Are flywheels worth it?

[tstage]

Since the OP has gotten his answer and the flies are beginning to stick to the wheels, let's move on.  Thanks.

Tom

[locked]

[ATLANTIC CENTRAL]

rrinker

 The TE must have some sort of torque compensation built in, because while PWM has many advantages, it has one serious DISadvantage - at low speeds the pulses are so short the motor generates very little torque. DCC decoders have a (often adjustable) torque compensation to improve performance at low throttle settings - since the TE seems quite capable of low speed performance, they must be doing something similar

                       --Randy

 

 

Interference from track and wheels as well as the ever changing resistance from the throttle to motor would prevent a BEMF circuit from working.

Based on measurements and data gathered and published by George Schreyer, the following is an expaination of the TE output.

Dispite all theory to the contrary, the Aristo Train Engineer works using a very high frequency pulse width modulation, about 25 kHz. The only "compensation" factor seems to be a short "spike", or temperary larger pulse just as it turns on.

The pulses are very square except at the lowest settings where they seem to look more like a half sinusoid with about a 1 microsecond period at the half power point. But this is after the intial burst which is higher.

As the throttle is advanced the pulses simply get longer, remaining very square and at full votlage of the power supply in use. At the highest setting the pulses fill in completely.

It is my understanding from other sources I ave read that it is these very high frequency pulses that actually load and unload the motor windings to cause the motor to not turn until it is willing to turn and stay turning, even at a slow speed.

The starting speed of any given loco does depend on its quality, smoothness, etc. But the best locos perform as well or better than on DCC. Some lesser models still easily out perform conventional DC power packs and similar models on DCC are often not so smooth or slow either.

Lights come on nearly full brightness before the loco moves. I do suspect the power drawn by the constant lighting circuits genrally helps improve slow speed startup. But since all my locos have such circuits, either from the maker or installed by me, it is not an issue.

As a "System" it all works well and very few locos require any changes, or only minor ones I would have made anyway using any other DC throttle.

Just like flywheels, the math might say one thing, but the proof is in the pudding.

Sheldon 

 

[rrinker]

 The TE must have some sort of torque compensation built in, because while PWM has many advantages, it has one serious DISadvantage - at low speeds the pulses are so short the motor generates very little torque. DCC decoders have a (often adjustable) torque compensation to improve performance at low throttle settings - since the TE seems quite capable of low speed performance, they must be doing something similar

                       --Randy

 

[ATLANTIC CENTRAL]

Paul3

Mark,
Some of us belong to model railroad clubs where the track quality is, shall we say, variable.  Some of us have old brass models that still have (gasp!) open frame motors.  Some of us run on layouts that are not in FED-STD-209E cleanrooms.  Some of us think that worrying about unbalanced flywheels damaging HO motor bearings is laughable.

Now, I'm sure that on a perfectly clean layout with perfectly clean wheels on perfectly built track with nothing but perfect motors running on them, flywheels are totally unnecessary.  Unfortunately, I don't have this perfect scenario, and therefore flywheels are a boon to my loco operation.

Paul A. Cutler III

Two thoughts:

Club or not, to quote the late Paul Mallery - a great club promoter - "Excelent trackwork is a MUST".

One of my two brass locos has an open frame motor and no flywheel - it runs as good as any can motor loco I own, even if does draw a little more juice - but each throttle has its own 5 amps - so no problem.

Sheldon

[ATLANTIC CENTRAL]

fwright

Which all begs the question, "How slow is slow enough?"  I find smooth operation at scale 3 MPH to be slow enough for me unless I am trying to win a tie-crawling contest.  3 scale MPH takes 10 seconds to go 6" in HO.  That's 10 full seconds to go through one turnout from frog to points.

I'm with Fred on this point, while many of my locos will run slower than 3 SMPH, that is truely slow enough for normal operational goals.

This is one additional beauty of the Aristo Train Engineer, I don't know the exact freguency of their PWM, but any slow speed the loco will start at, it will maintain easily with little or no stalling. A feature that not even BEMF decoders do any more perfectly than my TE.

Sheldon 

[fwright]

tbdanny

Hi all,

I'm in the process of re-motoring a West Side C-25.  I would like to fit a flywheel into this model, but doing so may interfere with the motor wires without serious re-engineering (by which I mean cutting another hole in the loco shell).  It's a NWSL 12mm flywheel with a 1.5mm shaft, and I want to know if it would be worth making additional modifications in order to fit this in? 

tbdanny

tbdanny

Given the responses in this thread, the answer is either heck yes, install the flywheel regardless of how difficult, or you will ruin model railroading forever by perpetuating the myth that flywheels help performance.

The answer to your question as to whether the installation of the flywheel is worth the effort is of course, "It depends."

• It depends on how smooth your new motor is, and the mass of the armature.  If it's a very small motor or 3 pole or coreless, the mass the small flywheel effectively adds can be a real benefit.  OTOH, the small flywheel isn't going to add that much mass to the existing armature of a smooth skew-wound 5 pole can motor with a reasonable diameter.
• It depends on the gear ratio and motor RPM and desired operating speed.  If you are right at starting voltage at the desired operating speed, a flywheel is probably quite desirable.  If you have plenty of slower speed capability in reserve, the flywheel is probably not worth the extra effort.  I find flywheels to have the greatest benefit when operating very near the stall/start speeds of the model.  At higher speeds, having the drive train coast a few revolutions instead of locking is nice, but not critical.
• It depends on your throttle and the pulses it generates, if any.  A throttle with pulses at a fairly high repetition rate (above 3KHz) isn't going to need as much coasting mass from the motor and flywheel as a 60 Hz pulse train with sharp pulses.  But the latter combination in conjunction with a flywheel will give you slower speeds than the former.
• It depends on how you feel about flywheels, and on you feel about cutting that second slot/hole in the superstructure.

Which all begs the question, "How slow is slow enough?"  I find smooth operation at scale 3 MPH to be slow enough for me unless I am trying to win a tie-crawling contest.  3 scale MPH takes 10 seconds to go 6" in HO.  That's 10 full seconds to go through one turnout from frog to points.  If I have the option on gearing, I want to gear for 45 scale MPH on 12 volts (Shays and Climaxes I prefer to have 15 scale MPH 12 volt speeds). 

A flywheel is one of several means to gaining smooth operation at low speeds.  It can be used by itself or in conjunction with other solutions. 

my thoughts, your choices

Fred W

[rrinker]

 Nickle silver track, metal wheels ONLY, no plastic, and run lots of trains. At leat, mine never seems to need cleaning. But I only have a fraction of that amount of trackage.

                --Randy

[Paul3]

Mark,
Okay, c'mon and take a trip to my club in Hingham, MA.  www.ssmrc.org

By a quick count, we have something like 1000 feet of mainline track to keep clean (and we're not even halfway done).  It's constantly getting dirty.  You name it, we've tried it: gleaming, mineral spirits, laquer thinner, alcohol, brightboys, Centerline "flapper" cars, Walthers pad cars, the CMX Clean Machine, the Atlas track cleaning car, masonite under boxcars, etc.  No matter how much it's cleaned, it's always dirty to some degree.

We'd sure appreciate it if you can tell us how to keep our track so perfectly clean that flywheels are unnecessary.

Paul A. Cutler III

[Forty Niner]

You hit the nail on the head Sheldon when you said "virtually no dirty track issues", and I'd be willing to bet that if you have a rough spot in your track work you fix it as well.

It's not rocket science, it's common sense............

Mark

[ATLANTIC CENTRAL]

Boy am I glad I stayed out of this one.

Flywheels? I don't bother to take them out, I don't go out of my way to add them if they are missing.

I judge the performance of each loco on its own merrits and use various methods to gain improvement when needed.

The MATH says at worst they won't hurt, at best they help, sometimes a little, sometimes a lot.

How much that math holds up in real life is truely the heart of this debate.

As for the electronic solutions, well I split the difference - I use pulse width modulation, but no BEMF, since my PWM is on the track, not from a decoder.

But I know this, nice big flywheels, no flywheels, cheap flywheels, open frame motors or can motors, cheap or expensive, all my locos run slow and smooth with virtually no dirty track issues using my Aristo Train Engineer throttles.

Sheldon

[Paul3]

Mark,
Some of us belong to model railroad clubs where the track quality is, shall we say, variable.  Some of us have old brass models that still have (gasp!) open frame motors.  Some of us run on layouts that are not in FED-STD-209E cleanrooms.  Some of us think that worrying about unbalanced flywheels damaging HO motor bearings is laughable.

Now, I'm sure that on a perfectly clean layout with perfectly clean wheels on perfectly built track with nothing but perfect motors running on them, flywheels are totally unnecessary.  Unfortunately, I don't have this perfect scenario, and therefore flywheels are a boon to my loco operation.

Paul A. Cutler III

[Forty Niner]

If you're going to run cheap motors on rough track work that's also dirty maybe what you need to consider is RC cars, not model trains.......

Mark

[Paul3]

Dr. Wayne,
I would agree that on a small boilered steam engine with a good skew-wound motor on clean, smooth track with clean wheels, a flywheel isn't going to make much of a difference.

However, on a larger engine with a lesser quality motor on on rougher track that's not clean with wheels that aren't clean, flywheels do make a difference.

Paul A. Cutler III

[doctorwayne]

Texas Zepher

doctorwayne:

 

Texas Zepher:

 .....For DC a good set of flywheels on a locomotive is a nearly essential thing.

Care to elaborate on the DC aspect of this?

I thought the others had already done a good job elaborating that point.

 

So any elaboration that agrees with the premise that "flywheels are worth it" is valid, but my experiences that show their benefits to be negligible aren't? 

I have seen that some carbody-type diesels with large diameter and large mass flywheels do have some coasting abilities, and others claim similar results with hood units, although I'm uncertain as to why this is a requirement for DC operation in particular.  I also can't see why anybody would want to crank a loco up to full throttle, then cut the power to watch it coast - seems kinda silly.  I had many diesels (hood units) that had flywheels but didn't coast much, if at all.  I removed the flywheels, installed better motors, and added more weight and got units that still didn't coast, but ran so reliably that there was no need to coast over "dirty" track.  If you want coasting action in DC, most good throttles offer it (thankfully as an option that can be turned off). 

None of my steamers have flywheels.  The one that was originally equipped with one ran very nicely, but could barely pull its own shadow.  I removed the flywheel and added some weight - now it runs just as nicely as before but can pull a respectable train.  It's obvious to me that the flywheel contributed no measureable benefit, but that it did contribute a measureable drawback.  (Both of which, I'd guess, would apply to either DC or DCC.)

As has been stated by others, the original poster's question was concerning a flywheel in a small steamer.  A good motor/drive train combination wouldn't get a readily measureable benefit from a flywheel of the size which one would be able to install in such a loco.

 

Wayne

[Forty Niner]

OK, that settles it then, installation of flywheels will now be mandatory, anyone refusing to comply with this policy will be deported to Cambodia to produce flywheels for $2 per day and all the fish heads they can eat!!!

The people have spoken!!!!!

Remember, as a famous American once said: "There is nothing wrong with individuality as long as we all do it together"!!!

Mark (laughing my "bum" off!!)

[jeffrey-wimberly]

Strange. My steamers have flywheels and they roll on for a bit if the power goes off but my flywheel equipped steamers are on the larger side with the smallest being a 4-6-0. Now looking at some of these tiny steamers where the flywheel is barely larger than the shaft, no I can't where that would have a benefit.

[hminky]

The original question was concerning a flywheel in a small steam locomotive. Flywheels don't work in steam locomotives. Smooth running is all about pickup.

Diesels are an abomination of man.

Harold

[jeffrey-wimberly]

I did a little experiment with 4 of my locomotives. A pair of Athearn F7's (no super weights) with flywheels and a pair of Athearn GP38-2's from which I removed the flywheels. All four locomotives are fitted with Digitrax DZ125 decoders with BEMF enabled. When I run the F7's up to full speed and kill the power they coast to a stop. But when I run the GP38's up to full speed and killed the power they slammed to stop. Indeed, they skidded with the wheels locked. But when I put the flywheels back in and repeated the test they rolled to a stop. The only difference between the two tests with the GP38's was first the lack of flywheels with a degree of extra weight added to compensate for the loss of their weight and then the presence of flywheels with the locomotives at their normal weight. Skid to a stop without flywheels and roll to a stop with flywheels. Seems pretty conclusive to me. The flywheels make a difference.

[Texas Zepher]

doctorwayne

Texas Zepher:

 .....For DC a good set of flywheels on a locomotive is a nearly essential thing.

Care to elaborate on the DC aspect of this?

I thought the others had already done a good job elaborating that point.

[rrinker]

 It may indeed be true the a single pitch worm can't be driven fromt eh opposite side - but then explain all the locos with flywheels that DO coast. Something's keepign the motor turning after power cuts off, and it's not just the inertia of the armature. In fact I can clearly demonstrate this with a Stewart Baldwin switcher, they come with Canon can motors in them. At 12V DC, cutting the power lets them coast for a good 5-6 feet - and for most of theat time, the headlight LED continues to glow fromt he motor output as it acts like a generator. That's with the power completely disconnected from the rails - the only way to properly test this, as I will explain. While said loco is coasting, if you short the track with something, it WILL stop dead. BOOM, like it hit a brick wall. Dynamic brakes in action. So if your power supply doesn;t completely disconnect fromt he rails at the stop position, it's not a valid test. Put a toggle switch in line, run it up to full speed, and then opent he toggle.

 Of course we are getting sucked back into the "see how long it coasts" isea that if it does not coast the flywheel is doing nothing. I'm not sure how you would go about measuring it, but the cogging action you feel when turning the motor shaft by hand should also manifest itself after the gearbox. That would be the thing to measure with and without a flywheel. The only way you can get long coasting is if the inertia of the flywheels greatly exceeds that of the armature and the drag of the loco. Bu that doesn't mean a smaller flywheel that does not enable 6 feet of coasting is doing nothing to smooth power delivery of the loco.

                                     --Randy

 

[fwright]

My personal preference is for flywheels.  I have a variety of motors in my locomotives - some are open frame, some are can, and I have one model so far with a 24volt coreless motor (my favorite).  Both the open frame and coreless motors benefit significantly from flywheels, and I would definitely want a flywheel in these locomotives due to smoother operation at switching speeds and starting and stopping.  The better and/or bigger can motors clearly don't benefit as much from flywheels as the other motors do.

Even my near-stock Roundhouse Climax with its pitiful small out-of-balance cast (not turned) flywheel has smoother performance at switching speeds with the flywheel.  Yes, the flywheel will be replaced with a much bigger, turned and balanced piece when I revamp the mechanism.  But the existing mechanism won't jerk to a sudden stop (or sudden start), which I do appreciate.

My natural preference is for hardware instead of software solutions.  In my mind, the flywheels are the first choice with software (electronic) augment being 2nd choice for fine motor performance.  But that's why I'm an engineer instead of a box jockey.

Now my locomotives are tiny, being HO models of smaller 19th Century prototypes in both standard and narrow gauge.  Flyweels are difficult to install, but worthwhile when the space can be found.

my thoughts, your choices

Fred W

[hminky]

rrinker

 That still does not prove the flywheel is useless. Without a large enough mass the loco won;t coast much more, but even a small one that has at least the same inertia as the armature WILL smooth out the motor pulses.

            --Randy

 

Single pitch worm gearing will only allow movement if the motor is rotating. It may slide but it ain't gonna coast.

Isn't that how they disprove myths on Mythbusters, do it with and without.

Harold

[rrinker]

 That still does not prove the flywheel is useless. Without a large enough mass the loco won;t coast much more, but even a small one that has at least the same inertia as the armature WILL smooth out the motor pulses.

            --Randy

 

[hminky]

Testing a from the box HO Athearn/Roundhouse 4-4-0 with a flywheel running as fast as it's little behind will go and cutting off track power causes it to stop dead in it's tracks just like my Roundhouse/IHC merge without a flywheel.

Testing a HO Bachmann 2-8-0 the same way produces the same results.

Harold

[Paul3]

I have several non-flywheel equipped brass steam engines.  They do okay, but the 4-6-2 has some interesting characteristics.  Namely, when it's traveling at 80mph and it hits a dirty spot, a dead spot, short, or what-have-you, the drivers stop turning instantly and the loco slides for a few inches while all the slack runs in on a 10-car passenger train.  Then when it's past the point of the bad section, she spins her tires and takes off again while all the slack runs back out.

If she had a flywheel, that wouldn't happen.  It would coast to a halt, not slide.  And people here think flywheels are a "myth"?  Seriously, open a Dynamics text book and do the math.  Declaring that a flywheel is a myth is like declaring that the coeffecient of friction is a myth.  Sure, one can question a flywheel's effect on performance, but they are no myth.  Heck, just look at P2K E-units or PA-1's...  They can coast several times their own length if you just chop the throttle off.

As for out-of-balance flywheels damaging motor bearings?  The wheel wipers will wear out long before the motor bearings go the vast majority of the time.  Just ask David Harrison on the Atlas Forum.  He runs the Chicago MSI HO layout where they run literally thousands of miles on locos.  He goes through wheel wipers like crazy.  Sure, the motors all go bad eventually, but these are hobby motors, not precision-tooled, laboratory-grade motors.  Most of us will never put 3000 actual miles on one locomotive even in our lifetime like MSI has done multiple times.

Paul A. Cutler III

[BRAKIE]

If a manufacturer realized that flywheels were a myth and had no pupose you can bet that those turned brass pieces would be eliminated. This is especially true for non DCC people which I believe that Brakie is in that group. In a perfect world they not be needed.

---------------------------

The sad part is our world is not perfect and that includes DCC.I been there and Murphy rules there as well..

Maybe eliminating Murphy would be a better choice?

[Darth Santa Fe]

bogp40

I have never seen an out of balance in a flywheel.

That's because I keep getting all of them. I've had off balance flywheels in most of my blue-box Athearns, in my Proto 2000 E7, from A Line, and even from NWSL, and that's not the whole list. Some of these were so minor that the only reason I noticed was because of a faint humming, but others, like the Athearn and A Line, were so bad that the poor balance was clearly visible to the naked eye. Fortunately, drilling holes and counter-balancing (if there are two flywheels) has fixed most of these to the point of near-perfect balance. So far, I've found that Bachmann, IHC, and Kato have the very best flywheels. Athearn RTR and Genesis, modern Proto 1000/2000, and NWSL come in close second. Others I don't have enough experience with to know for sure.

As for the original question, with an engine so small, a flywheel would be pointless. The mass of a single 12mm flywheel is only enough to work with a coreless motor and perfectly free running mechanism. You would need at least two to have any effect at all on a regular motor and good quality mechanism in a small engine.

[bogp40]

I agree that almost all newer drives are drastically improved over those old open frame or suito-can motor types.  Flywheels still improve overall driveline peformance. Yes thes Bueler, Cannon, Sagami and Masima's are excellent. They run smooth and draw very little amp. Just because you have a smooth operating motor that responds to increased/ decreased voltage doesn't nec mean that this is transfered through the driveshafts, worm and gearcase.  As mentioned any hiccup in track voltage, uneven trackwork/ switches etc. can cause that "herky-jerky operation that we all have seen from the past.

If a manufacturer realized that flywheels were a myth and had no pupose you can bet that those turned brass pieces would be eliminated. This is especially true for non DCC people which I believe that Brakie is in that group. In a perfect world they not be needed.

Now as for sound equipt drives, any instantanious interuption of power will stop the loco, the momemtum of the flywheels won't help in this instance.

As for out of balance in the flywheel, this may be true on a power tool spinning @ 4-5k RPM, but if any minute imbalance exists for our puposes it would be insignificant at the speeds we run thes motors. I have never seen an out of balance in a flywheel. Yes worm motor shaft bushings, bent motor shaft , sloppy drivline/ u-joint and irregularities in the gearcase, etc would more likely be the culprrit.

[Forty Niner]

I'd say you are making a wise mover there...........

Mark