What is the purpose of the flywheel in a PS2 diesel with two motors that doesn't have the sensor for the stripe tape? In other words how does a flywheel work?
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When a locomotive is in motion and power to the motor is cut, the flywheel, which is relatively heavy, tends to keep the motor spinning, so the locomotive slows down gradually rather than stopping suddenly. Conversely, when a locomotive is at rest and power is applied to the motor, the heavy flywheel prevents the motor rotational speed from increasing suddenly, so the locomotive accelerates gradually rather than abruptly. Bottom line is the flywheel makes locomotive acceleration and deceleration look more realistic.
MELGAR
However, the size of the flywheels in most of our trains makes that effect fairly minimal. In order to really make a big difference, they flywheel would have to be a lot heavier.
I think that's true. What I said above is the theory, but not necessarily how it behaves in practice. I would be interested in knowing the moment-of-inertia of a flywheel compared to the rotating parts of the motor.
MELGAR
It can help with the timing of the fields on motors, pulling the armature thru dead spots or slightly reversed field pull which though slight can be present at times, depending on motor design. At our ratios, I think the motor itself benefits more than the visual of operations. Herk a jerk action cuts on an already limited lifespan of can motors too. If we used more poles in the designs I think we'd see less flywheels; especially with better command features like momentum. There are other less size obtrusive methods of reading rmp than a flywheel tape. Some more reliable (imo). The tach tape however is more easily "adjustable", and fits our customized applications better. So even if the electronics eliminated all herk a jerk action, I think we'd still see them, or at least a plastic version.
Early MTH "high hood" diesels (like GP's, the H-10-44, etc.) had good-sized flywheels that did confer some useful coasting and stored energy. MTH even created a marketing video demonstrating that the combination of flywheels and PS1 electronics were able to carry the loco across a piece of masking tape placed on the tracks.
Their early steam locos are a different story. My first was the 20-3020-1 Premier Hudson. Our club used to run with a CAB-1 and Powermaster to vary the track voltage. Once in a while, if a little kid showed a lot of interest I would hand him the CAB-1 and let him run the train. Usually this worked out just fine. But if he pressed the direction button (or another operator fouled my track causing a short), the whole train came to a sudden halt with a horrible graunching of rods and gears. I was concerned that eventually a hex screw holding the driving rods on would be sheared off, or the steel worm would cut a bur into the bronze worm wheel (basically ruining the loco.) The rubber tires exacerbated this problem because they prevented the loco from skidding, and further shortened the stopping distance. The small flywheel was ineffective, and the whole loco was much less kid-friendly than my friend's Lionel 18005 (reissued 700E.)
K-Line's 1992 re-issue of the Marx 333 Pacific had no flywheel at all, and suffers from similar operating flaws. Which is a real shame, because it actually has very good slow-speed performance for a traditional toy train!
Fast-forward to 2010 and I was fortunate enough to obtain a Lionel 11203 Pere Marquette scale Berkshire with Legacy. Like the Vision Hudson, this loco had a Buehler motor with TWO large flywheels and a back-drivable worm gear (wheels can turn the motor.) It has very smooth starting characteristics, and if someone kicks the plug out at full song, it will coast about two feet! The drive wheels will continue to turn for a couple of seconds, even if the loco and tender are lifted from the track.
I also have a set of MTH Reading FT's with PS2. In order to fit inside the carbody, the flywheels in this loco are very thin- maybe the size of two Kennedy US half-dollars stacked together. They are too small and turn too slowly to be mechanically effective--you can see the two motors snatching and bucking below about 4 scale mph. So why the 2nd flywheel then? One motor has to have a flywheel to feed the tach sensor. So the other motor needs to have one too, because the worm gears are self-locking. The trucks are not connected--each motor powers its own truck. If the 2nd motor didn't have a flywheel, it would stop turning a fraction of a second sooner than the one with the sensor. Its power truck would lock up, and get dragged a very short distance by the other truck driven by the motor with the striped flywheel. This would stretch the tires and possibly cause damage to the gears.
Personally, I don't like the ubiquitous vertical motor arrangement because height constraints force the motor(s) and the flywheel(s) to be smaller than they should be. The Atlas SW switcher and some recent diesels offered by 3rd Rail are a much better design, IMO. Over the last 10 years, Lionel's "LionDrive" diesels and many Legacy steam locomotives have back-drivable gears, that in combination with a flywheel and their electronics, allow for smoother and more forgiving operation. Lionel's struggles to tame the Odyssey "lurch" led to a genuinely better mechanical design.
My $.02, I hope I answered your question.
Ted S posted:Personally, I don't like the ubiquitous vertical motor arrangement because height constraints force the motor(s) and the flywheel(s) to be smaller than they should be. The Atlas SW switcher and some recent diesels offered by 3rd Rail are a much better design, IMO.
While you might like the drive characteristics of the horizontal motor, it usually limited room for electronics. Also, the gear train is more complex for the horizontal drive. A redeeming quality of "China drive" vertical motors is you get space for the electronics package and a simpler drive train.
gunrunnerjohn posted:While you might like the drive characteristics of the horizontal motor, it usually limited room for electronics.
All the better in my opinion, plus both trucks will be turning at exactly the same rate.
PRRMP54 posted:gunrunnerjohn posted:While you might like the drive characteristics of the horizontal motor, it usually limited room for electronics.
All the better in my opinion, plus both trucks will be turning at exactly the same rate.
Well, if you don't want the electronics in your train, I guess you could look at it that way. I'll pass on that option, thanks.
The manufacturers don't really give us a choice. But it's like building a car with a rough, cut-down V6 instead of a big-block V8, so you have more room in the dashboard for a Becker Grand Prix stereo and navigation. Those things don't turn a Chevy into a Mercedes. Some of us take pride in knowing that our locos have the highest possible mechanical pedigree.
The electronic gimmicks are a HUGE "value add" (read: profit) item for the builders. They're also the cause of trouble in a lot of cases. I admit I like my steam chuffing sounds, but that fits in the tender, and I would choose quality over gimmicks ten times out of ten. Give me US Hobbies steam in die-cast, gauged to run on 3-rail track. The last locos I'll ever need... Maybe this is what the manufacturers really fear? If they finally get it right, we'll never buy another!
gunrunnerjohn posted:While you might like the drive characteristics of the horizontal motor, it usually limited room for electronics. Also, the gear train is more complex for the horizontal drive. A redeeming quality of "China drive" vertical motors is you get space for the electronics package and a simpler drive train.
I agree with GRJ on this. The horizontal drive requires universal joints and driveshafts (sometimes plastic) - both potential wear/failure points. The vertical drive does not.
MELGAR
Thank you all for the information on the purpose of a flywheel regarding toy train motors.
I had some early Weaver E8's that did not have fly wheel can motors and the starting an stopping was jerky more so on bring the Locomotives coming to a stop. I replaced those can motors with replacement flywheel motors sold by Frank Timko and they made for a smoother running Locomotive which I later up-graded to MTH Proto-2.
Trains41
