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Self-Decoupling Dual Mass Flywheel

For Better Response at High RPM
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Flywheels are essentially a rotating mass most commonly used to smooth out the pulses of a piston engine. Car engines have them, usually a few kg worth on the end of the crankshaft. In practice, they smooth out the power pulses from the engine to reduce shock loads on the transmission in addition to adding to the total rotational momentum of the engine at low RPM. This gives a little bit of leeway when engaging the clutch, a slight mismatch between engine output and clutch friction can be drawn from energy stored in the flywheel.

At high RPM this is much less important, the power pulses are much closer together, the rotational momentum of the engine without the flywheel starts to become significant in its own right and the power output meets or exceeds the energy demands of accelerating up the drive-train. At this point, a heavy flywheel becomes a liability. At high RPM the engine has far more energy stored in the flywheel than it needs and RPM changes become difficult. For this reason, racing engines have much lighter flywheels. This destroys much of the low RPM benefits needed in regular driving however.

The solution. A two part flywheel. Closest to the engine, mounted to the crank is the driven flywheel #1. This contains weights on radial tracks held close to the center by springs. As the rotation speed increases the weights are driven centrifugally outward moving levers. Through significant mechanical advantage the levers retract pads, similar to brake pads, into the flywheel, so that they no longer contact flywheel #2. The second flywheel, mounted in front of the first is not driven by the crank. It is bearing- mounted and now may spin freely. As the engine speed falls again, the weights move inward and the pads emerge a small distance from the face of flywheel #1 where they contact flywheel #2 and accelerate it up to engine speed.

This engine will perform like one with a heavy flywheel at low RPM and an engine with a light flywheel at high RPM. Smooth low speed driving and good throttle response at high speeds. I'm aware that dual mass flywheels already exist, however these are radially coupled by springs. The dual masses cannot decouple. The second sprung mass functions to dampen torque oscillations. This idea is essentially a second flywheel actuated by a reverse- centrifugal clutch.

bs0u0155, May 11 2016

Obviously inspired by Self-geared_20flywheel
[bs0u0155, May 11 2016]

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       // As the engine speed falls again, the weights move inward and the pads emerge a small distance from the face of flywheel #1 where they contact flywheel #2 and accelerate it up to engine speed. //   

       That's going to release as lot of heat, wasting energy.   

       Also, as the engine slows, the second flywheel starts to engage, increasing drag and slowing the engine further, thus inducing the second flywheel to engage more. Hard to avoid a "snatch" effect on slowing down. The rate of re-engagement would need to be damped (slower reconnection, hence more slippage, more wear, more energy wasted as frictional heating).   

       Some sort of viscous coupling ?
8th of 7, May 11 2016
  

       Or a magnetic coupling perhaps. Potentially yields the option for selectable coupling/decoupling and limiting torque.
Custardguts, May 11 2016
  

       //that's going to release as lot of heat, wasting energy.//   

       Hmm, this isn't like the brakes, we're talking a few kg which is free to spin up.   

       //as the engine slows, the second flywheel starts to engage, increasing drag and slowing the engine further, thus inducing the second flywheel to engage more. Hard to avoid a "snatch" effect on slowing down.//   

       This would be true if the second flywheel was a fixed object. It isn't though. As the engine speed slows, and the first flywheel engages the second, the second begins to move, the differential speed between them decreases and therefore the first flywheel experiences less torque.   

       Put a manual transmission in neutral, then dump the clutch. There's a tiny change in engine note, but it equalizes quickly. The second half of the clutch and the input shafts of the gearbox are in the kind of mass territory I'm talking about... Similarly, the synchromesh in such gearboxes happily uses friction to match a few kg of differentially spinning metal all the time, with minimal heat or wear.... So, beefier than a synchro, much less beefy than the clutch.
bs0u0155, May 12 2016
  

       // The second flywheel can also be engaged at high RPM to drop engine speed faster between gear changes//   

       And the beauty of this is that as you lose rpm in anticipation of a gear change you GAIN rotational momentum which translates to free torque when you engage the next gear. The beauty of that is that it works when you are changing up or down (provided there's braking).   

       In fact, there's no reason you cant have more nested flywheels. You could have 2-3 nested flywheels which engage/disengage at strategic points in the rev range where gear changes normally happen.
bs0u0155, May 12 2016
  

       // the differential speed between them decreases and therefore the first flywheel experiences less torque. //   

       But in your design, the amount of brake pad pressure is only proportional to the rotation of the primary flywheel. Once the "clutch" starts to bite, any further slowing makes it bite harder, irrespective of the relative speed of the driven plate.
8th of 7, May 12 2016
  

       It seems to me that if the first flywheel physically moves part of its mass away from the axle, then that increases the average moment-arm of each radial section of the flywheel, somewhat counteracting the attempt to disengage the second flywheel.
Vernon, May 12 2016
  

       Forget the mechanical centrifugal clutch. What you need here is a ferrofluidic clutch.
RayfordSteele, May 12 2016
  

       I like the nested flywheels.   

       There's an effect (can't remember what it's called) where it takes a bit of time for a magnetic field to establish a "full lock", so if the relative rotational speed of a flywheel is vastly different than the one next to it, it won't drag as much. (Or vague blather to that effect.) So the system might not require calculated shift points at all.
FlyingToaster, May 12 2016
  

       // vague blather to that effect //   

       If there's no conductive path to remove the energy, you're going to generate eddy currents, and a lot of heat. If the permanent magnets get heated above their Curie point, they'll lose their magnetism.
8th of 7, May 12 2016
  
      
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