are ideal for burning hydrogen (ie: http://msnbc.msn.com/id/6343414). Particularly I have interest in the companies now looking at generating hydrogen while running on gas. In effect, a full sized car may may achieve 50+mpg via a single engine and 3 tanks - gas, hydrogen and water. Simply cannot do this with pistons.

With respect to the negative statements about Dr. Moller's efforts ... please take another look. I've been present for 3 of the test flights of the old M400 prototype. It flies rather well and that was with the smaller engines. I have no doubt there will be Moller skycars in the air over major cities within the next 5 years. Rather cool to be running 8 x 1060cc rotary engines at 7,000rpm (~1240hp) all directly mounted to a metal frame without rubber bushings and there was no vibration. These engines are showing a MTBF at a projected 8K-10K hrs (equivilant to 200K-300K miles in a car).

AIXRO WANKEL RACING ENGINE XR50 FROM GERMANY IS AROUND 30-LBS 50-HP AT AROUND 10,000-RPM BEAT THAT [PISTON HEADS] PLUS A AIRCRAFT VERSION OF SAME ENGINE AT 65-HP NOW ARE THERE ANY PISTON ENGINES EVEN CLOSE TO THAT POWER TO WEIGHT RATIO , IF THERE ARE POST THEM .

I'm sorry, intend on*

Eight year later and nothing. Andrey's post was good.

Electric motor traction is infinitely superior to direct internal combustion engine traction. It has max torque at zero revs. No power sapping, space consuming, heavy, complex transmission is needed. Decoupling the power source, the IC generator, and the electric traction motors, gives great benefits. Having a constant speed running Wankel engine generator provides electricity for the electric motors, up until now it was not feasible as piston engines were so inefficient.

Matters are now better with more efficient electric motors, generators and now, and only "just" some IC engines. The Chevy Volt's piston engine cannot provide efficient power via the generator having to drive the car directly at some speeds. The problem is the engine. But things are improving to the point a full electric transmission is possible.

Using supercapacitors 90% plus of kinetic braking energy can be reclaimed and then given back to accelerate improving efficiency. The generator Wankel engine can be run at a maximum, efficient, constant speed & load at its most efficient "sweet spot". The Wankel engine generators can be much smaller than a direct drive engine using a transmission. The Wrightbus for London has a 7 litre diesel engine but a 2.5 litre engine when the same bus is used as a hybrid - a third of the size. And this 2.4 engine will be running at maximum efficiency for most of the time, while the 7 litre engine will not.
http://www.busandcoach.com/featurepage.aspx?id=1725&categoryid=0

A hybrid runs on the concept of an energy buffer, the battery and supercapacitors. Batteries consume about 33% of the kinetic braking energy while supercapacitors can reclaim 90% plus. Eliminating the mechanical transmission and having an electric transmission with the engine/generator providing electricity direct for the electric traction motors, without a battery (energy) buffer, is now feasible because of more efficient electric motors, generators and Wankel engines running at constant efficient speeds. The small, light, quiet and smooth Wankel engine now comes into it own in this application.

So, making very light and small Wankel engines more efficient, running at an efficient constant speed is the answer.

A piston engine and transmission plus the weight of a full tank of fuel (total car weight) is getting close to the weight of an EV and Lithium batteries and its total car weight for the same energy storage. Recall that 80% of the energy in a tank of fuel is wasted, so the energy density then is not great at all in that tank of fuel. A set of batteries will give off 90% plus of the stored energy. So, total EV vehicle weight with batteries and a normal vehicle with a full tank of fuel, can be about the same, but the EV will store more "useful" energy. And low slung batteries in car give a lower centre of gravity improving road holding.

Using a Wankel generator engine running at a constant speed and load the efficiency rises dramatically offsetting any state change losses. Only 66% of the energy in the tank is wasted while 80% is lost with current direct drive setups. Plus there are all the other gains.

Laser ignition, still under R&D but working, and direct injection should solve many of the Wankel's problems. A lean burn can be achieved with laser ignition. Running a Wankel at a constant speed will improve efficiency for sure and give the engine its niche at last as a range extender.

The BMW i3 is showing the way with direct drive electric traction motors, but the inefficient two cylinder motorcycle engine used as a range extender needs replacing ASAP with a small, light Wankel engine. The motorcycle engine was not designed for generator use, as is the case with the Chevy Volt's engine.