Another Keep-Alive Thought

[peteski]

Weren't large-ish flywheels considered a mechanical form of Keep-Alives?

Sure!  And  in most N scale locos as large as physically possible flywheels are still being used for that purpose.     But due to the laws of physics (small size of N scale models) even those "large" flywheels are not very effective (especially at slow speeds, where the intermittent electrical contact problem is the most pronounced).

[MarkInLA]

Keep Alive circuit (by definition) is there to keep the model running though temporary power interruptions (between the track and a loco). As such, it has to reside inside the moving loco.

There are analog throttles factory-equipped with momentum feature, but if the loco stalls on a switch or dirty track, that will not help any.

I'm with Peteski on this !!! Sorry Toots !! Because you're insinuating the throttle (NCE ?) could have capacitance ability enough to toss some 13 V to the engine's motor across some 1-7 seconds, deeming wheels/pickup from rails irrelevant at the time of 'rescue', if you will..
I can't see that system too easily. But then again, I'm not a techie..I think peteski's call is the most logical.....M

[MarkInLA]

PS..
We always skip over an aspect of steam, model-wise, that there are little to no steam with FLY WHEELS and is one major factor in why diesels seem to fare well-better than steam, sales-wise, today, along with the very fact that diesel is all you see on the 1:1 scale system today (less the steam excursion brothers and sisters out there !)...

[MarkInLA]

Belated thanks again for the myriad of descriptions and experiences with KA ..M

[greenwizard88]

Another factor that added to the lack of any electronics is that while designing and building a circuit board was expensive, using heavy (dense, not radioactive) metal wasn't. So it was much more economical to simply use a flywheel than to try and create a circuit that could handle polarity changes.

Some of the higher end diesels from the late 90's that had circuit boards also had fantastic flywheels that could get over just about any sort of power interruption.