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switches between operating as a low-rpm internal combustion engine and a regenerative-storage high-rpm flywheel.
  [vote for,

The rotary-radial engine, used in WW I aircraft, rather uniquely has several design properties that make it quite amenable to today's need for a lightweight regenerative power system for automobiles:

• the entire engine rotates, making it a de-facto flywheel, RE=œmv²: energy stored is exponentially proportional to rotational speed.

• all piston reciprocation can be suspended by centering the crankhub¹ from its normal offset ².

In IC mode the vehicle is simply a car, driven by its engine through a CVT transmission. At the low RPM these engines run at (800-1,200³), there is very little rotational momentum being stored.

In regen mode the engine-turned-flywheel stores braking energy (spinning up as far as 3,500rpm³), then releases the energy to recelerate the vehicle, eventually spinning back down far enough to recommence IC operation.

In between the two operating modes "Start/Stop"(the engine keeps spinning, but all the IC components are shut off and battened down) is completely seamless, noticeable only by the lack or presence of exhaust noise.

A flywheel-engine flywheel/engine.
[post retitled and retexted August 30,2012]


¹ The crankhub is the radial-engine's equivalent to a crankshaft piston-rod journal on an inline-engine. On all radial engines the piston rods share one journal/hub.

² In order to facilitate operation as a flywheel, the pistons have to stop reciprocating within the cylinders. Moving the crankhub to the center does this very elegantly. (As a bonus the engine's geometric-compression-ratio can be changed, by moving the crankhub slightly in or out from its normal offset position, during IC operation.) The crankhub on the old rotaries are fixed.

Naturally it turns out somebody else thought this up <"darn" link>, I'm sticking with this post though, it's a different operational paradigm.

³ The IC rpm figure is what the WWI engines rotated at, which works out fine for this purpose. The flywheel rpm figure is based on the energy differential of an econobox between 0 and 60 km/h.

FlyingToaster, Aug 01 2011

9 Cylinder Radial in an econobox http://www.youtube....watch?v=f2V7B7-gdRA
Call that a backseat driver ? THIS ! is a backseat driver. (okay, the video has nothing to do with the post even though it's a radial engine, I just thought it was cool) [FlyingToaster, Aug 05 2011, last modified Sep 02 2012]

possible cooling solution with minimal aero-drag Steam_20Cooled_20Rotary_20Engine
[FlyingToaster, Aug 06 2011]

How to put a flywheel between an engine and a driveshaft flywheel_20between_202_20CVTs
[FlyingToaster, Aug 07 2011]

True "Rotary" engine http://en.wikipedia.../wiki/Rotary_engine
"An early type of internal-combustion engine" [8th of 7, Aug 08 2011]

Barrel rotary and other swashplate engines http://en.wikipedia...i/Swashplate_engine
A more compact rotary engine, with variable compression. [Twizz, Aug 09 2011]

darn http://www.greencar...ie/comments/page/2/
went and got patents and everything, both for "using a rotary engine as a flywheel" and what I call "variable offset crankhub"(anno 8/21) and he refers to as "moveable crank journal". However he's got flywheel/IC happening simultaneously and his rotary is inside-out. [FlyingToaster, Sep 05 2011, last modified Sep 01 2012]

Flywheel-balanced monorail http://www.absolute...pics/Gyro_Monora il
How about using the rotary engine as a combined power source and flywheel in a monorail? [bs0u0155, Sep 07 2011]

The Brennan Gyro-Monorail. http://www.aqpl43.d...brennan/brennan.htm
Some people have waaay to much time on their hands ... [8th of 7, Sep 11 2011]

Rotary vane engine http://www.youtube....j-k&feature=related
variant of a swing piston engine [metarinka, Sep 11 2011]

And another http://www.rotoblock.com/howitworks.shtml
whatever happened to these [metarinka, Sep 11 2011]


       A few questions:   

       What kind of displacement/output and rpm are we talking? For that matter, what type of vehicle?   

       What method of drive transmisson?   

       How will the engine be oriented and where will it be placed?
Alterother, Aug 01 2011

       There's no set displacement in the post. Rotaries are generally low RPM: 1200? during normal operation.   

       I also had no set vehicle type in mind though I did some rough regen math for a car/light-truck of 2 tonnes @ 100kph with very reasonable results [edit: then I did them again using the proper math and they sucked... but an econobox at urban speed works out fine). A CVT transmission allows for smooth interface between flywheel and wheels: not as efficient as a manual tranny, but not as crappy as an automatic.   

       Let's not think too hard about Newton's Third Law or precession. :D
FlyingToaster, Aug 01 2011

       (sorry [Ao], I accidentally deleted your anno. I'm having my mouse shot at dawn; I assume that will provide satisfaction ?)   

       //I guess I'm thinking too hard//

       If the engine was mounted in a horizontal plane and allowed say 10-15 degrees of movement each way, that would mitigate precessional problems for normal driving patterns. Off-roading might be a no-go or at least interesting.   

       Newton on the other hand would much prefer the engine to be spinning parallel to the roadwheels.   

       However there does appear to be mechanical regen flywheel systems for vehicles, so somebody figured it out.
FlyingToaster, Aug 01 2011

       // kinesthetically //   

       That's not the right word. Go away and look up what "kinesthetically" actually means. Then write a 1000-word essay on the subject. Study carefully, you will be asked questions later. Do not be alarmed, the electrodes will not cause you more than minor discomfort, as long as your answers are correct. There is no point in struggling, you cannot free yourself from the straps.   

       We wish to point out that true "rotary" aircraft engines use total-loss lubrication, based on castor oil. While "green" in many ways. there is a non-zero amount of uncombusted lubricant in the exhaust stream.   

       // Let's not think too hard about Newton's Third Law or precession //   

       Fine with us, as long as you're the one taking it round the test track. If we find any bits of you, do you want interment, or cremation ?   

       // hit/miss cylinder-firing means efficiency at any load condition //   


       The problem you have failed to note is that, in the nature of rotary engines, each cylinder will still induct fuel/air mixture even if the spark is withheld; so you get the same fuel consumption, just less power, and unburned fuel in the exhaust (to mix with the unburned castor oil) (although it won't, because castor oil isn't soluble in petroleum) (check it out, it's true). To achieve this, you need to be able to selectively gate the inlet and exhaust valves.   

       // go down the highway sounding like a Sopwith Camel or Fokker Triplane //   

       Immediate bun.
8th of 7, Aug 01 2011

       "kinetaesthetically" ? But apart from anthropomorphism that *is* what I mean.   

       Anyways, I wasn't really considering stealing a 1912 LeRhone from a Spad and dropping it into the engine compartment. "Rotary" as a generic design concept.   

       Assuming the engine is inside a shell for various reasons (safety, muffling), we can let lubricant spatters run down the wall and be collected for recycling.   

       DI should take care of any fueling problems. It'd be neat to see if it could be made uniflow design, where air comes in through a valve on the piston, then out an exhaust valve on the cylinder head.   

       I don't see any problems with hit/miss except that it should also use stop/start; whichever is most efficient at the time.
FlyingToaster, Aug 02 2011

       Rotaries are two-strokes; you'd be doing well if DI could deliver efficient charge mixing, although the flow in the cylinder is going to be pretty turbulent.   

       Aircraft rotaries get a lot of their cooling from propwash, so enclosing the powerplant means you're going to need a big fan, like on the Beetle engine.   

       The design of having the inlet valve in the piston crown and the exhaust valve in the head has been used and is perfectly workable, if complex compared to Schnurle porting.   

       The power curve is likely to be a bit peaky.
8th of 7, Aug 02 2011

       The flywheel regen systems use a small flywheel spinning at unimaginably high speeds. The limiting factors for aircraft style rotry engines prevent them from turning fast enough to store the kind of energy you're looking for.   

       8th - Rotaries are NOT generally 2 strokes. Some used induction through the crankcase (like the Gnome) with an inlet valve in the piston, but these were difficult to throttle and relied on total loss lubrication with castor oil. (This was the reason for the pilot wearing a scarf - inhaling castor oil vapour has a rapid laxative effect).   

       A rotary 2 stroke would be very difficult to arrange, since there is no net change in crankcase volume to provide induction.   

       FT - Is uniflow any advantage in a reciprocating IC engine? It works for steam engines where the heat pattern follows the piston travel, but I can't see how it could work with IC.   

       For the sound and the fact that I love rotaries [+]
Twizz, Aug 02 2011

       // castor oil vapour has a rapid laxative effect //   

       Granted, but is said effect large compared to, for example, being airborne at 5000 feet in what is effectively a garden fence wrapped in canvas and covered with inflammable paint, propelled by a largely experimental and unreliable engine based on seemingly impossible mechanics, and then have someone chase you and shoot at you with a machine gun- as if life wasn't uncertain enough already…   

       Rotary 2-strokes may be crankcase-scavenged, but they use pressurise air feed through the carburettor to effect charge flow into the cylinders. The pressure needed isn't very high, it's just flow, not supercharging, although make the blower big enoug and it does confer significant performance benefits, particulary at altitudde. Again, the simplicity of the engine aids reliability and maintainance, against which must be offset the gyroscope problem. There are some interesting German designs from WW2 that used the concept.
8th of 7, Aug 02 2011

       Hmm - not sure about the forced induction 2 stroke thing. This is similar to the split single, which fires once per rev, but divides the four cycles between two connected cylinders. The split single is commonly described as 2 stroke, but 2 cylinders firing once per rev? Sounds like 4 stroke to me.   

       The laxative effect of castor oil in addition to all the factors listed would be unwelcome.
Twizz, Aug 02 2011

       Figures: the one time I don't specify "two-stroke" in an engine design everybody thinks it's important. The important bit is the flywheel. If you want to think of it topographically as a normal engine clutched to a very heavy flywheel attached to a CVT etc. go right ahead. The design lends itself quite well to intermittent operation.   

       [Twizz] you're right, uniflow doesn't convey much in the way of advantage in this design except a certain amount of gracefulness: air coming from the crankcase, combusted then shooting out the cylinder head. It does work in IC engines though, albeit the other way 'round.   

       Perhaps we could go with uniflow the right way'round: air intake at the cylinder head and exhaust through a port closer to the crankcase; the oil, being heavy, wouldn't tend to fly out with the exhaust.   

       Could diesel fuel handle all the cylinder lubrication by itself ?   


       ...could take care of both Messr's Newton and Gyro's objections with counter-rotating cylinder banks (and very heavy bearings), but it would make freewheeling (without engaging the piston/cylinders) rather complex....   

       Or not: just treat them as two separate engines: if they're out of sync, so what ? 2cyl up top and 2cyl on the bottom.   


       //fast enough to store the kind of energy you're looking for//

       A 2 tonne vehicle @ 100kph has about 1.4mJ KE.   

       A handy flywheel calculator shows that a 250lb uniform disk, 2' in diameter, spinning at 7,000 rpm has also about 1.4mJ RE. (A uniform ring of the same stats has about 2.8mJ RE)   

       This is the other reason we want to be able to decouple the crankshaft from the frame.
FlyingToaster, Aug 02 2011

       [Ao] Orientation is an odd question. I'm gonna say rear-engined transverse, or longitudinal if the other proves too interesting.   


       Calculation for a light urban vehicle:   

       1tonne, 60kph = 140kJ   

       Flywheel disk of 80kg, 50cm diameter.

       1200 RPM: 20kJ, rim speed of 31m/s
3425 RPM: 160kJ, rim speed of 90m/s

       Or, if you want the translation of the above... a VW Beetle weighs under a tonne. With a rotary engine (which we're simulating with an 80kg uniform flywheel disk for the calculation) that normally runs at 1200RPM, stopping from 60kph (40mph) would transfer the energy into the spinning-engine, making it revolve at ~3400rpm. Which sounds quite reasonable. You wouldn't turn the engine back on until it had gone down to 1200rpm or lower.
FlyingToaster, Aug 03 2011

       3425 rpm is far from reasonable for a rotary engine. At that speed, a 10kg cylinder head would exert a force of 35 tons on it's retaining bolts.   

       A 50g valve would exert 177 kg against the rocker, pushrod, tappet and cam, even with no spring. Good luck designing that engine.   

       Gnome rotaries run at around 1200 rpm and have carefully balanced valve systems.   

       Flywheels for KERS systems are made from continuous wound fibre to provide enough strength.   

       There are fundamental reasons why the rotary engine does not make a useful KERS device.
Twizz, Aug 04 2011

       Didn't the "nuance" of the gyroscopic effect give Sopwith Camel pilots an edge in WWI dogfights? Something about being able to pull off hairy dives/climbs with a tight twist that the opposition just weren't able to match - unless of course, you wanted to climb and turn the *other* way, in which case you're screwed, literally.   

       On a car, whose pitch is going to remain relatively stable in the course of a journey (or at least only change incrementally) this shouldn't cause too much of a problem.   

       That's assuming a mounting where the axis of rotation is in parrallel with the forward direction of travel. If you mounted it with the axis pointing vertically, then given enough revs, and a slippery enough road surface, and presumably you'd be able to spin the car on the spot.
zen_tom, Aug 04 2011

       //3425rpm is far from reasonable//
When the regen kicks in and starts spinning the engine up faster, the crankshaft is decoupled and the engine turned off. So even though the thing might be turning at a very high RPM while the driver waits for the light to change, the pistons, valves and rods aren't doing anything except spinning around in the same circle as the engine. When the light changes and the driver steps off the brake and onto the "gas pedal", the engine is *still* not powered up until the rpm's get back down to a reasonable level at which time the crankshaft clutch is re-engaged and the engine restarted on-the-fly.

       The Sopwith Camel's rotary weighs 180kg(dry), has a diameter of 95cm and produced 130hp at 1300rpm. Plugging those figures into the flywheel calculator it turns out that it stores more rotational energy while operating normally than the proposed engine stores while operating in high-speed flywheel mode.   

       [zt] With a longitudinal axis the car will nose-down when turning one way and nose up while turning the other.   

       With a lateral axis the car will lean into both turns, unless it's spinning the other way in which case it will lean out of both turns. Of course the leaning will have nothing to do with compensating for g-force and everything to do with the amount of energy stored in the flywheel.   

       A vertical axis would make sudden (regen)braking, or acceleration, rather interesting.
FlyingToaster, Aug 04 2011

       What about a rotary engine that spins in a chamber filled with a high-conductivity coolant ?   

       Oil would be OK and with clever design could double as part of a torque converter.   

       Water is cheap and has good specific heat.   

       NaK would give superb cooling but there might be a few safety issues to address.
8th of 7, Aug 04 2011

       Well, you'd probably want to streamline/fair the thing: while operating as an engine the rim is moving at 70mph, 210mph as a fully-loaded flywheel. Wouldn't want to do completely without a fan even though the vehicle's engine would mostly be off when the vehicle's at a low enough speed not to have ambient airflow.   

       Liquid cooling would be sorta neat: as long as you're streamlining the engine, might as well build in some channels. The coolant could be recovered from the shroud sump.   

       //NaK// wasn't it your turn for a test drive ? There's a good borg: don't start the engine 'til I'm well back thanks. § x1
FlyingToaster, Aug 05 2011

       FT: 3425RPM will still destroy the engine, whether it is making power or not. The figure I gave for the valve train load is the EXTRA load generated by spinning, without considering valve springs or opening valves against cylinder pressure.   

       The Sopwith Camel engine might store a bunch of energy, but is far too large and heavy for use in a car. Do you really want a 400lb engine, 3ft diameter, in your car?
Twizz, Aug 05 2011

       //Do you really want a 400lb engine, 3ft diameter, in your car?// Sounds good, let's go!
pocmloc, Aug 05 2011

       // wasn't it your turn for a test drive //   

       Yes, but we're happy to let [pomloc] take our turn.
8th of 7, Aug 05 2011

       //Do you really want a 400lb engine, 3ft diameter, in your car?// Not as much as these guys <link> A German metal-working company shoehorned a Vedenyev M14 into a Goggomobile. Quite a few videos, most accompanied by German ober-music which is amusing since the Vedenyev is a Russian design.   

       But my point (obfuscated as it might be) was that an engine that was mass produced over 90 years ago and was reportedly quite reliable, stored even more energy during normal operation.   

       The g-force at the rim of 50cm engine @ 3425 is about 3.5x that of the 95cm engine @ 1300. BUT, those valves etc. that you're going on about are not operating at that speed.   

       The engine does not power itself up to 3425 rpm, the CVT does. The engine doesn't kick in at 3425 rpm. The engine is crafty and waits until it's backed down at least to 1200rpm before engaging the crankshaft clutch which engages the mechanicals.   

       (Think of it this way: if you were to take a regular engine in a regular car and turn the engine over, I mean *literally* turn the engine over, then while you were turning it, if the clutch was engaged, the pistons would run up and down in the cylinders and the valves would open and close. But if you were to disengage the clutch, then the engine would turn over without the pistons running up and down or the valves opening and closing). My apologies if you already know what I'm talking about.   

       The g-force at the rim of a 50cm engine @ 1200rpm is about half that of an engine of 95cm @ 1300rpm.
FlyingToaster, Aug 05 2011

       //Water// How fast will steam rise in water under pressure? specifically under the pressure of being inside a 1200rpm flywheel, and "rise" a matter of geometric perspective. [posted separately <link>]   

       //torque converter// electromagnetic: combination starter, alternator, and finally torque-converter (to (de)couple the crankshaft to/from the frame when entering/leaving flywheel mode).
FlyingToaster, Aug 06 2011

       (in a vain effort to keep the thread moving...)   

       Operation Modes:
Efficiency is a matter of keeping the engine at its best BSFC range, but of course you don't need all the power all the time so we turn to stop/start and hit-miss techniques.

       If the engine economically produces 40-50kW @ 900-1200 RPM, but the vehicle only needs 20kW then the engine is run from 900 up to 1200 rpm with the CVT compensating to maintain a constant speed, then turn the engine off, disconnect the crank, and take power from the flywheel until it's back to 900 rpm again, rinse and repeat.   

       If the power requirements are closer to the best efficiency output, but not quite there (say in this example 35kW), then we keep the crank connected but don't fire all the cylinders all the time (hit/miss).   

There are friction brakes on the vehicle, but the most efficient method of storing and recovering deceleration energy is to turn the engine off (disconnecting the crank) and smoothly turn the CVT ratio up, dumping the cars kinetic energy mechanically into the flywheel. To recelerate, the operation is done in reverse. Eventually the flywheel will be spinning slow enough to reconnect the crankshaft and restart the engine.


       This isn't a normal KERS system: that requires equipment: an extra flywheel, two extra electric motor/generators and voltage regulator or two.   

       This is almost completely native to the design of a rotary engine. The flywheel, being the engine, doesn't have its own separate geartrain, and is not spinning at an absurd 20-100k rpm.   

       A quick survey of normal car engine flywheels turned up that they usually run between 20-30lbs, but a reference to a truck flywheel was for 80lbs. So it's not that much of a stretch... a 180 lb flywheel could even be put onto a standard car engine (clutched) in lieu of it's regular one, and add computer control to get much the same effect.   

       [edit: see [xaviergisz]'s "Flywheel between 2 CVTs" <link> which pretty well nails down using a regenerative flywheel with a normal engine.]
FlyingToaster, Aug 07 2011

       "The g-force at the rim of 50cm engine @ 3425 is about 3.5x that of the 95cm engine @ 1300. BUT, those valves etc. that you're going on about are not operating at that speed."   

       It doesn't matter if the valves are trying to open or not - my point is that spinning the whole engine at the speed you need imposes massive forces on the components, requiring everything to be stronger and stiffer, therefore heavier and less effecient.
Twizz, Aug 08 2011

       // effecient //   

       "You're talking shit, mate".   

       Just a moment ...   


       What if the cylinder block is running inside an enclosure which houses a circumferential track or tracks which have a profile equivalent to a camshaft ?   

       There are rotating-block designs with a roller on the bottom of the piston, running in an enclosure.   

       One of the problems with single-driven valves (spring return) is that at higher RPM the springs need to be extremely strong to slam the valve shut fast enough.   

       But with valves in the individual cylinder heads, the centripetal force with increasing RPM means that all that's necessary for fast valve operation is to make the valves heavier, with just a light spring to assist "idle" running, and reduce bounce.   

       So, is it the inlet valve in the head, or the exhaust? Or both ?   

       If it's the inlet, then the enclosure will probably need to be sealed and pressurized, either with air or a fuel/air mix.   

       If it's exhaust, then it can be vented to atmosphere, but has the disadvantage that the block is spinning in a pocket of hot gas, reducing cooling - unless stub exhausts are used to direct the gas flow away from the block, perhaps to a turbocharger.   

       Another scheme might be to have the block liquid-cooled, with the stubs venting to the circumference, and a smooth exterior; it could in fact be a disc. It would be heavy ... so no flywheel required.   

       FT, you may be on to something, if only you can find a way to cancel the gyroscopic forces. Contrarotating cooling fans of sufficient mass might be the answer, but the hub forces will be massive.
8th of 7, Aug 08 2011

       Are you talking about a Wankle Rotary engine, or a radial engine? If a Wankel, then have you ever heard of a Mazda RX-7 or RX-8? These use rotary engines. So this is baked. Your RPM figure sounds like you are talking about radial, as Wankel (rotary) engines run at high RPM when making power.
dlapham, Aug 08 2011

       Not a Wankel engine, or a Radial engine - both Widely Known To Exist.   

       He means a "rotary" engine, where the cylinder block spins round a fixed crankshaft.   

8th of 7, Aug 08 2011

       //        (sorry [Ao], I accidentally deleted your anno. I'm having my mouse shot at dawn; I assume that will provide satisfaction ?)    //   

       Yes, this satisfies the debt of honor quite nicely. Especially considering my anno contained no useful contribution, and I promptly dropped out of the discussion because I've been busy writing for the last week and could barely be persuaded to put down the Cherry Kijafa, backup my work to the flash drive, and come to bed, much less do anything as complicated as log onto the Internet.
Alterother, Aug 08 2011

       Valve placement: might as well go with the Gnome for the time being: intake through grooves in the axis end of the cylinder, exhaust through a single valve in the head... Or a sleeve valve(s). Of course that precludes 4-stroke with the intake being at the axis end. Since it'll be in a shroud, might as well just vent without mufflers, that gives a chance of recovering splatters off the wall as well.   

       Or one valve on the head which does both intake and exhaust and make it a 4-stroke.   

       Oh did I mention that unlike an aircraft mount, the engine can be supported on both sides of the axle. That's worth a few points.   

       [high rpm vs.valves]//heavier and less effecient//
Heavier, in itself, isn't an issue. "less efficient" in the sense that it takes more energy to open certainly, but quite a bit of that energy is reused (opening valve A is powered by closing valve B type of thing).

       //water cooled// pre-emptively posted <link> including your credit.   

       I came across a design on the 'net a few years ago: a compact 3 cyl rotary: 2cycle, diesel fueled and lubricated. Possibly au or nz inventor. Of course I can't find it now.   

       [Ao] welcome back; run out of cherry sherry ?
FlyingToaster, Aug 09 2011

       // // effecient //   

       "You're talking shit, mate".//   

       So you don't think that repeatedly accelerating large masses uses energy?   

       If there were no losses in the valvetrain, there would be no power required to operate it, since *all* the energy put into a valve spring is returned to the system as the valve closes.   

       In reality, each motion involves loss of energy, broadly in proportion to the load. Heavier valvetrain parts = higher loads = higher losses.   

       Have you ever wondered why cambelts are so large and need replacing?   

       All the energy going into the camtrain is lost as heat, so it represents ineffeciency.   

       Or perhaps you know of some super-effecient mechanisms that don't lose energy every time a valve is opened or closed?   

       Please enlighten us.
Twizz, Aug 09 2011

       okay, dunno if you're challenging me or [8th] but...   

       a) "efficient"   

       b) The valves on the proposed, fictional, specs-pulled-out-of-my-arse engine, when they're actually being opened and closed, are doing so under less than half the g-force stress of a Sopwith Camel engine's valves, which reportedly did just fine.   

       Yes, the fly-rotary's valvetrain (or at least the mounting brackets) would probably need to be a bit more robust than a normal rotary, which needs to be more robust than a static-radial, which needs to be more robust than a V or I engine that you can nail an overhead cam onto.   

       //cambelt// pushrod I'd imagine. or 8th's rails. Or something else...You realize this post started out as "hey wouldn't it be nifty to use a rotary engine as a regenerative flywheel", collect buns, spurn bones, carry on.   

       Pullrod would be cool because for a 2-stroke you could use the same axis as the crankshaft for the rods.   

       The 9N (gnome/camel) engine is outwards uniflow: as the piston approaches BDC it passes over (longitudinal) channels cut into the cylinder, which allow air in: sortof a sleeve valve effect with the piston as the sleeve. However this means that the exhaust-valve has to be opened before-before BDC to avoid exhausting into the crankcase. So it's a bit wasteful IMHO.   

       The same effect could be achieved with sleeve valves, one at each end of the cylinder.   

       I like the idea of an exhaust valve halfway up the cylinder: the piston pushes half the exhaust out while the scavenger pushes the other half out, making an Atkinson-cycle engine (and almost no work for the blower). But I don't see any way of doing that on this engine.   

       4-cycle could be achieved simply, by using a single valve in the head both for intake and exhaust. But of course that requires a more complicated valvetrain since the engine spins twice for each complete operating cycle.   

       Even though so far rear tranverse mounting seems to be best, I'm having trouble not picturing a vehicle with a wide arced hood scoop, a blur of flashing pistons inside.
FlyingToaster, Aug 09 2011

       It was 8th who used the phrase "talking shit", to which I took exception.   

       Perhaps a barrel rotary (a variant of the swashplate engine concept) such as the Macomber (see link) would be better suited to the original proposal.
Twizz, Aug 09 2011

       "Effecient", from" faecies", i.e. "that which stimulates or promotes the production of faecies", as derived from the Latin…   

       Hence the double quotes … it's called a 'pun', or play on words…
8th of 7, Aug 09 2011

       //Macomber// Hmm... how would you hook that up ?
FlyingToaster, Aug 09 2011

       Easy, the driveshaft comes straight off the back of the swashplate.
8th of 7, Aug 09 2011

       as a flywheel   

       and "effecient" would more properly stem from "effect"(verb).
FlyingToaster, Aug 09 2011

       The Macomber engine is described in the Wiki page on swashplate engines.   

       Any pun that requires explanation wasn't worth it. Or perhaps I'm being facetious.
Twizz, Aug 09 2011

       Maybe you are, but that's still better than being "ineffecient"   

       (Note: presence of double quotes indicates location of poor-quality attempt at pun, requiring explanation).
8th of 7, Aug 09 2011

       //       run out of cherry sherry? //   

       Nope, I was granted a 36-hour pass from my keyboard so I can shave, shower, say hello to my wife, and log onto HB. My Kijafa will be topped up and waiting upon my return, fear not.
Alterother, Aug 09 2011

       //        engine mounted in a horizontal plane and allowed say 10-15 degrees of movement each way ... Off- roading might be a no-go or at least interesting. //      

       For off-roading applications, I reckon a mid-engine, parallel-vertical oriented rotary might fit the bill, especially as it won't be operating at higher rpm for extended periods. Dunno how you'd build the drivetrain, though.
Alterother, Aug 09 2011

       Yeah well I always wondered when to use single vs. double quotes. I still do.   

Let's see... valvetrain components (and ignition) on a barrel engine are closest together because the heads are right next to each other, as are intake and exhaust. Nice. And close to the spin axis too. Decouple the static swashplate from the frame with a simple manual clutch for freewheeling @ 1000rpm. The pistons will move around during precession, not that that's much of a concern.

       Looks clearly superior in several respects, except you might have to spin a barrel-rotary faster than a radial-rotary to store the same amount of energy... or add weight on the outside which somewhat compromises the idea of a 'free-as-in-beer flywheel'. So post it so I can try to poke holes in it :D
FlyingToaster, Aug 09 2011

       //        when to use single vs. double quotes. //   

       First of all, it depends on your nationality, becaus the Brits insist on doing it the wrong way around, like so many other things.   

       Double-quotes denote dialog. Single-quotes denote implication or alternative terminology. Single-quotes are also used inside double-quotes to denote a reference or quotation included as part of the dialog; when used in this manner, any punctuation comes _after_ the following single-quote.   

       It's really very simple.
Alterother, Aug 09 2011

       // off-roading applications, I reckon a mid-engine, parallel-vertical oriented rotary //   

       You're right, and it's baked ... an Austrian company (Steyr) knock out 4x4 and 6x6 go-anywhere amphibians, powered by centre-mounted rotaries, due to their excellent power-to-weight-and-size ratios. The high gearing means that the torque curve isn't an issue.   

       // like so many other things //   

       Like, for instance, spotting an ambush but not driving straight into it ? (Kasserine, Kasserine, Kasserine, will they never learn ?)
8th of 7, Aug 09 2011

       Caught him hook, line, and sinker. Didn't even have to wait.   

       // Like, for instance, spotting an ambush but not driving straight into it ? //   

       Would being shown photographic evidence of the presence of not one but two panzer divisions garrisoned in Arnhem and yet still dropping paratroopers with almost no anti- armor capabilities directly on top of them qualify?
Alterother, Aug 09 2011

       //Steyr...powered by centre-mounted rotaries// cite. Unless you mean 'Wankel' or 'radial'.   

       //off-roading// Retrospectively I don't imagine regenerative aka 'flywheel' mode would be useful during off-roading, at all.   

       The bit where this system doesn't compare to other hybrid systems is that the 2 modes aren't additive. Normal mode would just be 900-1200rpm with little energy storage (20kJ) or precessional effects, whereas Flywheel mode goes from there up to say 3500 rpm, with quite a bit of energy storage (160kJ), and quite a bit of precessional effects. *But* you can't use the engine to get up to 3500 rpm, it's not built to run at that speed: flywheel mode is run on braking regeneration.   

       Of course where the system compares quite smugly is that the energy storage part of it adds zero extra weight.   

       Either way, off-roading you don't want a fully loaded flywheel helping out with navigation.
FlyingToaster, Aug 09 2011

       Please do cite, because I searched for mid-mounted _rotary_ engines and found nothing. I was just too busy borg-baiting to comment on it before.
Alterother, Aug 09 2011

       <sound of tumbleweeds waiting for a rotary-engined amphibious vehicle>   

       Meanwhile, barring other complications, the 9N's intake arrangement lends itself quite well to fuel injection: wait for a hole to appear in the cylinder then pump fuel into it along with air. That would lessen the amount of lubricant lost since the crankcase would be dry of fuel.
FlyingToaster, Aug 11 2011

       [8th] is just sore that I landed and stuffed him, so he's taking the typical British approach to unexpected defeat: he's ignored it and buggered off up the pub.   

       Agreed, the flywheel would be a serious detriment, but I was taking the 'if you have to put it somewhere' approach. I figure having it straight and center with a forward-over rotation would minimize the risk of gyro effect in side-to- side bouncing. It might even help a little in slope-climbing.
Alterother, Aug 11 2011

       Pitch-axis coaxial (the vehicle goes up and downhill with no precession): spinning forwards, every time you turn, the vehicle will tilt away from the turn. Backwards on the other hand and it tilts into the turn. I'm not sure if it will actually help the vehicle grip the road better with the inboard tires.   

       Tilting it works the other way'round: forward-spinning and the machine will try to turn to run downhill when being tilted, backward-spinning and it tries to turn and run uphill.   

       Mid-mount makes the most sense for most reasons, but with a front-mount for front-spinning or a rear-mount for rear-spinning, if the engine falls off it doesn't come bouncing through the passenger compartment.   

       And people think I'm stoned because I've been staring at my thumb in various angles, trying to remember the right-hand rule, for the past few minutes.   

       //exhaust// If you look at a running Camel with its cowl off, you'd notice that the exhaust always comes out of one part of the circumference: that's where all the exhaust ports open.
FlyingToaster, Aug 11 2011

       // directly on top of them //   

       That was the RAF's fault.   

       // the typical British approach to unexpected defeat // is to find one silly bugger to do something so stupidly and breathtakingly heroic that the enemy are taken aback, thrown off balance, and ultimately defeated.   

       The problem of precession still does tend to suggest that an element of contrarotation somewhere in the design would solve a lot of problems.   

       With the cylinder bank in the centre, and two contrarotating flywheels each half the mass of the cylinders - one on each side - the forces would cancel. The directional reversal could be achieved by epicyclic gearing at the hub.   

       Power pickup could be from the circumference of one or both flywheels, or from one side of the hub from the cylinders; it doesn't really matter, as long as the epicyclic can handle the torque. Contrarotating props are Baked so the technology exists in a refined and reliable form.   

       Assume a nine cylinder air cooled 4-stroke, of say 100cc displacement per piston. That's 900cc ... d'oh ... a 900cc motorbike engine can produce anything up to 150 BHP (race tuned) but 100 - 120 BHP is not unreasonable; these units are very compact (albeit liquid cooled) and do not suffer (noticeably) from precession issues.   

       You need to get your rotary into a volume of 100 litres or less, and a mass in the 100Kg dry weight range, to get close to that.
8th of 7, Aug 11 2011

       Why not simply make your engine out of two small rotaries in counter-rotation?   

       //        That was the RAF's fault.   //   

       What, like if it went as Monty planned and they dropped the 1st slightly to the right of the 9th SS Panzer, everything would have gone off without a hitch? M-G was bad from the top down, my assimilated friend.
Alterother, Aug 11 2011

       //Single-quotes denote implication or alternative terminology.// I would very much like for that to be true. You gotta cite?
mouseposture, Aug 12 2011

       As an aspiring professional novelist, I am automatically an authority of such subjects as the proper usage of punctuation, and I take great offense, sir, at your dubiousness.   

       No, I don't have a cite. Given the wide variety of style manuals used in modern publishing, I'm almost certainly wrong according to somebody. Frankly, I use punctuation however I damn well please and leave the arguing with my editor to my wife.
Alterother, Aug 12 2011

       James Joyce would be so proud.   

       // two small rotaries //   

       Because in that case there would still be precession forces. Only by 'slicing' the contrarotating flywheel can symmetry be achieved..
8th of 7, Aug 12 2011

       //Assume a nine cylinder air cooled 4-stroke, of say 100cc displacement per piston. That's 900cc ... d'oh ... a 900cc motorbike engine can produce anything up to 150 BHP (race tuned) but 100 - 120 BHP is not unreasonable; these units are very compact (albeit liquid cooled) and do not suffer (noticeably) from precession issues. //   

       A 900cc bike motor can produce 100+ BHP by running at 7000+ RPM. Halve the speed and you pretty much halve the power.   

       If you think precession in a bike engine is insignificant, ride something with inline crank (BMW boxer, Moto Guzzi etc.)   

       Also, the bike engine has it's rotating mass kept to a minimum, which is the opposite if the intention of this idea.
Twizz, Aug 12 2011

       //'slicing'// dueling flyrods ?   

       //motorcycle engine// From what I can tell, heavy engines with a lower power rating are usually the ones which are most efficient and last the longest.   

       (At last update) the application is for a VW Beetle, so 50kW is sufficient... still trying to figure out the flow to get an Atkinson-like cycle.
FlyingToaster, Aug 12 2011

       // Halve the speed and you pretty much halve the power. //   


       Wow, amazing ! If only every other member of your species had such mental acuity and insight ...   


       // something with inline crank //   

       We had in mind the more typical transverse inline-4.   

       // the bike engine has it's rotating mass kept to a minimum //   

       For very good reasons, which you've just pointed out.   

       Possible application of the rotary: railway locomotives. They tend to make very gentle turns, so the gyroscopic forces would be much less of a problem. On non-electrified commuter lines, involving frequent starting and stopping, the energy conservation system would have many advantages.
8th of 7, Aug 12 2011

       //locomotives// I don't imagine flywheels would be incredibly useful on trains... subways/underground maybe.   

       Anyways, found the paper and pencil:
Unlike an aero-rotary, weight isn't that much of a concern, so we don't have to deal with the lossy 2stroke cycle. So a four stroke can be used which is much more efficient yet still mechanically quite simple.

       Since it's a rotary, each cylinder does its thing at exactly the same point, so all the exhaust would be going out one side of the engine along the circumference of travel and all the intake on the other.   

       A single valve on the cylinder head would be open for a full rotation for exhaust and intake, then closed for a full rotation for compression and combustion.   

       It's really tempting to use a single fuel injector mounted outside the engine: just spray into the open port as a cylinder whizzes by.   

       Along those lines, the valvetrain might be operated in the same fashion: an external simple gizmo that, as each cylinder swings by it, opens a closed valve and closes an open valve.   

       As a refinement (okay a total rewrite) of the crank clutch, simply (or "simply" as the case may be) move the crank hub in line with the crankcase hub whenever the engine enters flywheel-mode, thus keeping all the pistons centered in their cylinders.
FlyingToaster, Aug 21 2011

       Another advantage of a movable crank-hub is that it allows variable CR on the fly. Since the crank is not involved in the drivetrain, no other adjustments have to be made.   

       Did I mention that the whole thing is a fuel tank ? might as well: add to the active-weight and uncomplicate the fuel delivery system. Of course you'd have to stop it to gas up.
FlyingToaster, Aug 24 2011

       You've really got your teeth into this one, haven't you ?
8th of 7, Aug 24 2011

       A hundred years ago these things were used as aircraft engines, which is an entirely different application: weight was a big issue and fuel economy wasn't, thus the lossy 2-stroke. Constant vehicle speed also.   

       Regenerative Operation:
Current and future automobiles require a regenerative braking solution. The rotary is its own flywheel and could easily be its own hybrid: using it as a regenerative flywheel while the engine is turned-off is well within physical limits of its design, without requiring additional power storage, transfer and mixing systems.

       Pulse and Glide:
Eco-modders use a technique while highway driving: speed up the vehicle in the engine's best bsfc range, then turn the engine off and coast back to a lower speed; rinse and repeat. But with this, the flywheel can "pulse and coast" instead of the vehicle, _and_ do so not only on the highway, but during rush hour as well.

- The engine requires a CVT. Standard or Automatic won't cut it given rotational momentum (lag time while switch gears).
- It would take 4-5 seconds to start the engine from scratch (ie: from a non-spinning state).
- Precessional forces may be an issue.

       Like a piece of spinach firmly wedged between the front uppers.
FlyingToaster, Aug 24 2011

       And Gary Greenwell holds patents on using a rotary engine as a flywheel in a car, and moving the crankhub around, but the rest of the engine's way different <link>
FlyingToaster, Sep 05 2011

       I thought this was gonna be one of the various swing piston engines. I've heard a lot about them but never seen more than a few demos   

       see links
metarinka, Sep 11 2011

       //swing piston// pistons might get wedged... scotch yokes... pain to machine... could be feasible though, but development time probably pretty well nixes it.
FlyingToaster, Sep 13 2011

       I wonder why nobody bothered to equip the cylinders with a 'spit valve' for lubricant recycling: raise the exhaust valve a bit to keep castor oil from escaping that way, and slope the cylinder head into a small 'lubricant drain port which opens for a short period before the compression starts. Centripugal force should move the lubricant rather efficiently from the cylinder walls across the head and to the exit port.
FlyingToaster, Sep 20 2011

       ah got it... 2 2cyl engines, counter-rotating, vertical axis (horizontal plane), coaxial (but not joined),30-40kW ea. One connected to the front wheels, the other for the rear.   

       The good: extra engine for passing, long uphills and towing; choice of front, rear or all wheel drive on demand; all wheel regenerative braking and acceleration. Precessional effects cancelled out, Newton's reasonably happy and it should have the ability to float over potholes a bit when the flywheels are spun up :)   

       The bad: extra CVT transmission (but no transfer case); a bit of vibration when the vehicle changes pitch or roll orientation (since 2 cylinders don't form a disk).   

       The ugly: trying to get a mechanic to work on it.   

       (I'll just continue to natter on, giggling occasionally, off in the corner)
FlyingToaster, Sep 21 2011

       FlyingToaster, I just don't know this was posted, until this day. My current invention does exactly what your post had proposed. So, one big bun! My previous invention progressed in leaps and bounds with other proprietary technologies integrated into it in a much more compact and synergistic form. Anyway, one of its greatest attributes is entirely exactly what is mentioned in this idea. The package primarily consists of rotary engine and integral Infinitely Variable Transmission working hand in hand to convert its steam chambers into chambers for air compression immediately when the steam is cut off (thereby acting as regenerative brake when done). The 300hp engine-IVT combo that act as one big flywheel too can be placed inside an SUV tire complete with active suspension system and plethora of innovative systems. The regeneration/acceleration set-up, exactly described in this post, together with compressed air storage, renders the conventional brake unnecessary. With IVT, the engine is somehow decoupled, that is, only the power transmission is cut off without actually decoupling the engine as with ordinary clutch of conventional CVTs. BTW, mine is both ICE and ECE, with hybrid thermodynamic cycle: the reason why steam was mentioned.
rotary, Aug 30 2012

       You really need to get out more ;D   

       so post your idea including paragraph breaks; I can share.   

       The major difference between my idea and Greenwell's (link entitled "darn") is that I see IC and flywheel operations as being separate, whereas he has them running concurrently. Mine's better of course :) since there's no moving IC parts to be stressed when it's being a flywheel. Also he has it as an inside-out rotary (cylinders on the inside, pistons on the outside). A bit of research turned up that he had a model built as a variable displacement hydraulic pump.   

       The main question of course is whether a rotary engine could be built at all these days.   

       After that, making it into a mono-hybrid, while totally brilliant if I do say so myself :) is a cinch.
FlyingToaster, Aug 31 2012

       Oh, you messed your original post, FlyingToaster, like a charred toasted bread! Anyway, in my first annotation I am not referring to rotary piston engines but to rotaries as a whole, specifically my rotary cam engine.   

       The primary function of my IVT is to regulate the alternate air-compressor function of the engine to modulate the regenerative brake system all the way to extreme abrupt stop the components may be able to tolerate. Due to its extreme lightweight construction, I relegate the flywheel regenerative braking/acceleration as secondary, although this engine-IVT combo is high-reving, thus with significant rotational momentum.
rotary, Sep 04 2012

       I just thought I'd leave you thinkin'room for your design which, I imagine, declutches the entire engine from the frame with a clutch, allowing it to spin freely as a flywheel(?)
FlyingToaster, Sep 04 2012

       No, it has IVT which normally operates without clutch when in neutral position, akin to the IVT Paul Pires of Epilogics has conceived. Mine is a gearless IVT integral to the rotary engine, at its side, consisting of lever mechanisms and modulator which are purely mechanical.   

       The concentric positioning of the eccentric modulator would translate into zero movement, but approaching it from eccentric position is likened to applying brake to a spinning wheel which is clearly opposite to the effect of a clutch decoupling the engine from a rigid frame. It's somewhat like how engine braking operates whereby the driver will quickly engage the lowest gear ratio from a much higher ratio.   

       So, in principle, the momentum of the car would be translated to higher engine rpm when shifting to lower ratios, especially near the neutral position, whereby the engine will now temporarily function as air compressor and flywheel energy-storage device to effectively slow or stop the vehicle than with flywheel effect only.
rotary, Sep 04 2012

       BTW, the engine is rotationally fastened to the wheels (not discounting the suspension system that allows its translational movement) and not to the car frame. The component that the flywheel effect and rpm are based is the inner rotor.   

       So, while the engine frame can be held stationary the inner rotor would rev it to a certain engine rpm. And, what normally would be an output shaft from the transmission is fastened to the car frame.
rotary, Sep 04 2012


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