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Flywheel Hybrid

Flywheel? - Can you say CVT?
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(+6, -2)
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I have always wondered about the logic of converting rotational energy to DC to charge batteries, only to bring it back to rotational energy. A direct drive flywheel eliminates all that mucking around.

But, solidly bolt a "500 HP minute" flywheel into your car. Come back 12 hours later, and the car is upside down!

Any flywheel with significant power must be a dual counter rotating, gimbal mounted flywheel. The gimbals can, and should have, a lot of drag. (The drag should be low enough to avoid "exciting" moments cresting a hill, or going around a corner)

Getting power from a directly connected flywheel to the tires, requires one or more CVTs with a planetary gear for neutral and reverse.

Use the flywheel like a conventional engine, one CVT would work. However, I like the replacing the differential(s) and ABS systems with 4 CVT's, one to each tire. I would still use brakes, but they would be much smaller than "normal", allowing regenerative braking to consume much of the power.

Four CVT's would also allow traction control by slowing tires as required.

The engine part of the hybrid would be much lighter, not needing a starter or flywheel. A magnetic clutch that ties the flywheel to engine would start it, and provide plenty of flywheel.

The engine should be big enough to provide the average required power, but that is much less than the peak power required to climb a hill, or pass a slower driver. A compact car should need 10 to 20 HP. Run this on natural gas or alcohol to be green.

On the fun part of things, a direct drive flywheel (in contrast to the flywheel to DC volts) would make the quarter mile really exciting. I figured 500 HP minutes would allow driving up our local foothills. Of course, if you dump all that energy in 10 seconds.... (I love the idea of stomping a Dodge Viper in a "green" car)

My flywheel of choice is made of carbon fibers (fibers disintigrate on failure), in a vacuum (to lower losses), surrounded by fluid to dump the energy.

When buckey tubes (carbon fibers on steroids) are economically viable, flywheels speeds (energy) will step up significantly. I see no equivalent increase in batteries.

Now we need a really efficient CVT.

Stephen92082, Jul 20 2006

flywheel_20between_202_20CVTs You seem to know far more about flywheels and CVTs than me, but here's my attempt at something similar. [xaviergisz, Jul 20 2006]

has energy densities for some materials http://zebu.uoregon...2001/ph162/l10.html
[jmvw, Jul 21 2006]

Flywheel buses http://ate.sitewave...rchive/s76a3683.htm
A few notes on existing flywheel buses [neutrinos_shadow, Jul 26 2006]

(?) Torotrak press release http://www.torotrak...y+recovery+syst.htm
(As linked to by halfawakery.) [jutta, Jun 12 2007]


       Hang on. It's been a long while since I studied gyros, but I think that, "Come back 12 hours later, and the car is facing the other way" would be more correct; it will precess at 90 degrees to the applied rotation.   

       Further to that, I highly doubt you'd get a CVT to react quickly and reliably enough to act as an ABS system. Better to stick with differentials - they're simple and cheap - and have 2 CVTs, one for each axle.
david_scothern, Jul 20 2006

       Stupid Question: What's a CVT?
zen_tom, Jul 20 2006

       CVT, continuously variable transmission.   

       You may be right on precession. It has been a long time for me as well.   

       I expect the reaction time of a CVT is in number of revolutions. A 60,000 RPM flywheel needs a 60:1 gear reduction. Connect the CVT directly to the flywheel reduces reaction time (and torque) by 60 compared to a CVT connected directly the wheels. 60:1 could be done in 2 steps, with the CVT in between where the RPM is low enough to balance friction losses and torque.   

       As far as reliability, one CVT per tire would allow use the CVT's off the Insight, with a reliability track record.   

       Thanks for the feedback.
Stephen92082, Jul 20 2006

       ...I see. The Insight already uses twin CVTs for this purpose? I can see the logic of extending this approach, in that case. Unless the Honda's using its CVTs for ABS though, I remain skeptical on that bit.
david_scothern, Jul 20 2006

       //flywheels speeds (energy) will step up //   

       Flywheel speed increases may or may not mean an increase in 'energy'.   

       //I see no equivalent increase in batteries//   

       You aren't looking hard enough then.   

       //Any flywheel with significant power must be a dual counter rotating, gimbal mounted flywheel//   

       Nonsense, the most powerful are simply rotated at a slight angle - it's a simple calculation.   

       [marked-for-deletion] bad science
ConsulFlaminicus, Jul 20 2006

       This is very cool and even a steel flywheel would be able to store your 22.38 kJ, but your vehicle will not do so well in traffic when going up a long hill, let alone climb a mountain.   

       We need to replace the human driver with cars that drive themselves. A 20 hp car would be fine, even without flywheels, if everyone used one: if you can take both the egos and the slow drivers out. Weight based road tax would help too, it would help to get all the needlessly heavy bulk off the road that puts efficient cars at risk.
jmvw, Jul 20 2006

       They had a fully functional hybrid car test driven in Scientific American... like a decade ago.
ye_river_xiv, Jul 20 2006

       [Consul], that's awfully harsh. I don't see any bad science in here at all. An increase in flywheel speed, given the mass and dimsensions of the flywheel remain constant, will see an increase in energy. Since mass and size are easy to control, but the strength limits of materials are not, stating that advanced materials will allow increased speeds and thus increased energy is an oversimplification of the situation, but hardly bad science.   

       Lack of confidence in emerging battery technology can't be bad science--since the batteries don't exist yet, [Stephen]'s predictions can't be false (yet).   

       Belief that a powerful flywheel must be counterrotating and gimbal mounted to be controllable--maybe false, but I don't know any different (though I have doubts about the gimbals--I think counterrotating should be sufficient to balance the forces). You should explain your "simple calculation", and in particular explain what "rotated at a slight angle" means, because I can't tell. Slight angle relative to what? How does this eliminate gyroscopic forces? Can this be as easily accomplished, mechanically, as counterrotating wheels on gimbals?   

       No bad science here, inasmuch as nothing here is physically impossible or even implausible AFAICT.   

       For myself, I'd just like to mention I once read about a bicycle drag-racing competition in which the "unlimited" class allowed the use of flywheel assitance for faster starts.
5th Earth, Jul 20 2006

       Thanks for the feedback. Some clarifications and comments:   

       A flywheel at a slight angle works if the flywheel is stationary, and the angle allows the flywheel to rotate in parallel with the earths axis. That doesn't apply in a car unless you are storing very little energy.   

       As best I can tell carbon nanotubes are about 11 times stronger than carbon fiber, allowing 11 times the energy storage for the same flywheel weight. (3.3 times the RPM, E=MV^2, 3.3^2 ~ 11) The containment vessel would be heavier, or made of carbon nanotube.   

       Lithium ion batteries are pretty refined. I am not aware of any chemistry that will increase their energy density 11 times. The new lithium ion batteries for power tool only have half the energy density of your cell phone battery - that is the penalty for high discharge rates.   

       I calculate 500HP minutes as 22.38 Mj instead of 22.38Kj. Did I miscalculate?   

       Counter rotating flywheels doesn't eliminate the forces, just the tendancy for the gimbal to spin in the opposite direction.   

Stephen92082, Jul 21 2006

       Stephen, sorry, your calculation is correct.   

       1 hp = 746 W = 746 J/s
1 hp min = 746 J 60 s/s = 44760 J
500 * 44760 J = 22.38 MJ

       This is 6.22 kWh. I found a link with some energy densities for flywheels. Unless I made another miscalculation, a carbon fiber flywheel would weigh 31.1 kg. Doesn't seem too bad.
jmvw, Jul 21 2006

       Would it be possible to have something engage the gimbals at a certain orientation to leverage the gyroscopic force to assist with things like correcting body roll while cornering?   

       Actually now that I think of it. Wouldn't it also be possible to manipulate the gimbals to transfer inertia into or out of the flywheel while cornering? Transfer engergy out of the flywheel to assist in rotating the car when the tires can't handle it. Transfer energy into the flywheel when the tires are rotating the car.
gordy, Jul 26 2006

       There are a few instances of flywheel driven buses (see link for an example) about the place. Most seem to use flwheel -> generator -> motor -> wheels rather than the more direct flywheel -> wheels route, but with the use of a CVT, the varying speed of the wheels relative to the flywheel can be overcome, removing the extra weight and complexity of motors etc.
neutrinos_shadow, Jul 26 2006

       I have been playing with this for a long time, but in the interest of clarity skipped the idea of using the flywheel to offset body roll, etc. I hadn't thought of using it to augment turning, great idea! Taken to extreme, it would make for an interesting "drifting" competition.   

       Most flywheel implementations I have seen use it as a battery (no CVT, no gimbaled mount). I have designed UPS's - the losses from multiple conversions drives me nuts.   

       I stand corrected on battery technology - there is some really exotic stuff out there. But, I still like the rush of dumping 500 HP minutes in 10 seconds – hard on the CVT’s, but really hard on batteries.
Stephen92082, Aug 03 2006

       I think it can work with cheaper flywheels - no need for fancy materials, vacuum or high rpm. All the energy it needs to store should be just enough to accelerate the car to its top speed.   

       Then run the engine in shorter cycles. ----   

       There are some patents/companies that intend to make an CVT based on gyros and precession forces. That might be developed further to provide both energy storage and variable transmission within the same device.   

       See http://gyrotorque.com http://www.gyroenergy.co.nz   

       There is also a simple exercise device (one moving part) that transfers hand movements to a high speed flywheel - the Powerball gyro.
blimpyway, May 12 2007

       The flywheel won't turn the car around if you've parked the car oriented east-west.   

       Unless the flywheel is mounted horizontally, in which case when you get back to it the car will be on its side.   

       Those had better be some pretty impressive bearings.
elhigh, May 14 2007

       If you mount two counter-rotating flywheels then your car doesn't turn round or flip over due to gyro effects, because they cancel out - you might get some pretty large forces in the bearings on the flywheel if you try to change the axis rapidly though. If you want to minimize forces on the flywheel bearings, mount the pair in gimbals and allow the axis to point where it will - the flywheel assembly then occupies a sperical space, which isn't very friendly to the vehicle layout. It also makes for interesting mechanical connections for getting power in and out (even electrical connections would be interesting in such a system).   

       If you want to maximize the use of the space in the sphere, you could (if you were daft enough) put a whole lot of flywheels of different diameters (running at appropriate different speeds) all sharing a common axis.   

       For a suitable CVT, see http://www.torotrak.com/
Cosh i Pi, May 14 2007

       I think this being the *half*bakery, ideas that are implausable or unfeasable should be allowed as long as they are not impossible. Even then, without the odd exception, we'd have lost gems like the hullaballoon.   

       ConsulFlamicus, the idea seems to have offended you (perhaps you work with batteries), but I don't think you've offered any real proof or motivation of bad science here. Please remember that the bad science tag is for 'scientific "facts" that are known to be wrong' not just poorly applied but valid science (not that I'm saying that's what this idea is either).   

       In general, being promiscous with m-f-d tags, or adding them in anger, or applying them for personal reasons makes works for the moderators, all of whom are already very busy people.
yamahito, Jun 08 2007

       Busy? So that's why we never see them laying down the smack on people any more?
david_scothern, Jun 09 2007

       sorry guys but this one's no longer half-baked. See recent Torotrak news release: http://tinyurl.com/36582q   

       "05.06.07 - Torotrak and Xtrac expertise will help F1 teams develop new kinetic energy recovery system Torotrak and Xtrac transmission expertise will help F1 teams develop new, highly efficient, mechanical kinetic energy recovery systems ... technology also applicable to road cars   

       5 June 2007   

       Toroidal traction drive specialist Torotrak plc and vehicle transmission design and manufacturing company Xtrac Ltd are pleased to announce that on 4 June 2007 they entered into a licence agreement to enable Xtrac to develop highly efficient and compact continuously variable transmissions (CVTs) for use in the new kinetic energy recovery systems (KERS) proposed for Formula One ("F1") motor racing.   

       In 2009, F1 is introducing new rules that will lower the environmental impact of the sport. Part of this is to recover deceleration energy that can be stored for acceleration. Xtrac will exploit Torotrak's full-toroidal traction drive technology for use in kinetic energy recovery systems within the motorsport industry, to assist its customers in meeting these new obligations." [...] "The innovative combination of a Torotrak variator - providing mechanical efficiency that should be in excess of 90 per cent - with a flywheel of advanced construction, results in a highly efficient and compact energy storage system. Whilst Xtrac will supply variator units to its customers, the flywheels for these energy recovery systems are being developed separately by the Formula 1 teams themselves and their specialist suppliers. Torotrak will provide the control system expertise.   

       Torotrak and Xtrac believe that the variator-flywheel solution provides a significantly more compact, efficient, lighter and environmentally-friendly solution than the traditional alternative of electrical-battery systems."
halfawakery, Jun 12 2007

       Further thought - not sure if it's actually a separate half-baked idea but maybe someone here will be able to comment.   

       I see from the F1 rules ( http://tinyurl.com/2a7u4t ) para 5.2 describing the KERS that it's very limited in scope. A Formula 1 car will have far more braking power available than it's allowed to reuse under these rules, however that's unlikely to be the case for a road car.   

       Does anybody here know the PowerBall? It's a small hand-held gyroscope, that you can spin up to high speed by suitable wrist rotations. As far as I can tell, it works by forcing the precession energy back into the rotation of the wheel (don't ask me how this works, but that's exactly how it feels to use). I wonder therefore whether a road-going car could use the same principle ie using precession force generated by cornering (or bounce/rebound depending on the flywheel orientation?) to add power to the flywheel at no cost. This would supplement the recovered braking energy.
halfawakery, Jun 12 2007

       Why not kill three birds with one stone.   

       1. Spherical geodesic rotor with 20 magnets. (bowling ball size 8 1/2" diameter) 2. x and y axis stator for generating and receiving energy. 3. High frequency dynamo can be self stabalizing by magnetically controlling its precission. (500khz) 4. Vacuum sealed in a battery shaped box 5. Gyro Stabalzer for ship or car mounting using electronic dampers like the bose suspension system to contain and generate energy from the inertial forces and movement.   

       Portable 20Kwh intelligent motor / generator / battery / stabalizer.
Shapharian, Sep 12 2007


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