Mechanical battery.

[Bob Eager]

It's a South African electrical storage device.

[williamwright]

Now you see, in your haste to be rude, you've missed my point. Why does a moving object have energy to give away? Moving relative to what? I personally am travelling very very fast indeed relative to certain other bodies in the universe, but I'm stationary relative to the Earth.

Bill

[Jethro_uk]

Don't planes also spin up their wheels before landing ?

[Chris Hogg]

I don't think so. I once read that it's the commonest suggestion made to aircraft mfrs, but they don't adopt it for some reason. The fact that there's always a pronounced shriek when the tyres hit the tarmac, and that the first 100 ft or so of landing runway are a mass of rubber streaks, also suggests they don't spin up the wheels.

[Max Demian]

That's the essence of the "twin paradox" (often misstated). If motion is relative, why is it the twin in the spaceship who ages less fast?

[Vir Campestris]

They definitely don't. As you say, it has been suggested; I think the problem is you have to carry the motor all the time, but only ever use it for a few seconds. On an aircraft extra weight means more fuel consumption.

<fx googles>

suggests that one of the problems is the gyroscopic effect on handling. And that at least one aircraft does do it on the nose wheel. Andy

[#Paul]

ASPOI, the twin in the spaceship accelerates to change direction and return, the stay-at-home does not.

#Paul

[tabbypurr]

2k5 rpm is unusually low. Buses use 50k rpm

NT

[tabbypurr]

Yes, though that's mostly solvable. 2 counterrotating flywheels in one casing with a mechanism to jam them together on impact.

NT

[williamwright]

Ever thought I have these days seem to end in a cul de sac, and I have to call it a paradox. Is all of life an unanswerable mystery?

Bill

[tabbypurr]

too many errors

what's con about that?

The big issue people have with gyro balancing is that if things go wrong, stability is lost & carnage results. And IRL things go wrong & lawyers get greedy.

NT

[tabbypurr]

There's no upside to prespinning the wheels, other than less tyre wear, which is trivial compared to the other differences. No pre-spin means a lighter cheaper mechanism, a little free braking on contact, and a brief period of reduced friction which helps with landing stability in crosswinds.

NT

[tabbypurr]

Sorry, that question is an unanswerable mystery

NT

[harry]

Some aircraft had curved fins on the wheel that spun it up when it was lowered into the airflow.

[Chris Hogg]

That was suggested by many people, but I think the gyroscopic effects of the spinning wheels overrule any possible benefits and it was never actually implemented.

[The Natural Philosopher]

I have no idea. Not sure that this one did.

[The Natural Philosopher]

The energy expresses what needs to be removed or added to make two objects stationary *with respect to each other*.

[Dave Liquorice]

everyone

Er, Where does all the kinetic energy go? OK in theory you have equal an opposite amounts so they "cancel out". But two identical cars traveling at the same speed in opposite directions into each other end up a right mess disspiating their kinetic energy,

I think you'd get a big BANG, the desruction of the flywheels and generation of lots of high speed shrapnel. The latter might be possible to contain, they manage it with blade failures on jet engines.

[Clive Arthur]

The con is that, while it can balance, it can only be an impractical novelty, and I'm sure that Daniel Kim (Lit Motors owner) knows that. All these years and you just get a few seconds of video, usually without sound and without tripod. It's noisy - maybe that could be overcome - but it's constantly rocking about it's balance point, which can't be.

The gyros can only supply one-way torque for a limited time (newton-metre-seconds?) before they hit their 'end-stops', no way round that, so to balance, the thing has to actively push against a side force so that its weight counteracts it. In the large Brennan prototype for example, as the passengers move to one side, the car tips sideways the other way to maintain balance.

If you push on it with a finger, it will actively push you back, I mean actually move you back so that its weight balances against your finger. Of course, that's how it automatically leans into a curve.

Imagine that in traffic with constant changing blustery side winds. Imagine one stationary near a solid object and trying to squeeze past - it would crush you.

I think Kim revived the idea with a view to getting lots of investment and advance orders, he seems to have disappeared.

An interesting subject though. There have been a few prototype vehicles, mostly very old, and Ford experimented with their 'Gyron'. There are some youtube videos of home made toys using the idea, I think a properly made say OO scale monorail would be fun, and maybe some sort of fairground ride - the idea of using a wire rope as a bridge is appealing.

[The Natural Philosopher]

Yes.The problem of energy storage and safety is simple. If it all gets out at once - BIG trouble!

That is why coal and uranium are so good. Its bloody hard to get it all out at once.

diesel level hydrocarbons are a decent compromise as is petrol

hydrogen and batteries and flywheels are plain dangerous.

As is water-up-a-hill. To an extent large fixed installations can be remote and built strong, but transport needs low weight and that means compromising safety