Flywheels - mechanical or electronic?

[tbdanny]

Hi all,

While preparing a brass loco for installation of a TCS M1 decoder, I got to thinking about the role of BEMF as opposed to the role of a physical, mechanical flywheel.  It seems to me that they serve a more-or-less similar role - to keep the motor turning smoothly and ease out any sudden changes in speed caused by the mechanism or abrupt changes in trackage (not that there should be any).  So my question is this: if I have a locomotive that runs smoothly without a flywheel on DCC, would a decoder with BEMF be enough to act as a flywheel as well?

Thanks in advance,

tbdanny

[rrinker]

 A flywheel has one huge advantage over BEMF - it doesn't need power. So the flywheel can keep the mechanism turning even with a momentary loss of power. Now, if your loco runs smoothly and has no power pickup issues without a flywheel, BEMF or no BEMF it will still run smoothly. I can't empirically test this, every loco I own has a flywheel, even the tiny 44-tonner. I don't have the opposite problem, BEMF fighting the flywheels, but that would indicate the need to probably dial back the BEMF a little.

                                 --Randy

[Hamltnblue]

 Pretty much covered. If you aren't having problems running without a flywheel then there probably isn't a need to add one.  I wouldn't take one out that's already installed though.

[gandydancer19]

 If you have good track with no dead spots, and good smooth throttle control, electronic flywheel (Momentum) is fine.  BEMF doesn't serve as a flywheel as it's main function.  That is momentum's primary function.  A mechanical flywheel tends to smooth out throttle changes, and IMO was developed early on because the DC throttles back in the day were not very refined or smooth, therefore, mechanical flywheels smoothed them out.  However, mechanical flywheels do work very well, even today. 

On the other hand, if you are going to build your own motive power, I feel that mechanical flywheels are not necessary.

[CSX Robert]

gandydancer19

...BEMF doesn't serve as a flywheel as it's main function.  That is momentum's primary function.  A mechanical flywheel tends to smooth out throttle changes...

I would have to disagree with this. A mechanical flywheel, at least from what I have seen, is not for the purpose of smoothing out throttle changes, but for smoothing out low speed motion of the locomotive. No model locomotive flywheel I have seen is large enough to have an appreciable effect on the acceleration or deceleration of the locomotive, but they do allow for much lower speed operation without stalls. That is also one of the benefits of Bemf compensation - smoothing low speed operation and allowing for lower speed operation without stalls, although Bemf has other uses as well.