flywheels

from my HO, N, and TT experience, I get the sense that what makes the difference between smooth starting, running, and stopping locos and ones that zip around like toys are flywheels. Anything I have with flywheels runs awesomely, anything without does not. So....what about Z? It seems that everyone's favorites are the flywheel-equipped product from MT and AZL. How could I stick some flywheels on my Marklins?

You first find out where to put them. This is a composite photo I put together some time ago:


And head on:


Now you tell me where there is space left... And the little pcb inside is already removed...

If you do the math, for having any effect of flywheel, you will realize for the weight and the RPM of the flywheel that is being used in Z loco it has almost no effect. Flywheels are least effective at lower speed (effectiveness is square of RPM) and Z needs most help at lower speeds. It is the motor that you see on the newer locos that makes it run better, and it has come a long way. You dont need any flywheels to make Z look realistic. We have run at shows and slow speeds both DCC and non DCC they run all day at scale slow speeds. Just have to keep the tracks clean. Actually I have seen the HO scalers with blocks and sandpapers scraping the tracks and running the locos like toys. Mostly it comes down to the track and your how well the loco is maintained.

Kim

Flywheels are least effective at lower speed (effectiveness is square of RPM)

Don't you mean at higher speed?

Anyhow, another thing is that flywheels need to concentrate the most of their weight at the outside rim and that has to be as large as possible. At the sizes involved in Z this won't amount to much.

It is the motor that you see on the newer locos that makes it run better, and it has come a long way.

Agreed on that. The difference between the old 3-pole motor and the new 5-pole. Going to Faulhabers would still be better but I don't think there are plug-in replacements available.

Havoc wrote:

Flywheels are least effective at lower speed (effectiveness is square of RPM)

Don't you mean at higher speed?

...

No, he means what he says and he is right
Most effective at high speed - hence the flywheel is attached to motor shaft (high rpm), not to the loco wheel axle (low/geared down rpm)

Of course they are most needed at low speeds, but that's another story ...

ps he is also right when he says that you will get more improvement by using better motor than by adding flywheel to a crappy motor

The friction present in the drivetrain is also a factor. The Micro-Trains mechanism has a very high amount of friction owing to large inboard axle bearings and wheel wipers. In this situation, flywheels are less than useless, yet M-T still insists on adding them. Why? It's a selling point. People see "flywheel" and automatically think "better quality." However, you can remove the flywheels and the loco will run exactly the same. It's all down to the quality of the motor, as Kim said. The rest is marketing.

The AZL mechanism has a much lower-friction drivetrain, and the effect of the flywheels can be seen; however, it is only seen at high speeds. Cut the power of the loco at full throttle, and it will coast a little (while the M-T loco will stop dead in its tracks). However, if it is running at low speed, there will be no coasting. Why? The flywheel is only effective at high speeds, as noted by Kim.

It's kind of sad, because if Z scale manufacturers did away with flywheels, we'd have locos that run the same and cost less. But then sales would likely drop because people will think they're not as good. When you get something into their heads, it can be really hard to fix it...

And of course, if the flywheels were turned from tungsten they would have greater effect than piddly things made from brass (at least in theory and before the effect is dissipated by other losses in the system)
As you guys say - get the axle resistance low, use decent coreless motor, make loco frame from sintered tungsten moulding and Bob is your uncle
Flywheel is a gimmick (particularly if you are using DCC)

No, he means what he says and he is right

I see now. shouldn't post when drinking

Havoc wrote:

No, he means what he says and he is right

I see now. shouldn't post when drinking

Thanks to all for the contributions - this has been a most illuminating topic and I've learned a lot. I had been one of those who thought that flywheels always improved performance.

David K. Smith wrote:

It's kind of sad, because if Z scale manufacturers did away with flywheels, we'd have locos that run the same and cost less. But then sales would likely drop because people will think they're not as good. When you get something into their heads, it can be really hard to fix it...

Thank you, Mr. Smith!
Once AGAIN, you have presented an opposing view that has provided valueable information.

Alex
Tokyo, Japan

...you can remove the flywheels and the loco will run exactly the same.

It's not true. Locomotives equipped with flywheel run smoother with substantially less "jerking". To call the flywheel a marketing gimmick is highly irresponsible. A real scientific and objective test can prove the advantage of flywheels regardless the type of motor.

Lajos

ausman2001 wrote:

I had been one of those who thought that flywheels always improved performance.

Actually, I used to think the same. I believe I inherited this line of thinking from larger scales, where flywheels could make an impact, especially with traditional pole-type motors. But there comes a point of diminishing returns, and Z scale is pretty much the point where flywheels make virtually no practical difference.

This is not to say flywheels could never make a difference; for instance, if a novel mechanism were designed for a big fat cab loco, where one could fit a pair of comparatively massive tungsten flywheels, and with nice low-friction trucks, then things might be different. Doubtful if many of us could afford such a beast, and it won't work for hood units...

zthek wrote:

...you can remove the flywheels and the loco will run exactly the same.

It's not true. Locomotives equipped with flywheel run smoother with substantially less "jerking". To call the flywheel a marketing gimmick is highly irresponsible. A real scientific and objective test can prove the advantage of flywheels regardless the type of motor.

Lajos

Sorry, but I have run some performance tests, not "scientific," but sufficient to prove for me that they have no practical benefit. With the very same motor and drive train, with and without flywheels, I found no discernable difference in the behavior of the locomotive.

Larger scales, flywheels absolutely help. Three-pole motors, flywheels absolutely help. Modern Z scale locos with coreless motors, I find no measurable difference in performance.

And, so... it begins.

I knew these comments would turn this subject in to a hot debate. Let's see how long this goes before someone wants to moderate it.

TechRep wrote:

And, so... it begins.

I knew these comments would turn this subject in to a hot debate. Let's see how long this goes before someone wants to moderate it.

Naturally, when two different people make two different observations, there will be clashes. I have reported what I have observed and measured with Z scale locos having coreless motors.

Actual mileage, as they say, will vary...

David,
I always enjoy reading your blog and website.

I'm just waiting for the two representatives from the two manufactures to log-in and provide their rebuttles (is that a word? I'm a terrible speller).

Alex

OK, Test #1: Power a 10 mm Faulhaber motor with a 1.5 V battery. Turn off the power and time how long the shaft keeps turning. Power an identical motor equipped with flywheel, turn off the power and time how long the flywheel equipped shaft keeps turning. If the two times are identical, I'll admit science sucks.

Lajos

Not to sound contrary, but shouldn't test#1 be conducted with a 8mm motor since this would be the predominant size in Z today?

Then Test#2 add in a drive-train and compare. Will the force the flywheel adds be enough to over come the friction in drive-train?

I won't presume to know the answer to these questions. I only seek to try establishing objective tests.

~Paul E.

pmx wrote:

Not to sound contrary, but shouldn't test#1 be conducted with a 8mm motor since this would be the predominant size in Z today?

Then Test#2 add in a drive-train and compare. Will the force the flywheel adds be enough to over come the friction in drive-train?

I won't presume to know the answer to these questions. I only seek to try establishing objective tests.

~Paul E.

Thank you Paul. Tests with a motor alone will always show improvement with a flywheel. Now add the friction of the entire drive train (try an M-T unit), and just for kicks, add the load of a few pieces of rolling stock. It ought to be a test that reflects real world conditions, after all, since we don't place bare motors on our track and watch them spin...

Obviously the results are similar with an 8 or 6 mm motor too. The friction level of mechanism doesn't know the motor has flywheel or not, so the added momentum of flywheel equipped locomotive is always measurable.

Lajos

PS: Don't write off the 10 mm (even 12 mm) motors yet.