High Energy Flywheel

[AndyID]

Adding a flywheel to a locomotive can make a big difference, but sometimes it's not so easy to find enough room for one, particularly in smaller steam-outline locomotives.

 

This might be one way to solve that problem. I say "might" because I have not actually made anything like this. It's more of a concept than a design, and it could be impractical for many reasons, so don't blame me if you can't get it to work    It's probably not a new idea either.

 

Flywheels store energy, and the bigger they are, the more energy they store. The energy stored is also a function of the speed of the flywheel, but the interesting thing is that the stored energy isn't proportional to the speed; it's proportional to the square of the speed. If you double the speed the energy is four times greater. Three times the speed means nine times the energy, etc.

 

This arrangement should (in theory at least) multiply the speed by around four times. It's basically a planetary gear system. However, gears are noisy and expensive so this version substitutes rubber tires (actually O-rings) for gears.

 

 

 

The motor shaft is attached to the carrier (violet). The carrier drives planets fitted with O-rings (red). The planets (yellow) are free to rotate on the four shafts projecting from the carrier plate. The O-rings bear on a V-shaped groove in the outer ring (green). The outer ring is prevented from rotating either by a fixed stop or by some friction means that allows a certain amount of slip during high torque conditions. The actual flywheel (blue) is driven by the O-rings bearing on its V-shaped groove. The flywheel is free to rotate on the motor shaft.

 

 

 

[Titan]

Unfortunately rubber O rings used like this are very inefficient and will sap loads of energy - think why steel wheel on steel rail is so much more efficient than car tyres. I expect that you will find that the additional resistance of the o-rings will absorb all of the extra energy and more, especially at the speed they will be rotating...

[PatB]

I like the concept but I'd agree with Titan that the o-rings may not be the ideal drive option. Mind you, the picture in my head is of a rrelatively soft rubber. if something harder but still high friction could be found it may be more feasible.

[AndyID]

I like the concept but I'd agree with Titan that the o-rings may not be the ideal drive option. Mind you, the picture in my head is of a rrelatively soft rubber. if something harder but still high friction could be found it may bfe more feasible.

Yes, getting enough friction to prevent a lot of slip without creating too much rolling resistance will be a challenge. O rings are available in many different materials and hardness. Might take a lot of experimenting!

 

I'll probably take a shot at a prototype.

[Nearholmer]

"Friction motor" toys use the principle you identify, and they manage with metal gears (or they did when I was a lad), operating at very high speeds.

 

One issue in a model train drive might be spinning-up the flywheel through very high gearing - the traction motor might struggle.

 

Getting the ratios right to achieve all the different functions will be interesting - do you envisage using a clutch, or having the flywheel engaged permanently?

 

Kevin

[AndyID]

"Friction motor" toys use the principle you identify, and they manage with metal gears (or they did when I was a lad), operating at very high speeds.

 

One issue in a model train drive might be spinning-up the flywheel through very high gearing - the traction motor might struggle.

 

Getting the ratios right to achieve all the different functions will be interesting - do you envisage using a clutch, or having the flywheel engaged permanently?

 

Kevin

 Hi Kevin,

 

Yes, it's a variation on the old friction drive toy motor. I agree about the starting load. That can be altered by changing the "gear" ratio, or the mass of the flywheel itself. Not sure if a clutch is necessary or not but there is one built into the design. The outer ring can be allowed to slip if the motor is attempting to accelerate the flywheel too much. That has the same effect as a clutch.

 

Regards,

Andy

[Nearholmer]

Somewhere, a very long time ago, I saw this idea applied to clockwork trains, all but the best of which have a tendency to take-off too quickly, then run out of wind too soon.

 

A brake van was attached, equipped with a big high-speed flywheel, geared off one axle of the van. The idea was to soak-up energy on starting, then release it once the spring of the clockwork began to run down. It was claimed to be very effective, but I had my doubts about the effectiveness of passing energy into the flywheel through the wheel/rail interface .......... however, such a flywheel fitted direct to the clockwork ought to work ....... hmmm ...... an idea involving meccano is beginning to form in my head .........

 

K

[AndyID]

Somewhere, a very long time ago, I saw this idea applied to clockwork trains, all but the best of which have a tendency to take-off too quickly, then run out of wind too soon.

 

A brake van was attached, equipped with a big high-speed flywheel, geared off one axle of the van. The idea was to soak-up energy on starting, then release it once the spring of the clockwork began to run down. It was claimed to be very effective, but I had my doubts about the effectiveness of passing energy into the flywheel through the wheel/rail interface .......... however, such a flywheel fitted direct to the clockwork ought to work ....... hmmm ...... an idea involving meccano is beginning to form in my head .........

 

K

 

I once saw a H0 US boxcar that had a flywheel in it. I believe the flywheel was belt driven from an axle. The boxcar could be loose shunted in a very realistic fashion but I never actually saw a locomotive try to start a whole train of them. Might have been a bit tricky.

 

I suppose if this planetary arrangement could be made to work and sufficiently miniaturized, it could be installed on a wagon's axle to achieve a similar inertia effect, but I must admit that's pretty unlikely. I'd be happy if it turned out to be a good solution for reducing the size of locomotive flywheels. If it does not work with O-rings I'm pretty sure it could be made to work with gears, but that would require some significant tooling.

[Nearholmer]

What is the gearing inside a small battery-screwdriver, the in-line type? That might be a planet-set, running the other way round, to give a low-speed, high- torque output.

 

And, Maxon make planetary gear assemblies in possibly relevant sizes http://www.maxonmotor.co.uk/maxon/view/content/gear-overview they go up to 6000:1, which should get your flywheel whizzing!

 

K

[AndyID]

What is the gearing inside a small battery-screwdriver, the in-line type? That might be a planet-set, running the other way round, to give a low-speed, high- torque output.

 

And, Maxxon make gear assemblies that might be planets.

 

K

 

I believe some of the screwdrivers do use planetary gearing, but wouldn't they be much too large for this application? (I'm interested in 00 gauge).

 

Maxxon might be an option, but probably too "spendy" for me. I think I have seen small motors for sale on E-bay and other places that include planetary reduction gears. They might be small enough and IIRC they are not very expensive either.

[bertiedog]

I will have to look up some flywheel theory, but one thing springs to mind, power in equals power out, and getting the speed up in proportion to a square law means a reciprocal reduction in the time the power out is available, in other words you get 'ought for 'nout.

 

Four times in will be available for 1/4 the time out, so it may not be practical once the losses due to the gears, and certainly due to the use of O rings, which are soakers up of energy into heat.

 

In normal flywheels the energy is best stored in a heavy rim, solid flywheels have dead mass and ruin bearings.

possibly the most practical "flywheel" is a storage device like a super capacitor to store electrical energy to give a longer run on power shut off, or act as a power maintainer.

 

Stephen

[Nearholmer]

My battery screwdriver is about the same diameter as some of the motors in my locos ....... but they are 0 gauge.

 

Yes, having checked, the Maxon ones do seem reassuringly expensive; clearly superfine precision engineering doesn't come cheap.

 

(Bertiedog - I don't think the problem will be around speed, because the speed at the input/output shaft will only ever be less than the maximum input speed, but torque. Loading the flywheel will require extra energy to flow through the motor, it will have to deliver extra torque, above that needed to shift a train. If the gear ratio is too high, or the flywheel too heavy, the motor will simply stall. Toy friction drives use a quite lightweight flywheel. The option taken with "real" ultra-high-speed flywheels is to run them seriously fast, sometimes using magnetic bearings, and not to couple them to the load mechanically, but electrically. The flywheel is the rotor of a motor/alternator.)

 

K

[AndyID]

I will have to look up some flywheel theory, but one thing springs to mind, power in equals power out, and getting the speed up in proportion to a square law means a reciprocal reduction in the time the power out is available, in other words you get 'ought for 'nout.

 

Four times in will be available for 1/4 the time out, so it may not be practical once the losses due to the gears, and certainly due to the use of O rings, which are soakers up of energy into heat.

 

In normal flywheels the energy is best stored in a heavy rim, solid flywheels have dead mass and ruin bearings.

possibly the most practical "flywheel" is a storage device like a super capacitor to store electrical energy to give a longer run on power shut off, or act as a power maintainer.

 

Stephen

 

Hi Stephen,

 

It's really just a flywheel. The flywheel stores kinetic energy. A massive slowly rotating flywheel can store the same kinetic energy as a much smaller flywheel that's rotating very quickly. Of course the friction inherent in any gearing will dissipate some energy so a single flywheel with no gearing is preferable, but that's not always possible due to space limitations.

 

Regards,

Andy

[bertiedog]

Hi Stephen,

 

It's really just a flywheel. The flywheel stores kinetic energy. A massive slowly rotating flywheel can store the same kinetic energy as a much smaller flywheel that's rotating very quickly. Of course the friction inherent in any gearing will dissipate some energy so a single flywheel with no gearing is preferable, but that's not always possible due to space limitations.

 

Regards,

Andy

Unfortunately it is a bit more complex than the intuitive approach suggests, the faster wheel stores as much, but it is available at the higher energy level only for a proportionately shorter time.

If the power is drawn a lower level as the slower wheel then the energy is available longer from the speedier wheel.

but in all cases energy in equals energy out.

But the model railway rule is the bigger the better!!! and use ballraces to support the shaft.

 

Stephen.

[Nearholmer]

"but it is available at the higher energy level only for a proportionately shorter time."

 

I'm not at all sure that I understand that.

 

Surely, if the flywheel had loss-free bearings, and no windage losses, the energy would remain available forever.

 

And, the use of magnetic bearings and evacuated flywheel chambers aims to get as close to that unobtainable as possible. Not that I'm advocating such sophistication for a toy train!

 

In a sophisticated system, the rate of discharge of the flywheel can be controlled, but in a directly-coupled mechanical system, even one with a geared-up flywheel speed, there isn't any control of discharge rate. As soon as input shaft speed drops below current flywheel speed (as geared, where applicable), the flywheel releases energy at a rate dictated by the resistance provided by the load that it is attempting to sustain.

 

K

[AndyID]

Unfortunately it is a bit more complex than the intuitive approach suggests, the faster wheel stores as much, but it is available at the higher energy level only for a proportionately shorter time.

If the power is drawn a lower level as the slower wheel then the energy is available longer from the speedier wheel.

but in all cases energy in equals energy out.

But the model railway rule is the bigger the better!!! and use ballraces to support the shaft.

 

Stephen.

 

Hi Stephen,

 

Are you sure about that? Surely the reduction of the stored kinetic energy in the flywheel depends on the rate of energy consumption, and that is determined by whatever load the flywheel is driving, not by the flywheel itself.

 

Another way to look at it: If high speed flywheels are not much use, why are they used in F1 racing cars and "push-and-go" toys?

 

Regards,

Andy

[bertiedog]

it all depends on the volume of the power, not a numeric level, a high speed wheel will deliver more work at first, but the overall stored power means it runs out quicker overall,

Think of a battery, it can store so many watts, and can delver bursts of power, or steady high power, for a certain period before it runs out, A big battery can delver more for longer, the smaller battery can do the same discharge, but for a shorter time.

So a toy with a high speed wheel can give high power, but only for a shorter period.

This is why kers is limited in cars to a short burst.

But in model railways it needs power over a time, and the high speed flywheel would be as effective, but for less time, and less the wasted power in the gears.

You cannot go over unity, thats perpetual motion territory, with both a low and high speed wheel for the same power input, the output will be the same (less loses).

[bertiedog]

In the toy car analogy, the fast flywheel with run the car for x seconds, and the power out is power x tine.

The input to get that power is the same, but at a lower speed before the gears, therefore the push has to be made for longer to build up the power(the flywheels speed)

You may remember having to apply several pushes to the toy to get the flywheel up to speed. that is the secret, the power in is over time at a low level, and the power out is over a short burst at high level,

But it is stil power in equals power out, and at the levels needed for model locos there would be no advantage to using a high speed wheel

 

Using one would load the motor on acceleration in storing up the power, then as it is released it will cause massive over run.

 

That might be your aim of course, but may make the loco a bit undriveable.

 

The best known use of very high speed flywheels in railways was the Gyros in Brennans Monorail, they ran in vacuum chambers at 50.000 Rpm on tests.

[AndyID]

Hi Stephen,

 

I think you might be confusing two different things. It's not power in = power out. It's energy in (or work in if you prefer) = energy out (assuming no parasitic losses of course). Power is the rate of doing work or, the rate of consuming energy. Flywheels don't store power, they store kinetic energy. Batteries don't store watts. They store watt-hours or joules which are measurements of energy, not power.

 

You could use a small amount of power to "charge" a flywheel over a long time then "discharge" the flywheel by having it produce a large amount of power for a short time, but in either case the work input equals the work output. Two different flywheels (different mass, different speed) can be "charged" with the same amount of kinetic energy and they will both do the same amount of work when discharged. If they didn't they would violate the law of conservation of energy.

 

Regards

Andy

[bertiedog]

just simplifying it to equate it to model railway, power in is understood, rather than energy, thats all, it makes no difference.

[bertiedog]

The point still applies that a high speed flywheel will be a little odd in operation in a loco, it needs time to build to speed, and would cause a long overrun as power is cut off or reduced, even causing run ons that you could not stop, (without shorting the track to cause dynamic braking).

A loco running fast would drift on for many feet, perhaps far to much, when turned off.

And as it starts it will take a lot of power and time to reach speed, which might make a start up a slope much more difficult than with a slower flywheel.

 

A possible way to store the energy would be an auxiliary motor dedicated to powering a flywheel at high speed, and when the speed is lowered the flywheel powers the dedicated motor as a generator to feed the traction motors. It might just fit a diesel outline loco. It would certainly over run when the power is off from the track though, and might need dynamic braking to bring things to a quick halt. Such a system was tried by Bob Symes in 0 gauge in experiments he did into his hybrid diesel electric loco.

 

The aim in his case was to provide smoother stopping as the diesel engine was cut back to come to a halt, as it was to abrupt a halt when the RC control was backed off, there was no space for a big flywheel on the diesel generator itself, so the motorised flywheel was adopted to store energy.

 

Stephen

[Nearholmer]

I wouldn't be so pessimistic about a high speed flywheel in a model loco; with careful selection of ratios, mass etc, I think it could be quite fun, and quite realistic. Next move might need to be a remotely controlled brake though!

 

The electrically coupled flywheel has even more potential, though, and it could be really tiny, a light flywheel whizzed up to very great speed by one of those teeny motors that is used for the tail rotor in toy r/c helicopters.

 

K

[bertiedog]

I wouldn't be so pessimistic about a high speed flywheel in a model loco; with careful selection of ratios, mass etc, I think it could be quite fun, and quite realistic. Next move might need to be a remotely controlled brake though!

 

The electrically coupled flywheel has even more potential, though, and it could be really tiny, a light flywheel whizzed up to very great speed by one of those teeny motors that is used for the tail rotor in toy r/c helicopters.

 

K

Perhaps an AC generator in the form of a stepper motor as they are more efficient than DC in generation, and a very good model would be the GWR gas turbine, which would explain the ear shattering whistle of a stepper generator at 20,000 RPM or more.....who would need DCC sound!

A coreless motor could drive the stepper, and it could come on before the traction engines engage, giving a realistic pull away. The generated AC could be rectified to supply the motors, or stored in a super capacitor, the added as power is turned off. Shorting the track would bring it to a halt, albeit with a large current flow.

At medium speeds you would have full control, plus the gas turbine whistle.......

 

Stephen

[Grovenor]

 

just simplifying it to equate it to model railway, power in is understood, rather than energy, thats all, it makes no difference.

It wasn't simplification it was just plain wrong and caused anyone who knew the difference between power and energy to misunderstand you without helping anyone else to understand. Simplification by deliberate error is not a good idea.

Regards

[34theletterbetweenB&D]

What hasn't been explained by the OP is the why.

 

I was all for flywheels with DC control, but will remove them now from RTR when practical, (and have done so on my old kit builds) since DCC does it much more efficiently, and that's without charge storage. I was much enthused when starting into DCC by the availability of the Lenz 'uninterruptable power supply' module, and was expecting to make use of it. Thirteen years on and no loco has required one, current collection reliability is so good from the permanently full-on track power. Wind the CV 3 and CV 4 values up above 100, and see the effect: you have to drive properly, particularly in allowing for the long distances to come to rest. The big advantage over a directly coupled mechanical flywheel is that in event of misjudgement, instead of your heavyweight flywheel monster uncontrollable ploughing an entire train off the rails or some other incident, you can toggle the CV4 defeat and it stops.