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preface: I know very little about cars, transmission etc. so I won't be surprised if this is baked or un-bakeable.
I'm thinking this might be a good way to get the most out a really small engine (for motor scooters etc).
This way your motor can be constantly operating at optimum speed (even in
stop-start traffic).
Also one (or both) of the CVTs could act as a clutch, by disengaging the (grey) transmission wheels.
flywheel between 2 CVTs
http://imgur.com/a/oyop3
illustration [xaviergisz, Jun 15 2006, last modified Dec 13 2011]
Toroidal CVT
http://auto.howstuffworks.com/cvt1.htm
[BJS, Jun 15 2006, last modified Jun 16 2006]
(?) Torotrak IVT
http://www.torotrak.com/IVT/works/
I think you should look at this site. [BJS, Jun 15 2006]
Flywheel_20Hybrid
similar idea by [Stephen92082] [xaviergisz, Jul 21 2006]
yaw, pitch and roll
http://en.wikipedia...w%2C_pitch_and_roll
see illustration to make more sense of what I'm rambling about. [xaviergisz, Aug 05 2006]
bike hub with two motors
[xaviergisz, Aug 07 2011]
Hayes Auto Transmission
http://www.austinme...age139/page139.html
scroll to the illustrations halfway down the page [xaviergisz, Jan 02 2013]
Friction globoid variator 2
https://www.youtube...watch?v=RI7lQuxPOl4
[xaviergisz, Aug 18 2020]
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[BJS], its symmetrical so it doesn't matter... see illustration. |
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as heavy (or better still - with the highest rotational inertia) as possible. |
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Could you clarify what it is about this idea that is an improvement over a conventional CVT? More flywheel mass means more energy to spin it up. Thats one of the benefits of a CVT is that you can take full advantage of all available torque without needing heavy flywheel. |
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Sorry, I don't really understand. Can you expand a bit? |
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I think the idea is to run a small engine at constant speed, and use the flywheel to take out the peaks and troughs in energy usage - i.e. the flywheel assists the engine in acceleration and stores it during braking. The two CVTs take care of the speed differential between the wheels, flywheel and engine. Not sure of the efficiency, but I like the concept. [+] |
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Thanks [david_scothern], couldn't have put it better myself. |
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[BJS], its bad form to delete annos, even if you think they were unnecessary in retrospect - it breaks the flow of the annotations and makes the responder look silly. (his questions were: 1) which end connects to the engine and which end to wheels 2) do you want the flywheel to be heavy or light). |
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[xaviergisz], you looked silly before you annoed :-) |
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You could just modify your original idea to include the answers to the questions I asked. That way people wouldn't have to ask them... |
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would not a single flywheel mounted on the output shaft of the engine(the conventional arrangement)with a single CVT attached, serve the exact same purpose? |
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good question [jhomrighaus]. The first CVT mainly acts to smoothly accelerate the flywheel from stationary to fast spinning (the second CVT to tranfer energy from flywheel to vehicle wheels). |
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**edit** the first CVT also allows the flywheel to be rotated faster than the optimal engine speed (for example when going down hill or while temporarily stopped at the traffic lights (obviously while disengaging the second CVT)). |
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I don't know what applications this would be useful/necessary (I'm still thinking scooters since they need to start/stop regularly). |
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It may also be useful for turbine engine vehicles that have only a small window of RPM efficiency. |
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Sounds like you are using mechanical storage to do what the toyota prius does with its power split device. |
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I thought turbine engines were efficient throughout their rpm range. |
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Turbines are fairly efficient through thier RPM range, which is really really huge which means for most applications they either a) do not need a transmission to change gears(ie just to transmit power, speed controlled by RPMs, Jay leno has bike like this) or b) they are run at optimal speed and power is drawn off to run transmission(like helicopters) |
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OK, maybe its not accurate to say //turbine engine vehicles that have only a small window of RPM efficiency// |
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But the essence of what I'm saying is from wikipedia on turbines:
//Gas turbines offer a high-powered engine in a very small and light package. However, they are not as responsive and efficient as small piston engines over the wide range of RPMs and powers needed in vehicle applications// |
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[Galbinus_Caeli], yep thats exactly it. The flywheel has a large moment of inertia relative to the engine capacity and is thus used to store energy rather than just smooth engine output. |
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Storing energy in the same form that it is being used in is much more efficient than converting it to a different form (and then back again). |
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OK, I've got a variation to the invention. I've replaced the first CVT and flywheel with a speed governor flywheel (see first link for illustrations). This should have the same effect of the original device with the improvement that it's passive (ie doesn't require the CVT control mechanisms). |
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This way the (stationary) flywheel doesn't present a impediment to the engine. |
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It seems to me that the idea in its original form would work best. For a cold start (flywheel stationary) the engine-flywheel CVT would be geared as low as possible and the flywheel-road wheel CVT geared up as necessary. Once less power is needed, the engine-flywheel CVT would progressively gear up to spin the flywheel faster. The problem I see with the second version is that as the engine gets into its high-power RPM range the flywheel would start to suck up energy when you want it to be going to the road wheel. |
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Also, you want to be able to rotate the flywheel very fast (much faster than the engine) to give high energy density, so the first CVT should stay. |
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[BJS], [xaviergist], I prefer the original idea to remain unchanged and the annotations to tell the story of its development in halfbakery land. de gustibus non est disputandum. (+) |
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I agree [spidermother], my speed governor version of the idea is not as good as the original. |
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I have another variation on this idea (in the first link). I have added a "dual counter rotating, gimbal mounted flywheel" that [Stephen92082] says would be necessary (in his idea "flywheel hybrid"). I'm not sure if the axis on which the gimbal turns is what [Stephen92082] had in mind. |
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The new picture in link is kind of hard to follow. basically, the counter rotating flywheels (blue) and cvt wheels (grey) are mounted on gimbals (brown rings). To change the gear ratio, orange rings are pushed in or pulled out (hence the double headed black arrows) which pivots the cvt wheels (grey). The purple and red things are the input and output. |
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Regarding the double CVT double flywheel gimbal, firstly, very inventive design. However, let us consider the 3 conventional rotational axes: |
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1) Roll. Except when the flywheels are coasting (neither powering nor being powered), there will be a net torque on the gimbal, causing it to rotate undesirably. |
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2) Pitch. Since this is in the same direction as the flywheels' rotation, this will cause a trivial change in angular momentum. |
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3) Yaw. There appears to be no freedom of movement in this direction, as the CVTs would move out of correct alignment. |
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OK, I have an addition to the variation I posted on 21 July (see a few annos up). I've added the pictures to the first link. |
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Basically the problem with the gimbal mounting in previous incarnation of idea is that it only allows for rotation in the roll and yaw. When mounted in a car (on the axis I have in mind), this would allow the car to turn and bank without resistance from the flywheels. However changing inclination (pitch) of the car would put strain on the flywheels. So I've added a mechanism that also allows for rotation in the pitch direction. |
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Explantion of mechanism:
The brown rings of previous illustrations are attached (by a rotatable collar - not shown) to the brown pins - this allows the entire mechanism to rotate in pitch. |
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So how does the energy get transferred into and out of the double CVT with flywheels? Well, I'm glad you asked. |
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The purple and red input/output of previous illustrations are attached and thus almost completely enclosed by the purple and red hemispheres in the new illustrations. This allows the rotational energy input from the green wheel to be output through the aqua wheel (while still allowing pitch rotation). |
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Unlike the 'roll' gimbal which allows full 360 degree rotation, this added 'pitch' gimbal limits rotation to slightly less than 90 degrees. So although this allows limited movement in the pitch direction, it must be 'biased' into its default position shown (with the use of springs for example - not shown) so it doesn't come 'unstuck'. |
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As the purple and red hemispheres rotate (changing pitch), they are essentially changing gearing with the green and aqua wheels. However this is easily compensate for by the CVTs already in the system (being cleverly controlled by onboard computers). |
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Hopefully this makes sense to someone out there. |
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Likey [+]: you've captured the essence of an energy storage/release system that is smooth at both ends. I assume the engine operates without an integral flywheel. |
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But the weight ! CVT transmissions weigh more than automatics (which weigh more than standards), and you have two of them... plus a flywheel(s). |
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How efficient are CVT's across the ratio spread ? |
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A 200kg scooter @ 60kph has ~ 55kJ KE.
A 20kg flywheel, 30cm in diameter running @ 7,000 rpm holds about 60kJ RE. |
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Have you considered running with a simple(ish) clutch on the engine side instead of a CVT ? The flywheel could be kept at 1:1 speed with the engine within its most economical rpm range, then the engine disconnected when the regen kicks in and spins the flywheel way up. |
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ps: the technical term for a flywheel that tries to run in two axes is "the thing that made the hole in that wall" [edit: hang on there...] |
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I really miss my 2CV......best car ever made. I was always very impressed by the advertising that highlighted its "unburstable engine". |
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I take it the illustration for this post would be #5 ? with #3 being an option which doesn't transmit precessional forces to the vehicle. |
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I think [spidermother]'s right about the gimballed one #4. Can't wait to hear what #6&7 is all about. |
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Most of these deserve their own post. |
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I made it confusing by throwing all my illustrations into a single link. |
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The basic idea is in illustration #5. Illustration #3 is an intermediate step in the gimbaled version (illustration #4) of the idea. |
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Illustrations #6 and #7 are an addition to the idea of #4. The intention being to gimbal the apparatus in a third plane of rotation (see my anno of 5 August 2006). |
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My idea "bike hub with two motors" is similar to this idea (if you imagine the light purple ring cog of the illustration in that idea is a flywheel). |
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Contrary to [sm]'s evaluation of #4, I'd suggest a transverse mount of the driveline (pitch axis), with the flywheels on a vertical (yaw) axis. This would allow vehicle turns with no movement of the gimbal and up/downhill by letting the gimbal move itself back and forth a bit. The problem would be a road tilted to one side or the other (roll). |
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Comparing #3(&4) to #5 I do like how you've managed to place the cones such that you get the best contact area and no longitudinal forces on the transfer-disks (is that original ?). |
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I'm taking a break on #6/7 for a bit; it makes my brain hurt. |
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Have you considered dropping the flywheel-in-the-middle idea and making the CVT cones into flywheels ? |
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