flywheels or DCC - Oops

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proto87stores

flywheels or DCC - Oops

Postby proto87stores » Sun Feb 03, 2019 4:02 pm

Just wanted to make a small clarification. It's bemf that controls motors well without flywheels, not DCC per se. You can have bemf on DC controllers and DCC decoders without bemf - although nowadays its almost standard on newer DCC decoders.

However if you want closed loop motor absolute speed and position control from a control panel or by computer control, DC bemf has more options.

Andy

nigelcliffe
Posts: 488
Joined: Mon Jul 21, 2008 8:31 am

Re: flywheels or DCC - Oops

Postby nigelcliffe » Mon Feb 04, 2019 10:14 am

proto87stores wrote:Just wanted to make a small clarification. It's bemf that controls motors well without flywheels, not DCC per se. You can have bemf on DC controllers and DCC decoders without bemf - although nowadays its almost standard on newer DCC decoders.

However if you want closed loop motor absolute speed and position control from a control panel or by computer control, DC bemf has more options.

Andy


With DCC there is another choice: use the space for a mechanical flywheel or use the space for an electronic flywheel (aka "stay alive module"). The electronic version can work when the motor is stationary (see Zimo's very clever "nudge the loco along when it looses power on stopping until pickup is restored" trick). The mechanical's effect is proportional to the motor rotation speed; faster the motor is going the more effect the flywheel offers.

All of which becomes irrelevant when on-loco battery control systems improve from their current experimental phase.

- Nigel

proto87srtores

Re: flywheels or DCC - Oops

Postby proto87srtores » Mon Feb 04, 2019 4:05 pm

nigelcliffe wrote:
With DCC there is another choice: use the space for a mechanical flywheel or use the space for an electronic flywheel (aka "stay alive module"). The electronic version can work when the motor is stationary (see Zimo's very clever "nudge the loco along when it looses power on stopping until pickup is restored" trick). The mechanical's effect is proportional to the motor rotation speed; faster the motor is going the more effect the flywheel offers.

All of which becomes irrelevant when on-loco battery control systems improve from their current experimental phase.

- Nigel


I have seen a few practical circuits (RM Web?) for DC keep alives. But either way, Keep alives are a practical patch for poor pick-up, not smoothing a basic motor's slow speed rotation. Perhaps wrongly, I assumed the need and the DCC alternative suggestion was for the latter.

My personal preference is to strive for near perfect starting and stopping mechanisms (first at least), before adding electronic assistance. But superb (and long lasting) motors and gear chains become exponentially more expensive as size decreases.

To keep up my grumpy old Luddite image, I must say, I have severe misgivings about universal "dead rail". Rechargeable batteries aren't free and don't last for ever (not soon anyway) and the thought of opening up a hundred or so emu bodies and buying and replacing new batteries in them every three years or so, does not appeal. (all my such cars will each have lighting and soon working sliding doors to keep powered). OH wire OTOH has no such limitations . . . .

I also wonder if dead rail (no wiring benefit) enthusiasm extends to individually battery powered, wireless controlled, point motors, signals and occupancy detectors ? Recharging systems for those would seem to be even more inconvenient than keeping charged more trains than you have track space to leave them stored on.

Am I missing inexpensive solutions to the above, that I am not aware of?

Andy

nigelcliffe
Posts: 488
Joined: Mon Jul 21, 2008 8:31 am

Re: flywheels or DCC - Oops

Postby nigelcliffe » Mon Feb 04, 2019 6:15 pm

proto87srtores wrote:
nigelcliffe wrote:
With DCC there is another choice: use the space for a mechanical flywheel or use the space for an electronic flywheel (aka "stay alive module"). The electronic version can work when the motor is stationary (see Zimo's very clever "nudge the loco along when it looses power on stopping until pickup is restored" trick). The mechanical's effect is proportional to the motor rotation speed; faster the motor is going the more effect the flywheel offers.

All of which becomes irrelevant when on-loco battery control systems improve from their current experimental phase.

- Nigel


I have seen a few practical circuits (RM Web?) for DC keep alives. But either way, Keep alives are a practical patch for poor pick-up, not smoothing a basic motor's slow speed rotation. Perhaps wrongly, I assumed the need and the DCC alternative suggestion was for the latter.

My personal preference is to strive for near perfect starting and stopping mechanisms (first at least), before adding electronic assistance. But superb (and long lasting) motors and gear chains become exponentially more expensive as size decreases.



Your first paragraph raises the often said "stay alive is the Band-Aid bodge for bad pickup". Well, it may be for some but, I'd suggest it isn't when I'm doing it.


Like you, my preference is to get for near perfect running by mechanical work. Good pickup, good suspension or compensation, choice of motor, gears, etc.. etc.. Then, I'll add every electrical trick available at sensible prices. I evaluate which decoders give the best performance on the locos I have, then only buy those which give the best performance: my old tests of my 2mm scale locos had the majority of decoders on sale as offering significantly worse control than DC from a Pentroller (so no point buying any of those decoders!), just two makers were better than the Pentroller. Then I'll add to the decoder if I can to improve it further.

Good decoders with stay-alive units can transform locos. Not in a massive way, but very small subtle changes. The effects are more marked on locos with few wheels, so they already face a pickup problem.
Locos run smoother because there are not microscopic changes in their pickup, they no longer stall now-and-again when performing shunting moves. And, its not just me, its people who ask me to do the same to their locos, spend a little on electronics, see the result and then come back for the same again on other locos.


- Nigel

proto87stores

Re: flywheels or DCC - Oops

Postby proto87stores » Mon Feb 04, 2019 9:06 pm

I didn't intend "practical patch" to be a negative connotation. Apparently they make a huge helpful difference for sound decoders. (which I don't have).

Personally I would opt for small keep alives rather than large. I hate the idea of a heavy fast moving train to be disconnected from it's speed commands for more than a inch or so of travel.

Andy

nigelcliffe
Posts: 488
Joined: Mon Jul 21, 2008 8:31 am

Re: flywheels or DCC - Oops

Postby nigelcliffe » Mon Feb 04, 2019 10:55 pm

proto87stores wrote:I didn't intend "practical patch" to be a negative connotation. Apparently they make a huge helpful difference for sound decoders. (which I don't have).

Personally I would opt for small keep alives rather than large. I hate the idea of a heavy fast moving train to be disconnected from it's speed commands for more than a inch or so of travel.


Decent decoders have a setting for that problem, they limit how long the loco will run without a DCC signal. Cheaper decoders don't. So, if there is space for a big energy store, there is a solution to the "run away without control" locomotive.

Most of the installations I've done recently don't have room for huge energy stores, I'm cramming tiny spaces to get maybe 1/10th to 1/4 of a wheel revolution, and pushing components closer than ideal towards their maximum operating voltage. But, that's necessary to get the difference in running quality.

proto87stores

Re: flywheels or DCC - Oops

Postby proto87stores » Tue Feb 05, 2019 4:53 pm

Thanks for the heads up on the decoder lost signal feature. I'd forgotten all about that.

Better US (diesels at least ) models typically have less pick-up problems because they have a solid metal non-insulated wheel on one side of each their axles and so can pick up directly through metal side frame axle bearings on alternate wheels. No wipers to worry about mounting, springing and cleaning. I'm hoping to somehow use a similar technique on my legacy UK steam loco models. That's the only significant drawback I can see to 3D printing wheel centers.

Andy


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