As a longtime 3-rail O gauge model railroader I’m used to seeing my locomotives- -both with and without Magne-Traction- -come to an abrupt stop when current to the track is shut off. I’m slowly getting started in HO modeling and wonder just how credible manufacturer claims are about the ability of a locomotive with a flywheel to simulate a prototype “rolling stop.” Are there any guidelines that govern selection of a flywheel-equipped loco?
Bigger is better. More rotating mass, the longer the stopping distance. They make quite a difference. If I run my Athearns at about half speed and kill the throttle, they take about 1’ to stop.
Add DCC to that and you can make them take almost forever to stop.
And you can get the same result with analog DC if you use a good MRC power pack with the momentum. switch, ‘on.’
Chuck (modeling Central Japan in September, 1964 - analog DC, MZL system)
Electronically regulated deceleration is not exclusive to DCC. Adjustable automatic momentum has been around in transistor DC throttles for quite a while. And you can get much of the effect by being patient with the throttle manually.
The inertia provided by a flywheel depends on RPM, mass, and distance of mass from the axis of rotation. So a thin, large diameter flywheel of the same weight (mass) is more effective than the small diameter version.
Features provided by back emf on some DCC decoders can be defeated by too large a flywheel. The large flywheel prevents instant response to the emf-based power changes - or any other power changes. But back emf does nothing to help a locomotive coast over a dirty spot on the track.
I’m a believer in flywheels, although the coasting and slowed acceleration is more flexible and adjustable when provided electronically. A reasonable flywheel (all that will fit in my small prototype HO engines) helps with electrical contact, minimizes DC motor cogging, minimizes gearbox “slamming”, and provides a fixed augment to electronic momentum.
my thoughts, your choices
Fred W
I’m primarialy an N scaler. My limited experience with HO indicates that the flywheel effect is much more pronounced in HO than N scale, owing to the greater mass of the flywheels. However, as has been said, the “rolling stop” effect is built into DCC decoders, although you can vary the effect by programming “configuration variables”. For anyone getting into model railroading today, or changing scales as you are, I recommend getting into DCC from the start. The benefits of digital control are tremendous. I’ve nerver heard of anyone who changed to DCC and then went back to DC (or in the case of your three-rail trains AC).
Best!
I like the effect the flywheels have on a locos operation. I can really tell the difference between one that has flywheels and one that doesn’t. An example would be Athearn BB (with DCC decoder) and Bachmann DCC OnBoard. If the
[quote user=“jeffrey-wimberly”]
I like the effect the flywheels have on a locos operation. I can really tell the difference between one that has flywheels and one that doesn’t. An example would be Athearn BB (with DCC decoder) and Bachmann DCC OnBoard. If the Athearn loco hits a bad spot on the track it will keep rig
It’s realistic, but bad when you mess up… I have a friend that programmed one of his locos to respond just as the prototype (an Alco S4) would with a full cut of cars. Very realistic, but I’ve made quite a few really hard couplings because I underestimated the time it takes the loco to stop… On my home layout it went into the loco servicing track, didn’t stop in time, and slammed into the bumper at the end of the track, which came loose. The loco proceeded to continue off the end of the roadbed and into a wall. Damage? One coupler, plus the bumping post. Luckily he was the one running it…[swg]
Flywheels are definetely worth it; I have two Bachmann locos on my layout (one mine, one belonging to a friend who doesn’t have a layout) and they’re never run alone, due to this problem and the fact that they have a tendancy to “cog” when headed downhill, creating a ton of slack action that can destroy couplers and derail cars. I’ve had one car that had it’s entire coupler box ripped off the underframe. (It was a Kadee box screwed onto the underframe, the screw was pretty short and it was ripped out of it’s hole.) Those two locos always run with a higher quality loco (with flywheels!); normally my Spectrum C40-8W and my Atlas SDP35.
The basic reasoning behind flywheels is to keep the loco running over minor dead spots - either switch frogs or dirty track (we know that none of us have dirty track!!). Momentum switches on DC packs or DCC programing gives that slow-down throttle action. As for DCC, dirty track will make the loco shut off & re-start - making the flywheels pretty much useless. I use a Prodigy Advance system that has a red button “kill switch” - the loco will still go a few inches if the grandson has the throttle high. DON’T ASK HOW I KNOW THIS!!![:O][:I]
That’s why I know where that emergency stop button is (I see Lou does too). More affectionately known and the “oh poop” button. If I was a real engineer I would have been terminated long ago.
Sorry for this late acknowledgment.
Thanks to everyone that responded to my question. You’ve convinced me that flywheel-equipped locos are definitely the “way to go.”
True. But momentum and DCC aren’t supposed to be compatible. In any case I’d rather be able to control the locomotive than the track power.
I just ran my first decoder equipped locomotive yesterday. It was great and I immediately saw the difference between DCC and a momentum controlled locomotive then. Momentum isn’t anything like the performance of a real locomotive but it’s as close as you can get without a decoder. Anyone who drives a car should know that.
Irv
Irv said:In any case I’d rather be able to control the locomotive than the track power.
Funny,I been controlling my locomotives for the past 57 years with DC.
Again the lunatic that came up with that old ad saying"Run your trains,not your track" didn’t have the foggiest idea…Must have been a non modeling ad man.
As far as the whistles,bells,lighting effects etc all one needs is a Quantum Engineer.