Flywheels in small 4mm shunting locomotives

[AndyID]

No, you may be reading that into my question but you're obviously disregarding my last sentence:

 

 

Going back to the test, Chaz also suggested that back on the first page. I would try it but  I have only 4 locomotives that are fitted with flywheels Two are RTR and I can see that the flywheels definitely have an effect but one is a main line diesel type, where the flywheel is almost as wide as the bodywork and where the flywheel probably weighs as much as some of some of my small shunting types do entirely. I would assume that, being a main line type, the gearing is a lot higher than the type of loco we're discussing anyway so that's not really relevant.

 

Another is a 009 loco by Minitrains. It also has a flywheel that can be seen to have an effect but I have no idea what the gearing is on that. The other two are kitbuilt and have flywheels that are stuck on using Loctite, so I can't run a fitted/unfitted comparison without a great deal of trouble and the distinct possibility of wrecking the motors. It is these very low-geared locos where I can't see any effect in being able to over-run when the power is knocked off, hence the original question.

 

As far as the original question goes there have been people giving the pros and cons, someone saying that a flywheel definitely works, based on nothing more that the fact that he's spent money on it!, people saying that in such small locos a flywheel can't have enough mass etc.and every opinion inbetween.

 

You and Chaz are absolutely right about a test but I can't perform the test and until someone does such a test on low-geared (I would suggest the typical gear ratios offered by High Level - 60:1, 80:1, 90:1 and 108:1) small locomotives then everything else is just theory and opinion.

 

On the other hand, it has been said that fitting a flywheel  isn't necessarily about observable overrun anyway and is about smoothing out the running of the motor, and that is something they know that I didn't, as asked in my original question. Another question could be how we do we test for smoother running but I guess that opens another can of worms...

 

You may be missing an important point. The outer diameter of the flywheel is very important, but the angular velocity (speed) is also very important. The energy stored in a flywheel isn't proportional to its angular velocity, it's proportional to the square of it's angular velocity. Double the speed means four times the stored kinetic energy.

 

Because of that is quite possible for a small flywheel on a motor driving a very low gear (> 80:1) to store more energy than a large flywheel on a motor driving a high gear. The downside is that large gear ratios also tend to create a lot of friction and that can dissipate the energy stored in the flywheel quite quickly. To get the greatest benefit from a flywheel it's important to make the gearing as efficient as possible.

 

BTW, really fast flywheels can store energy at densities that are comparable with electronic storage devices.

[DCB]

I'm not entirely sure what you are trying to do here but if you want to make a flywheel that can slip a bit under a lot of torque you could embed magnets in the flywheel. They would be attracted to a steel/iron disk attached to the motor. Put some sort of friction material (paper?) between the flywheel and the steel disk and you have a clutch. The magnets produce a force to keep the plates compressing the paper but they take up a lot less room than some sort of spring.

 

I am trying to come up with a way of protecting the gear train.  I want something which will let the final drive slip before the gears strip. If it is on the final drive gear it will only revolve at about 500 rpm max,  If the device is on the flywheel it will be a minimum of 10X the revs of the driving axle possibly 60X or 80X the revs and that will need some pretty careful balancing.  

A clutch to let the motor spin up before taking up the drive is a different thing altogether though it seems the Dyna Drive concept failed because its bevel gears couldn't take shock loadings such as when a loco rammed the buffers. As soon as my magnets arrive in mid April I will commence some experiments.

[RAF96]

You may be missing an important point. The outer diameter of the flywheel is very important, but the angular velocity (speed) is also very important. The energy stored in a flywheel isn't proportional to its angular velocity, it's proportional to the square of it's angular velocity. Double the speed means four times the stored kinetic energy.

E=MC2 where E = energy, M = mass and C squared = velocity. Therefore you can see the same energy from a heavy object going slowly as you can from a much lighter object going not that much faster. Plot mass versus velocity squared to see what I mean.

Rob

[Jol Wilkinson]

E=MC2 where E = energy, M = mass and C squared = velocity. Therefore you can see the same energy from a heavy object going slowly as you can from a much lighter object going not that much faster. Plot mass versus velocity squared to see what I mean.

Rob

 

The formula for kinetic energy is E = 1/2 M * V squared (also written as KE = 0.5 x mv 2, plus other options).

 

You have quoted  Einstein's formula where C is the speed of light.

[RAF96]

The formula for kinetic energy is E = 1/2 M * V squared (also written as KE = 0.5 x mv 2, plus other options).[/size]

 

You have quoted  Einstein's formula where C is the speed of light.

Close enough for government work though.

Rob

[DCB]

Just wondering if anyone has considered driving a flywheel from a loco axle rather than the motor. Thinking about something like the old "Friction" drives, it would take the load off the final drive gears. I reckon it might be worth a try. while I wait for my magnets to come from China  I have a friction drive toy or two lurking in my scrap box. I already have worm wheels loose on axles on a couple of chassis driven be a pin through the axle engaging a horizontal pin through the worm wheel which gives up to 300 degrees free movement.

[bertiedog]

Couple of points, flywheels on axles do not work, they would as suggested have to be geared up, and it is wasted duplication of a drive, keep it simple....

 

The chance of gear stripping on a flywheel system is zero in practical terms, stripped gears occur for other reasons. When a loco hits the buffers under power from the flywheel it will simply break traction between the track and wheels, by far the weak point in the transmission.

 

The break traction and slip will protect the gears unless very fine pitch, poorly mounted or miss aligned in a major way..

 

The more complex the drive, the more to go wrong and there is little space to spare in OO drives.

 

Magnetic and clutches are best confined to O gauge or above, where space can be found more easily.

 

However some larger diesels in 00 would lend themselves to more experimental drives.

 

As said, shunting or any loco, benefits from a flywheel ....that is not trying to be technical but 50 years experience of building locos with them fitted.. If you want technical details of flywheels and gyros I can give you the fullest details, but this is not needed to improve a motor in a model loco.

 

Stephen.

Edited March 10, 2018 by bertiedog