The most Futuristic Car I have ever seen

[Mr. Analog]

BEHOLD!
http://www.allpar.com/mopar/turbine-photos.html

[Shayne]

I prefer the rotary engine

http://auto.howstuffworks.com/rotary-engine.htm

[Darren Dirt]

BEHOLD!
http://www.allpar.com/mopar/turbine-photos.html

"Who Killed The Turbine Car?" (apologies to Chris Paine )

I prefer the rotary engine

http://auto.howstuffworks.com/rotary-engine.htm

Wow Shayne, thanks for that -- an extremely neat way of going through the combustion cycles.

Flash animation


...and apparently the rotary engine is (will be?) used in the "SkyCar"

it will be completely controlled by computers using Global Positioning System (GPS) satellites, which Moller calls a fly-by-wire system. ... MACRO Industries' SkyRider X2R will also use this fly-by-wire system to safely transport passengers to their desired destinations. Drivers will simply get in, turn on the power and enter the address or phone number of their destination. SkyRider will do the rest. MACRO said that the system will be almost fully automatic, but may allow some manual control.

Anyone else's noggin playing back scenes from "The Fifth Element"?

[Shayne]

Rotary engine can be had in a number of Mazda vehicles today!   The great thing about it that I like is that you can go from Gas to Hydrogen with the flick of a switch.

http://www.ultimatecarpage.com/frame.php?file=car.php&carnum=1792

[Mr. Analog]

Rotary is pretty boss, Zapata had one of those rotary RX-7s a few years ago. That was a fun car to ride in 

[Thorin]

Of course, the pistonless rotary engine does have its disadvantages:

In practice, the main problem of the Wankel engine has proven to be the seals, and as of 2005 all proposed designs have some of the same potential weaknesses.

Although in two dimensions the seal system of a Wankel looks to be even simpler than that of a corresponding multi-cylinder piston engine, in three dimensions the reverse is the case. As well as the rotor apex seals evident in the conceptual diagram, the rotor must also seal against the chamber ends. Worse still, these two sets of seals must somehow join at sharp corners at the ends of the apex seals.

An additional problem is that the seals at the Wankel rotor apexes meet the chamber walls at an angle that varies plus and minus ~26 deg; during the cycle, while a piston ring meets the cylinder walls at a constant angle. As well as making the seal design itself more difficult, this means that while multiple rings are easily fitted to a piston, a corresponding approach is impossible with the Wankel apex seals. This limitation is addressed in the Quasiturbine AC design, but the simpler Quasiturbine SC design has the same problem of varying seal angle as the Wankel.

Piston rings are not perfect seals. Each has a gap in fact to allow for expansion. Moreover the sealing at the Wankel apexes is less critical, as leakage is between adjacent chambers on adjacent strokes of the cycle, rather than to the crankcase. However, the less effective sealing of the Wankel is one factor reducing its efficiency, and confining its success mainly to applications such as racing engines and sports vehicles where neither efficiency nor long engine life are major considerations. A further problem caused by the shape of the seals in Mazda engines is that carbon particles can become trapped between the seal and the casing, completely jamming the engine and requiring a partial stripdown to rectify. Wankel engines should never be started and run unless the engine will reach operating temperature; most such instances of jammed engines occur when a car is started and moved a few yards, e.g. from a garage to a driveway. In these situations it is better to manually push the car.

Another disadvantage of the Wankel engine in particular is the large surface area of the combustion chamber which reperesents a large heat transfer and quench area, combined with an unfavorably long rather thin stretched combustion space necessitating long flame travel. The combustion is less complete than in e.g. an RPE having a more compact chamber shape with smaller area per chamber volume. The Quasiturbine has similar disadvantages with its concave combustion chamber, and in the AC design the sharp angles of the carriers hamper the propagation of the flame front leading to incomplete combustion.

Granted, the Mazda engineers are working on it, but the Mazda's RX cars were always known to need more than average engine work done, and the motors have always been thirsty.  They have a great power-to-weight ratio, though.  Then again, so does a two-stroke chainsaw engine.

Here's some more info on the disadvantages of the Wankel engine: http://en.wikipedia.org/wiki/Wankel_engine#Disadvantages.

I still say electrics with micro-transmissions mounted at each wheel, with a small gasoline-powered electricity generator to recharge the batteries, is the way of the future.  It doesn't require building a bunch of hydrogen stations, it doesn't require building a bunch of electrical stations, and it offers significant savings on fuel costs.

[Shayne]

The great thing about cars of today are the relatively simple principles and areas of failure. To go electric or hybrid increases the amount of parts and complexity their by increasing the areas of failure.

Ya, those Wankel's sure do have seal problems, their biggest fault by far.  Fuel economy and cold weather starting is also sorta crappy.

[Adams]

At Weber Motors, I was talking to one of the sales guys, the only reason he did not have one is because of the winter driving. He said they are very rough running when they are cold and take a bit to heat up. Also he said the the fuel milage sucks ass in winter... well I added ass he said it sucks.

He said it was a solid car and for the 2 he sold they have only been back for oil changes. He also said something about oil changes being more frequent... I might be mistaken.

[Cova]

The great thing about cars of today are the relatively simple principles and areas of failure. To go electric or hybrid increases the amount of parts and complexity their by increasing the areas of failure.

Ya, those Wankel's sure do have seal problems, their biggest fault by far.  Fuel economy and cold weather starting is also sorta crappy.

Ouch - to call regular piston engines simple and then bash at the wankel, even if in areas other than simplicity.  Thats the best thing about rotary engines, they're so incredibly simple.  A 2-rotor engine only has like 3 moving parts in it (the 2 rotors and the drive-shaft).  A single-cylinder 4-stroke engine is already far more complicated than that, and if you consider a modern I4 or V6 with the overhead cams and all that other crap, it just gets rediculously complex.  I still believe that if as much money had been put into research/dev of rotary engines over the last 100 years as we've put into piston-engines, that rotaries would be far ahead and used in the majority of applications.

I do agree however that the future is electric - an electric engine inside each wheel hub can provide acceleration and braking (and regenerate energy during the braking), no transmissions required.  But I think the power-source of the near future for these is going to be hydrogen fuel cells, moving to some type of battery or capacitor array in the future if fusion power ever finally comes along and every person can have an electric recharging station in their garage.

[Shayne]

Oh for sure the Wankel is great in terms of simplicity it does have its faults though.  Im saying a simple 4 cylinder engine is less complex then the 4 cyl + hybrid system Honda is dropping into their machines and what future planes are in terms of fuel cells and such.

2 stokes have 3 moving parts

[Thorin]

Thats the best thing about rotary engines, they're so incredibly simple.  A 2-rotor engine only has like 3 moving parts in it (the 2 rotors and the drive-shaft).  A single-cylinder 4-stroke engine is already far more complicated than that, and if you consider a modern I4 or V6 with the overhead cams and all that other crap, it just gets rediculously complex.

I agree that a rotary engine has less moving parts than a piston engine.  A rotary engine has more than 3 moving parts in it, though.  Air intake, spark distribution, exhaust, coolant, lubrication, starter system, electricity generation; these all use moving parts (well, spark distribution used to).  Notice I don't list power transmission or gearing, as those are generally considered not part of the engine.  And yes, piston engine has all these systems as well; what I'm pointing out is that of the whole system, reducing the number of parts in the combustion chamber doesn't suddenly make it a dirt-simple design.

I still believe that if as much money had been put into research/dev of rotary engines over the last 100 years as we've put into piston-engines, that rotaries would be far ahead and used in the majority of applications.

If research and development were the same for both systems, they'd be in use the same amount.  In the early years, though, it cost a lot less money to build a semi-reliable four-stroke piston engine than a semi-reliable rotary engine.  Therefore, the car companies sank their money into piston engines and left the rotary engines for the airplanes.

I do agree however that the future is electric - an electric engine inside each wheel hub can provide acceleration and braking (and regenerate energy during the braking), no transmissions required.  But I think the power-source of the near future for these is going to be hydrogen fuel cells, moving to some type of battery or capacitor array in the future if fusion power ever finally comes along and every person can have an electric recharging station in their garage.

Electric engines become less powerful as their RPM increases.  This is why hybrids presently use a gasoline engine to help out at highway speeds.  This is why I say that we will need micro-transmissions if we mount the electrical engines right by the wheels.  Now, what kind of transmission?  I think a CVT (Continuously Variable Transmission) is best in such a situation, so that the electric engines can spin up to a certain speed and then stay there.

[Shayne]

What if one of those engines fail?  I guess it could disengage and the rest of the motors would compensate.  4 times the chance of failure

[Adams]

Instead of 1 point of failure you have 4 points of failure.

[Thorin]

What if one of those engines fail?  I guess it could disengage and the rest of the motors would compensate.  4 times the chance of failure

Yes, four times the chance of failure, but not necessarily four times the chance of getting stranded by the side of the road.

The question here is whether having one engine fail equals getting stranded.  I surmise that the vehicle could still move on a regular road with only one engine working; the rest of the wheels would simply free-wheel.  Thus, you could say that the system is quadruple-redundant, although that's not exactly accurate, either.

In a vehicle with a single engine, the engine either works or it doesn't.  In a vehicle with multiple engines that can be disengaged if they don't work, the engines either work 4/4, 3/4, 2/4, or 1/4.  So if the engines could be disengaged, I'd rather have the four-engined design...

[Cova]

What if one of those engines fail?  I guess it could disengage and the rest of the motors would compensate.  4 times the chance of failure

I'm going to go on the assumption here that you guys are talking about the Skycar now, since I can't think of anything else in this thread with 4 engines.

First off, the M400 (the popular skycar that most people think of) actually has 8 rotary engines, 2 in each one of the 4 little pods that provide thrust.  Each of those pods can suffer an engine failure and the skycar will continue to operate properly.  I don't know if it can suffer 2 failures in the same pod, I think that would cause problems with balance during takeoff/landing (it uses VTOL), but it might be able to continue horizontal flight and make some type of emergency landing still, which is better than falling like a brick out of the air.

Second, it is not 4 times the chance of failure - it's more like 1/4 (or 1/8) the chance of failure.  It would be a higher chance of operating in a degraded state if a single engine does fail, however that no longer constitutes failure of the entire system.  All of my servers here at work have 2 PSU's in them - it doesn't give them 2x the chance to fail, it allows them to continue to operate even if a single PSU does fail.  They all have RAID disk systems (and not RAID-0) - again more disks doesn't increase the chance of a server dying, it gives them redundancy and allows them to continue to operate through a single disk failing.  The trick is always to find and eliminate single points of failure - single items that if they fail the entire system will go with them. Regular cars have a single point of failure in their engine, transmission, etc. however say a commercial airliner can suffer the loss of an engine (sometimes more, depending how many it has) and in that degraded state still make it to an airport and land safely.