Speed Burst Question

[JulianKeller]

Is there a way to store motion?

 

I never got the chance to go to high school and I live far from a computer but I am wondering is there a practical way to store the ability to move from one place to another faster

 

Kind of like when I run I feel a sudden burst of energy in body, is there a way to develop that scientifically?

 

From a physics standpoint what is happening in my body when I am running then burst forward. I'm not sure if I put this in the right section or not, sorry.

[Moontanman]

Julian, I'm not sure I'm as qualified to answer your question as some are but "yes" in a broad sense it is indeed possible to store motion. A flywheel can store motion and motion can be turned into electricity and used to charge a battery. Some braking systems on electric cars use the braking system to store motion as a battery charge or as flywheel motion. I'm not sure if I understand what you mean by storing your own motion but if indeed you had a generator and battery hooked to a bicycle you could store human energy as well.

[Pyrotex]

I vote for the flywheel. It can store "motion" (actually, energy) and release it with no batteries or motors required.

They actually sell cars in Switzerland with flywheels so that as you brake going down a steep mountain road, the flywheel speeds up. When you start up the next ascent, the flywheel keeps the car going without having to slow down.

Stealing from Peter to pay Paul. :hihi:

[Qfwfq]

They actually sell cars in Switzerland with flywheels so that as you brake going down a steep mountain road, the flywheel speeds up. When you start up the next ascent, the flywheel keeps the car going without having to slow down.

On a full sized car, all the way up and down the Alps? ;)

 

When I was a kid there were plenty of toy vehicles with a very geared up flywheel in them. You charged them up by pushing them along the floor a few times and then they would roll a few metres by themselves. That's a small amount of energy though.

[CraigD]

They actually sell cars in Switzerland with flywheels so that as you brake going down a steep mountain road, the flywheel speeds up. When you start up the next ascent, the flywheel keeps the car going without having to slow down.

I’m curious about you Swiss flywheel-powered cars reference, Pyro – got any links?

On a full sized car, all the way up and down the Alps? ;)

According to old Popular Science magazine articles, at least as early as 1951, full size vehicles were using flywheels to store enough energy to propel them at least a km. This Aug 1970 article describes a 70-passenger Swiss bus that used a 3300 pound (about 1500 kg) flywheel spinning at up to 3000 RPM in a hydrogen gas-filled enclosure to propel it between bus stops, where it would respinup its flywheel from overhead electric contacts, and a proposed tiny commuter car with a 222 pound (100 kg) “superflywheel” spinning at 23700 RPM in a near vacuum that could travel at highway speeds for about 110 miles (177 km) after a 24 minute electric-power spinup. These old references are quite low-tech compared to later ones with which I’m familiar, using air bearings and wet mechanical shaft vacuum seals metal particles suspended in olive oil. Later power flywheels would, I recall, use magnetic bearings and induction to transfer energy from within better sealed vacuum containers.

 

As best I know, improvements in electric batteries rendered flywheels something between out-of-fashion and obsolete by the early 1990s. The high point of power flywheels in cars may have been the 1973 Chrysler Patriot Le Mans race car, which had a 147 pound (67 kg), 58000 RPM composite flywheel – here’s a nice, though regrettably low-resolution image of it:

[Qfwfq]

According to old Popular Science magazine articles, at least as early as 1951, full size vehicles were using flywheels to store enough energy to propel them at least a km. This Aug 1970 article describes a 70-passenger Swiss bus that used a 3300 pound (about 1500 kg) flywheel spinning at up to 3000 RPM in a hydrogen gas-filled enclosure to propel it between bus stops, where it would respinup its flywheel from overhead electric contacts, and a proposed tiny commuter car with a 222 pound (100 kg) “superflywheel” spinning at 23700 RPM in a near vacuum that could travel at highway speeds for about 110 miles (177 km) after a 24 minute electric-power spinup.

On more or less level ground is one thing, Pyro was talking about up and down the mountains. The potential energy becomes sizeable. Also, I was reckoning on fairly ordinary angular velocities, that figure of 23700 rpm is truly amazing, even though 100 kg isn't such a huge flywheel.

 

BTW, now that I read a bit of that article, it looks like the commuter car was never built.

[Pyrotex]

On more or less level ground is one thing, Pyro was talking about up and down the mountains. The potential energy becomes sizeable. Also, I was reckoning on fairly ordinary angular velocities, that figure of 23700 rpm is truly amazing, ...

Oy!

I did not say "up and down the mountains" with the interpretation that ALL the car had was a flywheel.

I have no links -- it was years ago -- but the diesel powered car had a flywheel that stored energy when the brakes were applied, and helped accellerate the car at low speeds. It wasn't for driving ALL the way up a mountain. It was for driving roads that had a lot of short, steep stretches, both up and down. The diesel was small and did not accellerate well, but could maintain a moderate speed on the level. The flywheel enhanced both performance and fuel efficiency.

[CraigD]

On more or less level ground is one thing, Pyro was talking about up and down the mountains. The potential energy becomes sizeable. Also, I was reckoning on fairly ordinary angular velocities, that figure of 23700 rpm is truly amazing, even though 100 kg isn't such a huge flywheel.

The engineering “bottom line” of power systems is energy density – how much energy is stored per unit mass by a given fuel or device. According to these wikipedia tables and their supporting references, the energy density of the best present-day flywheels is about 0.5 MJ/kg, compared to typical oil-based fuels that have about 100 times that, around 50 MJ/kg, or about the same as typical high-performance rechargeable batteries, at 0.46 to 0/72 MJ/kg.

 

In short, flywheels have about the energy density of batteries. Their advantage over batteries are, in principle, very fast charge (“spin-up”) and discharge rates, and longer life because they don’t chemically degrade with use. Their disadvantage is mechanical complexity and safety – the Chrysler Patriot race car’s had was a history of explosive disintegration of prototype versions, and raised concerns with drivers and race officials that a failure in racing might injure or kill drivers and spectators, a reasonable fear, as disintegration of the Patriot’s 67 kg flywheel was roughly equivalent to the detonation of 7 kg of TNT, with its energy density of about 5 MJ/kg.

BTW, now that I read a bit of that article, it looks like the commuter car was never built.

I get that impression also – which is why I’m so curious to see any references Pyro has about a present-day purchasable flywheel powered car, in Switzerland or anywhere. (PS: as he didn’t have any handy, looks like I and other interested folk will have to hunt for them ourselves)

 

I’m suspicious that they may be a technological myth, inspired by the 1950s+ buses described in this Mar 1951 Popular Science article. According to the article, the 12 ton Oerlikon “Gyrobus” had about a 4 mile range, and the flywheel would spin without load for about 10 hours. According to it’s Wikipedia article (do Wikipedists miss nothing! :)), there were around 20 such buses of varying size in service Switzerland, the Congo, and Belgium from 1953 to 1960. There’s one surviving operable one in a museum in Antwerp, Belgium, which occasionally still carries passengers at special events.

 

OTOH, if the busses were technically viable and even moderately successful, I’d not be surprised if smaller passenger vehicles of similar or more modern design rolled at various times in the last 75 years or so.

 

Ultimately, though, I think flywheels are a dead-end technology. :thumbs_do Though arguably at present more long-lived and faster-charging than chemical batteries, I expect technologies such as Lithium-titanate batter to soon dramatically improve these characteristics, leading to domination of the land vehicle technological niche by pure battery electric vehicles. :thumbs_up

[Turtle]

...

Ultimately, though, I think flywheels are a dead-end technology. :thumbs_do Though arguably at present more long-lived and faster-charging than chemical batteries, I expect technologies such as Lithium-titanate batter to soon dramatically improve these characteristics, leading to domination of the land vehicle technological niche by pure battery electric vehicles. :thumbs_up

 

just saw a piece last night on one of the pbs shows on a new type of battery intended to store mega-watts of electricity on a scale suitable for power grids. i don't recall a mention of the energy density and this following article doesn't mention it either, but it's a fair starting point for some more looking. no mention either of its use in vehicles, but fitting anyway as i have seen flywheels bandied about as storage for solar/wind power and these liquid batteries deliver the burst the op requested. as you mention catastrophic failures for small models, it's extremely really bad business when a large scale flywheel disintegrates. :P anyway, new type of battery: >> . . . . . :)

 

Liquid Battery Offers Promising Solar Energy Storage Technique

... Recently, researchers from MIT have designed a new kind of battery that, unlike conventional batteries, is made of all-liquid active materials. Donald Sadoway, a materials chemistry professor at MIT, and his team have fabricated prototypes of the liquid battery, and have demonstrated that the materials can quickly absorb large amounts of electricity, as required for solar energy storage.

 

"No one had been able to get their arms around the problem of energy storage on a massive scale for the power grid," says Sadoway. "We're literally looking at a battery capable of storing the grid."

 

The battery consists of three layers of liquids: two electrode liquids on the top and bottom (electrodes are usually solid in conventional batteries), and an electrolyte liquid in the middle. In the researchers' first prototype, the electrodes were molten metals - magnesium on the top and antimony on the bottom - while the electrolyte was a molten salt such as sodium sulfide. In later prototypes, the researchers investigated using other materials for improved performance. ...

[Qfwfq]

Oy Pyro!

I did not say "up and down the mountains" with the interpretation that ALL the car had was a flywheel.

I kinda figured it would have to be combined with an ordinary engine, as you did talk about Swiss mountain roads. My point is: Is the flywheel worth it?

 

The engineering “bottom line” of power systems is energy density – how much energy is stored per unit mass by a given fuel or device.

Exactly. Except in calm cases such as the town bus that recharged at each stop.

 

I find the idea that flywheels have about the energy density of batteries somewhat surprising, at least without being quite dangerous ones. What you also seem to be neglecting is the angular momentum; it is no sweat in the town bus case but troublesome in more general road conditions: [imath]\tau=\frac{dL}{dt}[/imath]. The only way to partly obviate this would be a pair of counter-rotating flywheels kept at well matched revs. Of course this wouldn't do much about the problems in designing the friction free bearings to withstand the vehicle's rotations about non vertical axes.

 

According to the article, the 12 ton Oerlikon “Gyrobus” had about a 4 mile range, and the flywheel would spin without load for about 10 hours. According to it’s Wikipedia article (do Wikipedists miss nothing! :)), there were around 20 such buses of varying size in service Switzerland, the Congo, and Belgium from 1953 to 1960. There’s one surviving operable one in a museum in Antwerp, Belgium, which occasionally still carries passengers at special events.

 

OTOH, if the busses were technically viable and even moderately successful, I’d not be surprised if smaller passenger vehicles of similar or more modern design rolled at various times in the last 75 years or so.

I've no problem with the town bus (as I had implied from the start). In such a case the extra mass is no issue and neither is a long distance needed between charges and, to be fair, a redox chemical accumulator will never have the same efficiency. All the same, here in Padova, an electric accumulator is used in the hi-tech metro-tram for where it traverses a brief stretch in which they absolutely didn't want an aerial line.

[Pyrotex]

...I find the idea that flywheels have about the energy density of batteries somewhat surprising, at least without being quite dangerous ones. ...

Arrrrh,

there's the rub, now ain't it, laddy? :)

 

Using the strongest composites, like Kevlar, one can make a sizeable rotor that spins upward of 30,000 RPM. That's 500 revolutions per second! The limit is of course determined by the sheer mechanical strength of the rotor material. The amount of energy stored can be the equivalent of, say, a quarter stick of dynamite.

 

Can you say, "kaboom", boys and girls? ;)

[CraigD]

I find the idea that flywheels have about the energy density of batteries somewhat surprising, at least without being quite dangerous ones.

It’s important to note that the published energy density ratings for modern flywheels ignores the mass of supporting machinery, which in non-vehicle applications may be much greater than the flywheels themselves.

 

To the best of my knowledge, the most common present day flywheel power application is in computer UPS systems, where massive, low-power-density units are often preferred because they don’t leak, burn, spew poison gas, etc. as chemical battery equivalents are known to do. Here’s a random manufacturer’s webpage describing the technology, with a nice cutaway diagram of a single flywheel motor/generator unit.

What you also seem to be neglecting is the angular momentum; it is no sweat in the town bus case but troublesome in more general road conditions: [imath]\tau=\frac{dL}{dt}[/imath]. The only way to partly obviate this would be a pair of counter-rotating flywheels kept at well matched revs. Of course this wouldn't do much about the problems in designing the friction free bearings to withstand the vehicle's rotations about non vertical axes.

As one might imagine with a technology at least 60 years old, this issue hasn’t been overlooked. While counter-rotating fixed flywheels does eliminate precession issues (the Wikipedia article on the 1950s Gyrobus accounts that drivers, and presumably passengers were predictably un-fond of their tendency to pitch sideways when cresting ridges or dips in roads :eek2:), they don’t prevent these vehicles from being difficult to pitch or roll (especially amusing to me in the 1970 Popular Science article’s drawing of a flywheel powered cordless hand drill – I can imagine trying to drive screws with a tool that must be torqued hard at a 90° angle to the direction you want it to point :doh:).

 

An ideal solution (at least in the opinion of my teenage self in the 1970s, when I must have included hundreds of them in mechanical sketches of cars I dreamed of building) appears to enclosing the flywheel in a spherical chamber, supported either by gimbals, or, more exotically, arrays of electromagnets in the chamber wall capable of actively changing configuration to match the orientation of the flywheel and server as bearings, motor, and generator coils. As the flywheel can rotate independently of the vehicle, all gyroscopic effect are eliminated.

 

I recall reading descriptions of such systems in pop print magazines of the 1970s, but haven’t yet stumbled upon any links to such. This EVWorld article discusses a new vehicle flywheel power system that uses spherical vacuum chambers.

[Qfwfq]

To the best of my knowledge, the most common present day flywheel power application is in computer UPS systems

That's a viable idea too.

 

An ideal solution (at least in the opinion of my teenage self in the 1970s, when I must have included hundreds of them in mechanical sketches of cars I dreamed of building) appears to enclosing the flywheel in a spherical chamber, supported either by gimbals, or, more exotically, arrays of electromagnets in the chamber wall capable of actively changing configuration to match the orientation of the flywheel and server as bearings, motor, and generator coils. As the flywheel can rotate independently of the vehicle, all gyroscopic effect are eliminated.

I'm not sure it would be workable unless it's also a counter-rotating pair, both acting mutually as rotor and stator of motor-alternator. Otherwise, are you sure you can have the necessary external torque although eliminating the unwanted ones? I'd have to switch myself to engineer mode and give it a thought.

[modest]

...enclosing the flywheel in a spherical chamber, supported either by gimbals, or, more exotically, arrays of electromagnets in the chamber wall capable of actively changing configuration to match the orientation of the flywheel...

 

Looks like somebody modeled a flywheel on gimbals (the flywheel itself making up the third) with Bullet:

 

(F) Gyroscopic Effect - ジャイロ効果 http://video.google.com/videoplay?docid=-6467136080088201077&ei=kaW8SvOdEpjqqwLXs4jhBg

 

~modest

[Qfwfq]

OK here's the engineering problem to be solved:

 

In terms of the above design, the stator would presumably be fixed to the inner gimbal. Whenever this comes to the position in which the flywheel's axis is aligned with that of the base, the degree of freedom of rotation of the base would need to be surrendered else there couldn't be much mutual torque between rotor and stator. This of course coincides with when any rotation of the vehicle about the same axis causes no problem, but an good automatism is called upon to smoothly transit between free and lock, as that situation is approached.

 

Perhaps a small gyroscope on the base would be the thing; sensors for torque on its mounting could pilot a larger torque on the axis of the base, such as to limit its angular velocity in inertial coordinates.

 

In any case, it's a bulkier and presumably more massive thing than the designs linked to here. I still doubt the idea being viable and effective on vehicles for more than short hauls on level ground. That design is typical for gyroscopes having the purpose to simply maintain a fixed direction in inertial coordinates; they usually aren't large and don't require much torque for just maintaining the necessary angular momentum.

 

I was meaning to say, Pyro, in the Alps there are not always so many short scale alternations between up and down slopes to make it worthwhile, it would make more sense in many parts of France but much less in Switzerland. Besides, the down isn't always before the up! Going from one side of a vally to the other isn't as frequent as going from valley to valley over a pass.