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Motorcycle Flywheel Sidecar

More room and less tilt
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Using a large flywheel (and an associated motor/generator electrical system) to power an ordinary automobile is old news, even if it never entered the mass market. The problem is that the average automaker seems to think that a flywheel car needs to have the same range as a gas-engine car. But that is not necessarily true if the car is intended mostly for commuters and other short transits.

Well, the main reason that a flywheel car can't have the range of an average car is because the average car is a pretty massive object, often between 1 and 2 metric tonnes. The more massive the car, the more energy it sucks from a flywheel during acceleration.

Note that designed-for-commutes cars are typically fairly lightweight, and thus a good match for flywheel-power. But we can do even better than that! Motorcycles are much less massive than even commuter cars!

However, putting a flywheel on a motorcycle is problematic --beginning with the fact that a flywheel is a wide object while a motorcycle is a narrow object. The flywheel needs to be oriented so it's disk is horizontal, not vertical, because of gyroscopic effects that will be very annoying whenever the cyclist wants to drive around a curve --even a long gentle curve. And even a horizontal mounting is not so good on a motorcycle, since the cyclist typically leans the vehicle when following **any** curve.

So, this is why we associate the flywheel with a motorcycle side-car. It provides the width-space to hold the flywheel, and, because the overall vehicle has three wheels, it does **not** always lean when following curves in the road. There may even still be space for a passenger, in the side-car. And the range of the vehicle will be very nice.

Vernon, Apr 09 2012

Prior art. http://en.wikipedia.org/wiki/Gyrocar
[2 fries shy of a happy meal, Apr 09 2012]

Inspiration strikes TwinFlywheel
Thanks, [MB] and [8th]. [Vernon, Apr 09 2012]

A vector diagram http://i.imgur.com/294hs.jpg
A vector diagram of counter-rotating flywheels. Confirms what FlyingToater said. [xaviergisz, Apr 11 2012]

Precession http://geophysics.o.../precess/index.html
Tau = L x F [xaviergisz, Apr 11 2012]

[link]






       If you have two flywheels, mounted side by side on a horizontal axis but spinning in opposite directions, does their gyroscopy cancel out?
MaxwellBuchanan, Apr 09 2012
  

       Almost. But ...   

       ... there will be enormous forces set up between the two flywheels; that axle had better be a strong one ....   

       A motor capable of spinning up two huge heavy flywheels is gong to be pretty heavy unless by some cunning means it's integrated into the hub.
8th of 7, Apr 09 2012
  

       The simplest way to produce balanced flywheels is to have three in a row, two at half the weight to the exterior, and one at full weight in the interior. If they're all spun up to the same speed with the outer two in the opposite direction from the center, they produce no net precession. Since this cancels out any forces, they can be separated a bit from each other, allowing for a heavy shaft and bearings between them.
MechE, Apr 09 2012
  

       // heavy shaft and bearings //   

       Doesn't need to be heavy - just strong ...
8th of 7, Apr 09 2012
  

       // by some cunning means //   

       Chain or shaft run from the final drive. Spins up the flywheel as you work through the gears.
Alterother, Apr 09 2012
  

       // by some cunning means //
A resonant ballance rod near the center of the hub tunes its frequency to a tempo miniscule-y faster than the rpm's of the flywheel itself every time the vehicle sits idle to add impetus. Braking energy and gearing down while descending hills could be recaptured.
If the entire vehicle raised as it came to a complete stop then the lowering weight of the vehicle could be used to attian initial speed before the flywheel even engaged turning the negative,
//average car is a pretty massive object//
,into a positive.
  

       ...   

       I'll be here all week,
tip your server.
  

       //does their gyroscopy cancel out// I don't think so: precession would cancel, but it's going to be just as difficult to reorient them as it always is.
FlyingToaster, Apr 09 2012
  

       ^ I second this. The direction of the rotation will change the gyroscopic effect at all.
WcW, Apr 10 2012
  

       My sidecar rigs burns about 20% more fuel than the motorcyle did before the addition of the car. Will this invention give more than a 20% savings in fuel?
cudgel, Apr 10 2012
  

       [cudgel], how efficiently does a motorcycle engine convert fuel into energy-of-motion? 25%? 30%? Modern electric-power plants can manage about a 50% efficiency of conversion of fuel into electrical energy. And a flywheel motor/generator system is 90+% efficient at storing and using electrical energy for vehicular motion. So the answer to your Question is, "Probably". 90%x50%=45%, and the value "45%" is 50% greater than the value "30%" (and more than the 20%-greater that you asked about).
Vernon, Apr 10 2012
  

       sp "yes, in the city or on very hilly roads".
FlyingToaster, Apr 10 2012
  

       ////does their gyroscopy cancel out// I don't think so: precession would cancel, but it's going to be just as difficult to reorient them as it always is.//   

       It's an interesting thought. Instinctively I'd say you're right. On the other hand, a pair of opposed flywheels has zero net angular momentum, doesn't it? Or not. Maybe.
MaxwellBuchanan, Apr 10 2012
  

       that's... ... ... hmm.
FlyingToaster, Apr 10 2012
  

       No, the stacked flywheels have exactly twice as much flywheel effect, proximity irregardless. MB, you feeling all right?
WcW, Apr 10 2012
  

       //No, the stacked flywheels have exactly twice as much flywheel effect, proximity irregardless.//   

       Yes, I sort of intuitively expected that. But is their net angular momentum zero or not?   

       //MB, you feeling all right?// Very not. But that's a whole other story.
MaxwellBuchanan, Apr 10 2012
  

       Their net angular momentum is, indeed, zero. However precession is cumulative around the nominal axis between the flywheels.
MechE, Apr 10 2012
  

       //precession is cumulative around the nominal axis between the flywheels.//   

       Ah, yes, silly me. What? (Not disagreeing, just not understanding.)   

       OK, suppose I have a flywheel mounted like the front wheel of a bicycle, and spinning "forwards". I try to steer to the left, and the flywheel produces a torque in some other weird direction.   

       Now I do the same, but with the flywheel spinning "backwards". When I try to steer to the left, does the flywheel still produce a torque in the same direction as before?
MaxwellBuchanan, Apr 10 2012
  

       No. The torques will be opposite.   

       I think [MechE] is saying that if I had two perfect, thin flywheels arbitrarily close together on the distal end of a stick, I could not distinguish by waving it around between (a) both wheels stationary, and (b) the wheels exactly counter-rotating. But if they were separated by a non-trivial amount along the length of the stick, then I could. I'm also not disbelieving, but I don't immediately see why.
spidermother, Apr 10 2012
  

       In that case, simply make the two flywheels very close together, or quasiconcentric, for energy storage without the torque.
MaxwellBuchanan, Apr 10 2012
  

       I've posted a diagram on facebook of two counter-rotating flywheels (sorry can't link to it at the moment, but its easy to find). The L represents to angular momentum, the F represents the applied tilting force, the T represents the resultant force (the circle with an x represents an arrow going into the screen, the circle with a . represents an arrow going out of the screen).   

       I think the gyroscopic effect is dependent upon the centre of rotation of the tilt. If the centre of rotation is between the centre of mass of the two flywheels the flywheels will resist the tilt. However if the centre of rotation is distant from the centre of mass of the flywheels, then the flywheels will not resist that tilt.   

       disclaimer: my physics is rusty so treat with healthy scepticism.
xaviergisz, Apr 11 2012
  

       My own 2-cents-worth on the topic of adjacent contrarotating flywheels:   

       Consider each, separately, on its own axle. When spun up, each will resist an effort to change the direction at which the axle points. This resistance **might** be associated with a kind of "inertia" --one might say that a rotating flywheel has an associated "inertial field". You must overcome **that** inertia in order to change the direction at which the axle points.   

       Well, with two adjacent contrarotating flywheels, I see nothing to cancel-out the **individual** inertial field of each flywheel. That is, each inertial field seems to me to be "monopolar". If they were dipolar I could see that since the total angular momentum of the flywheels is zero, then the associated total inertial field should also be zero.   

       But if the fields are monopolar, the way gravitation always sucks, then all we have done is double the amount of "inertia" that must be overcome, in order to change the direction at which the flywheels' shared axle points.
Vernon, Apr 11 2012
  

       //This resistance **might** be associated with a kind of "inertia" --one might say that a rotating flywheel has an associated "inertial field".// Fine, except that it's not, and it hasn't. There is no //inertial field//, unipolar or not. It's just ordinary matter, obeying ordinary inertial mechanics, in a perfectly symmetrical manner. It just happens to get a bit more complicated when you have rotation and applied torques that are not parallel.
spidermother, Apr 11 2012
  

       //This resistance **might** be associated with a kind of "inertia" //   

       My understanding is that it's simple inertia. As the flywheel spins, all of the point-masses around it have a high velocity, each tangential to the circumference. When you tilt the flywheel, you are trying to change the direction of all those fast-moving point masses, and they of course resist this change. In effect, you are trying to put an acceleration onto all the point masses; the acceleration is large because, although the tilt may be small, the speed of the point masses is high.   

       However, with contrarotating flywheels, a tilt will try to accelerate the point masses of one flywheel in one direction, and those of the other flywheel in the opposite direction. Hence, no net force should be needed and the contrarotating flywheels should give no net resistance to twist.   

       Maybe.
MaxwellBuchanan, Apr 11 2012
  

       I usually like to have an intuitive understanding of something before applying the maths, but this might be an exception. In other words, just trust the maths.   

       I illustrated my understanding of the situation with a vector diagram (link). I just applied the "right hand rule" to the two vectors (angular momentum L, and applied force F) to get the resultant vector (torque T).   

       The first vector diagram illustrates a rotational force applied with centre of rotation at the centre of the system. The second illustrates a rotational force applied with a centre of rotation outside the system.   

       My diagram confirms what FlyingToaster said: the counter-rotating flywheels will cancel out the precession but not the gyroscopic effect.
xaviergisz, Apr 11 2012
  

       //My diagram confirms what FlyingToaster said: the counter-rotating flywheels will cancel out the precession but no the gyroscopic effect.// You mean, //that's... ... ... hmm.//?   

       I don't think you've got that quite right. Precession is a manifestation of the gyroscopic effect. And purely translational forces (which your Fs appear to be) don't affect rotating bodies any differently to non-rotating ones.
spidermother, Apr 11 2012
  

       //Precession is a manifestation of the gyroscopic effect//   

       Perhaps, but maybe not. Gyroscopes are counter-intuitive things, and counter-rotating gyroscopes even more so. As I said, I just did the maths and that's the answer that fell out - if the maths is wrong I'm happy for the error to be pointed out.   

       //And purely translational forces (which your Fs appear to be)//   

       The Fs are instantaneous tangential force vectors not translational forces. I may have made a mistake here in their representation - it's been a while since I studied physics.
xaviergisz, Apr 11 2012
  

       Again, not disagreeing, just not quite understanding. It seems to me that the lower system could be seen as identical to the upper, but with the addition of a circular translation of the midpoint of the two rotating masses. But I could be wrong.
spidermother, Apr 11 2012
  

       [MaxwellBuchanan], I'm pretty sure it is not "simple inertia". If it was, then the force you apply to change the direction of a gyroscope's axis should cause that axis to keep changing its orientation (in Zero Gee, say), after you stop applying the force. And I'm pretty sure that doesn't happen.
Vernon, Apr 11 2012
  

       It _is_ simple inertia. Absolutely every behaviour of ordinary gyroscopes - paired or otherwise - can be explained from first principles using classical mechanics, and nothing else. There's no need to make up semi-mystical theories to explain plain old matter moving in complicated, but ordinary, ways.
spidermother, Apr 11 2012
  

       //It _is_ simple inertia.//   

       Exactly. (What else is there apart from inertia? There's no vis viva in a spinning wheel.) The complication arises because the elements of the gyroscope are usually continuous, and hence their rapid movement is not intuitively obvious.   

       However, if you replace the gyroscope with, say, two masses on either end of a rod (spinning propellor-style), it will behave pretty much like a gyroscope but the inertial forces are more obvious.   

       (It won't behave quite like a gyroscope, because there are only two point masses; make it a four- bladed propellor and it will be very close to a gyroscope.)
MaxwellBuchanan, Apr 11 2012
  

       When one turns the axis of a gyroscope, does the speed of rotation slow?   

       I am thinking about tiny neutronium gyroscopes as a sci-fi concept energy source. 4 inches high, 3000 lbs. I wonder if an assembly of small, supernaturally heavy, very rapidly spinning items could be assembled in such a way that the torque generated by a positional change could be used to help an unaided person carry them about and counter any inertia they might develop.
bungston, Apr 11 2012
  

       //torque generated by a positional change could be used to help an unaided person carry them about//   

       You're into Laithwaite territory there...
MaxwellBuchanan, Apr 11 2012
  

       Eric, or the wine merchants?
Anything that helps my manservant's valet carry my weekly cellar replenishment is always welcome.
AbsintheWithoutLeave, Apr 11 2012
  

       Laithwaite - yes. Which reminds me; Ling likes gyroscopes. Maybe he will weigh in with some wisdom or witticism.
bungston, Apr 11 2012
  

       [spidermother], neither you nor [MB] addressed the specific point I made in my last post. Perhaps I should have only quoted "simple". Because it is **not** simple. Otherwise we wouldn't be discussing their behavior across so many posts.   

       So, in Zero Gee, if you have a floating and spinning gyroscope, and you grab its cage with both hands and try to smoothly change the direction its axis points, what happens when you let go? If we were talking about SIMPLE inertia, constant motion of an object should result (therefore constant change of the direction the axis points).   

       But since I fully expect the axis to stop changing its point-direction the moment you let go, that is why a spinning gyroscope does not have SIMPLE inertia. (And remember, a gyroscope's ordinary/constant axial precession at Earth's surface is due to the constant-applied-force of planetary gravitation. Not present in a Zero Gee environment.)
Vernon, Apr 11 2012
  

       It will do neither of those things. Instead, it will wobble, a bit like a wobbling spinning top (or, indeed, exactly like a wobbling fully gymballed gyroscope). This is because at the moment you let it go, its moment of inertia is not parallel with its axis. And it does so because of simple inertia, regardless of the position of quotes.   

       I don't understand in detail how a straight 6 engine can be perfectly balanced, but I'm confident that with sufficient study I could, and that there would be no fundamental principles involved beyond the laws of classical mechanics (and their abstractions, such as angular momentum or harmonic motion). Just because a system and its behaviour are complex does not mean that the underlying physics is.
spidermother, Apr 12 2012
  

       Waves goodbye to [Vernon] as I turn a corner and [Vernon], motorcycle, sidecar, passenger and flywheel enter the scenery at speed.
UnaBubba, Apr 12 2012
  
      
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