Flywheels

[Andy W]

I'm finishing off a couple of chassis with Mashima motors. I spoke to someone at a show who claimed that flywheels weren't needed with such motors. What do others think?

[Tim V]

Probably yes on DC, not needed on DCC.

[grovenor-2685]

I would not consider flywheels to be "needed", afterall there are thousands of models running without, with all sorts of motors, I don't believe there is anything special about a Mashima motor that makes a difference to the need for a flywheel. However, I do think flywheels are beneficial if you can fit one in, irrespective of DC or DCC. DCC can simulate some of the features of a flywheel but does not prevent hesitation from momentary current interruptions unless you also include a "keep alive" capacitor circuit.
Keith

[Will L]

Flywheels is a secondary solution to get over problems you're better addressing directly. A free running chassis with good pickups on clean track doesn't need one.

Will

[Jan]

For me, flywheels work to negate anything untoward in the supply of volts to the motor. I agree that decent pick ups* and clean track are necessary, but would argue that this kind of perfection is not achievable across the whole layout, for all stock, over an extended operating period. Thus, I'd say if you can fit on, do so. Belts and braces.

*current collection via pick ups is an area I have always had trouble with, so anything I can do to mitigate my inability in that area gets the thumbs up

[Russ Elliott]

A flywheel will lengthen the time taken for a motor to change its speed. It would be interesting to know why Ealing's show correspondent thought this wasn't 'needed'.

[andrew jukes]

Given that the space is often pretty much fixed, I think the interesting question is whether it's better to have a smaller motor and flywheel or a larger motor. My inclination is to go for the larger motor every time, but that's not based on any analysis.

I'm intrigued by Keith's 'keep alive' capacitor circuit. I imagine you can only use that with DCC as for DC the loco has no knowledge about which current direction it needs from the capacitor(s).

Andrew Jukes

[nigelcliffe]

I'm intrigued by Keith's 'keep alive' capacitor circuit. I imagine you can only use that with DCC as for DC the loco has no knowledge about which current direction it needs from the capacitor(s).

Andrew Jukes

Keith did say it was in the context of DCC. Such circuits in DCC can work superbly if setup well (including getting over pickup problems as a loco comes to a stop, which a flywheel cannot.).

I have seen a circuit demonstrated for DC. But, it was large and messy. It also made controlling the loco somewhat of a skill (as the stay-alive also acted as a large momentum component on speed changes). It was built by someone to prove it could be done, rather than as a sensible design to be incorporated inside models.


- Nigel

[allanferguson]

I had always understood that flywheels could give problems with feedback controllers; something to do with the feedback circuit expecting a particular level of inertia in the motor. Both DC and DCC controllers may of course use feedback. Someone might amplify my ignorance.....

Allan F

[Russ Elliott]

Given that the space is often pretty much fixed, I think the interesting question is whether it's better to have a smaller motor and flywheel or a larger motor. My inclination is to go for the larger motor every time, but that's not based on any analysis.

I'm inclined to agree, since a small motor will need to do more work to accelerate a large flywheel, and could in extremis overheat. It does depend though on the qualification of 'small' and 'large' respectively, and I suspect there could be a flywheel size range that will reasonably match a motor of a particular power rating.

[DougN]

I'm with Keith actually. I believe the stay alive in DCC will be of good use. From what I have read but not used.... I'm very tempted to try them on a small loco in the future. I beleive they will continue the direction of travel of the loco until it picks up the signal again. I also believe, others may be able to correct me on this, if the decoder picks up a signal from just one rail it will continue. I think this may be what I will use in my Q6 when I get around to chipping it (nice big capacitor will go in the boiler also.

[nigelcliffe]

I'm with Keith actually. I believe the stay alive in DCC will be of good use. From what I have read but not used.... I'm very tempted to try them on a small loco in the future. I beleive they will continue the direction of travel of the loco until it picks up the signal again. I also believe, others may be able to correct me on this, if the decoder picks up a signal from just one rail it will continue. I think this may be what I will use in my Q6 when I get around to chipping it (nice big capacitor will go in the boiler also.

Various comments/clarifications....

If pickup is lost loco will continue to run following previously set instructions*** until either capacitor is discharged (fractions of a second to 30 seconds, depending on capacitor size and capacitor technology used) or pickup is restored. As the capacitor voltage drops away the loco will slow a bit, then eventually stop.
*** I said "instructions". This means that if you've told the loco to come to a stop, and it is following internal pre-set momentum, the loco should continue to follow that momentum and will stop.

With one maker of DCC chips (Zimo), if the loco comes to rest without pickup, then the loco will attempt to move along very slowly until it finds current again, and then stop. This is to try to prevent a loco stopping on a dead bit of track. ( I have a test loco where I can demonstrate this at will, it does work ).

With one maker of Chip and stay alive components (Lenz, with the Gold chip and Power-1 module), the loco can sense DCC signals from either one rail, or even through paper from both rails. It does this through a capacitance trick. Consequently, a Lenz chip with the Power-1 module can tell if it is on the rails or not, and can receive changes to instructions if on the rails but without full pickup. If off the rails, the decoder stops the loco even though there is power in the capacitor module. With all other systems, the loco will continue to run until the capacitor discharges (This can be a problem - think what damage you can do to a loco in 30 seconds of running without any control over it ! - that might be a reason to not fit a capacitor system which can run for 30 seconds.).


Capacitor technology, size and storage time. There are broadly four types of capacitor (and circuit) available for stay alive. Each has different size and storage times.
The simplest, cheapest and least time per unit volume comes from Electrolytic capacitors. You might see half a second with a huge bank, but really its less than 1/10th of a second. Makes a big difference to microscopic "stuttering" and consequently running quality, but can't do "tricks". 16v rated capacitors are smaller per unit of energy stored than 25v. There are regular arguments about whether you should use 16v or 25v rated components; fundamentally this comes down to the track voltage from your DCC system.
Next in storage time per unit volume come tantalum chip capacitors. These are often rated below 3v, so you need a bank of them in series to get up to DCC voltages (at least 16v, some would argue for 25v). They are slightly more compact than electrolytics.
Next comes "gold caps" or "super caps". Again usually need a bank in series to get the required voltage. The storage can easily be seconds to half a minute or more. The capacitors inside the TCS KA1 and KA2 are half a dozen super-caps in series plus a few other parts for controlling in-rush current, a KA2 can run my test loco for half a minute.
Finally, there are gold caps with step-up voltage circuits. This is what Lenz have in their Power-1 module. They use a low voltage capacitor and electronics to push the voltage up to that required by the chip. Makes the circuitry more complex, and in practise most devices like this are specific to certain decoders.


Hope this helps


- Nigel


- Nigel

[DougN]

Thanks Nigel, I will have to find out if the local model shop to me has any of the TCS KA's in stock. I would quite like to give them a try. Not sure about the Q6 but the Black Hawthorn might be a big challange..... Umm it gets my mind going on what I could do....

[Chris Mitton]

It also made controlling the loco somewhat of a skill (as the stay-alive also acted as a large momentum component on speed changes).
- Nigel

Let's not forget that a moving steam locomotive did have rather a lot of momentum, and you only got to drive one after an apprenticeship lasting maybe twenty years, longer than any other occupation. This all sounds promising in the pursuit of more authentic operation!

think what damage you can do to a loco in 30 seconds of running without any control over it !

....not to mention the rolling stock, track, "passengers", platforms, buildings, anything else that gets in the way. Just like the real thing in fact.....

Regards
Chris

[nigelcliffe]

Thanks Nigel, I will have to find out if the local model shop to me has any of the TCS KA's in stock. I would quite like to give them a try. Not sure about the Q6 but the Black Hawthorn might be a big challange..... Umm it gets my mind going on what I could do....

If you are talking of a High Level Black Hawthorn small tank loco, then I don't think there is space for a TCS KA unit. You might squeeze in a few small capacitors here and there which may overcome "stuttering".

I used the KA2 with a Zimo decoder; you do not have to use a TCS decoder, just have one where decoder positive and decoder ground are available. I also fitted a discharge resistor across the KA2 to ensure it would fully discharge in about 30 minutes (making it much safer to work on the loco without a massive energy store about to discharge).


- Nigel

[Andy W]

Thanks for all the feedback (no pun intended) re controllers etc. I tested my loco - without a flywheel - on the NLG test track last night. It ran fine backwards, but like a three legged pig forward. Something that needs fixing before any flywheel is considered. I think (I hope!) the problem can be solved by opening out a coupling rod just a tad.

I think the chap who mentioned that Mashimas etc didn't need flywheels was just assuming that their efficientcy was enough to ensure good running. Not in my case!

[Will L]

Like I said earlier, until you have the basics of a smooth running chassis, no flywheel on earth will make any significant difference. Then, not until you have good pickups and clean wheels and track, will you be able to get the loco to start reliably and run slowly, and again the no flywheel will help. It is true that a nice big flywheel will help to keep you big passenger trains running continuously at speed round the club tail chaser through dubious track conditions but, is that what your railway looks like?

Will

[Ian Everett]

Thanks Nigel, I will have to find out if the local model shop to me has any of the TCS KA's in stock.

That sounds like a good idea if only a) I can find a local model shop and b) if the chap behind the counter has a clue what a TCS KA is!

Can anyone advise on sources of TCS KA and flywheels on the web so I can try them out?

I do have a flywheels on a couple of my locos and they run more smoothly than others. I am sure that with DC at low volts and small light engines, such as the dock shunters on Humber Dock, they will prevent stuttering over dirty patches of track (especially necessary at exhibitions) but, as has been mentioned they will not help if the loco is stuck on a dirty patch when starting.

Ian

[nigelcliffe]

Thanks Nigel, I will have to find out if the local model shop to me has any of the TCS KA's in stock.

That sounds like a good idea if only a) I can find a local model shop and b) if the chap behind the counter has a clue what a TCS KA is!

Can anyone advise on sources of TCS KA and flywheels on the web so I can try them out?

For the TCS KA1/2, you could try Kevin at Coastal DCC (mail order and shows only, and Kevin is a friend of mine).

Mechanical flywheels, I don't know. I'd turn my own !

I do have a flywheels on a couple of my locos and they run more smoothly than others. I am sure that with DC at low volts and small light engines, such as the dock shunters on Humber Dock, they will prevent stuttering over dirty patches of track (especially necessary at exhibitions) but, as has been mentioned they will not help if the loco is stuck on a dirty patch when starting.

Ian

TCS KA devices won't be any use on a DC layout. They are no use even if running a DCC decoder under DC control (which many decoders will permit).


- Nigel

[Jol Wilkinson]

Nigel has provided an excellent description of what DCC can provide, so I'll try to do the same for mechanical flywheels.

If I remember my engineering course lectures correctly, the energy in a moving body is a function of the mass and twice it's velocity. So in simple terms the effectiveness of a flywheel is a product of it's effective mass and the square of it's speed of rotation. Bigger diameter and faster means better.

Of course we are limited in the diameter of flywheel we can install, especially in smaller and therefore, lighter locos. In addition, the requirement for a flywheel is usually to overcome slow speed "stalling" or jerkiness, when a flywheel will be rotating slowly and therefore it's effect will be far less than at higher motor speeds.

So, compensation/springing/CSBs for better adhesion and pickup are the first priority, but we probably already do that anyway. More pickups (but with the lowest possible friction) will also help, as will correctly aligned gears, etc. while a flywheel becomes the last part of the solution. But it needs to be the biggest diameter you can fit in.

As has already been said, DCC will only be totally effective when all else is correct, the same goes for a flywheel.

Jol

[Andy W]

Thanks Jol and others. As Will pointed out, it's no good fitting a flywheel to a loco that isn't running well - it's not a cure. In the case of my 0-6-0T the problems seem to have been solved by opening up the coupling rods. However, I could only fit a small flywheel anyway so in this case it's not worthwhile.

I was prompted to post the original query as a response to the idea that Mashimas etc "don't need flywheels" - I'd assumed due to their efficiency. As I only build small locos that just pootle around I don't think I'll be using them.

[Jol Wilkinson]

I was prompted to post the original query as a response to the idea that Mashimas etc "don't need flywheels" - I'd assumed due to their efficiency. As I only build small locos that just pootle around I don't think I'll be using them.

Andy,

I think that the original statement may have been made in relationship to the motors that went before. Larger, open frame motors with less effective magnets than are used nowadays.

A couple of Sagami can motors I have (now over twenty years old) also suffer from "cogging" at low speeds which a flywheel might help overcome. Not a problem I have experienced with a Mashima.

Jol

[Petri Sallinen]

As has already been said, DCC will only be totally effective when all else is correct, the same goes for a flywheel.

I agree that. If you have space enough inside your locomotive you are also able to use centrifugal cluthes with massive flywheel. It is very difficult to get the same effect with DCC. This totally helps your loco to go.




http://www.brimalm.com/en/current/brima ... l-clutches

Petri
6549
Helsinki, Finland

[Brian Harrap]

Anyone who hasn't driven a loco with a Dynadrive clutch (other clutches are available) and a LARGE flywheel, as in Petri's example, has a rare treat in store if they ever get the chance to try it, Brian.

[Russ Elliott]

That's excellent, Petri. It would be nice to have a closer shot of your transfer gearbox, and I assume you have allowed it to move laterally across the frame to cope with bogie rotation?