Flywheel / Inertia Effects

[Hobby]

The Minitrains one is attached to the other end of the shaft to the gears. Look at the first photo on this link.

https://www.rmweb.co.uk/community/index.php?/topic/88311-chivers-kits-on-a-minitrains-fc-chassis/

[B.Meldon]

The Minitrains motors have a shaft at both ends. One end has the worm the other the flywheel.

When I replaced a Minitrans motor a few months ago I did try the loco without the flywheel and there was no obvious diferance in the performance! I did however re-fit the flywheel.
As I mentioned before in these Minitrains locos their good running is more about the gearing than it is the flywheel.

Brian Meldon

[Retiarius]

You can work out the energy stored in a flywheel here:
https://www.botlanta.org/converters/dale-calc/flywheel.html

A MiniTrains flywheel, unless spinning extremely quickly has minimal energy stored and at low speeds are probably a waste of space IMHO. DCC and Radio Control battery power are probably the best way to go for smooth low-speed running.

[Hobby]

To be fair the simulator controllers mentioned at the beginning do work very well, as do the modern "ordinary" analogue controllers by GM. I remember spending a whole afternoon on a model of Longridge station at a Preston MRC openday shunting in the yard using a GM simulator controller and using a Triang X04 powered loco, if you can do it with one of those motors then you should be ok with a modern loco.

Whilst you can use DCC or RC you don't have to. Modern DC controllers are a world away from the old H&M and Triang and HD controllers, as are modern chassis. Times have moved on.

[JulienW]

Can anyone suggest a suitable mass for the flywheel as I'll probably have to 'turn down' my lump of brass.

Thanks,
Dave

Thinking about the physics it's not so much about total mass but where that mass is. I've not done the calculations but I'd have thought that a flywheel with a 'fat' rim and a hollowed-out center (so the mass is concentrated towards the outer edge) would have more of an effect than a 'solid disc' of the same mass.  The same may be true for 2 flywheels of the same overall diameter as a 'hollowed-out' one may have more angular momentum than the 'solid' one with greater mass.

Essentially though the size of any flywheel needs to be as big as possible and as heavy as possible to have maximum effect.

[Dave Cooper]

Hmmm, much food for thought there folks...

Looks like the way to go would be a 'modern' controller with a 'modern' loco (haven't tried that combination yet !) - ie the "Electronic" route.

However, I have some older chassis (eg Diesels with pancake motors) that may be fun to experiment with - just to see what could be achieved...I think I would go for a heavy(ish) flywheel, axle supported at both ends, linked to a 5-pole motor. Strikes me that if the flywheel was placed near-centrally, it could also aid traction ?

Once I have got one or two other projects out-of-the-way, I'll let you know how I get on.

Thanks for all the input so far,
Dave

[Hobby]

If it's the Lima 4 wheel diesel shunter bin it.

[Dave Cooper]

No it's not that one - but, there are a couple of Lima's lurking in dark places - having seen their performance though I know what you mean !
Dave

[MickT]

Nothing to do with flywheels, but in defence of the much maligned Lima chassis in the 4 wheel diesel, I've got 3 of them, one with the pancake motor and 2 with traditional motors - and no sign of them ever being re-motored as far as I can see. All 3 of them work fine, very smooth and responsive and all 3 are amongst the best very slow runners that I have. The only difference between the one with the pancake motor and the other 2 is that the one with the pancake motor makes a very convincing 1:76 scale "diesel sound" whilst the other 2 are silent!

Maybe I have just been lucky.

Mick

[Hobby]

You have, Mick... I am referring to that thing which looked like some overscale American body numbered D2xxx in BR green and with the pancake motor. Horrible thing!

[B.Meldon]

You have, Mick... I am referring to that thing which looked like some overscale American body numbered D2xxx in BR green and with the pancake motor. Horrible thing!

These things also came in BR blue as well as several (at least 4) US railroad colours.
Yes they are quite poor chassis. Out of the 15 or so I have aquired over the years I had two that ran ok, I still own one that works ok under a Matchbox diesel body, and have a box of bits from the others!
Some of these also have a probelm with the brass gears on the back of the wheels being too large (or the wheels too small) and shorting out on electrofrog point blades!

[Hobby]

This beasty!

https://www.ebay.co.uk/itm/Model-Railway-N-Gauge-Lima-B-R-Diesel-Shunter-D2790/264590416186?hash=item3d9ad1593a:g:deEAAOSwlTheE3il

[Stephen Rainsbury]

BTW I now have sprung buffers fitted to my 'road-ends' in case I get it wrong (with rubbish driving !!).

You could try isolating one rail for last 2 or 3 cm of track so the loco stops. You should be able to do something clever with diodes so you can still back up, but that would depend on how you wired it up  ;)

[Dave Cooper]

Hi Stephen

Yes, I've already got isolating 'dead-ends' but I still manage to "back" trains into the buffers occasionally though bad driving !

Also, on the standard gauge platform, some twin-bogie diesels actually 'span the gap' - interestingly, I don't have this problem on the NG platform.

There's a moral there somewhere...
Dave

 

[Stefan Krebs]

Dear David,

Reading through all the comments I suspect I might be the most competent to provide you an overview. Let's dissect your question:

Option 1, flywheel:
It requires space in the engine, which even in small H0 is insufficient for creating a marked inertia, i.e. 'train mass' effect. I have the original Roewa/ ROCO V215, which has 2 massive flywheels (1st ever commercial model to do so, at least in Europe) that create a discernible inertia, but that's hardly more than an real engine running light, about 4cm from full speed. Each of the flywheels is bigger than some 009 engines! This comment already highlights the issue with flywheels: speed, i.e. their inertia is speed dependant. At low speeds, where you need the inertia the most (to overcome contact issues) they don't give you enough.
Flywheels are commonly found in commercial off-the-shelf (COTS) models, and they have their place and usage for 2 purposes:
1. Overcome contact issues.
2. Smooth uneven motor performance, e.g. 3-pole and 5-pole motors.
As stated, to do their job they need size and speed, i.e. not really much use on small models, especially at the low speeds typical on narrow gauge lines.
To simulate train mass, i.e. achieve more than 100mm  'coasting',  you need sizes bigger than H0/00 allow.

Option 2:
Electronics.
Here we have to split the subject into 3 sections.
1.  Digital Control: you can set specific parameters in your digital chip to simulate train mass, for acceleration and braking individually. Even the most basic DCC chips facilitate that, easy-peasy. Only snag: as the chip does not know the size of train you're hauling it doesn't necessarily match your train, so you need to make a compromise.
2. Analog controls:
2.1 Capacitors on the track voltage  have already been mentioned, and we experimented with those. You need a capacitor the size of 2 fists (11000 mF, if I remember correctly) to achieve about 500mm coasting for a big H0 loco (Rivarossi V320 was the guinea pig), and you need 2 of those because of the polarity issue electrolytic capacitors have. Goldcaps weren't invented then, they bring the size down somewhat, but not enough. Problem with this solution: the coasting distance is heavily dependant on the motor and train load, a high-current motor (Rivarossi; Maerklin) might coast 500mm, while a low-current motor (coreless) will do 2500mm;, and a heavy train pushes those figures up.
2.2 Electronic mass-simulating controllers use a fairly small capacitor to 'delay' the power transistor's response to your input. This way the inertia performance is more or less independent from the motor/ gear-train quality, and engines perform roughly similar, unless they have serious mechanical issues (cheap motors, insufficient gearing). I have a DIY-version (built following an article in a 1980s Model Railroader), which cost about £5 to build. If the handheld controller is unplugged, the engine coasts to a standstill over about 15m, if you accelerate, you need 700mm from standstill to top speed, and braking is about the same distance (unless you use the emergency stop button). Controls are push buttons, i.e. there is no knob to turn. Snag with this solution: no easily adaptable to various locomotive performances (some have controls to facilitate that, but unless you do trials and keep a record of settings for each engine, there'll be no consistency), and not proportionate to train mass.
Common snag with these solutions: they don't help with contact issues. That's why 'staying-alive' solutions are offered for DCC (which are too big for a lot of 009 engines).
Option 3:
Clutch that facilitates free-wheeling. fantastic solution that reflects train mass and helps with contact issues. More interestingly: it can be made small enough to fit most 009 engines (self-engaging gear-trains have been used in wrist watches).
3.1 Centrifugal clutch; I drove a class 08 at a Fremo meeting, which was fitted with centrifugal clutch, and it was a revelation. Coasting distance is seriously dependant on train weight and slope (up to 2,5m; !), a real feel of driving the real thing. Braking is by reversing, and has to be done with a lot of sense, great.
3.2. Self-engaging gear-train, Rivarossi produced a BR18 with this neat trick, and I got me one when they were sold as bargains. They weren't popular in the market as these engines were not compatible with existing layouts and any automatic block control! But performance is level-par with the centrifugal clutch, minus 1 detail: no braking, you can't engage the gear-train reliably/ predictably by going into reverse, and if it does, its a crunch stop. Shouldn't be an issue really as the rolling resistance of our models roughly equates to a wagon with brakes at least half on, but modellers are so fuzzy. I love it, it's a skilled drivers only engine, and with the driving school wagon attached (see John Allen for that one) provides endless fun for even experienced driver!   :laugh:
Common snag to both these options: trains and engines can't be stopped on slopes; as their is no brake they'll roll all the way to the bottom if power is off!

There are your options, so take your pick, none is without a downside, but some are better than others; so choose wisely!


Food for thought
and a Happy New Year to all!
Waldschrat